exhaust in relation to mpg

[woa_its_j3ff]

I just recently installed a new exhaust on the 'lara, after that I noticed that my gas went down dramatically faster. I filled up on Saturday and by today, it's already near half tank. I use premium fuel. I don't floor the car, except on the ramp sometimes to hit the highway, but other than that it's just regular acceleration for me. Before when I had my stock exhaust, I wouldnt need to fill up the car for about 1.5 weeks. My car is usually driven locally with a range no more than 75 miles a week (work +school). I asked my friend about this he said "it's because you car is producing more power so it's eating more gas" (??) I'm not sure what the real reason is behind all this, just hoping you guys can help me out.

[DaTwUnKrAziEpInOy]

what exhaust do you have ?? I'm going through the same thing with my JIC exhaust but then again when you add performance parts your car will consume more gas. Obviously when you make more HP you need fuel to produce more HP. That's my .02

[SleeperSolara]

Hey Jeff, since you added an exhaust on your car.
Your car will get rid of more shite that is burnt faster, so it will take in more air and fuel.
Your aftermarket/custom exhaust is more free flowin' than your stock one.

[woa_its_j3ff]

^ ah. i mean i can feel a SLIGHT gain in power. but would it really mess with the gas that much? because before with stock. in a day the gas hardly goes down, but then since i put on the exhaust, it goes down half a line in just one day. .. and my car now engine/performance wise is nearly stock, just the K&N air filter. ..

[Sentinel]

1st: You need to compute your actual MPG. Otherwise you're just guessing. Are you sure you're not driving more/faster because of the new exhaust?

2: Sure, the car makes more power by using more gas; however, the power required to accellerate and cruise does not change. It is possible to make more power AND increase MPG, if you are using the fuel more efficiently. No telling what your setup will do, tho.

3: (most important) Some headers (hey: what exhaust didja install, anyway?!?) have "fake" o2 sensors and other trickery to fool the computer into thinking there is a stock exhaust on the car. This can cause efficiency problems, as the o2 sensor can be used to adjust the fuel:air ratio.
In addition to that, the headers are going to change the engines operating dynamics, and the computer takes a certain amount of time to reset itself to the new situation.

Tell us more about the exhaust!

[indiglosolara]

You still haven't answered the question in regards to what kind of exhaust it is....

The design of a exhaust can change MPG based on design and how it will make you engine perform. Piping size bends and flow of the muffler can change that even if you didn't change your driving habits...

So first let us know what kind of exhaust you got. If you got one of those ebay exhaust then sorry to say you should remove it as they are worthless and do nothing..

Not to be harsh, but when you start doing mods to your car you should be expecting little changes such as MPG or even noise levels and don't expect your car to perform like stock...

Kenny

[SleeperSolara]

^ ah. i mean i can feel a SLIGHT gain in power. but would it really mess with the gas that much? because before with stock. in a day the gas hardly goes down, but then since i put on the exhaust, it goes down half a line in just one day. .. and my car now engine/performance wise is nearly stock, just the K&N air filter. ..

No matter what you do mod wise, you mpg will drop alittle cause you lettin' the car breath and exhale better.

[woa_its_j3ff]

Exhaust is skunk 2 with custom piping.

[jhenty]

exhaust, intake, those kind of things should in theory IMPROVE gas milage, but being in the times we are with the computers and sensors being so precise this is not always the case. Reset the comp for one by unplugging the battery for a little, and see if you have any change. I really dont think your milage should be going down, these things should improve gas milage by making the car run more effiecently. I mean if someone heres an engineer and can correct me in this case, many performance mods can increase gas milage in normal driving.

[solow1605]

bwahaha when I floor it with the blower and all that business i can WATCH my gas guage go down. Don't worry buddy comes with the territory

[WSkids97]

Hey Jeff, since you added an exhaust on your car.
Your car will get rid of more shite that is burnt faster, so it will take in more air and fuel.
Your aftermarket/custom exhaust is more free flowin' than your stock one.

100% accurate. When dealing with exhaust systems the more emissions or exhaust removed from the combustion chamber during the forth stroke of the engine the more acceptable the combustion chamber is for allowing air and gasoline to enter during the first stroke.

[woa_its_j3ff]

oh alright thanks guys. i knew the gas would go down, just not that much. thanks for the information.

[indiglosolara]

Jeff,

What kind of piping did you get installed??? Pressure bend or mandrel bend..??

Resonators???

Skunk??? isn't this muffler made mostly for Honda;s?? I heard that brand onthe honda forums allot.. but rarely on a toyota...

[WSkids97]

Be sure to reset your computer by disconnecting the battery for at least 30 seconds other wise your ECU will not adjust the timing to the current conditions after the change and will not reach it's full potential. The ECU might be expecting more back preasure and providing to much fuel mixture. Be sure your O2 sensors are in good shape on both ends of the spectrum and you might want to replace just in case (take forever to die but why spend all your time guessing when you can eliminate the small things for 20 bux). All can help ensure your cars running at peak performance for you aftermarket changes. Remember, race day can happen at your next red light, don't let them catch you off gaurd.

[Fletch]

Toyota OEM O2 sensors are more like $70 bux each.