Re: EGR operation 95 SL2

On Jul 22, 3:16 pm, "Oppie" <op...@xxxxxxxxxxxxxxx> wrote:
Speaking in general - the vacuum operatedEGRis driven from a vacuum
sensing port in the throttle body. This vacuum signal is usually shut off
until the engine is at operating temperature. The vacuum signal is also
combined in a control valve with an exhaust back pressure measurement. The
objective is to getEGRonly when engine is warmed up and then at a rate
proportional to the intake air mass-flow to the throttle body.
Ultimately Exhaust gas recirculation reduces available oxygen (totally
counter-intuitive) in the cylinder. That reduces peak temperature which
controls pinging and reduces NOx formation.

The Electric EGRs are sometimes modulated solenoids and others are step
motors. Some have a feedback device on the pintile position and others are
completely open loop. Your '95ECU is looking to control theEGRand is not
seeing anything. Automatic tests that the onboard computers are getting
devilishly smart at finding bypassed or defective emission control systems.
At a most simple level, the ECU tests theEGRdrive coil(s) for opens or
shorts. Then it tries to move theEGRpintile (with engine warm) and detects
a change in the pintile position feedback (if your motor used that) or looks
at the O2 sensor for a corresponding change.

Given all that, probably best to use theEGRthat was on the original motor,
make an adaptor plate and plumbing adaptation. My guess is that swapping the
ECU from the new motor will give you other compatibility issues. I hope
someone can prove my assessment wrong.

    Oppie

<eric.ellswo...@xxxxxxxxxxxxxx> wrote in message

news:13aa215e-21ce-4608-8bcc-be228eeed20e@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx





I have a question for the super-nerdy, need to know how everything
works type.  If this is you, read on, perhaps you can shed some light
on the situation.
I swapped the motor on my95SL2, that motor had the electrically
operatedEGR. The motor I installed is a 94 twincam with vacuum
operatedEGR. Unfortunately for me, theEGRmounting is different
between the two model years. The head for the95is junk, so a head
swap is at this time not the preferred option.
Can someone describe in detail, theEGRprocess for the electrically
operatedEGR. The vacuum operatedEGRI assume is controlled by the
PCM, as it has an electric solenoid to switch the vacuum to theEGR.
The check engine light comes on after I drive a short distance, with
noegrconnected.  This is more of a nuisence than anything.
Is it possible to "convert" to a vacuumEGR, and eliminate the check
engine warning, short of installing a PCM and chassis harness from a
MY94?

** Posted fromhttp://www.teranews.com**- Hide quoted text -

- Show quoted text -
Thanks Oppie for the detailed explaination.
One more question, will the lack of EGR keep the engine running in
open loop? The gas mileage isn't as good as I had expected
.

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