QuestionHey, thanks for your help. What do you think would be the best way to solve it? Also, do you know of any O2 sensors that would work ok without the added heat from the cats?
I appreciate your help greatly, most people seem to blow me off as "the little more power you get from the open exhaust eats up gas mileage," but i simply won’t take that answer as i have talked to a few people running the same setup and without losing the gas mileage. Thanks again.
Marc D
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Followup To
Question -
Hello there, i have a 1995 Mustang GT that is stock aside from a Tremec 3650 transmission and a Pypes 'Beast' exhaust (uncatted x-pipe, mufflers, 2.5" tubing all the way back). My question is since I installed the exhaust i have experienced a dramatic decrease in gas mileage, from about 210 miles per tank before install to about 160 miles per tank after the install.
I have checked the oxygen sensors and they are taking readings (I haven’t changed them since I purchased the car 6 years ago and will probably change them anyway as I heard they were recommended they be replace every 30k miles). I did notice that the reading would constantly shift from 63mV to 750mV, would this indicate they were going bad? What i have theorizing that one of them was giving the computer a reading that was off a little bit and causing the ecu to overcompensate.
I have talked to a person I work with that is very familiar with Mustangs (especially Fox bodies) he suggested getting another ecu (he went on to say that the 94/95 ecu’s were a bit flaky and had some problems with them). He also said that it might be wise to install a fuel pressure regulator. I have talked to a few guys running the same exhaust system as myself and a stock car otherwise and didn’t loose the gas mileage as I did. Have you ever seen or heard of the problems I am having? Do you have any suggestions? Thanks for your time.
Marc D.
Answer -
Marc-
I'm guessing that it is the O2 sensors...but not in the way you're thinking. The stock sensors depend on reaching a certain temperature to operate correctly and they use the cats in a small way to reach said temperature. Without the cats the O2 sensors might not heat up properly. I doubt it's the ECU. They do go bad sometimes, but it's pretty rare and since the problem popped up only after the exhaust install I'd say that's a prett good indicator. Hope this helps.
Steve
AnswerMarc-
Man...I know there are fixes out there, but I can't think of specifics at the moment. You might look around Bosch's site and see what they have to offer. You could always try welding the current O2 sensor bungs shut and moving them forward. I'd also take a look at Dallas Mustang's site. They make MIL Eliminators to get rid of the check engine light caused when O2 sensors get screwed up by long tube headers. Hell...they may even work for your problem (I never really got into how they worked). Trust me...anyone who blows you off by saying it's normal to lose mileage because of a simple exhaust swap might as well just tell you they don't know. Hope this helps.
Steve
