WRD Round Shim Question

[jedwards]

My WRD stays on well  past the  155F  (68C) temperature at which it should be fully closed.  Additionally, I have a rich mixture during warm-up in spite of removing all oval shims from under the WRD.

I currently have 1.4mm of round shims  installed and I want to increase the amount of shims to try to correct the two issues outlined above.
I was planning to do this in 0.2mm increments but I am not sure if this is too much or two little.  As I can only do this over the weekends,  I only get a coupler of cold starts to work with per week, so any guidance about sensitivity would be really helpful.

Can anyone share the thickness of  round shims relative to ovals that they are running?

Jeff

[garymand]

Yes, its complicated.  All the adjustments only act on the fip act on the Rod but this one.  It act both on the rod and it add gas and air for cold starts.  For me. most importrtant is to have the air shut off at 70 to 75 degrees C.  Mine is closed at 72.  You uncrew the filter/muffler, put your finger over the opening, you will feel the suction that should stop as the motor warms up.  The gas is then more complex.  Idle gas is controlled by the center black screw and idle air is controlled by the 'big screw' near the air cleaner.  Seat-of-your-pants adjustment is if the motor rpm is oscillating (going up and down) too much air -turn CW 1/2 turn at a time until it smooths out.  Then check RPMs.  750? Great.  >750 stop motor turn idle gas screw CCW 1 click/500 rpm.  Too low, turn idle gas screw CW 1 click/500 rpm.

Now you have the idle set, 3 more step to go: full throttle, high end mild load, and low end mild load (partial throttle).

 If your SL doesn't move eagerly all the way past 100 MPH, (as mine did), install an O2 sensor and get ready for a science project.  You need to adjust the rod for 12 to 13 (a little rich) for max acceleration.  This car will fly! Then attach the high end partial load with the white screws and then the low end partial with the black screws.   

I am in the lengthy process now.  its lengthy because I have the newer open lubricated pump, that gushes 400 ML of oil each time you open it to adjust the screws.  I much prefer the older closed pump with the big (32 mm?) closure nut.  The oil is clean and stops gushing  at maybe 3/4 full.  I can live with that while adjusting the pump.  When you have to open the pump 5 or 6 times to go through 'too much' that's 2 liters of oil added and somehow, collected under the car as it gushes out. 

Yew, some people advocate shimming the altitude sensor, but it, and the wuv work the rod through lever arms.  And, the screws / governor work the rod directly.  Therefore (I prefer So), the engineers intended for the primary adjustment to be made at the screws in the governor.  This puts the 3D cam in the right geometric location.  So the cam is the primary adjuster for power / performance.  While the WUV and Altimeter move from there.  If you are not on the best place on the 3D cam, the 2 gross adjustments only optimize the mixture in a narrow power band.

The governor cam looks like a cupped, out-stretched hand; sort of a concave hillside with a gradual hollow that is deeper for the lower poser  and shallower, but stepper for higher power needs,  The slope matches your cars mass to the motor's power and torque.  My problem is a 280SEL motor pulling an SL.  The cam thinks the car weighs much more than it does.  So the cam is set up to deliver more gas than this car needs.  The screws, mostly the white screws, set your place on the face of the hillside. 

I'm working on this now.  I'm close. I have the cold start and acceleration dialed in.  (this motor has surprising power when the rod is sufficiently rich on WOT!) I am still working on cruise economy vs partial load.  My motor runs a little too rich cruising at 70 mph / 3500 RPM.  So I am hoping I can find a sweet spot where the governor backs the gas off when I'm just cruising with minimal load. 

[stickandrudderman]

Excellent advice.

[jedwards]

Thanks Garymand,

Overnight, I added 0.2mm shims to the top of the WRD piston and now (on a bench top anyway) have it closing at 68 degrees (155F). 

I will need to reinstall it to see how this has effected warm-up mixture, but I am hoping this will  lean it out during warm up to give me some degree of control. I expect that I will need to readjust e warm running idle mixture as well, as the WRD pin does influence the IP rack.

You recommend installing an O2 sensor. Can this be done temporarily or do I need to take out the exhaust system and have a special port welded in?

Also, as I have the earlier IP pump, when I get to adjusting the partial load mixtures,  (white and black) can I do this with the IP cover removed?
 
Many thanks

Jeff

[garymand]

I went to a muffler shop and they knew that toyota sensors come with a threaded flange.  The welded the flange in to one of the down pipes.  The sensor screws into the flange.  The wide band sensors come with a nut and plug so you can eventully just plug it.  I might leav my gauge in.   I have recently seen wideband sensors with an accessory muffler pipe clamp with the flang welded into the clamp.  Tha allows you to drill a hole and do it yourself with no welding, but the clamp is a bit big and you put the plug in the clamp.  When I bought mine, only the narow band type were available at about $100 total.  the wide bands can be had for $160?  Better to go that way.  They come with the nut and plug.  I have mine wired in its original box just sitting on my floor.  I haven't decided if I want to make it permantent somehow.  For what we are doing, this temporary housing is just fine for me.

The WRD adj will effect the idle a little.  Disconnect the pump link and give it a little extra gas when still cold.  that tells you if you need move the WRD in or out with shims.  shut the motor off fast to avoid warm up and add or remove shims under the WRD until adding gas by the link only slows the motor (the colder the better).  Unfortunately, the WRD air passage is not sealed off from the hole into the pump.  So, when you loosen the two pan head retaining screws you add both gas and air.  Other wise we could easily determin the amount of shims by backing out the screws.  I had some stainless sheets and punched and cut my own extra shims.  The have to seal the air out when you screw the WRD back down.   Its could be alittle balancing act between the air screw and the idle gas screw once the motor is warmed.

The black and silver screws are (like the idle gas screw) adjusted with the motor stopped.   They are connected to the regulator and they spin with the motor.  And, oil will fling out if you forget to put the plug (IP cover) back in.  You will loose some oil out of the cover hole. the fill level is a little above the hole.  Don't worry, their is enough oil to make the pump happy if you leave it that low for a while.  The oil should be fresh looking.  It is a private stock and not shared with the motor oil as on the late 280. 

Get a not pad and take copious notes on what you are changing and what the results are.

[stickandrudderman]

shut the motor off fast to avoid warm up

You can either clamp off or disconnect & bypass the coolant hoses in order to give more time for playing around.

[garymand]

Yes, sort of.  I remember doing that once, a long time ago.  Pull two clamps and move one hose to bypass the WRD.  I can't remember why I did that, I've never done it again.  In this case I think the problem is  as ithe motor warms up, the air/fuel needs change.  If you are trying to get the 'cold start' needs met, and how much shim to have unter the WRD, the motor needs to stay cold and not warm up.  Once it starts, it warms up and moves the WRD ampual quickly and the heat disipates slowly, so each time you start the motor the motor gets a little warmer. 65 to 72 degrees is not very warm for a motor and thats were the WRD shuts off the air.

I move pretty quick on a cold start, have the hood popped, link disconnected, window down, key in, start motor, push the link, shut the motor off.  Maybe I'm just a little anal, but if you have to do this three or four times, the motor isn't cold anymore. (well here in California anyway.) And the WRD should be adjusting for the rising temp, and having a lesser effect on the air/fuel coming from the IP govenor. 

[MrAZ]

I highly recommend installing an Innovate Motorsports oxygen sensor gauge kit.  They are around $150 on Amazon and are pretty simple to install except for a bung that needs to be welded to an exhaust pipe.  I have installed one on a hot rod and it allowed me, a rookie carburetor tuner, to set up dual quad carbs correctly The LED gauge inside the car shows your air/fuel mixture digitally and with a sweeping dial as you drive.  It saves the cost of a dyno tune and you accurately know if your car is rich or lean throughout every part of
the rpm range.

Whenever I have an exhaust pipe off, I will weld on the bung on my 250SL and wire it up.

[garymand]

Get back to us when you do, I could use the sanity check on another
SL. 

[66andBlue]

..... Whenever I have an exhaust pipe off, I will weld on the bung on my 250SL and wire it up.

... and please take plenty of photos and do post them here.
Thanks!