I have emissions here. I dont know if it'll matter alot. I plan on getting a custom chip soon. What would you guys do?

 

I'd keep it.

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"Question with boldness even the existence of a *** ; because, if there be one, he must more approve of the homage of reason, than that of blind-folded fear."

-Thomas Jefferson

 

I'd like to see Vader's response, but I personally think the EGR is one of the best devices on a computer controlled engine.

First, at WOT, the EGR is disabled so it does nothing to hurt performance. At part throttle, besides helping in controlling NOx emissions, it also allows you to get better gas mileage (and run higher spark values to reduce the "mushy" feeling of the throttle).

When the EGR is functioning, it partially fills the cylinder with "inert exhaust gas". Basically, it causes a larger engine to becoming a smaller engine since the cylinder has less air to mix with the fuel. This results in less fuel consumption.

If you get into eprom burning and invoke "Highway Mode", the EGR is a key part to running the higher spark advances (I run over 47* when in Highway Mode) with lean Air Fuel Ratios (I run 17:1) that eliminates detonation while retaining throttle response.

The key part is, since the EGR only functions at part throttle, you actually get the benefits of lower NOx emission, better gas mileage AND when you stomp on it, you can "pollute good like a Chevy should".

Now, I have a better question. Give me some good reasons WHY you should remove it? The ONLY valid reason I can see for not running an EGR is because your heads/intake have no provision for it. If I was to run a Miniram, I would seriously think about trying to hook one up ala Corvette.

 

If you have emissions testing it might be best to leave it alone. I dont see the EGR as the gift to humanity however, the new LS1's dont have them and seem to run just fine.

 

Mkos,

Before you cut anything, if you don't believe Glenn's response, check out SEThirdGen.org. GMTech has a short but sweet article on why the EGR is actually a performance improver. Then again, Glenn already covered the major reasons for having a fully functional EGR in detail.

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Glenn,

You evidently already know my position. Your explanation was better than I would have given, and you have real world data to substantiate it. (You must be getting eleven-teen miles per gallon on the highway! 47° total advance? Sounds like you have the binary tweaked very well, with thought given to a lot more than just WOT power.)

If you ever get in to a bind with an EGR install on Vortecs or aftermarket intakes, the Corvette L98 works, but so does the system from the L99s and LT1s. They are a lot alike, and have a separate flexible tube to the EGR from the right rear exhaust mainfold, and a stand-alone EGR valve that is vacuum operated instead of digital stepper motor. Pretty easy conversion and cheap parts from older Caprice L99, LT1, and F-car LT1s.

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Later,
Vader
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Justice and Freedom will Prevail
Adobe Acrobat Reader

 

One question.. Doesn't a functioning EGR heat up the plenum? That would cause hp loss at WOT. See past issues of CAR CRAFT, they did a cold air kit on a rustang. I am not running a EGR, the engine has never pulled harder. MPG is unchanged so far.

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1988 L98
Vette Heads/no EGR
SLP Headers/Y-Pipe
ARAP bin

 

Yes, a functioning EGR does add some heat to the plenum, but it is not that much. I have measured the MAT temp (I have both setups) from the plenum during a very cold day last year, and I could easily "snuff out" the EGR by just opening up the throttle.

On my SD car, an MAT temp of less than 5*C would cause the EGR to cease to function. It was -5*C last year and my MAT was just hovering above 5*C due to the temp of the EGR and plenum itself. When I went WOT, the MAT temp quickly dropped to 0*C and the EGR ceased to function. The extra 5*C above the ambient air temp was soley due to the heat of the plenum itself from the motor.

Turning on the relocated MAT always kept the EGR from functioning and switching back to the stock MAT showed again a 0*C temp.

I did a LOT of testing an playing with the MAT, EGR and burnt a variety of eproms to see the real effect of the EGR and measured the performance differences. I conversely noticed no increase in performance with a non-functioning EGR but I noticed a definite effect on my gas mileage.

If a person wants to do some testing, all you do is set the EGR Enable Temp in the eprom to 150+*C. This will cause the EGR to never work since your engine will never hit that high.

I should add that when I did all this testing, I discovered the stock SD eprom DOES NOT like a reloctated MAT unless you modify the MAT Inverse Multiplier table. I am still trying to find a function for a relocated MAT for the MAF system. So far, the only thing I can find that it affects is the turning on/off of the EGR.

These MATs really seem to function differently from ECM to ECM. In fact, the SD 7747 used in trucks don't even have a MAT like SD TPI! And there is no reference to one in the eprom. Don't ask me how it corrects for differences in air temperature as they don't even have a MAF which does compensate for intake temperature, air density and to a lesser extent, humidity. The believe the 7747 has a separate Temp Sensor for the EGR but that's about it. Maybe Vader can explain more about the 7747.

[This message has been edited by Glenn91L98GTA (edited October 11, 2001).]