EGR valve info needed!

[pstrbrc]

OK, I'm building a car with one of the goals being fuel mileage. No need to get bogged down in the details, but I'm fuel injecting it with a MegaSquirt system and a wide band o2 system. But, I'm also aware that accurate exhaust gas recirculation is good for mileage as well as emissions. So I need some information about various egr valves that can be electronically controlled. (A friend says he can design me a stand-alone control unit for an egr valve if I can't get MegaSquirt software modified to do it.)
The two most common electric egr's seem to be the ubiquitous GM unit used from the mid-90's on, and the same era Honda/Acura unit. What I'm looking for is a schematic and pin layout for each of these units. Anybody?

[fatsog123]

Man you sound high tech,plus the stuff you and your friend are talking about solves your problem.You sound like a master of this.We're bums with the questions.lol

[RahX]

The EGR is designed for NOx reduction, not for fuel mileage.

[534BC]

I agree, egr will not help mpg. It will probably hurt. In fact most emmision reducing components/systems will take away mpg/power. It is almost a non issue today, they have them going pretty well.

sorry we didn't help with the pinout.

[KiwiBacon]

Originally Posted by RahX

The EGR is designed for NOx reduction, not for fuel mileage.

EGR can reduce your pumping losses, that's where the fuel economy benefit comes in.
Basically car at cruise has the throttle mostly closed to restrict power to what is needed. The EGR can let the car engine run with a more open throttle by feeding in exhaust which has no oxygen in it, thus less power is required to suck air past the throttle plate.

But if you're building from scratch, you'd get a better result from a smaller engine which requires the throttle to be open further at cruise. That way you get the benefits of less internal friction and less weight too.

[pstrbrc]

Originally Posted by RahX

The EGR is designed for NOx reduction, not for fuel mileage.

Ahhh... But if the car came with an egr, and one expects to pass emissions inspection, one should have one of these little buggers!!!

You are right, they weren't put on for mileage, and the way most of them are integrated into the rest of the engine systems, they make everything work worse. Less power, lower mileage, heck, I even think they aggravate my constipation on long trips!!! But, since I have use one, I'm going to make the best of it.

[pstrbrc]

Originally Posted by 534BC

I agree, egr will not help mpg. It will probably hurt. In fact most emmision reducing components/systems will take away mpg/power. It is almost a non issue today, they have them going pretty well.

Yeah, and the pulse width modulation ones that GM use now is the reason why!! Actually, on both my wife's 3.8 Windstar and my daughter's 3800 Grand Prix, you actually lose mileage by blocking the egr passage. Not much, but about 1 mpg on the van, 3 mpg on the car. ~5% on the Windstar, ~10% on the Grand Prix. And looking at mpg numbers across the board, GM cars seem to get a little better mileage than the Fords. I think it's because the pwm egr valves on the GMs are better controled by the ecu than the Ford vacuum-with-electronic-doohicky setup.
The early egr setups were just to pass emissions. But when they first came out I was an engineering student, and some of us did some serious work with them. Don't remember the specifics, but we were able to improve mileage in a couple of full-size sedans by ~ 20% just with a manually adjustable egr bleed valve.

[pstrbrc]

Originally Posted by KiwiBacon

But if you're building from scratch, you'd get a better result from a smaller engine which requires the throttle to be open further at cruise. That way you get the benefits of less internal friction and less weight too.

Yeah, but mileage is only PART of it. looking for a decent level of performance, too. See, this is the tradeoff. So, most people think, small engine w/turbo. So when you aren't boosting, you have just enough engine for cruising economically. Good thought, but this means higher stress on parts. And I'm partial to American iron. So I'm gonna play with egr.

[curtis73]

Originally Posted by 534BC

I agree, egr will not help mpg. It will probably hurt. In fact most emmision reducing components/systems will take away mpg/power. It is almost a non issue today, they have them going pretty well.

sorry we didn't help with the pinout.

whoa, guys... As a former GM fuel systems engineer, I feel confident chiming in on this.

EGR will help MPG in most cases. It will not hurt it. In fact, emissions equipment was never responsible for hurting HP. EPA regulations were. The low-powered vehicles of the 70s and 80s coincided with the massive power drops from the muscle car era, but it wasn't the emissions components. The problem was abyssmal compression and tiny cams with pathetic heads.

EGR is a valve that opens only during part throttle cruise. It is closed at wide open throttle, so there is no physical way it can affect HP production. Its not possible unless its malfunctioning, but if it has stuck open, the engine won't idle. The only emissions component that hurts MPG and power is the air pump. It takes approximately 1/3 HP to operate, so it probably affects fuel efficiency by about .0004 MPG.

I also can't really help you with an electronic EGR pinout, but I can say that most of the mechanical (vacuum operated) EGRs are dirt cheap, easy to adapt, and don't require any programming other than re-adjusting fuel trim for open loop operation during cruise.

I always chuckle at people who start with a 170 hp 1975 engine and pull off all the emissions components thinking it will gain them power. All they have now is a 171 hp engine that is now really lean on part throttle cruise and polluting about 7 times as much as it was before.