Cosmo459sx

iTrader: (3)

Since I've added my budget y-pipe I've dropped my average mpg from around 22 to 19. My driving habits haven't changed. This doesn't seem to fall in line with any other intake/ exhaust mod I've ever done on a car, or for that matter, any one else has either. Any thoughts? Also, with y-pipe and cat, is it really worth doing b-pipe and muffler? Looking for input from those that have tried. Thanks..

99se5speed

iTrader: (8)

Wow...i'm totally in the same situation! I really hope you guys can enlighten us!!!

Cosmo459sx

iTrader: (3)

At first I thought it was just driving a little more spirited since getting it. But after a few months and tanks of gas where I didn't romp on gas once, I could confirm with my fillup amt. vs distance. Wierd. Maybe the ecu hasn't properly adjusted. Then again, i also get the downstream code half the time because of my test pipe. The downstream theoretically shouldnt make a difference since it is only a backup sensor, but something makes me wonder

NYC32798

iTrader: (3)

I didn't really pay attention to my before and after gas milage with the y-pipe. I get pretty crappy gas milage but that's cause I have a heavy foot. When I drove from NY to FL on i-95 with the cruise control set, I made close to 475 miles per tank driving straight through only stopping for gas. Wonder what it would have been with the stock y-pipe. I get good highway milage but crappy city milage but that's cause I have a heavy foot.

Cdg2125

iTrader: (7)

I always read that gas mileage was supposed to increase with the pipe...this is not good to hear!

Fang_DH

iTrader: (5)

Yea now I'm a little nervous to be getting a y-pipe....

D-Bo

iTrader: (9)

I think that you have to expect trade offs...Performance vs Mileage

99grnmaxgxe

iTrader: (11)

Maybe a little leak? A free flowing exhaust should help mileage but....

Supermax95

iTrader: (2)

A less restrictive exhaust system should not give you worse gas mileage....that just doesn't make sense...unless ofcourse the ecu itself is not adjusting correctly.

aznsap

iTrader: (29)

hmm, were you careful not to touch or get anything on the 02 sensors when you installed the y pipe? do you have any leaks?

Fr33way™

iTrader: (23)

Like mentioned above, if you have a leak it could be messing with your 02 reading and thus creating your problem.

99se5speed

iTrader: (8)

Damn now idk if i want to put on the y-pipe and high flow cat i just got. I have a new o2 just in case something does happen to the stock ones. I'm going to the dealership today to pickup my order of all OEM gaskets so that i have no leaks because the crap the budget sends with the y-pipe is definitely not going onto my car!!!

I also wanted to know...can i rest my ecu after i install the pipe and cat? Will this help it get used to the setup so that the air/fuel ratio will improve? I was told the best way to reset the ecu is to take your battery terminals and smack them together a few times to reset the ecu (I'm very skeptical of this). Any info on this? Thanks.

nupe500

iTrader: (13)

something with your setup is OFF....I know that I get better mileage as well as response since putting on my warpspeed...but I also have a full cat back (Greddy SP1) but all in all...a mod that I love and would definitely recommend for anyone that wants to unlock the potential of the maxima

sdoherty_tjm

its cus your 02 sensor and ****...plus you do lose a little lowend "speed limit" range torque so you need to push the pedal more. yeah i usually get 19 but i romp on it a lot

devilz05

iTrader: (2)

As a general rule, more power=more gas consumption. Im sure that a more free flowing exhaust increases a lil gas mileage but the actual increase in power output is a larger sum. Also, keep in mind its the summer now and you are blasting your a/c and the car in general is choking to death with all the humidity. I would def expect a small drop in gas mileage with a y-pipe.

VQuick

iTrader: (17)

I think that's wrong. Most exhaust mods lessen the resistance, making it easier for the engine to pump out the exhaust, which allows the engine to be more efficient. That is FREE power.

So theoretically there should be a slight increase in gas mileage with a Y-pipe, headers, test pipe, B-pipe, etc. However, if you tend to drive a lot harder because of the newfound power, then obviously your mileage will go down.

Check for exhaust leaks and check all your O2 sensors, which are known to seriously hurt gas mileage when malfunctioning. Might as well check for a knock sensor code while you're at it.

NmexMAX

iTrader: (22)

exhaust leak FTMFL

Cosmo459sx

iTrader: (3)

No exhaust leaks (at least large enough to be detected). The only code i get is downstream sensor, which will not affect a/f mix or in effect gas mileage/performance unless upstream sensor malfunctioning. Tests were done within a few weeks of each other, so temp diff spring vs fall had nothing to do with it. ? !

VQuick

iTrader: (17)

I'm wondering if on 99s the downstream sensor actually does affect things...just wild speculation there. Otherwise I'm stumped.

nismology

iTrader: (8)

I concur.


Either that or the o2's were compromised somehow.

ionicmax

iTrader: (30)

What type of intake do you have? I would suspect a problem with your set up or a sensor that is not working properly, dirty MAF or broken o2 sensor. I had a cone intake and the y-pipe and got better gas mileage.

Good luck

BEJAY1

iTrader: (19)

I too saw a drop after my install 6 yrs ago. My mpg dropped from 23mpg to 21.5 and the only other change was the addition of a b-pipe. Both were 10 tank averages same exact time of the year with no MIL problems.

Blackwind

iTrader: (9)

365per tank city/420 per tank hyw

before and after y pipe instal.

check the ecu, you may have a ghost code.

VQuick

iTrader: (17)

I got 29MPG on the highway with some A/C use and a fully loaded car, and this was after I installed my Y-pipe