Gas milage after mods

[Theo]

After installing the STI up-pipe and the turboxs exhaust my gas milage is way down. I'm getting less that 20 mpg. I was getting 23 - 27 before teh mods. I commute and keep close track of my mileage. I can usualy tell when I need an air filter.

I was expecting to get better milage.

Any ideas?

Theo

BTW - Scott, do they have a spel cheker for this form software?

[dknv]

How can you tell (time to replace air filter)?

[Theo]

My gas mileage would go down . The first time it happened was after driveing some miles on dirt. I noticed the next week that the mileage was down. The air cleaner brought the mileage right back up.

I changed the filter last about 1000 miles ago...

Theo

[ZER026D]

Cause you are now running hoter then stock so the car is using more fuel to cool the EGT's down I think. I might be wrong but this what I think if not maybe now that you like the way you car sounds so you are pushing the gas more.

[STIwish]

I'm with the second reason... just gotta put ur foot in it more with the new sound

[Theo]

After very carfully weighing my right and left feet I have determined that my right foot is 2 lbs heavier than my left. It seems to be causing excessive gas consumption.

Theo

[ArthurS]

Originally Posted by Theo

After very carfully weighing my right and left feet I have determined that my right foot is 2 lbs heavier than my left. It seems to be causing excessive gas consumption.

Theo

[ZER026D]

[STIwish]

[sperry]

Originally Posted by ZER026D

Cause you are now running hoter then stock so the car is using more fuel to cool the EGT's down I think. I might be wrong but this what I think if not maybe now that you like the way you car sounds so you are pushing the gas more.

Actually, freer flowing exhaust runs cooler. Those cat's in the stock exhaust heat everything up a ton. A common CEL from turbo-back exhaust is the "inefficent cat" warning. Basically the EGTs are too low, so the computer assumes the cat's aren't doing their jobs and it throws a CEL. I get one if I jump on the throttle hard while the car's still cold and my single cat isn't up to operating temperature.

My guess for the reason your fuel mileage goes down (mine's low too these days, around 19mpg) is simply due to the higher flow. You run the car up to higher revs a lot easier now, and more revs and more flow means the injectors are open longer. But that's just my guess. Basically it boils down to what Evan's staying... it's easier to stop on it now, so you do. I know I have to really try to drive conservativly, or I'm constantly bombing around at 1bar of boost with the exhaust roaring.

Oh, and afaik, there's no spell checker module for this board. I'm currently writing my own, so I'll check into how hard it'd be to add spell check.

[Theo]

I would agree, it is running cooler.

I noticed an additional change in the character of the motor. It has more engine braking when going down hill. A hill I drive down every day in 2nd gear used to rev right to 5000 rpm. The same hill now only rev's to 4000 rpm. It feels like the motor has more compression.

Theo
[/quote]

[sperry]

Originally Posted by Theo

I would agree, it is running cooler.

I noticed an additional change in the character of the motor. It has more engine braking when going down hill. A hill I drive down every day in 2nd gear used to rev right to 5000 rpm. The same hill now only rev's to 4000 rpm. It feels like the motor has more compression.

Theo

That's wierd, I'd expect the opposite... engine braking results from the wheels having to push the motor, and the exhaust stroke (pistons pushing the exhaust gasses out) would be less restrictive, meaning less engine braking...

but again, I'm only guessing...

[MattR]

Yeah, in theory that should be the way it works, Scott. When I had my jeep,. it had awesome backpressure and engine braking in stock trim, when I put on a cat back, the backpressure sucked, I lost almost all the engine braking. Then, coincidentally, a rock solved my problem by pinching my tailpipe into a smaller oval shape, hello backpressure...I left it that way

[Theo]

OK, Third tank of gas and I'm back up to 25 mpg. I checked and the right foot is, if anything, heavier. It feels like the ECU has tuned down the power from the mods and has recovered if not improved the fuel milage.

It's nice. I realy was worried I was going to be at 19 mpg after the mods.

Theo

[ZER026D]

I still get 300 miles per tankwith like half city driving.