i have a 96 maxima and i just put in a warpspeed y pipe, magnaflow hi flow cat, and pacesetter monza cat back. it was put in when i had a little under half tank and its now at the next mark down ( not quite a quarter but a little less) and ive only driven like 110 miles. i dont drive aggressively at all really. im wondering if i have a problem or bad o2 sensor and something. i just want to know if i could replace anything to get my mpg up.

 

Go to Oilstop and have codes checked. if the CEL is not on, then you may have a knock sensor, thats about the only thing that could throw timing without a CEL on.

 

Perhaps the loss in low end torque resulting from lower back-pressure has caused you to use more fuel.

 

110 or 120 miles for a quarter tank seems normal. Did you get better mileage before the exhaust?

 

110-120 for a 1/4 tank is more than i get...theoretically you should be getting 440-480 a tank which is amazing

 

Seems normal for the first half tank or so, I usually get about 330 to a full tank and thats filling up before the light comes on. I was under the impression that putting a "high flow" exhaust system on a car should increase mileage but from my experience I usually get a little less because I drive it harder to hear my investment.

 

My gas mileage increased as long as I wasn't flooring it every time I drove it with the new mods.

 

Drive the full tank, refill, then keep track of your mileage. Do this a couple of times. Then report back. Until then, your theories are well......just theories...

 

hunh???? i wish i got 110 to 120 mpg to a 1/4 tank!!! im lucky to get like 65 to 75 per quarter tank. i have the exact same setup as you dude and your not gettin any better than that. knock sensor is a ghost code and does retard the timing so get a scan and see if thats an issue, otherwise thats not bad at all.

 

How much would a bad knock sensor affect mileage? When I got my max I ran the codes and it came back with downstream 02 as well as the knock sensor, I've still yet to replace either because after clearing the codes they still have not come back on after 2K plus miles and I'm getting on average 23.5 MPG every time I fill up (around 340 to a tank "without the light coming on") is this about average or on the low side?

 

Maybe you can manage to type smaller next time.

but thats about the average...if you have a Code fix it...fill up...do math then report back

 

fix the knock sensor!

what grade of gas do you use?

 

Dude, 110 miles / 4 gallons = 27.5 mpg.

EPA estimates is 27 hwy/ 21 city.

What are u complaining about? U arent drivin a civic so dont expect civic gas numbers

 

Very low back pressure will reduce MPG, however it doesnt sound like your at that point yet. Ther lower half of my tank seems to disapear faster than the first half, fuel sender arc and tapered tank probably, so judging by 1/4 tank is not accurate.

 

Answering your question by what's in the thread title, no you should not expect measurable improvement by changing the exhaust.

Based on your description of watching the gas gauge, you need to know this is not an adequate way to look for improvements in fuel economy. You need to record fuel consumption at the gas pump and mileage traveled for a few consecutive tanks. Total miles / total gallons = mpg. You need to do this both before and after the modification to really know if the changes made any difference.

Dave

 

I have a similar setup and did two fillups and came up with 420+ , i think that mine is very ok then, still i wish it could get better.

 

420+ for 2 tank fulls? or just one tank?? and what is your exhaust set up?

 

hell yea i wanna know what your set up is at this point.