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Pre-98 EGR Bypass How-to

amc49 said:
Nothing personal player #3, but if this is the best you got you need to stay home too.

'The mod though wouldnt count as a vaccume leak though. The PCM knows when it opens the EGR valve, and the O2S would moniter the change at the same time, so the PCM wont throw up a CEL. It only knows if its getting extra O2 if there is a leak after the EGR valve or if the valve is stuck open.'

I can find so much wrong with that it's not even funny. Just where do you guys get this stuff??? No wonder so many of the cars this site have so much trouble. You're hopelessly lost.

Save one of those whistles for me mcgarvey, these boys are flat tripping me out. They should consult Webster's and define the 2 words VACUUM LEAK and see if they can figure out what that means.

On second thought, maybe they can't. HOO boy...........

Here goes AGAIN. FORD........you remember them right?..... defines unmetered air as ANY that has not been measured by the MAF unit. EGR does not count because it is NOT AIR, as soon as air goes through that opening it IS AN UNMETERED VACUUM LEAK. If you can't grasp that you need to stay out from under your hood. Your car will thank you for it.
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you're wrong. i broke the EGR tube right at the cat right after i got my car when i was punching out the cat. i let that go for a few weeks before i replaced it and it never threw a code and the car ran fine. Last year, the gasket right after the EGR valve had a hole in it and that did throw a CEL. Also, the O2 sensor DOES know when the EGR valve is open. O2 sensors dont moniter oxygen, they tell the rich/lean by temp, and nox are created at high temp. how do you think the EGR valve knows when to open?
 
Lol @ unmetered air. 95_Mystique is right. The PCM knows what's going on. The only difference is the type of air entering. When it is commanded, EGR will open. Otherwise, it is closed and you are NOT GETTING UNMETERED AIR!

And to elaborate even more, stock tunes on stock cars are conservatively rich to keep the engine from detonating and causing irreversible internal engine damage. Do you really think that swapping exhaust gas for clean air will push the car SO far lean that you'd be out of the "normal specs" as the PCM would command? I'll be very surprised if this throws a lean code.
 
alright, lots of •••• being said here.

first, it is technically unmetered air. why? because while the PCM knows how much gas is flowing through the EGR tube when its commanded to open, it is expecting inert (noncombustible) gases, instead the engine actually receives burnable oxygen that its not expecting. any burnable air that the engine receives that does not flow through the MAF is unmetered air. as such this would lean out the mixture some. now, i know that in the case of the Zetec the PCV system is the same way but that is taken into account in the tune.

now, since the EGR is only open during cruise/light throttle conditions where there is little load on the engine, running slightly leaner is not an issue (that also means this isnt a continues vacuum leak). in fact, you can run up to about 16:1 or even 16.5:1 at light load without issues (assuming you have a healthy engine without any carbon deposits) and may never trip a CEL doing so. think about when you decelerate with the car still in gear, it goes insanely lean, past 18:1, and at least in the Contour the PCM doesnt actually fully shut off the injectors so i know its still getting some fuel (i have watched the pulse width on my scan gauge on both my old Zetec and my old SVT and both function the same way). the reason decelerating doesnt through a light is because the PCM knows you are at 0 throttle and its only for a relatively short period of time (you could go down a mountain like that and it would never through a code). the EGR functions in a similar manner in that you are at very little throttle, and its only open for short periods of time (during that time though it is flowing unmetered air).
 
mcgarvey said:
"O2 sensors dont moniter oxygen, they tell the rich/lean by temp"

LOL
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are you trying to cause problems here or what? i havent seen you say one informative thing here. you're just picking sides here, and giving no facts. I've also said this already, there is no need to be picking fights here or getting nasty.

Also, what i said about O2S's is partially true. The do change readings according to temp, but they also moniter how much o2 is needed to completely oxidize any remaining combustibles.

Striker is right though, there isnt enough O2 being sucked in to throw a code.
 
Discussion was not about whether a code would throw, was about whether unmetered air or not. Just what do you think an O2 sensor does? It does NOT read temperature, temperature is required for it to function properly. Two different things. They do NOT monitor O2 content, the PCM does. They only relay to PCM amount of unburned O2 left in exhaust. That is ALL they do.

A code will not throw as long as errant ratio is still within the realm of correctability by the fuel trim. PCV is unmetered air also, but small amount that is figured into software fuel map. Technically there will be no lean out until fuel trim limits are hit, therefore no lean condition, just the big fat possibility of one. Now what about this mod would possibly make someone see value in that?

striker2 you are a breath of fresh air. They do indeed run these motors quite lean at low load and decel, that's how you get 30+ miles per gallon. EGR open then actually beneficial as it holds temp and pressures of lean running down.

For zorrex: 'Do you really think that swapping exhaust gas for clean air will push the car SO far lean that you'd be out of the "normal specs" as the PCM would command?'

Wrong question. Should be 'What value is there here to even make me consider doing it????'

ANYTIME you narrow your window of tuning error you are MOVING IN THE WRONG DIRECTION. Doing this mod DOES THAT or if you think not, again I say unto you, please stop, your car will thank you for it.

Com'on guys this ain't rocket science, the information is there for anyone that will pick up a book and research it.
 
For EGR, The PCM expects unburnable air. If it wanted more burnable air, it would open the IAC more (which is metered by the MAF). I think any form of burnable air is required to be metered by the MAF with the exception of the PCV system which is accounted for in the PCM's calibration.

I think the above statement is true and has been stated and restated quite a bit.
 
A car is tuned slightly more rich than optimal. Optimal air/fuel ratio is 14.7:1. The actual air/fuel, stock, is somewhere between 13:1 and 14:1, closer to 14:1, right? I find it highly unlikely that swapping exhaust gas for clean air will push the air/fuel ratio past 14.7:1.

As for the oxygen sensors, they do not measure the amount of O2 left in the exhaust as you say. They actually read the amount of oxygen needed to oxidize any combustible gases that may be left in the exhaust. This information is interpreted from a voltage that ranges from 0.1 volts (lean) to 0.9 volts (rich).
 
Hope you have some really tall boots on zorrex as you are only burying yourself in it more and more. You are hopelessly lost.

'They actually read the amount of oxygen needed to oxidize any combustible gases that may be left in the exhaust.'

That is exactly the type of totally misplaced logic stream I was talking about. They absolutely and totally have NO WAY of doing that. The PCM does any presupposition of future actions to take place, the O2 sensor is totally reactive in nature not proactive. It can only give a RESULT, not infer FUTURE changes to be made. You have even confused the tense of your statement, 'needed to oxidize....be LEFT' (caps mine!) is incorrect, no correction possible at that point for sampled exhaust as the burn has already happened. The PCM looks for evidence of that burn to set FI pulse for LATER burns to take place.

Get this and lock it or stay stupid, after all it is your choice. O2 sensor signal is based on the oxygen LEFT IN THE EXHAUST.

It's only in like 500 different books. Why don't you look up the science of a lambda sensor and how it works???

Stock tunes on stock cars are NOT conservatively rich. With rich you emit HC and CO like a MF, just try passing an inspect like that. Again you are LOST. Conservatively rich only applies to wide open throttle/heavy load where the PCM dumps the O2 signal and goes to around 13/1 for max power and to avoid engine damage. 90% of the time though car is at 14.7/1 or leaner at certain times to save fuel.
 
Sure got quiet here in a hurry didn't it........................................(snicker).
 
On my zetec, the EGR tube has been broken since I got this stupid contour. No luck finding a replacement. Trying to remove it from the Cat without breaking anything would be a nightmare.
Anyways, everything else on the engine checks out fine, except the break in the EGR tube, which of course means some of the air sucked into the EGR is fresh air.
I have had problems with getting a code p0171 from the day I got this car running. I did not break the EGR tube, it looks like it was cut diagonally by a previous owner, he put in a smaller tube I guess trying to remedy the problem. Some fix, yeah?

Anyways one has to ask - if it was just as well to have fresh air going into the EGR, why would they exist at all? Some engines have a different type of "EGR" like the 4.0 on some jeeps (CCV I think it is called) but for engines designed to run with EGR, shouldn't it HAVE E.G. running? I imagine the engineers who designed the PCMs and engines probably know a lot more about the systems than any of us ever will.

Oh also for the OP - if someone did this mod, what about plugging the Cat outlet so exhaust gases are not produced under the hood and escaping into the cab? I know there is the Cabin filter but those things seem to get dirty and clogged in no time. When I replaced mine, I can't tell you how dirty it was.
 
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