Alright about 2 weekends ago I did custom cold air intake and when I did this I did away with the dryer hose that runs to the intake from the exhaust. I got under today to plug the hole on the exhaust and I realized that the pipe does a huge U thing to accommodate the cat shaped object that puts hot 'air' into the intake. Haynes doesn't list it and I don't know what it’s called, bare with me. Today after school I went to an exhaust shop and asked them about getting rid of the U shape and just going from the exhaust header - straight down into the pipe that leads to the muffler and they said they would do it for $20. Basically removing the whole U shape pipe that is totally useless to me right now. So would there be any problems with that? I mean I'm not using it and the only thing that I can think of is that since the exhaust is shorter, so the pipes are going to be generally hotter. Any input?

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This sig sucks

That hot air thingie helps you develop more horsepower and better gas mileage. It's needed to help improve fuel atomization in the intake.

Just a thought...

JazzMan

But when I had it hooked up I got check engine lights between 1700 RPM - 2100RPM. Then I removed it and I haven't had a problem with it since. I don't understand how hot air improves gas milage and horsepower. I thought it was the opposite. Can anyone sheld light on this?

it helps in cold weather - its kindof a leftover from carb's but i don't think its really necessary with TBI setup

Do you mean the EGR? Kill that POS!

quote Originally posted by lou_dias: Do you mean the EGR? Kill that POS!

Yeah that's what it is! Thanks!

quote Originally posted by IEatRice: But when I had it hooked up I got check engine lights between 1700 RPM - 2100RPM. Then I removed it and I haven't had a problem with it since. I don't understand how hot air improves gas milage and horsepower. I thought it was the opposite. Can anyone sheld light on this?

It's a scam. It replaces one form of polution with another (or is that the catalytic converter). Fouls up your intake system. Goes wrong often. And you are told that if you block it you will burn a piston.

There is as much outrageous propaganda on this as MDMA. But that's another topic for another thread.

EGR valve lets exhaust into the engine to keep the combustion chamber cooler to lower NOx (the stuff that causes smog). removing it will more than likely cause pinging or engine knock if you are running a high enough compression ratio. just food for thought.

quote Originally posted by Nikemann: EGR valve lets exhaust into the engine to keep the combustion chamber cooler to lower NOx (the stuff that causes smog). removing it will more than likely cause pinging or engine knock if you are running a high enough compression ratio. just food for thought.

I drove 40,000 with an EGR blocked off on a motor that dynoed at 149.8 rwhp with the timing advance with no pinging. If your car is pinging, your timing is to advanced or you have a fuel problem. It's just a scare tactic.

quote Originally posted by lou_dias: I drove 40,000 with an EGR blocked off on a motor that dynoed at 149.8 rwhp with the timing advance with no pinging. If your car is pinging, your timing is to advanced or you have a fuel problem. It's just a scare tactic.

It is possible to run without the EGR but only if your engine is running on the rich side. A lillte EGR action does help cool the combustion chamber temps at cruise conditions. It was put there to insure no chamber overheating while cruising with the lean mixtures that the Fiero ECM calls for. AT WOT the EGR is not used so it won't slow you down one bit.
You may be able to run without the EGR long term and get away with it but then again you may not. A common problem is that we find that many Fieros are missing the EGR restrictor gasket and too much EGR action carboned up the plenum. I believe it's wise to keep the EGR especially if you add a free flow exhaust system.

Okay well I got it removed today. I will post pics soon. No problems. The engine seems to be running better actually.

If the "U-shaped thing with the dryer hose" is on a pre-'87 4cyl, then you're probably talking about the heat stove (aka thermac system). There's a flapper valve (aka thermac valve) in the air cleaner box that the "dryer hose" goes into. The thermac valve routes hot air (heated by the exhaust manifold) into the intake when the engine is cold. Basically all it does is improve fuel economy when the engine is cold. If the valve is stuck open, the engine will probably run lean after it warms up.

[This message has been edited by Blacktree (edited 05-12-2005).]

quote Originally posted by IEatRice: Okay well I got it removed today. I will post pics soon. No problems. The engine seems to be running better actually.

Who would have thunk it?

Yes - I said 'thunk'!

Excessive EGR is bad for performance and if you find the engine running better without EGR , then you have too much EGR. The restrictor gasket is essential on the EGT tube for proper performance. Without it the intake floods with exhaust gases and the performance goes way down.

Alright! Pictures!

Sorry the pics suck, forgot to get my camera when they had it jacked up so I can't really get a good view of it. But if you know what you're looking at and what used to be there you get the idea.

The pics don't work. You can email them to m.blacktree@gmail.com and I'll host them for you.

quote Originally posted by lou_dias: With all due respect. Cars didn't always come with EGR systems and they ran fine. Even our ECMs have a no-EGR option. None of my cars have had a full cat or muffler or EGR that wasn't blocked off since '96. The 40k figure was my last one. I've never pinged or burned a piston across 4 different motors - 3.1 stroker, 3.4 rebuild, 2.8 stock, 3.4 used. Since '96 I have put on about 160k miles on Fieros without an EGR. Not everything you read on paper is actually based on real facts. Same goes for the internet. EGR is supposedly good for the air at the expense of the motor. Experience is what is real. Driving impressions for driving a car with the EGR blocked is that the car responds better. Now 1/2 throttle feels like 1/2 power instead of 1/8 power then going to WOT is like such a shock. Without the EGR, throttle movement and engine response are more directly related rather than dulled until WOT.

Experience may seem real, but if you've ever studied the placebo effect you'd realize just how unreliable experience can be. That's why there's such an insistance on dyno sheets and time slips when it comes to performance engineering in the car world.

Your bias against EGR (and presumably other emission control systems) aside, the EGR system has absolutely no effect whatsoever on power output. The reason? Above part throttle the ECM goes into Wide Open Throttle mode (WOT) and at that point it runs the mixture rich and disables EGR completely. EGR also has no effect whatsoever on idle quality. Why? Because at idle the ECM disables EGR completely. So, when does the ECM command EGR? Only at part throttle cruise when the engine is fully warmed up.

Yes, cars ran find without EGR in the old days, but they pumped out copious amounts of nitrous and nitric oxides that, when mixed with moisture in the air, formed nitrous and nitric acids. Those powerful acids cause all sorts of health problems and contribute directly to the deaths of tens of thousands of people every year. Modern cars use properly engineered EGR systems to significantly reduce NOx production, and guess what? Modern cars run just fine with EGR. In fact, with EGR to reduce peak combustion temperature you can run more advance timing at part throttle without having to add more fuel, that translates out into increased part-throttle combustion efficiency and better gas mileage.

Our ECMs do not have a "no-EGR" option at all. Nope, none. Instead, there's a table in the ECM where one can relate EGR function percentage to coolant temperature. By setting the temperature for EGR activation at 300°F you can fool the ECM into effectively disabling the EGR system. That is not the same as an actual option to disable the EGR function.

A common symptom of EGR failure is pinging, also known as predetonation. That's a basic fact. The fact that you aren't getting audible detonation in your motor doesn't change anything. When I had problems with my EGR system I got detonation on anything less than 93 octane. I may still have been getting inaudible detonation, but without a knock sensor there was no way for me to tell.

Long story short? The EGR system is an engineered part of the engine's fuel management systems, and in my opinion should be left intact and maintained in proper operating condition. It does not hurt fuel economy, it does not affect performance or horsepower in any way.

JazzMan

[This message has been edited by JazzMan (edited 05-14-2005).]

It killed my engines smooth running ability. With it in tact it would cause surging on my engine. With it Disabled I run fine now. I believe it was due to less pressure in the exhaust system though. Allowing the exhaust to not supply pressure to the EGR and starved the engine when open.

Throwing exhaust emissions into your intake is not good for your intake system. If dirties it up and you are no longer running at 100% intake efficiency at WOT throttle. If we are simply reburning exhaust emmissios, why didn't the original combustion process not do it's job the first time around? Design a better combustion process then. Having a motor breathe in exhaust is not an ideal solution in any way. If NOx emissions are too high then maybe there should be another process (similar to the catalytic converter) that takes NOx and converts it to something else. Reburning something that was already burned doesn't make sense.

I also don't see a problem with high combustion temperatures. Wouldn't that make the combustion process more efficient? Isn't it heat that expands gas and causes the piston to go down? Don't higher compression engines have higher combustions temps? There is some really strange logic behind EGR if you ask me.