Pagoda SL Group

W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: bootes on May 31, 2010, 14:04:48

Title: "Black Box" on Exhaust System?
Post by: bootes on May 31, 2010, 14:04:48

I bought my '71 280SL back in '02 from the original owner and was given a lot of receipts, notes and letters re the history of the car. One of the notes I come across periodically... but have never asked anyone about relates to a so called "black box." The note was given to various mechanics over the years apparently and states: "Do NOT reconnect the "black box" on the exhaust system for pollution control; it has been disconnected since 1973 for a good reason; it destroys the drive-ability of the car."

Anyone know what she is referring to?

Thanks!

Title: Re: "Black Box" on Exhaust System?
Post by: jeffc280sl on June 01, 2010, 00:10:41

I think she is refering to a pair of black boxes located near the battery.  They are emissions related and control when tiiming is advanced or retarded as well as some other functions MB used to reduce emissions.  Many have disconnected the boxes including me.

Title: Re: "Black Box" on Exhaust System?
Post by: jeffc280sl on June 01, 2010, 02:21:44

Search under the term "2 way valve"  for more info.

Title: Re: "Black Box" on Exhaust System?
Post by: bootes on June 01, 2010, 16:46:03

Thanks Jeff for your replies.

I have located the "black boxes."  They appear to be connected although I'm not exactly sure how you determine if it is disconnected. One line is to the distributor and one line is to the exhaust manifold. It looks like the power source may lead into the firewall. 

What are the steps to disconnect this? Any repercussions? If I do disconnect, is there marked improvement in performance?

Thanks!!

Rick

Title: Re: "Black Box" on Exhaust System?
Post by: jeffc280sl on June 05, 2010, 01:13:39

http://www.sl113.org/forums/index.php?topic=12238.0

Read this thread

Title: Re: "Black Box" on Exhaust System?
Post by: bootes on June 05, 2010, 22:02:11

Thanks but I guess I'm missing something. I'll have my mechanic look at it. I simply came across a note from the original owner stating that the black boxes  (disconnected since 1973) should not be reconnected as it cuts down on performance but from what I can tell they have been reconnected. Is it as easy as disconnecting the hoses from the manifold and distributor or does that cause problems with timing?  Do I disconnect the power source? Maybe I just leave it as is.

Title: Re: "Black Box" on Exhaust System?
Post by: jeffc280sl on June 07, 2010, 19:01:58

Bootes,

Based on the info you have provided I can't say what you should do about the emissions system.  At least now you have some documentation.  If you have time you can try and trace wires or ask your mechanic to do that.  With mor information we should be able to help out.

Title: Re: "Black Box" on Exhaust System?
Post by: bootes on June 09, 2010, 02:37:21

thanks Jeff,

how did you disconnect your system?

Rick

Title: Re: "Black Box" on Exhaust System?
Post by: Peter van Es on June 09, 2010, 09:09:19

Are you talking about this: http://www.sl113.org/wiki/Electrical/EmissionControlSystem or about http://www.sl113.org/wiki/Fuel/VaporTank which is also a kind of "black box".

Also read the following topics:

http://www.sl113.org/forums/index.php?topic=10066.0
http://www.sl113.org/forums/index.php?topic=6484.0
http://www.sl113.org/forums/index.php?topic=12238.0
http://www.sl113.org/forums/index.php?topic=10806.0

All found with a quick search on "emission control"

Peter

Title: Re: "Black Box" on Exhaust System?
Post by: Naj ✝︎ on June 09, 2010, 09:20:32

Hi, Rick,

I would only disconnect the 2 pin plug on the vacuum valve mounted on the same bracket as the black boxes.
This would disable the retard function on the distributor but still operate the fuel pump solenoid (on the IP) which stops the exhaust popping on decelleration.
Disconnecting the vacuum pipe at the throttle body or distributor is going to cause air leak issues.

naj

Title: Re: "Black Box" on Exhaust System?
Post by: bootes on June 09, 2010, 22:00:27

Peter, thanks for the links.  I have reviewed these.  I am referring to #4 and #5 in this link:  http://www.sl113.org/wiki/Electrical/EmissionControlSystem  I came across a note from the original owner that these "black boxes" had been disconnected since 1973 and to not reconnect as it would ruin the drive-ability of the car. It appears to me that a mechanic somewhere along the line has reconnected. I have been trying to determine how to disconnect or proper way to disconnect.  But from what I'm reading, timing may be affected and I would like to know, simply, how to disconnect (and if it's worth it? does it, in fact improve drive-ability?).

Naj (thanks for your reply as well) suggested disconnecting the 2 prong (#9 in the link above) which I've now done but have not been able to test due to inclement weather here in Pittsburgh.

Any other comments on disconnecting this and how it affects drive-ability would be much appreciated!

Thanks,

Rick

Title: Re: "Black Box" on Exhaust System?
Post by: jeffc280sl on June 09, 2010, 23:05:11

Naj,

It's my understanding the fuel shut off solenoid causes the popping noises on decelleration.  I have this solenoid and the 2 way valve disconnected on my car.  I use the 123 distributor.

Title: Re: "Black Box" on Exhaust System?
Post by: bootes on June 10, 2010, 00:16:22

Jeff,

How did you disconnect the 2-way valve? Did you do so by disconnecting the 2 prong going into the vacuum attached to the black boxes (as Naj suggested)?  I don't ever remember "popping" on deceleration but can you explain how you disconnected the solenoid as well? Thanks