MontieShaw

Hey everyone, im curious if you can help me out. I just installed pypes high flow cats and pypes off road H pipe on my car and now my average mpg is around 40 when driving. That cant be right. I already had pypes violators on my car and it never did this before. There are only two seals that leak and its at the front (towards the engine) of both cats. Nothing else leaks. How are MPGs calculated?Could it be an O2 sensor went bad, or could the 2 leaks i have right before the cats be causing this?

dawson1112

Not 100% certain, but I think they use a wideband 02 to calculate fuel economy.


If the leak in the exhaust is before the upstream 02 sensors there is a good chance that is causing it. Im surprised your not throwing a lean code.

outceltj

So u don't know how to hand calculate your mpg?????

MontieShaw

It actually threw a code after driving about 5 miles after swapping my downstream O2 sensors from before the cats (I drove about 100 miles with no code while was waiting until my O2 sensor extentions to come in) to behind the cats. I unplugged the battery and cleared the code because I thought maybe swapping the holes caused it. Ive driven 30 miles since clearing it and it hasnt come back yet.

MontieShaw

Are you talking about going to a gas station, filling up, drive and then come back and see how much gas you need to fill it up again?

LilRoush

Yes, you need to measure the amount of gas you actually burn and divide it by the miles you drove to burn it. That is the ONLY way to measure MPG. Also, make sure your miles are reading correctly. Over/undersize tires and aftermarket (uncorrected) gears will mess that up.

outceltj

Yes computers will vary by a lot or sometimes minimal