GT40P HEAD SWAP HELP PLEASE
- Thread starter 90stangLX302
- Start date
Michael Yount
Mustang Master
The P's don't have the openings for that air injection unless they've been drilled, I believe. If you don't have emissions issues, take the pump and plumbing off. The P's will also deprive your intake manifold of exhaust for the egr.
Michael Yount
Mustang Master
Properly functioning egr won't hurt your w.o.t. performance - the computer closes the egr when it senses w.o.t. However, not having it may impact part throttle drivability and fuel mileage. The egr system injects a bit of exhaust into the intake during part throttle conditions to cool the combustion chamber. This reduces NOx emissions and allows the computer to add more timing resulting in better mileage. When the computer tries to add timing, but no exhaust is present to cool the chamber, some people experience a bit of pinging or detonation requiring them to pull their timing back a bit - which does impact performance. There's no way to tell what's gonna happen with an individual car until you try it.
Michael Yount
Mustang Master
The egr exhaust gasses are now replaced with standard atmospheric gasses. I did notice an increase in pinging. This was tuned out (quenched) with an AFPR. Bit faster...not seat of the pants...but noticeable. I also ran a short belt...so it's hard to tell which variable had the greatest signifficance. But they are accumulative.
i also have p heads which are not drilled for smog and i pulled off the smog pump and pluming, i really did not notice a diffrence. i bought my car with the heads already on it. do you know the cc on combustion chamber. i am trying to figure out if there are two diffrent sizes90stangLX302 said:
I was talking to a Ford mechanic, and he said that removing the thermactor may affect the O2 sensor readings because it is depriving them of the carbon dioxide. It works by injecting fresh air into the exhaust ports, when it is mixed with hot exhaust gases, oxidation is increased reducing the concentration ofhyrodcarbons and carbon monoxide converting them into hramless carbondioxide and water vapor
Michael Yount
Mustang Master
As mentioned before, the egr valve is closed at w.o.t. - so there's no performance benefit to removing it or having it be non-functional; however, if you have to retard timing to stop the pinging, that can hurt performance. So, there may be a benefit to having the egr hooked up unless you turn off the egr function in the computer with a chip.
The air injection works as your mechanic friend described - excess oxygen is required for additional oxidation to occur after combustion has occurred in the chamber. The chemical reactions that the cats speed up need excess oxygen to occur. The O2 sensors will still, however, read the exhaust stream, and when you're in closed loop, they'll help the computer adjust the amount of fuel injected. At w.o.t., the engine goes back into open loop, and it ignores the O2 sensor readings anyway - the so the lack of excess air being injected is a non-issue performance-wise. One of the most common 'mods' out there is either removing or bypassing the air pump - and folks hardly ever report any drivability or check engine light issues. The computer will throw a diagnostic code into memory related to the malfunctioning components - thermactors - but it doesn't seem to harm anything. Unless, of course, you have an emissions test to pass.
The air injection works as your mechanic friend described - excess oxygen is required for additional oxidation to occur after combustion has occurred in the chamber. The chemical reactions that the cats speed up need excess oxygen to occur. The O2 sensors will still, however, read the exhaust stream, and when you're in closed loop, they'll help the computer adjust the amount of fuel injected. At w.o.t., the engine goes back into open loop, and it ignores the O2 sensor readings anyway - the so the lack of excess air being injected is a non-issue performance-wise. One of the most common 'mods' out there is either removing or bypassing the air pump - and folks hardly ever report any drivability or check engine light issues. The computer will throw a diagnostic code into memory related to the malfunctioning components - thermactors - but it doesn't seem to harm anything. Unless, of course, you have an emissions test to pass.
I have P heads with the smog pump removed. I have no pinging/detonation problems at all and this is with 17 degrees of timming (after it was tuned of course). I am usually between 42-45psi with my fuel pressure depending on conditions. If I remember correctly I usually get about 16 miles to the gallon and that would be a mix of highway and city driving.
Good luck with your combo!
Ken
Good luck with your combo!
Ken
