Horrible gas mileage after O/R X pipe

[jas142]

Its REALLY horrible, prolly 13 mpg or so. Anyone else have this happen? Will it balance out when the car gets used to it?

 

[Pootiestang]

Its REALLY horrible, prolly 13 mpg or so. Anyone else have this happen? Will it balance out when the car gets used to it?

I blame your right foot.

 

[rob1]

Mine seemed to get worse as well. I installed Magnaflow o/r X and American Thuners. It definitely dropped some but I also tend to rev it a little more in town for sound purposes

 

[LordJish]

Where do you drive mostly? I drive almost entirely in town and I never got more than 160 to a tank before my x-pipe. You might just be paying more attention now than before. I've heard people saying the same thing before though...like 20-30 miles less on a tank.

 

['96&'01Stang]

Probably running really rich now

 

[jas142]

It is running VERY rich. How can I fix this?

 

[ZeroOneStangGT]

This brings up a good point... Ill bet our cars are running really rich. I can really smell it behing the car, but Im sure the lack of cats causes a bit of the smell.... Is it really running rich, and is the only way to lean it our with a chip tune?

 

[ExtremeZ]

Listening

i get horrible mileage now w/ my catback an o/r. i mean like about 120-130 miles to the tank. is there a way to make it better? it sucks, especially with gas prices lately.

 

[DBMSTNG]

get a tune. problem solved.

 

[97f1fiddy]

i got the same problem on my 4.6 truck. I had dual flowmasters with no crossover and got pretty good mileage about 14.5 city. Then switched to a single magnaflow dual in/out with built in X pipe and now i barely get 12.5mpg city. Needless to say the muffler is coming out my flows are going back in.

 

[cjist1]

Thats weird. I still get really great mileage with my o/r pipe. It still smells behind the car when I get on it, but I think that it is just from the lack of cats.

 

[gnat]

wow, I have a cat'd xpipe but I still get 190-200mpt approx 15mpg

 

[2000GT]

My car was running lean after my Bassani X pipe was installed. Is your check engine light on?

I had my a/f corrected with a tune. Perhaps my car would have adjusted for the x pipe over time and leaned up the mixture a bit, but I wanted to be sure.

 

[COBRA90GT]

I blame your right foot.

Ditto. New exhaust systems always make people mash the go-pedal more often heh. There goes the MPG, trust me.

Also, if you reset the battery during the midpipe swap (like you're supposed to), it may take several driving cycles for your computer (PCM) to completely re-learn/adjust, so your MPG might be a little wacky for a few days.

 

[LordJish]

When I had my mil eliminators installed, the guy at the exhaust shop just plugged this device into my car somewhere and turned off the light, he did not undo the battery and re-connect. Should I go ahead and do that?/

JM

 

[jas142]

I never reset the computer. What do you do exactly? Will this fix it? Details please

 

[97f1fiddy]

to reset the computer. Disconnect the negative terminal of the battery, turn on the headlights for 10 minutes to drain any leftover power. Turn off headlights, reconnect battery and start car. Let it idle for abit then go for a drive.

 

[4.6 Rocket]

You are probably running rich but with mix freeway and street, 50/50, on average I get 260-285 to the tank and thats after the off road x pipe. Most of the time its your right foot so be careful. Around town I use 5th alot so maybe that helps.