Allright so around the time i put my headers on about 2 months ago my gas milage has dropped from a horrible 20-21 to now an even worse 17mpg. The thing is i drive about 50 miles a day to and from work and 80% of that is highway going 60-70mph. what is going on here? i realize that my car is probably running rich because of the headers but will tuning it regain back my gas mileage? there are no dyno's around my area so i was thinking about buying a wideband o2 and a SAFC2 to tune with. i really dont want to drop 500 bucks on that but if it makes my gas mileage increase it might be worth it. I have recently changed out plugs, cleaned my air filter and im lost as to why its so bad and at $3.50 a gallon my wallet is taking a beating.

Also if i buy the wideband o2 ill have to bung in the sensor but should i also bung in the 2 extra o2 sensors while im at it that are taken out when the hotshots are put on? i have never came to a conclusion as to whether they are important to have in. Some say it affects gas milage while others say it just checks to see if the precats are still working. i still have my simulator btw which i never installed.

Well as of now it looks like im going to be selling my 19's to pay for some tuning equipment unless someone has better ideas.

Thanks for any help.

-Nathan

 

you can tune with the safc but i never heard of anyone getting it to stick at partial throttle settings. the settings will only stick at wide open throttle which you are not most of the time. if you are, then thats the gas mileage problem.
the secondary sensors are only for monitoring the precats and serve no function for a/f. a/f is determined by the 2 primary o2 sensors & maf at partial throttle and solely by the maf at wot.
i would considering driving a good distance to discover your a/f at a dyno as opposed to just buying parts and hoping thats the issue. my old 2k1 ae had also perfect a/f with the mods i had until i went with headers. it went extremely rich at WOT which is why i picked up a VAFC2 and leaned it out. even when it was running rich at WOT, the gas mileage was about the same, maybe a less but nothing significant.

 

I don't know about the 5.5 gen, but my 3rd gen actually increased mpg with the mods I have. It also has a newer o2 sensor and a newer knock sensor.

I consistently get 28-30 mpg on long freeway trips at ~75 mph. The factory rating was 21-26 (the new ratings are 18-24!). I did over 28 mpg even with 17 inch wheels and it's the same with the 16s I have in my sig.

mods are: Y-pipe, cat-back, UDP, intake, fidanza and ACT clutch.

 

well i just used half a tank and filled up and got 20 mpg. i cleaned my air filter and changed from a CAI to just the filter right before the MAF. I should also mention that about 3 weeks ago my MAF sensor crapped out on me for the second time. maybe that was causing my crappy gas mileage. do they slowly get bad over time and then just stop all of a sudden?

i didnt realize that a safc2 only works at WOT. since im really not WOT a lot i guess that would be pointless. i guess if my mileage stays at 20 ill just blame the MAF sensor. I also need to probably disconnect my batter and let everything reset since i put the new MAF sensor on correct?

Thanks for the help guys. Im going to go home after work and get my simulator installed to get rid of my SES.