after doing my turboxs testpipes and borla TD exhaust i put my car on the dyno to see what kind of differance it made. the numbers were 255 hp and 247 tq and i was really happy about the numbers but a 14.5 a/f really freaks me out. why would my a/f ratio be so high? the only mods i have is a pop charger, the testpipes and the exhaust. can somebody tell me what the deal is?

 

a 14.5 afr at what point in the rpm range? post the sheet

 

im still waiting on the sheet to be emailed to me. it was 14.5 all the way across the board.

 

14.5 initially is pretty normal but it should drop as the rev's increase.

 

did you do a "before" dyno with afr? where was the sensor mounted? Do you know the last time it was replaced/calibrated?

 

my roommate dyno'd his 300c right after me and his a/fs were low 13's so the sniffer seams right.

my before dyno the a/fs were like high 12's and dropped really rich after 5k..just like a normal 350z

 

What did your tuner say about the air:fuel ratio?

 

he said it was a little lean but the was no knock that he heard so i should worry about it to much but i do lol im just used to boost and a/f's being high 11's lol

mid 14s seam high even for a n/a car with just pop charger, testpipes and exhaust...im not tuned at all and i dont understand why its so high

 

With or without mods, I have a G35 with the same A/F.

Not good, but not too uncommon on the VQ engine either. A lot of people have A/F in this range. Some even into the 15's WOT and nearly stock.

Nissan ECU.

 

Acutally it's not lean at all. Stoich is 14.7:1 which manufacturers consider a good balance between power and emissions. Granted, at WOT emissions are disregarded and the most commonly accepted AFR for power is 12:1, but you shouldn't have anything to worry about with 14.5:1.

 

For anybody who cares enough to get a dyno, 14+ sucks.

 

stoich is for partial throttle that is not under much load. at WOT and under a much higher load, the stoich comparison goes out the window. most sniffer tests that i have seen capture a leaner than actual a/f even when the unit is functioning correctly.

 

makes me wonder what mine is at. Good post.

 

thats what i am saying...i care about my car enough to do before and after dynos for mods to see my increase in power and changes to my a/f ratio and it being mid 14s make me a tad nervous lol i keep hearing "wow thats high...becarefull and get tuned asap" and then i hear "thats normal for a VQ motor and u have nothing to worry about"

im still kinda a n00b to this motor and i have done alot of research before buying my z but this is one thing im not really sure about. i run the **** out of my car...i take care of it by changing oil/tranny/diff fluids early but i beat on it cause its fun last thing i want is to pop my motor cause my a/fs are so high

 

i was about to buy a spacer myself but oh my gawd think what my a/fs would be with a spacer

 

14.7 is great for crusing, emissions and fuel efficency.

But not at WOT.

And yes, a tune is in order. An Osirus reflash would be very helpfull.

 

i plan on doing a spacer and a 75 shot by summer. i had planned on doing this with stock tune but im not so sure now....i have seen lots of guys spray a 75 shot on their Z and be fine without utec of a reflash but this makes me rethink my plans....

 

The spacer will work fine on a stock tune and won't have any effect on the nitrous A/F. Nitrous comes with its own fuel compensation.

 

75 shot is weaksauce do 100 shot with UTEC...the torque will blow ur mind trust me i know!!!

 

You should get a new tuner. Just because you're not hearing knock doesn't mean it's not happening. Only severe detonation is actually audible without any amplification. You can use an electronic device to check or you can build a set of det cans yourself and listen for knock. I am not out to bash your tuner but he really should know this.

Since you just had all kinds of exhaust replaced, my guess is you have a up stream air leak in your exhaust which is screwing up your A/F readings. Maybe one of your gaskets did not seal up correctly and you have a very small leak that could be responsible for this. I assume you got the sensor stuck in your tailpipe with a clip when you were on the dyno, right? Once you do a pull on the dyno, some extra oxygen will get sucked into the stream and mess up your readings.

14s at WOT is not good, if that is really your true reading. You would not be making the power that you're making with that AFR. Your EGTs would also be very high and you would probably be detonating pretty badly at high loads....badly enough to hear. Your AFR is most likely fine.