07 Test Pipes CEL, Non foulers don't work: FIX? (Read)
If you are getting that bad of gas milage, it strongly suggests you have an exhaust leak at the header/test pipe interface.
Air is drawn in through the leak during the scavenge phase of the exhaust pulse. Normal reversion pushes some of the air back toward, and in contact with, your O2 sensor.
The sensor detects excessive oxygen and is fooled into thinking your engine is running lean.
The ECU adds more gas to bring your A/F ratio back into nominal range but your engine was running right the first time. Now you are running excessively rich even though the ECU believes it is nominal.
That is why your MPG is taking a hit.
Find the leak, fix it and your MPG will go back up again.
Air is drawn in through the leak during the scavenge phase of the exhaust pulse. Normal reversion pushes some of the air back toward, and in contact with, your O2 sensor.
The sensor detects excessive oxygen and is fooled into thinking your engine is running lean.
The ECU adds more gas to bring your A/F ratio back into nominal range but your engine was running right the first time. Now you are running excessively rich even though the ECU believes it is nominal.
That is why your MPG is taking a hit.
Find the leak, fix it and your MPG will go back up again.
I'd love to put on some resonated test pipes or HFC.
Originally Posted by Hydrazine
Are you running stock cats?
Just starting to get the mod bug... again.
Originally Posted by Hydrazine
If you are getting that bad of gas milage, it strongly suggests you have an exhaust leak at the header/test pipe interface.
Air is drawn in through the leak during the scavenge phase of the exhaust pulse. Normal reversion pushes some of the air back toward, and in contact with, your O2 sensor.
The sensor detects excessive oxygen and is fooled into thinking your engine is running lean.
The ECU adds more gas to bring your A/F ratio back into nominal range but your engine was running right the first time. Now you are running excessively rich even though the ECU believes it is nominal.
That is why your MPG is taking a hit.
Find the leak, fix it and your MPG will go back up again.
Air is drawn in through the leak during the scavenge phase of the exhaust pulse. Normal reversion pushes some of the air back toward, and in contact with, your O2 sensor.
The sensor detects excessive oxygen and is fooled into thinking your engine is running lean.
The ECU adds more gas to bring your A/F ratio back into nominal range but your engine was running right the first time. Now you are running excessively rich even though the ECU believes it is nominal.
That is why your MPG is taking a hit.
Find the leak, fix it and your MPG will go back up again.
Originally Posted by jammin
Would you be able to hear an exhaust leak at that area? I've noticed I've been getting some bad gas mileage myself, around 15mpg. I know I have a minor leak, not too sure where, but it isn't very audible either. I thought maybe it is that minor leak causing it. Or maybe do I need a tune because I have the mrev2, 5/16 spacer, stillen airbox, berk hfc, and nismo catback. Would the HFC and mrev2/spacer be the ones causing my bad gas mileage?
But seeing that you have HFC's installed, that greatly increases the likelyhood of having a leak at the header (or exhaust manifold) interface.
That can decrease your milage.
Focus your leak search at the manifold interface. If you believe it is there but you can't find it fix it anyways. Take measures to create a positive seal.
Don't use cheap gaskets at that interface. Stock gaskets are the best.
3 sets were sent out for testing but I still havn't heard back from them yet.
One person had an air leak CEL the whole time.
Another hasn't replied back yet.
The other is supposed to be installing them this weekend at MRC.
One person had an air leak CEL the whole time.
Another hasn't replied back yet.
The other is supposed to be installing them this weekend at MRC.
I do, or should say did. I have the AAM TP unresonated with J bend tube sensor bungs, and light popped up after 25 or so miles. I had a vibration/resonating issue so bad, I removed my TPs and put the cats back on. Off topic, but I added a brace to the cats for reinforcement and the stock damper/isolators to my TurboXS exhaust and still had a crazy resonating ring. The pipes literally moved an inch when it hit the magic RPM. No contact with anything, all tight hardware, the largest I could utilize, all new gaskets. I should of gotten resonated pipes, I guess. If the CEL can be fixed, I would find a way to isolate the vibration and reinstall the pipes. Sorry for long off topic post, it just stinks to by a part for your car and have it sit in the garage...
i'm having this issue now... i just remember that I scraped under carriage when i went through the touchless carwash about 5days ago and damaged my veilside cf lip and I guess I also messed up something else 
I may be leaking air, I'll check tomorrow...
I may be leaking air, I'll check tomorrow...
