Where to buy a new throttle plate/flap

[Berggreen]

Hello everyone

I have a throttle house, where the brass throttle plate/flap is worn and not sealing the air-intake when the throttle plate/flap is fully closed - I can see light around the plate/flap, when it is closed, and "pirat-air" is therefore leaking into the intake-system at idle.

i can see that the plate/flap is just mounted with two screws, but I have searched around the i-net for a new plate/flap, but without any luck.

Any tip, where I can buy a new one?

Thanks,

Christian

[Tyler S]

The throttle plates do not seal 100%. If you can still adjust your idle down to spec using the idle air screw then dont worry too much about a little leakage at the throttle plate. These engines do not have any upstream sensors like modern cars so it is a non issue. Set the throttle plate stop screw until the throttle plate just drags in the bore. Then slightly screw it back in about 1/8 a turn or until it no longer drags. However if you still cannot get the idle down to spec using the air screw on the intake manifold you may also want to look elsewhere for a vacuum leak.

[Berggreen]

The throttle plates do not seal 100%. If you can still adjust your idle down to spec using the idle air screw then dont worry too much about a little leakage at the throttle plate. These engines do not have any upstream sensors like modern cars so it is a non issue. Set the throttle plate stop screw until the throttle plate just drags in the bore. Then slightly screw it back in about 1/8 a turn or until it no longer drags. However if you still cannot get the idle down to spec using the air screw on the intake manifold you may also want to look elsewhere for a vacuum leak.

Thanks Tyler!

Unfortunately, I cannot get idle speed down using the idle screw, and the only way currently to get the idle speed down is to "drown the pump", thus increasing the rod length linkage to the injection pump, so that it does not go into zero position. But I guess that this is not an ideal solution!

I have been looking around for a possible vacuum leak, but unfortunately without luck. So I thought I had found the issue with the throttle plate not sealing completely. I have already adjusted the throttle plate position with the stop screw, but no effect on the idle speed.

Do you know where to buy a new throttle plate to try to minimize the leak there?

Thanks,

Christian

[Tyler S]

I dont know where to buy a new plate. It is not a common failure point. Have you verified your timing at Idle? If the switchgear or vacuum retard system is malfunctioning it will advance the timing and no amount of adjustment will compensate to get the idle within range. Also, One more place to look for a vacuum leak is the brake booster.

[Berggreen]

I dont know where to buy a new plate. It is not a common failure point. Have you verified your timing at Idle? If the switchgear or vacuum retard system is malfunctioning it will advance the timing and no amount of adjustment will compensate to get the idle within range. Also, One more place to look for a vacuum leak is the brake booster.

Thanks Tyler - appreciate you advice! 

Yes, I checked the timing, and I have around 5 degrees ATDC at idle, increasing up to around 30-35 degrees ATDC at 3000 rpm.

The US switch-gear system has been disengaged and a 123ignition installed instead sourcing vacuum from the US configuration side port on the throttle port, giving constant vacuum. I have not yet changed to the the port under the throttle house (Euro configuration) with declining vacuum with rpms, instead of the US config. side-port with constant vacuum. But I don't think that should have any influence on engine behavior at idle. It should however give me more advance a lower rpms, as vacuum will reduce with rpms, when sourcing vacuum from the (euro) port under the throttle house.

Or am I wrong?

Good point about the brake booster. Any good way of checking this?

Thanks,

Christian

[Jonny B]

Checking for a leak in the brake booster is straightforward. With the car running, press on the brake pedal. If there is a marked increase in idle you most likely have a leak.

[Berggreen]

Checking for a leak in the brake booster is straightforward. With the car running, press on the brake pedal. If there is a marked increase in idle you most likely have a leak.

Thanks Jonny, I will try this out!

What do you think of my "vacuum port plans"? Am I on the right track?

Thanks,

Christian

[Tyler S]

Yes thats one way the booster can leak. It can also leak on the manifold side of the chamber. Easy way to eliminate it as a possible source is to simply disconnect the vacuum line and plug it for testing purposes.

Christian, your timing reading of 5 ATDC and 30-35 ATDC doesn’t make sense. Are you meaning “ BTDC” (Before top dead center)? Try setting your timing at Zero (0). If your timing is really at 5 BTDC then setting it at zero will lower the idle. Easy test.

Depending on which model 123 Ignition you have will determine if you will be able to use manifold vacuum for MAP advance purposes. Only the 123 “Tune”and “Tune +” can be set up this way.

[Berggreen]

Yes thats one way the booster can leak. It can also leak on the manifold side of the chamber. Easy way to eliminate it as a possible source is to simply disconnect the vacuum line and plug it for testing purposes.

Christian, your timing reading of 5 ATDC and 30-35 ATDC doesn’t make sense. Are you meaning “ BTDC” (Before top dead center)? Try setting your timing at Zero (0). If your timing is really at 5 BTDC then setting it at zero will lower the idle. Easy test.

Depending on which model 123 Ignition you have will determine if you will be able to use manifold vacuum for MAP advance purposes. Only the 123 “Tune”and “Tune +” can be set up this way.

Thanks Tyler, I will try that as well to rule out the brake booster as the source of "pirate air"!

No, I mean ATDC, so plus (+) 5 degrees. In the service manual, Mercedes states that timing at idle has to be +3 degrees ATDC with vacuum connected (for a 051 BOSCH distributor). See picture from service manual below.

If I had 5 BTDC and pushed it up to zero, wouldn't the idle speed increase, because you supply more advance, when you push the timing towards the ADTC regime? Or did I get something wrong here?

I did try to push the idle down by retarding the timing to zero and also into BTDC (minus regime) to try to lower the idle rpms. But with that setting the car was running horribly, and with cut-outs when pulling at medium rpms, clearing lacking enough timing advance.

But maybe by changing to the (euro) vacuum port below the throttle house, I get more advance at medium rpms, and I may therefore be able to push idle timing further down towards zero and thus lower idle speed. What do you think?

I have a standard vacuum retard 123ignition, and I am running it in program 8, corresponding to a vacuum retard 051 BOSCH distributor and euro throttle house with the vacuum port under the throttle house, and thus max. vacuum at idle and decreasing vacuum with rpms. I have heard this is the standard setting for a euro 280SL, which will give you the best performance. What do you think?

Thanks,

Christian

[kampala]

Christian

Tyler is correct - if you have the tune or Bluetooth version of 123ignition, you can use the side “vacuum all the time “ port but if you have the pre-programmed 123 and are using program E, it usually does exactly what you are experiencing.    Program E expects all emissions equipment to work and the two way valve to control vacuum. 

If you are using program 8 you need to have vacuum coming from below the throttle body like a euro 280 or any 250. 

Also once vacuum is correct you would time the car so at idle you are few degrees BTDC since you are not using any emissions equipment. 

Are you using side vacuum port or have you modified to have the port under the throttle body available?

[Berggreen]

Christian

Tyler is correct - if you have the tune or Bluetooth version of 123ignition, you can use the side “vacuum all the time “ port but if you have the pre-programmed 123 and are using program E, it usually does exactly what you are experiencing.    Program E expects all emissions equipment to work and the two way valve to control vacuum. 

If you are using program 8 you need to have vacuum coming from below the throttle body like a euro 280 or any 250. 

Also once vacuum is correct you would time the car so at idle you are few degrees BTDC since you are not using any emissions equipment. 

Are you using side vacuum port or have you modified to have the port under the throttle body available?

Thanks, very helpful.

I am still using the US throttle house with the constant vacuum side-port, and I found that using program 8 was the best compromise. I also tried program E, but found it even worse with the configuration I currently have!

But I have (over the winter) found a euro throttle house on Ebay, which I am currently restoring, but I also here see light around the throttle plate, when the throttle plate is closed, so I would also like to find a new plate for this house as well. Actually, when comparing the US and Euro throttle houses, they are actually physically identical, and both have both vacuum ports. However, on the US one, the (euro) port below the throttle house is blinded off, but I think there is still a vacuum channel, as i can see the small hole just next to the throttle plate on the engine side. Same for the Euro throttle house, it also has both ports, but the US port is here blinded off. Looks like Mercedes just made one house with both ports physically there, but blinded off one of them depending on the market (US/Euro). Have you seen this too?

Back to timing: Just for me to get on the same page as you guys, because I think I may have misunderstood how to read BTDC and ATDC using the scope. Up to now, I thought that, when I increase the rpms, and looking at the degrees on the scale using the scope, I see the degrees increase on the scale, and I though this was + degrees in the ATDC regime, and when degrees went in the other direction and down below zero, I would be in the BTDC regime, like _after_ zero (ADTC) and _before_ zero (BTDC). Am I wrong here, so that it is actually opposite?? 

The timing degrees in the picture from the service manual above is actually for a euro 280SL with an 051 distributor, thus without the emission control system. As you see, it says 3 degrees +/- 1 degree ATDC at idle.

For the US emission control version with US throttle house config and an 062 distributor, which my manual 280SL had, before I replaced it with the 123ignition, see the similar idle speed timing below, where it says 8 degrees ATDC!

What do you think?

Thanks,

Christian

[kampala]

The casting for the throttle bodies apprear the same to me as well.  I ended up drilling the port under the throttle body as I matched it to my 250 throttle body.  It’s better if you have a euro body and don’t need to drill.  Your problem seems to be the vacuum port.  That’s why you cannot get the idle down. 

Timing - what I do may not be the right way but the car runs good so I just keep doing it this way :  once the vacuum is connected correctly, I leave everything connected and time it at close to 35-38 degrees BTDC at 3000 rpm and lock it off.  Then I just adjust idle to get to correct rpm at idle.   Usually this means that at idle timing will be 5-8 degrees BTDC.

Car runs great with this method so I just do it like this.  May not be correct but it runs good and plugs look correct color. 

[Tyler S]

Christian, a higher number from “0” into the BTDC range is Advancing the timing. A number below “0” ATDC is Retarding the timing. So when you rev the engine you are advancing the timing into the BTDC range. (Before top dead center is earlier/advanced timing)
As far as your two late throttle bodies, yes they are identical in that they both have their ports on the engine side of the throttle plate.
However, The earlier throttle body that was paired with the 051 distributer had its port just aft of the throttle plate so that when the throttle was cracked open just slightly, vacuum would immediately raise to atmosphere. This is a different setup and function and is not achievable with the late throttle body and standard 123 ignition because the vacuum never goes to zero except maybe at wide open throttle. They can be modified as Oz states above or replaced with an early 051 type unit.
Yes, when you retard the timing the car will not idle well. You need to go back and adjust the air and fuel mixture in order to compensate for the removed timing advance.

[Berggreen]

The casting for the throttle bodies apprear the same to me as well.  I ended up drilling the port under the throttle body as I matched it to my 250 throttle body.  It’s better if you have a euro body and don’t need to drill.  Your problem seems to be the vacuum port.  That’s why you cannot get the idle down. 

Timing - what I do may not be the right way but the car runs good so I just keep doing it this way :  once the vacuum is connected correctly, I leave everything connected and time it at close to 35-38 degrees BTDC at 3000 rpm and lock it off.  Then I just adjust idle to get to correct rpm at idle.   Usually this means that at idle timing will be 5-8 degrees BTDC.

Car runs great with this method so I just do it like this.  May not be correct but it runs good and plugs look correct color.

Good to hear you have seen the same about the casting of the US and Euro throttle houses. I will investigate further, when I get the US throttle house off. Then I will try to open up the blinded Euro vacuum port and check by sucking, if there is a channel drilled - looks like it, but will double check.

I can clearly hear from what you write, that I have mixed up BTDC and ATDC! So advance means towards BTDC and retard means towards ADTC. Right?

But if so, then if you are to follow the timing numbers from the service manual for a Euro spec 280SL, I need to push the timing further down to 3 degrees below zero with vacuum connected. This will not work now with the US throttle house, as I would not have enough advance at higher rpms, because the constant vacuum from the US throttle house is retarding the timing too much even in program 8, especially for the low to mid rpms. But maybe when I change to the Euro throttle house, I will have more advance, because vacuum is now decreasing, and then I will reach the advance I need at higher rpms faster and more aggressive. Sounds like a theory, right?

Don't you lack acceleration (torque) at low rpms, if you have 5-8 degrees BTDC at idle? I have heard that you need low advance at low rpms to get enough torque for acceleration, and this is also why you retard the timing at low rpms. Correct?

Which 123ignition do you have, and which program do you run your 280SL in?

Cheers,

Christian

[kampala]

You cannot run a preprogrammed 123 on program E nor program 8 if you continue to use the side “vacuum all the time” if you are not using the two way valve to control the vacuum.  I have not been able to make it run right but others claim they can run.  I could not. 

On my 1971 USA 280, I am using a pre-programmed 123 with program 8.  I have bypassed all emissions and bypassed two way valve.  I have modified my throttle body to match my 250 throttle body with vacuum from underneath.  I did it very carefully but I had my 250 as a sample of what to do. 

[Tyler S]

But if so, then if you are to follow the timing numbers from the service manual for a Euro spec 280SL, I need to push the timing further down to 3 degrees below zero with vacuum connected. This will not work now with the US throttle house, as I would not have enough advance at higher rpms, because the constant vacuum from the US throttle house is retarding the timing too much even in program 8

You got it. This is exactly why the standard 123 does not work correctly with a late switchgear system thats inoperative or disconnected.
If your replacement throttle body was originally for a 051 distributer car then this will solve your issues.
Yes you are now correct in regards to ATDC and BTDC.
Remember that the 051 had a different curve than the 061/062 so trying to compare numbers for advance wont wont work. As far as the specs in the manual they are often strayed from in order to achieve a better running engine.

I have a 123 bluetooth in my 250sl with a custom curve that I made.

[Berggreen]

Christian, a higher number from “0” into the BTDC range is Advancing the timing. A number below “0” ATDC is Retarding the timing. So when you rev the engine you are advancing the timing into the BTDC range. (Before top dead center is earlier/advanced timing)
As far as your two late throttle bodies, yes they are identical in that they both have their ports on the engine side of the throttle plate.
However, The earlier throttle body that was paired with the 051 distributer had its port just aft of the throttle plate so that when the throttle was cracked open just slightly, vacuum would immediately raise to atmosphere. This is a different setup and function and is not achievable with the late throttle body and standard 123 ignition because the vacuum never goes to zero except maybe at wide open throttle. They can be modified as Oz states above or replaced with an early 051 type unit.
Yes, when you retard the timing the car will not idle well. You need to go back and adjust the air and fuel mixture in order to compensate for the removed timing advance.

Thanks Tyler!

Now it makes sense, and I clearly see that I have mixed up how to read ATDC/BTDC with the scope!  

But as I have discussed with Oz, it seems that the mismatch of US throttle house and Euro 123ignition program settings are messing up my advance, so that I don't get enough advance at mid-range rpms, especially in the 1500-2500 rpms range, where the car is misfirering, if I push the idle timing to zero or below, as the service manual demands. Hopefully, changing to the Euro throttle house and then lowering the idle timing to the required 3 degrees ATDC, while running in program 8 on the 123ignition will work.

The Euro throttle house I have is exactly as you describe. The port below the house ends in a small hole just behind the throttle plate on the engine side. The US throttle house has the same small hole just behind the throttle plate, but even though the port on the outside of the house is there, it is blinded off, and there is no tube for the hose. But I think, that if you take out the pin that blinds the port, and instead mount a tube, and put the pin into the US port and blind it, the originally US throttle house will be identical to a Euro house.

I think the very late Euro 280SL's still used an 051 distributor, and it was combined with the "dual" Euro/US house, I now have, but using the vacuum port in the bottom of the house for the Euro model. I don't think the older throttle house from the 250SL and early 280SL was used on the very late Euro 280SL's, but only the "dual" house with the two optional ports, but with the US port blinded off. Or what do you think?

As far as I have understood by reading the manual for the (standard) 123ignition and communicating with the 123-staff down in The Netherlands, program 8 corresponds to an 051 distributor with decreasing vacuum with rpms (thus a Euro throttle house), whereas program E corresponds to an 062 distributor with constant vacuum (thus a US throttle house) and with the vacuum cut-off mechanism working.

Thanks,

Christian

[Berggreen]

You got it. This is exactly why the standard 123 does not work correctly with a late switchgear system thats inoperative or disconnected.
If your replacement throttle body was originally for a 051 distributer car then this will solve your issues.
Yes you are now correct in regards to ATDC and BTDC.
Remember that the 051 had a different curve than the 061/062 so trying to compare numbers for advance wont wont work. As far as the specs in the manual they are often strayed from in order to achieve a better running engine.

I have a 123 bluetooth in my 250sl with a custom curve that I made.

Thanks Tyler and Oz, we fully agree now and are on the same page - great help from both of you, thanks a lot!!

I think I am almost there. I am already running program 8 and all the US emission things have been disconnected. I just need to make the Euro throttle house work, I found on Ebay, or alternatively open the Euro port on my current US throttle house and then blind off the US port. I think both will work on these late "dual" throttle houses.

I will make some pictures of the two throttle houses, when I have them on the table next to each other.

I may however still be sucking "pirate air" from somewhere, because the idle adjustment screw is not working with the linkage set correctly. Only when increasing the linkage to the injection pump and thus avoiding it to go to zero, I can get the screw to work slightly, but screwed almost all in. That may improve somewhat, when I get the timing/vacuum thing fixed, but I doubt it will solve the full problem. So I will check the brake booster possibility too searching for "pirate air", as well as try to remove the leak around the throttle plate by finding a new one with less leak.

Thanks,

Christian

[Pawel66]

I have a 123 bluetooth in my 250sl with a custom curve that I made.

  Your custom curve, also for 280 is now used by half of the world, I am sure.  Thanks for it!

[Berggreen]

Your custom curve, also for 280 is now used by half of the world, I am sure.  Thanks for it!

Fantastic....is that the curve that fits a US throttle house with constant vacuum, but with all the emission control things disconnected?

[Pawel66]

I have 051 and euro throttle. I got lost at certain moment in this (I do not have education as a mechanic), but I received three pieces of advise on the forum:
1. Forget all you learned about 051 and vacuum retard
2. Install 123 (bluetooth, programmable) and mechanically set ignition timing (may not remember correctly - 8BTDC idle, 38 3000rpm, everything connected)
3. Curves from Tyler

I did it all and it works. The car runs very well, although I had my ups and downs related to fuel delivery and fuel mixture, also recently.

[Tyler S]

Fantastic....is that the curve that fits a US throttle house with constant vacuum, but with all the emission control things disconnected?

Christian, No it is not the same curve as the one that replaces the 051 distributor.  I did make one for the late system with disconnected emissions gear but It also requires the programmable bluetooth version of the 123 Distributer. The curve can be found in the link below.  Though it could use some slight real world tuning specific to each car. The key ingredient in making this work is being able to set a starting point RPM. In the pic below it is set at 1000 rpm. That way the vacuum signal is ignored until throttle is actuated. Similar to the old 051 system. 

https://www.sl113.org/forums/index.php?topic=23210.msg214545#msg214545

[Berggreen]

I have 051 and euro throttle. I got lost at certain moment in this (I do not have education as a mechanic), but I received three pieces of advise on the forum:
1. Forget all you learned about 051 and vacuum retard
2. Install 123 (bluetooth, programmable) and mechanically set ignition timing (may not remember correctly - 8BTDC idle, 38 3000rpm, everything connected)
3. Curves from Tyler

I did it all and it works. The car runs very well, although I had my ups and downs related to fuel delivery and fuel mixture, also recently.

Great!

Tyler, how different are your curves and then Program 8 on the standard 123, which also is made for an 051 distributor and euro throttle house?

I did also considered getting the BlueTooth version a couple of months back, as a friend wanted my current standard 123. But I “chickened out” by the prospect of a BlueTooth 123 with no pre-installed curves and having to trial-and-error myself to some curved that would work. Had I known about Tyler’s curves, then I had probably jumped on it.
I did ask the 123-staff down in The Netherlands, why they do not put the standard curves from the standard 123 onto the BlueTooth version, so you have something to start out with. But apparently the current hardware will not allow that - not enough storage capacity to house them, as the unit can currently only store two maps! Hope they will improve on that in the future.

[twistedtree]

Back on your "pirate air", you can also pull off the vacuum line to the brakes and plug the manifold opening.    Also check to be sure the warm running device (WRD) is not stuck and allowing air to leak past.  Again, I think the easiest way to test is to disconnect the line and plug the hole.  I bought an assortment of rubber bottle stoppers at our local hardware store and they are very handy for plugging vacuum ports.

[Tyler S]

The Map curves between the two are different. Not so different that the car wont run but the starting RPM and point of initial advance relative to vacuum is very different. There are published curves for the 051 distributer on 123’s website. They are very easy to input on the bluetooth version. Basically its just inputing 5 numbers into the fields on the app and hit save. I’ll post my 051 curve below. Note the RPM set point is set at zero. It is not needed with the early/051 throttle body because vacuum control is still retained. 11 degrees of map advance and 22 degrees (not shown) of centrifugal advance with static timing set at 5BTDC for a total advance of 38 degrees.
 This is the one I have had the most success with.

[Benz Dr.]

I agree that you need at least 38 degrees of full advance to get anything out of a 113 engine - any 113 engine, running any of the different ignition systems used on our cars. If anything, the BBB has done more to confuse people about ignition timing specs than anything I can think of. Too many people go away with the idea that 30 degrees at 3,000 RPM should be what you shoot for when that's only what a 051 unit will produce without the extra ignition timing. I've attempted to explain how the late USA system works without any success.

Writing tech information is harder that one might assume and understanding it can be just as hard. It's NOT possible to fix something unless you know how it works. Explaining how it works is the hard part.

[Berggreen]

The Map curves between the two are different. Not so different that the car wont run but the starting RPM and point of initial advance relative to vacuum is very different. There are published curves for the 051 distributer on 123’s website. They are very easy to input on the bluetooth version. Basically its just inputing 5 numbers into the fields on the app and hit save. I’ll post my 051 curve below. Note the RPM set point is set at zero. It is not needed with the early/051 throttle body because vacuum control is still retained. 11 degrees of map advance and 22 degrees (not shown) of centrifugal advance with static timing set at 5BTDC for a total advance of 38 degrees.
 This is the one I have had the most success with.

Thanx Tyler for sharing this. Do you also have the points for the mechanical/centrifugal curve?

Let me understand, do you actually use vacuum to advance the timing like on the early 230SL's, and thus not for retarding the timing? If so, why is this better than using the vacuum to retard?

As far as I understand, program 8 on the standard 123 still uses a vacuum retard curve. You mention that the program 8 curves are published on the 123ignition website. Do you have a link for these you can share?

I tried to search myself, and I can only find a table with some fix-points for program 8 in the manual for the standard 123ignition, which look like this:

Advance starts: 1000 RPM
Max. advance: 22 degrees/crankshaft at 2500 RPM
Vacuum advance: "10 degrees negative vacuum"

However, it would be great to see the actual curves plotted as graphs. Have you found those on the website?

I did find some 051-curves in the manual for the BlueTooth-version (https://www.123ignitionshop.com/manuals/123_TUNEplus_manual.pdf), and I have attached it here. But I cannot see that these curves match the fix-points above for program 8. Can you? Also, why four curves and not just two - one for mechanical advance and one for vacuum retard? I also find the explanation under Example 2 very confusing. For starters it seems they are missing some minus on the degrees for the vacuum retard, don't they? But still the curves in the graph do not seem to match the points they have in the example. Or do I miss something here.

The BlueTooth 123ignition seems like a powerful tool, but the manual does not help much and is very confusing, same also goes for the manual for the standard 123ignition, which can also be very confusing, especially the table with the curves-points. I am a mechanical engineer by education, and I have big problems understanding what they write, and I guess that is not good for the average user of the manuals.

Thanx,

Christian

[Berggreen]

I agree that you need at least 38 degrees of full advance to get anything out of a 113 engine - any 113 engine, running any of the different ignition systems used on our cars. If anything, the BBB has done more to confuse people about ignition timing specs than anything I can think of. Too many people go away with the idea that 30 degrees at 3,000 RPM should be what you shoot for when that's only what a 051 unit will produce without the extra ignition timing. I've attempted to explain how the late USA system works without any success.

Writing tech information is harder that one might assume and understanding it can be just as hard. It's NOT possible to fix something unless you know how it works. Explaining how it works is the hard part.

Hi Dan

Thanks, but I fully understand how the US timing system on the late 280SL's work with the constant vacuum port on the throttle body giving a constant retard combined with the vacuum drive under the battery suddenly at 2100 RPM cutting all the constant vacuum retard and thus advancing the timing in one go.

However, as it may have been necessary for MB at the time to overcome US emission regulations that came up around 1969-1970, then I cannot see today that this system does any good for performance of our cars. To have a gradual increase in timing advance by a reducing vacuum retard with RPMs, like on the Euro 280SL, seems like a much better solution, which will give a smoother power delivery and engine performance up through the RPMs. I guess that was also why MB maintained this on the Euro 280SL, where they were not pushed by emission regulations. So in my mind, disengaging the US emission control system and replacing it with either an 051-distributor or 123igition combined with sourcing air from the vacuum port under the throttle house, is the best solution for an originally US 280SL, no matter if the emission control system works or not.

You mention a "BBB" above. Are you referring to the service manual, I showed some pictures from?

I agree the service manual  timing seems odd, as the degrees showed for idle timing (8 degrees ADTC for US late-280SL, and 3 degrees ADTC for Euro 280SL) do not match what people are normally timing their cars at today.

Also, the ADTC idle static timing would mean that neither the US nor the Euro 280SL would ever reach the 38 degrees at 3000 RPM using neither the 062 or 051 distributors respectively.

Actually, when you read the tables carefully, then for the US 280SL with the emission control system, they state that at 3000 RPM, you should have 25-30 degrees WITH vacuum connected, thus these 25-30 degrees would also include the static 8 degrees ADTC they specify in the table. Thus, they would never reach the 38 degrees, we want today.

Opposite for the Euro 280SL, here they state 30 degrees at 3000 RPM, but WITHOUT vacuum connected, thus also including the static 3 degrees ADTC they specify, but again not reaching the 38 degrees. But I guess for the Euro 280SL it will not make much difference at 3000 RPM, if vacuum is connected or not, because there will not be any vacuum at that RPM anyway, due to the vacuum port being located just behind the throttle plate on the engine side, where vacuum quickly goes away when the throttle plate opens.

But could it be that MB back then intentionally limited the performance of their cars as the standard settings for some reason, which we don't care about today? Any idea what that reason could have been?

I guess we see the same today, where factories limit the performance of their cars, but where you can chip-tune your car and actually pull much more power out, compared to the factory settings, if you want to.

Cheers,

Christian

Ps.: See also below the original advance/retard curves for the 051 and 062 distributors, sourced from the service manual.

[Benz Dr.]

Hi Dan

Thanks, but I fully understand how the US timing system on the late 280SL's work with the constant vacuum port on the throttle body giving a constant retard combined with the vacuum drive under the battery suddenly at 2100 RPM cutting all the constant vacuum retard and thus advancing the timing in one go.

However, as it may have been necessary for MB at the time to overcome US emission regulations that came up around 1969-1970, then I cannot see today that this system does any good for performance of our cars. To have a gradual increase in timing advance by a reducing vacuum retard with RPMs, like on the Euro 280SL, seems like a much better solution, which will give a smoother power delivery and engine performance up through the RPMs. I guess that was also why MB maintained this on the Euro 280SL, where they were not pushed by emission regulations. So in my mind, disengaging the US emission control system and replacing it with either an 051-distributor or 123igition combined with sourcing air from the vacuum port under the throttle house, is the best solution for an originally US 280SL, no matter if the emission control system works or not.

You mention a "BBB" above. Are you referring to the service manual, I showed some pictures from?

I agree the service manual  timing seems odd, as the degrees showed for idle timing (8 degrees ADTC for US late-280SL, and 3 degrees ADTC for Euro 280SL) do not match what people are normally timing their cars at today.

Also, the ADTC idle static timing would mean that neither the US nor the Euro 280SL would ever reach the 38 degrees at 3000 RPM using neither the 062 or 051 distributors respectively.

Actually, when you read the tables carefully, then for the US 280SL with the emission control system, they state that at 3000 RPM, you should have 25-30 degrees WITH vacuum connected, thus these 25-30 degrees would also include the static 8 degrees ADTC they specify in the table. Thus, they would never reach the 38 degrees, we want today.

Opposite for the Euro 280SL, here they state 30 degrees at 3000 RPM, but WITHOUT vacuum connected, thus also including the static 3 degrees ADTC they specify, but again not reaching the 38 degrees. But I guess for the Euro 280SL it will not make much difference at 3000 RPM, if vacuum is connected or not, because there will not be any vacuum at that RPM anyway, due to the vacuum port being located just behind the throttle plate on the engine side, where vacuum quickly goes away when the throttle plate opens.

But could it be that MB back then intentionally limited the performance of their cars as the standard settings for some reason, which we don't care about today? Any idea what that reason could have been?

I guess we see the same today, where factories limit the performance of their cars, but where you can chip-tune your car and actually pull much more power out, compared to the factory settings, if you want to.

Cheers,

Christian

I see too much confusion between euro and USA systems and just as much confusion between with and without vacuum. Then there's vacuum advance and vacuum retard which is even more confusing to many readers. Let me try and break this down a bit:

The USA system, when working properly, will give you 38 degrees of full advance. Set your timing to 3 degrees ATDC and a properly working system will do the rest. All other systems should be set to 8 degrees BTDC at idle.

All systems, VA or VR, should always be run with vacuum lines hooked up. Removal of vacuum lines is ONLY for testing purposes.

Vacuum advance and vacuum retard both result in timing advance and it's the method of how that's achieved that's different. Vacuum retard doesn't actually retard your ignition timing it simply moves the advance plate inside your distributor to zero or to the no advance position at idle or under 2,200 RPM with the USA system. Every one of the three different systems used on our cars behaves in unique ways but all of them accomplish the same end results; ignition advance. How that happens may be different but the results are the same.   

Figure out which system you have and concentrate on getting that to work. For the sake of your own sanity ignore all others.   


As I've said a number of times, it doesn't matter which system you use but it does matter that you make sure all of the parts of your system match and that they will all work together. If you only change one part of your entire system, will it work and be compatible with all the other parts? There are about four different ignition coils that are commonly used on our cars and each do very specific jobs. Some coils require no ballast resistors while others do and each one of them uses a different amount of resistance.

Before you start spending money upgrading your system become familiar with what you have right now. It might be better than you think.   

[Berggreen]

I see too much confusion between euro and USA systems and just as much confusion between with and without vacuum. Then there's vacuum advance and vacuum retard which is even more confusing to many readers. Let me try and break this down a bit:

The USA system, when working properly, will give you 38 degrees of full advance. Set your timing to 3 degrees ATDC and a properly working system will do the rest. All other systems should be set to 8 degrees BTDC at idle.

All systems, VA or VR, should always be run with vacuum lines hooked up. Removal of vacuum lines is ONLY for testing purposes.

Vacuum advance and vacuum retard both result in timing advance and it's the method of how that's achieved that's different. Vacuum retard doesn't actually retard your ignition timing it simply moves the advance plate inside your distributor to zero or to the no advance position at idle or under 2,200 RPM with the USA system. Every one of the three different systems used on our cars behaves in unique ways but all of them accomplish the same end results; ignition advance. How that happens may be different but the results are the same.   

Figure out which system you have and concentrate on getting that to work. For the sake of your own sanity ignore all others.   


As I've said a number of times, it doesn't matter which system you use but it does matter that you make sure all of the parts of your system match and that they will all work together. If you only change one part of your entire system, will it work and be compatible with all the other parts? There are about four different ignition coils that are commonly used on our cars and each do very specific jobs. Some coils require no ballast resistors while others do and each one of them uses a different amount of resistance.

Before you start spending money upgrading your system become familiar with what you have right now. It might be better than you think. 

Thanx Dan, I fully agree, but I am just trying (as an engineer - sorry I know we can be a pain in the ass! ) to understand how to read and understand the tables from the service manual. I do understand how the physical system works with advance and retard and what the highly valued experience (like yours ) says in terms of timing values - so that is not the issue for me.

But by looking at the numbers in the table, I am puzzled how MB could reach 38 degrees BTDC, with the adjustment values stated in the tables.

A part of this is also the static timing. I follow that experience says that without the US emission system 8 degrees BTDC is good, but in the tables both the US and Euro 280SL use ADTC values for static idle timing:

US: 8 ADTC
Euro: 3 ADTC

I am using BTDC static idle values and reach around 35 BTDC at 3000 RPM on both of my 280SL’s with 123ignitions and disengaged US emission control systems, and it works well - except for the effects of some missing euro throttle houses (both have US throttle houses at the moment), but I have found two euro’s on EBay and will install them soon.

But again I am just puzzled, why the service manual says something different than what we experience works well, both in terms of the static timing as well as the rest of the test values in the tables. 

Hope you can help to satisfy my curiosity!

Cheers and thanx,

Christian
 

[bracurrie]

Hi Dan

Thanks, but I fully understand how the US timing system on the late 280SL's work with the constant vacuum port on the throttle body giving a constant retard combined with the vacuum drive under the battery suddenly at 2100 RPM cutting all the constant vacuum retard and thus advancing the timing in one go.

However, as it may have been necessary for MB at the time to overcome US emission regulations that came up around 1969-1970, then I cannot see today that this system does any good for performance of our cars. To have a gradual increase in timing advance by a reducing vacuum retard with RPMs, like on the Euro 280SL, seems like a much better solution, which will give a smoother power delivery and engine performance up through the RPMs. I guess that was also why MB maintained this on the Euro 280SL, where they were not pushed by emission regulations. So in my mind, disengaging the US emission control system and replacing it with either an 051-distributor or 123igition combined with sourcing air from the vacuum port under the throttle house, is the best solution for an originally US 280SL, no matter if the emission control system works or not.

You mention a "BBB" above. Are you referring to the service manual, I showed some pictures from?

I agree the service manual  timing seems odd, as the degrees showed for idle timing (8 degrees ADTC for US late-280SL, and 3 degrees ADTC for Euro 280SL) do not match what people are normally timing their cars at today.

Also, the ADTC idle static timing would mean that neither the US nor the Euro 280SL would ever reach the 38 degrees at 3000 RPM using neither the 062 or 051 distributors respectively.

Actually, when you read the tables carefully, then for the US 280SL with the emission control system, they state that at 3000 RPM, you should have 25-30 degrees WITH vacuum connected, thus these 25-30 degrees would also include the static 8 degrees ADTC they specify in the table. Thus, they would never reach the 38 degrees, we want today.

Opposite for the Euro 280SL, here they state 30 degrees at 3000 RPM, but WITHOUT vacuum connected, thus also including the static 3 degrees ADTC they specify, but again not reaching the 38 degrees. But I guess for the Euro 280SL it will not make much difference at 3000 RPM, if vacuum is connected or not, because there will not be any vacuum at that RPM anyway, due to the vacuum port being located just behind the throttle plate on the engine side, where vacuum quickly goes away when the throttle plate opens.

But could it be that MB back then intentionally limited the performance of their cars as the standard settings for some reason, which we don't care about today? Any idea what that reason could have been?

I guess we see the same today, where factories limit the performance of their cars, but where you can chip-tune your car and actually pull much more power out, compared to the factory settings, if you want to.

Cheers,

Christian

Ps.: See also below the original advance/retard curves for the 051 and 062 distributors, sourced from the service manual.

Christion,
I have gone over this with Dan several times.  I have observed the full 38 advance even with my retardation system hooked up. Going by the published material I still do not see how timing advance on the 1970 model US M130 engines with 061/062 distributors could go past 34 or so degrees. It does make sense that the engine would thrive with 38 degrees after all the carburetor version of the M130 seems to get that much advance.   I have my 1970 M130 US version with 061 distributor set at 8 degrees BTDC at 900 RPM and it tops out at 31 degrees at 3000 RPM all with the retardation system disabled. I have been told that 12 degrees BTDC could work which implies that I will get to 35 degrees at 3000 RPM.
I REALLY want to get a 123 ignition programmable distributor and enable the vacuum connection to the throttle body like it is with an 051 distributor.

[Berggreen]

Christion,
I have gone over this with Dan several times.  I have observed the full 38 advance even with my retardation system hooked up. Going by the published material I still do not see how timing advance on the 1970 model US M130 engines with 061/062 distributors could go past 34 or so degrees. It does make sense that the engine would thrive with 38 degrees after all the carburetor version of the M130 seems to get that much advance.   I have my 1970 M130 US version with 061 distributor set at 8 degrees BTDC at 900 RPM and it tops out at 31 degrees at 3000 RPM all with the retardation system disabled. I have been told that 12 degrees BTDC could work which implies that I will get to 35 degrees at 3000 RPM.
I REALLY want to get a 123 ignition programmable distributor and enable the vacuum connection to the throttle body like it is with an 051 distributor.

Thanx, and interesting that you can’t get more than maximum in the low 30’es BTDC by combining the values from the service manual.

I have a suspicion that MB deliberately under-tuned their cars with the standard settings in the service manual for some reason, but that 50 years of experience by mechanics have shown that the performance can be improved by up-tuning to reach 38 BTDC.

For your car, why not connect the vacuum retard system again which will lower your current static idle timing, but then adjust static idle timing up to 5-8 BTDC? That would give you more advance at 3000 RPM, even with a US throttle house and the emission control system disengaged or not working.

[Benz Dr.]

I just rebuilt a 062 distributor so I made note of what it was doing on my testing machine. The mechanical advance moved 20 degrees and the vacuum portion moved 22 degrees for a total of 42 degrees of movement. 42 degrees allows for a lot of distributor movement - in this case ATDC and still give a proper full advance. Everything is built into the distributor and all you need to do is set your ignition timing at idle and if it's all working it will be just fine.

Setting your ignition to 3 degrees ATDC will give you a total of 39 degrees with the late USA system. Setting your timing to 8 degrees ATDC will give you 34 BTDC. I don't recommend anyone setting to 8 degrees ATDC because not only will you have a low idle speed you won't get enough timing for full advance. Any timing ATDC will make your engine run hot at idle and that's not a what you want. I have yet to see one of these engines without a warped head during a rebuild. 

[Berggreen]

I just rebuilt a 062 distributor so I made note of what it was doing on my testing machine. The mechanical advance moved 20 degrees and the vacuum portion moved 22 degrees for a total of 42 degrees of movement. 42 degrees allows for a lot of distributor movement - in this case ATDC and still give a proper full advance. Everything is built into the distributor and all you need to do is set your ignition timing at idle and if it's all working it will be just fine.

Setting your ignition to 3 degrees ATDC will give you a total of 39 degrees with the late USA system. Setting your timing to 8 degrees ATDC will give you 34 BTDC. I don't recommend anyone setting to 8 degrees ATDC because not only will you have a low idle speed you won't get enough timing for full advance. Any timing ATDC will make your engine run hot at idle and that's not a what you want. I have yet to see one of these engines without a warped head during a rebuild.

Thanx Dan, ok that seems to match the max. curves for the 062 from the service manual, I posted above and again below. Here the curve for mechanical advance tops out at 23 degrees and the vacuum curve also at 23 degrees.

So even though I agree the 8 ADTC from the service manual is not recommendable, it does start to add up. 23 x 2 = 46 minus the 8 ADTC gives you 38. However, this is using the max. curves for mech. and vacuum, and to reach the test values in the table MB has most likely used the average values from the curves which are 20 degrees for both, thus 40-8=32. Still a little higher than the 25-30 degrees test value at 3000 RPM they specify in the service manual, but we are getting closer.

The 8 ADTC and the 25-30 at 3000 RPM are probably not something MB was happy to specify, but they was forced to in order to squize into the new emission allowables in the US with the W113, which in 1970-71 was singing on its last verse anyway with the r107 coming up in late 1971 with a whole new era of engines better able to comply with strict emission control demands especially in the US.

Today with our cars not having to worry about emission (at least not yet!!), it makes a lot of sense to convert into the euro 280SL system with an 123 to avoid the points etc. and use BTDC idle timing. All to improve performance and driving experience in our great cars!

Cheers,

Christian

[Berggreen]

As a side-note, it is interesting to note by comparing just the 062 and 051 distributors alone, that if you disengage all US emission control systems, and can actually source the necessary vacuum somehow, the 062 has much more max. movement and advance compared to the 051:

062: 23 (mech) + 23 (vacuum) = max. 46 degrees + static timing
051: 22 (mech) + 14 (vacuum) = max. 36 degrees + static timing

So if you want to stick to the old BOSCH distributors and really want to tune your M130 engine, and need a lot of max. timing advance for that purpose, and can drill a port in the throttle house or manifold, where you can source the necessary vacuum at the right time, then the 062 dizzy would be superior to the 051 in terms of max. advance!

Now, that was not what I expected, before looking further into this.

You can of course also do this with the programmable 123ignition, by constructing the mechanical and vacuum advance/retard curves needed for the job.

Cheers,

Christian

[bracurrie]

As a side-note, it is interesting to note by comparing just the 062 and 051 distributors alone, that if you disengage all US emission control systems, and can actually source the necessary vacuum somehow, the 062 has much more max. movement and advance compared to the 051:

062: 23 (mech) + 23 (vacuum) = max. 46 degrees + static timing
051: 22 (mech) + 14 (vacuum) = max. 36 degrees + static timing

So if you want to stick to the old BOSCH distributors and really want to tune your M130 engine, and need a lot of max. timing advance for that purpose, and can drill a port in the throttle house or manifold, where you can source the necessary vacuum at the right time, then the 062 dizzy would be superior to the 051 in terms of max. advance!

Now, that was not what I expected, before looking further into this.

You can of course also do this with the programmable 123ignition, by constructing the mechanical and vacuum advance/retard curves needed for the job.

Cheers,

Christian

On the 061 the action of vacuum serves only to retard the mechanical advance 0 to +23 degrees offset by up to -17 to -23 degrees of vacuum retardation. The action of retardation simply cancels the mechanical advance and if the engine is stone cold or very hot the retardation system is off, which is why it seems that setting the static timing(without vacuum retardation) high enough to get to 38 degrees BTDC timing at 3000 RPM would run the risk of too much advance at lower speeds when the vacuum retardation is off because the engine is cold or too hot.
What I do not fully understand is the amount of vacuum at different throttle and load states. In other words: How does vacuum change when going from idle to opening the throttle with load under acceleration?

[Tyler S]

Christian, here is a 123 mech advance  curve you requested. I have since changed the static timing from 8 to 5 BTDC and increased the total mechanical advance. It is very easy to set the actual distributor timing to zero TDC and add/set your starting static timing via the bluetooth APP. Keep in mind every car is tuned different and may or may not be optimal for your situation. The whole point is it is very easy to experiment with the curves and find an optimal setting. The curve below is a good starting point.
 This is on a 250sl replacing a 051 distributer. Vacuum line connected to original throttle body with retard port just behind the throttle plate. (Vacuum falls to atmosphere when throttle is cracked open)

[Benz Dr.]

On the 061 the action of vacuum serves only to retard the mechanical advance 0 to +23 degrees offset by up to -17 to -23 degrees of vacuum retardation. The action of retardation simply cancels the mechanical advance and if the engine is stone cold or very hot the retardation system is off, which is why it seems that setting the static timing(without vacuum retardation) high enough to get to 38 degrees BTDC timing at 3000 RPM would run the risk of too much advance at lower speeds when the vacuum retardation is off because the engine is cold or too hot.
What I do not fully understand is the amount of vacuum at different throttle and load states. In other words: How does vacuum change when going from idle to opening the throttle with load under acceleration?

Vacuum retard does NOT retard ignition advance - it's either on or it's off on the 062/61 . It's only the method by which the distributor gets its vacuum signal. The mechanical advance isn't cancelled out by the vacuum system. Vacuum retard is in fact an advance system. 

[Benz Dr.]

Christian, here is a 123 mech advance  curve you requested. I have since changed the static timing from 8 to 5 BTDC and increased the total mechanical advance. It is very easy to set the actual distributor timing to zero TDC and add/set your starting static timing via the bluetooth APP. Keep in mind every car is tuned different and may or may not be optimal for your situation. The whole point is it is very easy to experiment with the curves and find an optimal setting. The curve below is a good starting point.
 This is on a 250sl replacing a 051 distributer. Vacuum line connected to original throttle body with retard port just behind the throttle plate. (Vacuum falls to atmosphere when throttle is cracked open)

That's basically what I'm using with my dual point 300SE distributor. This unit is vacuum advance so I had to change my throttle body. I adjusted the flyweights inside my distributor so the mechanical would open a bit slower in case I couldn't get premium fuel.
The unit I use is set up the same way as the 051 with 20 degrees mechanical and 10 degrees vacuum. I add 8 degrees idle timing and then I get 38 total advance. 

[bracurrie]

Vacuum retard does NOT retard ignition advance - it's either on or it's off on the 062/61 . It's only the method by which the distributor gets its vacuum signal. The mechanical advance isn't cancelled out by the vacuum system. Vacuum retard is in fact an advance system.

Dan, So the diaphragm on the distributor reacting to the vacuum doesn't retard timing?  In a properly operating 062/061 with speedswitch and vacuum retard, what would timing be at idle with vacuum turned off at cold start? We know it is supposed to be 8 degrees ATDC with vacuum at idle.

[Tyler S]

In a properly operating 062/061 with speedswitch and vacuum retard, what would timing be at idle with vacuum turned off at cold start? We know it is supposed to be 8 degrees ATDC with vacuum at idle.

The answer lies in the BBB distributer curve chart posted above for the 061/062 distributer. The vacuum portion of the distributor has about a 20 deg range.
So at an 8 ATDC static timing setting with no vacuum the advance would be 12 degrees BTDC.
(-8+20=12)

[Berggreen]

Christian, here is a 123 mech advance  curve you requested. I have since changed the static timing from 8 to 5 BTDC and increased the total mechanical advance. It is very easy to set the actual distributor timing to zero TDC and add/set your starting static timing via the bluetooth APP. Keep in mind every car is tuned different and may or may not be optimal for your situation. The whole point is it is very easy to experiment with the curves and find an optimal setting. The curve below is a good starting point.
 This is on a 250sl replacing a 051 distributer. Vacuum line connected to original throttle body with retard port just behind the throttle plate. (Vacuum falls to atmosphere when throttle is cracked open)

GREAT, thanks a lot Tyler!

What differences in performance have you experienced between using both mechanical and vacuum advance like your curves above, compared to mechanical advance and vacuum retard, similar to the eg. the 051?

[Tyler S]

My setup still uses the port on the throttle body that was used for my 051 distributer. So in effect it is still a retard style system. Thats why the curve on my 123 looks backwards. Either way the end result is it functions the same. I do have the curve set to slightly reduce the advance at lower rpm. Mostly because my head has been shaved and my compression ratio is higher than spec.
The biggest gains were in engine starting, idle quality, and light cruise.
The curve I made and experimented with for the later 061/62 throttle body setup seemed to give the car a little more punch at passing speeds. But without a Dyno its all by the seat of your pants so ymmv.
You need to build your curve appropriate to the type of vacuum supply you are giving the 123. (Throttle body type) Otherwise it wont work correctly. Once set and functional you can go back at any time and add or subtract points or degrees on the curve to tailor to your engine.

[Benz Dr.]

The answer lies in the BBB distributer curve chart posted above for the 061/062 distributer. The vacuum portion of the distributor has about a 20 deg range.
So at an 8 ATDC static timing setting with no vacuum the advance would be 12 degrees BTDC.
(-8+20=12)

I think that's where some discrepancy is coming from. Not every 062 distributor works exactly the same. Some have 20 degrees mechanical and some have a bit more than that. The vacuum portion on 062 units is NOT adjustable and you get whatever it gives. This unit is designed to work with the late 280 engine and is not compatible with earlier systems.

The 051 usually has about 18 - 22 degrees mechanical. I test this function on my distributor tester and then I adjust the pull rod on the vacuum cell until I get the right amount of total movement, or in this case 30 degrees. Add 8 degrees BTDC at idle and you will have the same 38 -39 degrees BTDC as the 061 at full advance.