I'm the proud owner of an '87 tin top with only minor surface rust and 98% original.  I'm going to restore it to 1980's perfection and keep it original looking with only performance upgrades in the engine, suspension and driveline.  It came with a Webber and I've started removing all unnecessary emissions components and wiring from the harness, in doing so I've come across two items that I can not identify and as such don't know wether to remove them or not.  Who can tell me what #1 and #2 are in the picture below?

Thanks,
J.T.

#2 is the high altitude compensator switch. don't see #1.
no pat

Thanks, not gonna need a high altitude compensator switch!  #1 is directly above it, I apologize for the small hard to see marking.

1 is a pressure switch for the alt solenoid

I have a question about #2, the high altitude switch. If I understand correctly, it keeps the the EGR valve from opening at high altitude (5000ft?). Their is also a 5th gear switch on the transmission, that when in 5th, defeats the EGR.

Why? More power  (but dirtier emissions) without the EGR?

I think I understand how EGR works on the carburetor equipped 1.3 Sami engine: The EGR siphons off a small amount of exhaust gases, via a small port that runs from one of the exhaust ports, through the head to the intake side, and out. The port is covered by the EGR diaphram that opens and closes depending on weather or not it receives a vacuum signal. At rpms greater than 2k I think, the EGR valve gets opened, and some of those exhaust gases are reintroduced into the intake manifold and run through the engine for a second time. I've got that.

So why not at higher altitudes or in 5th gear?

How many guys have the 5th gear switch disabled, and have EGR active in all gears?

I would never, ever, knowingly break state and federal laws and intentionally defeat an emissions device. But say I had a green stickered vehicle, and thought I could get more power without EGR: In theory I could just jumper the high altitude switch, or 'make' the 5th gear switch and defeat the EGR, right?

You likely won't see any difference (in power or MPG) whether the EGR system is working or not.

Thank you to all responders,

The whole issue of what to remove from the engine bay just became much simpler.  Over the weekend I found and bought an 81 Rabbit with only 175k and 1 owner, the thing has service records going back to the first oil change.  I had been on the fence about just doing a diesel swap but the steal I got this donor for made the decision for me.

I look forward to joining the community and sharing my experiences.

J.T.

So why not at higher altitudes or in 5th gear?
How many guys have the 5th gear switch disabled, and have EGR active in all gears?

The EGR valve only works effectively at part load. If you consider the compression ratio is around 9:1 and that that is calculated with a full cylinder then its obvious that at half throttle the real compression is considerably lower. In addition to that the engine is subject to pumping losses because its pulling against a part closed throttle. The EGR allows the engine to draw in spent exhaust gasses which are inert. Those gasses help fill the cylinder and improve compression as well as reducing the pumping losses. The important point is that you still get the same amount of oxygen and gas so the ngine is more efficient. At higher loads the throttle is open further and pumping losses are lower, in addition you need to draw the maximum amount of air and fuel into the engine so the EGR valve needs to be closed.

Quote from: TinTopTom on January 20, 2012, 10:22:58 AM

So why not at higher altitudes or in 5th gear?
How many guys have the 5th gear switch disabled, and have EGR active in all gears?

The EGR valve only works effectively at part load. If you consider the compression ratio is around 9:1 and that that is calculated with a full cylinder then its obvious that at half throttle the real compression is considerably lower. In addition to that the engine is subject to pumping losses because its pulling against a part closed throttle. The EGR allows the engine to draw in spent exhaust gasses which are inert. Those gasses help fill the cylinder and improve compression as well as reducing the pumping losses. The important point is that you still get the same amount of oxygen and gas so the ngine is more efficient. At higher loads the throttle is open further and pumping losses are lower, in addition you need to draw the maximum amount of air and fuel into the engine so the EGR valve needs to be closed.

Thanks! Sounds as though part throttle efficiency is actually improved by using an EGR, not just a cleaner tail pipe, but better fuel economy at the same time.

the hac(high altitude compensator) is used by the ecm to adjust the mixture control solenoid(in the carb).
i still don't see #1

#1 = Thermal Engine Room Switch (number is hadr to see)

#1 = Thermal Engine Room Switch (number is hadr to see)

Interesting, any idea what the temperature threshold is for it?