I have a quick question, has anyone had any ill effects to fuel mileage when they installed the EGR blockoff plates? I know this is a rather odd question due to the fact that fuel mileage is thrown to the wind when it comes to modifications.
The reason I am asking is because when I installed the EGR blockoff to my mothers 95 Talon she said she started to notice a decrease in fuel mileage.... I am trying to keep her car as fuel friendly as possible. I never even cared about mileage when I modified my NA, I dont think I could do anything to that car to get near the crappy mileage that my 91 gsx gets. Plus I did all of the mods to my NA all at the same time so it was rather hard to tell exactly what made a difference in mileage.
I am adding that, I have after, she told me about the decrease in mileage, replaced the plugs, o2 sensor, cleaned the air filter, and even sent the injectors off to be cleaned. So I have tried my best to diagnose any fuel mileage loss with no change in mileage.... MOM SAYS HELP!

EGR blockoff should actually increase the fuel mileage very slightly since the computer doesn't have to adjust for hot, dirty exhaust coming back into the intake.

My guess is that it's 2 unrelated items that happened around the same time. Try some really good fuel system cleaner, and/or do a seafoam combustion chamber cleaning to start with.

Another thing that's an inexpensive test is to have her fill up the next tank with higher grade fuel than she normally does. if the fuel economy jumps back up then the engine has carbon buildup in the cylinders that needs cleaning.

That was my thought also, I am a ASE master certified mechanic and currently own my own shop, the idea of the EGR is to reburn spent exhaust gasses for better smog controle as well as give a richer mixture because of the rich nature of a stock ECU, it will sence that and correct fuel trims. So with that in mind I also figured that if you take that semi rich exhaust out of the intake it will rely on a compleatly new fuel trim and run a slight bit leaner. As for the carbon build up, I can promise you that is not an issue, the motor doesnt even have 8k on it yet, as well as it has swirl polished stock size valves and the combustion chambers are smoothed and polished with new .020 10.5:1 pistons... no carbon there. And I have replaced the fuel filter and added 2 bottles of lucas fuel treatment to it since the issue occured.

I have not noticed any effect in my gas mileage.

The purpose of EGR is to recirculate exhaust gases back into the motor. By putting air back into the motor that has less oxygen in it (because it's already been burned once), there will be less fuel required. This also helps to keep combustion chamber temperatures below 2500°F to lower NOx emissions. Therefore theoretically you would loose a little gas mileage by removing it.

At least that's the way I understand it from what I have read. :shrug

Originally posted by adamzty
I have not noticed any effect in my gas mileage. The purpose of EGR is to recirculate exhaust gases back into the motor. By putting air back into the motor that has less oxygen in it (because it's already been burned once), there will be less fuel required. This also helps to keep combustion chamber temperatures below 2500°F to lower NOx emissions. Therefore theoretically you would loose a little gas mileage by removing it. At least that's the way I understand it from what I have read. :shrug

you're close but completely wrong. Even though the "air" (actually hot nasty exhaust) being recirculated has very little oxygen, the ECU overcompensates for the high temperature and runs MORE fuel to prevent detonation.

have you ever studied older rotary engines? They have a nasty habit of sucking hot exhaust back into the intake cycle during low rpms because of port overlap and the ECU compensates by running obnoxiously rich. those engines actually get better fuel mileage at mid rpms because the overlap is negated by the exhaust velocity.

Long story short, the ECU compensates for the heat first, not the oxygen content.