Hi guys, it seems that I lost gas mileage after I installed Longtubes and ory in my car (I haven't got a basic tune yet but I will end of Dec). Its been almost 2 weeks now since the install. On a full tank I usually get around 250-270 but this time I got only 200 miles on the tank. I don't think I drove it hard enough to be losing that much gas. I've been keeping and eye out on the gas and already in 2 days driving 30miles it seems that I've lost about 2 gallons.

I've done my search here and some say I will be losing mileage for the next few tanks of gas. Maybe because I haven't gotten a tune yet (but most done even get a tune after longtube install). I have no idea whats going on guys. Please help me out so I can solve this mystery asap.

NOTE: I have Flowtech LT's with 3" ory with no cats with 3" ipipe to muffler.

 

Double check to make sure there are no leaks and no unmetered air is entering the engine. When you say tune, who is doing what?

Sometimes, O2 sensors become lazy after header installs. Part throttle fueling can then be affected by LTFT's over compensating and creating a rich condition. This is why I believe the "headers make you run rich" state of mind exists. That's part of the reason why I ask who is tuning the car and how. If someone just goes in and turns a bunch of codes off, changing fan settings, etc., then the issue won't be resolved. If they're going in and actually dialing in the AFR with a WBO2, it should get better. I get 24~25mpg out of my H/C M6 (when I behave). For you to only get 20mpg seems like your fueling and maybe your O2 sensors are off.

 

I've checked and there are no leaks, I'm sure I would notice by sound if there was a leak correct? Also I will be getting the tune from NickN in Hayward California. Most of the people from norcal-ls1.com gets it from him which with reputation does a great job. I really dont know what is done to a tune besides deleting codes and making the car not run rich anymore.

If there is anything else you remember what I can do to fix this problem please help. Thanks for the quick response man.

 

If you find a solution let us know, my gas mileage went to hell as well when I installed my LT's and catback. The car seems to run very well but I don't think that I'm even getting 15 miles per gallon now.

 

How are you going to get away with LTs in CA?

 

Yea i only get around 200 to a tank no matter how i drive it. I only have lid and mac mids and a cat back.

 

Have you guys got a basic tune yet? I'm hoping that the tune will get my miles per gallon back up to normal. Lets all work together and find a solution.

 

Don't quote me on this, but your mileage will probably improve after the computer compensates for the adjustments you've made to your car.

Mine did the same thing, a drop in mileage after the installation and then about 2-3 weeks after, everything was back to normal if not slightly better. Give it some time.

 

2 words, "know someone"

 

Sorry but I had to quote you on this one but to not disagree with you. I was also told that my comp in time will learn the the new change. So I'm hoping it'll do that but I will be getting a tune in a few weeks anyways.

 

Exhaust leaks you would hear. Intake leaks you probably won't hear. They're usually accompanied by higher RPMs at idle though - unless they are within the range of the IAC's ability to compensate. As for basic tunes, I've seen a few and each time nothing was done about the fueling or timing. It's always been turn off codes, set rev limiter, adjust fans, etc. If you go to get your car "tuned" by someone and they're not hooking up a wideband O2 sensor in your car, turn around and leave 'cuz they're about to rip you off. Just my $0.02.

 

Thanks, I will make sure the tune will get more then that. As for the leak in the intake, I dont think we touched that when we did the LT install. But I just emailed the guy thats doing my tune and asked him what it will consist of. Thanks bro!

 

Don't the cops there like pull you over and do full under the hood inspections, with a smog test?

 

when you "know someone" you do not actually take your car to a smog shop...

and with the cops popping your hood, it'd be fairly hard to tell that they're longtubes and not just mids or shorties

 

Yes, but I thought cops had the ability to smog test your car on the side of the road?