Cooler EGR Charge

deekster_caddy wrote:

Given how misunderstood the EGR system is, you and I should make an "Universal EGR heat exchanger" and start selling it. There's money to part with some fools out there.

Now I think this is the MOST SALIENT point coming out of this thread






....seriously. I bet you could sell a million.

I like this guy.

Hey AA, you might want to take down all the GM propaganda I've posted over the years. I don't want anybody to get brainwashed....

Diesels? We're comparing apples and oranges now?

We're getting off track here. Diesels NEED the EGR cooler for gas mileage and efficiency. I suppose you could fabricate an EGR cooler and make it work IF you had the proper sotware. Ford uses them on their EcoBoost engines, which are designed like a Diesel (high compression, direct-injected turbo). However the fact still remains, you ARE NOT going to reduce any form of knock created at a high throttle condition when the EGR is CLOSED on an engine not designed for this type of thing.

If for some reason your Series 1 3.8L is running 12/1 compression, and your huge turbo is creating too much heat, then sure, let's make an EGR cooler. It'll probably help you out.

If you're engine is producing KR at idle, cruise, or wherever, fix it. There's something wrong.

ironclyde wrote:

However, the MAF was saying 130 degrees.

How is the MAF sensor telling you this? Are you aware the MAF sensor is heated to a specific value above IAT? The sensor can't measure actual air temp at its location.

Hey AA, I'm not sure how the MAF is telling me anything except the scantool gives me a temperature reading at the IAT and the MAF. The IAT reflects the incoming air at the airbox and the MAF temp tends to rise with the engine temperature. The MAF sensor cools down when at cruise speeds as opposed to warming up in traffic. I'll gladly post a picture of the scantool's readings, if I can figure out how to make this picture uploader work.
I thought it was the O2 sensor that has the heat element in it.

Okay. Now I see what you are talking about AA.
[url=http://www.sensorland.com/HowPage060.html]

So, the PCM can calculate the air temp at the MAF.

"Some MAF sensors use an internal "cold" wire to send ambient temperature information to the computer."

Do the 95s have this cold wire?

I'm not saying that a CAI has no performance value. The colder air you start with, the better things will go in the long run. The OEM airbox is a true FWI so even the factory acknowledges that. The supercharger generates a lot of heat, though, and the end result of 200 vs 190 post-supercharger IAT isn't going to have that much of an effect in the long run. An intercooler after the supercharger has proven results though. I wish I could find it, someone at one point put a real air temp sensor inside the LIM on a 3800 and tried a bunch of different things.

However, this tangent is about WOT and has nothing to do with the EGR, which is not used at WOT.

I hear you about the EGR not being opened at WOT. However, the introduction of EGR at cruise would still preheat the intake charge at the intake valve and thereby add additional heat to the combustion chamber at cruise. This is a concern to me, because theoretically the increased heat at cruise could lead to some detonation, which would cause the PCM to retard timing to eliminate knock at cruise.

So, what if we could reduce the incoming air charge temperature, say by 30 degrees; would it not be reasonable to assume a 20 to 30 degree drop in temperature on the output side of the SC? Also, I'm not looking at anything very complex to lower the EGR gas temp. It should be relatively simple and straight forward.

ironclyde wrote:

I hear you about the EGR not being opened at WOT. However, the introduction of EGR at cruise would still preheat the intake charge at the intake valve and thereby add additional heat to the combustion chamber at cruise. This is a concern to me, because theoretically the increased heat at cruise could lead to some detonation, which would cause the PCM to retard timing to eliminate knock at cruise.

So, what if we could reduce the incoming air charge temperature, say by 30 degrees; would it not be reasonable to assume a 20 to 30 degree drop in temperature on the output side of the SC? Also, I'm not looking at anything very complex to lower the EGR gas temp. It should be relatively simple and straight forward.

ironclyde wrote:

I hear you about the EGR not being opened at WOT. However, the introduction of EGR at cruise would still preheat the intake charge at the intake valve and thereby add additional heat to the combustion chamber at cruise.

I don't think it's a significant amount. Once you hit WOT the air is all replaced very quickly. Theoretically, yes you might add some residual heat to the metal intake components, but the air won't be spending much time there inside the intake manifold. But we are talking about the difference between 180 or 185 degree air on the 1500 degree combustion chamber.

ironclyde wrote:

So, what if we could reduce the incoming air charge temperature, say by 30 degrees; would it not be reasonable to assume a 20 to 30 degree drop in temperature on the output side of the SC?

You are looking at the difference between atmospheric pressure and compressed air, plus the heat added by the supercharger's work. I don't think the compressed air temp would be at a 1:1 ratio or even close. There are a few factors to it, pulley size, any potential boost stacking, resulting PSI and I don't know the math off the top of my head. (I just spent a few minutes trying to look up the math behind it and it's not easy) Every factor has a weight in the end result. The biggest will be a temperature increase simply by changing the air pressure from 1 bar to 1.5 bar (about 7 PSI as an example), plus the work and inefficiencies of the blower that will have a much larger weight in calculating the air temp. The factor from warmer metal in the lower intake manifold and intake valve will be a very small weight IMO.

I don't know where to tell you to look for exact numbers. Maybe the engineers from GM have them. Unless you are building a 9 second drag car that will also be street driven, the temp increase on the metal engine components from the EGR being active is insignificant. It has been proven many times that the combustion chamber temperatures during cruise decrease with the use of EGR. That's why they use it.

Okay. I'm hearing you on that. Thanks.