as the title says my mpgs are all over the place after my lt and ory install. I also replaced the plugs but not wires they looked good. Any ideas as to why my mpg's have gone down like 40 miles for a half tank roughly, and like 60 when the light pops on?

 

Most likely running rich... did you get a tune?

 

wow i couldnt get 60 miles to a tank if i tried to!

 

....He's saying that he's 40-60 miles OFF his normal mileage by half a tank. So if he got 200 miles by half a tank....now he's only getting 140-160 miles.

 

no i didnt get a tune. nowhere around central illinois and didnt really think it was necessary because its not messing with anything internal or changing anything besides deleting the rear o2's

 

You changed from stock manifolds to long tube headers. A tune would do a whole lot of good. Plus, if you just pulled the rear O2s, you didn't delete them...that has to be done in the ECU.

 

Can you don this with say hp tuners, without having a shop fully tune it for the fact it is my DD? The closest reputable tuning shop is atleast 4 hours away. Kinda new to all this, didnt know if there was anyway of doing this without a tune or a tuneing shop.

 

Have you checked for exhaust leaks? Air getting into the system will throw off your o2's and cause the car to run rich. Also like was already said you gotta tune out or get simulators for the rear o2's. What part of central IL are you from?

 

about right in the middle between Peoria, and Springfield. Any ideas where i could get a set of o2 sims???

also will a leak after the o2's cause them to be thrown off? I havent welded it yet just got some clamps on it. Im going to weld it maybe this weekend.

 

Leaks upstream of the front O2s are the most likely to cause problems, but a leak immediately downstream can also be a problem. Installing headers, even with no leaks, should cause it to run rich, and yes you gas mileage will suffer unless and until you get a tune.

 

and in saying tune you mean A) deleting the rear O2's B) adjusting the a/f ratio, or what???

 

By tune I mean adjusting the a/f ratio and whatever other changes the tuner makes to get the engine running parameters correct. The only purpose for A, turning off the rear O2s is to avoid the catalytic converter effeciency error/check engine light that otherwise sets.

 

tuning is completely new to me. would you have to go to a professional tuner or just somebody that knew they were doing with the right program?

 

There are at least three options. One, of course, is professional tuner which usually costs $300-$500 for thorough tune. Most tuners will make adjustments to the original tuner for some time period at little or no charge for additional modifications.

Another option is the mail order tune from folks like Frost, Wait4Me, or Texas Speed (I think). With a mail order tune you either send them your ECM or in the case of Wait4Me they can supply a spare ECM to reduce downtime. Mail order tunes are not as good as the hands on tune, particularly if you have a lot of modifications. On the other hand, if you only few mods the mail order tunes can be acceptable.

Finally, you can get some software such EFI live or HP tuners and learn to do it yourself. I think you have do buy a license for each VIN number you tune in addition to the cost of the software. There is also the risk that you will damage you car if you mis tune it while learning.

 

Ok you've been a tremendous help! last question and sorry if i sound stupid what so ever. Only mods to this date are headers with ory, free ram air, k and n filter. So, basically just headers and ory that really would cause problems. In your opinoin would a mail order tune suffice for my circumstances?

 

Based on my own personal experience I would say yes. I got a mail order tune on my LS6 when I got some Random Tech high-flow cats with no other mods from Wait4Me. Cost was $160 (a couple years ago), which included a spare ECM. I made about 30hp more than stock and picked 2 miles per gallon.

(I went to a professional tuner later as I did heads/cam/intake).

 

Every car Ive seen on the dyno that had headers just put on was way rich, had to be leaned back out.

 

TunedByFrost.com

 

yeah after my header install i immieditally got it tuned by frost so i really didnt drive it inbetween then but usually after a header install its a good idea to replace the o2's. When i started driving my car again i noticed the same thing u are bad MPG, and about a few months ago i finally got around to getting new 02 sensers and its back to normal

 

did you still notice bad mpg's after your tune until you changed your o2's?