EGR Corrections

[Bruce Plecan]

-----Original Message-----
From: Terry <thartman at gte.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Sunday, July 26, 1998 10:26 AM
Subject: Re: EGR Corrections


>Bruce Plecan wrote:
>>
>> The question is wheither the valve is open at WOT.  If it is then it
>> almost has to be because of backpressure opening it.
>
>I think MikeV was thinking that the excess Boost pressure might
>be opening the valve.  Which if it is - would be bleeding off
>manifold pressure right out the exhaust.

On most applications the exhaust back pressure is much higher than
the boost level.  From what I've seen it takes an open exhaust, and
a large compressor housing to get to cross over (less exhaust
backpressure than boost [turbos]).

One other thought is that they have a vacuum solenoid so the egr
valve never sees the increase in boost to help keep it closed.  So
any increase in boost will try to lift it off it's seat.

   Now on a N/A application,
>it might indeed be excessive exhaust backpressure does force open
>the EGR - hope not though...

Well I wouldn't count on hoping on something to make it so.  I have
attempted to make a movement sensor for "seeing" if the egr moved,
but I'm not absolutely sure of the results.  Also tried momentarily using
the thermal sensor from an oem application but it was way to slow
in acting,  waiting at WOT for 20 or so seconds results in using lots
of real estate.  My formal answer for racing is a stainless steel
plate.  But, that still left the ecm corrections intact.
>
>>  Then the
>> question becomes, is, is it designed to do that, or from the exhaust
>> being less than optimum.   Either way the "table" appears to be
>> using an addition amount of advance.
>>   Might be really messing someone up if they think they are at 36d
>> and actually are at 42d BTDC
>
>So with a Diacom connected and recording - are you saying that it would
>not show the requested timing?

Does the Diacom show the burst knock activity?.  I don't know what the
diacom shows or not.  Does it show the EGR timing addition?.
Becomes a matter of what they call requested timing.

  This would indeed be a bad thing as that
>would also imply that the data from the ECM diagnostics would be
inaccurate....

How would you figure that???..  Diagnostics is for fault finding, if
it's intended to operate a certain way, then there is no error.

>
>thanks,
>
>T.
>