hey guys, i got my vortech tuned back in the summer, temp was 80's - 90's. the weather is now in the 60's now. the car showed around 11.8 in the lower rpm's back when it was tuned. how it's showing around 12.2-12.8 when lower than 5k rpm. very jumpy around the 12's mostly through the entire run. anyway know why this could be happening ? im running 3.12 pulley with headers, test pipes, and borla td exhaust. is it possible that my injectors are giving out ? or a fuel issue in any way. possibly the FMU ? i've recalibrated the innovate wideband and also reset the ecu. any help is needed. thanks guys.

 

I dont think the colder temps would make that much of a change in A/F reading . It never did for mine . Better take in to the shop that tuned it and have it checked

 

any way to check it myself ? probably not i know. i read the fuel map off the ecu but i dont know the parameters that cpracing used when starting the fuel map and timing. i got it tuned in charlotte at cpracing. long drive back up there.

 

Im sure there is a shop in the area that knows the R4 . But I would think there is some thing going on to lean it up that much . Maybe some one else that knows for sure if temps can change it that much will reply

 

i guess i can also add that charlotte is above sea level and it was around 90 degrees. and im at even sea level and tonight it is high 50's. i have a CEL as well, last time i had it come i had autozone check it. said i had bad 02 sensors. the CEL went away when my A/C stopped working ( i ripped the ribbon cable) i fixed the ribbon cable the other day and the CEL came back. weird i know. not sure if any of this is related or not but thought i'd throw that in. any idea why the a/c issue would cause the CEL to not come on ? and the white ribbon cable that im talking about is hooked up to the white/greyish box behind the ac controls.

 

Backagain

Please refer to the manual. It's more than AC

Cheers Amy -

 

amy, could you explain a little for me, i have NO idea where my manual is. what all does that box do ?

 

A variance of up to an entire point A/F is common with a piggyback in the 350z under boost between colder or hotter temps. I can have a customers car fully tuned out being consistent as heck from run to run but then let it cool down for 30 min and then it goes up to a half point leaner.

Expect to retune your car with every seasonal climate shift. If you have an adjustable fuel pressure regulator, you may get away with going up and down with the base pressure as required.

 

so basically when it gets warm again my car should have the same afr that i had before when it was warmer ?

 

we will see how much it likes you when that time comes.

 

Could Someone aim BAckagain to a Copy of the Service Manual?

Thanks

Cheers Amy -

 

i have a copy of that, just found what you are talking about, wow, i had no idea that box does so much,

 

I had calculated the air density difference at 90deg F and 50% humidity and 40deg F and 30% humidity and the difference was approx 6.5% greater at cold temp..Don't know the sensitivity of o2 sensors but if they are not very accurate they may not accurately see the difference in air density and skew the A/F that the ECU is trying to maintain..

 

so with my factory 02 sensors being bad could that mess with the ecu therefor mess with my piggy back ? i was told that it wouldnt. if it goes then all i need to do is replace my stock 02 sensors.

 

O2 Sensors do not effect full throttle tuning... at least not in the 03/04s... but I know the new Zs have factory widebands which may have effects on full throttle performance but its probably not likely.

A standard O2 sensor like in the earlier Z's is not accurate in the A/F range that is preferred during full throttle, which is why the ECU switches from a "closed loop" cycle into an "open loop" and runs the car straight off the maps in the ECU and ignores all information from the O2 Sensors.

 

The MAF sensor is the only device that calculates(technically it doesn't even do that) the air density in our cars. The O2 sensor measures Air/Fuel Ratio and hot exhaust gas has no idea about density of air. With these piggy backs it is not using the ecu a/f feed back control, that is the point of the split second. Exhaust gas coming out at over 1000F doesn't care about a 6.5% difference in air density or the intake charge. What we are talking about right here is why so many of us would like to use dual maf's to tune. Maf's very accurately meter the amount of air coming in, taking into account air density. With a Map sensor it doesn't account for air density unless you have a 3 axis controller with boost, iat, and rpm.

 

The UTEC has an IAT offset feature that can be used for fuel and timing for this IIRC? I think EU has a similar feature for fuel only. I dont know much about the R4. Have any of you played around with the UTECs temp offset feature, how well does it work?

 

i did a video today of the wideband, boost, rpm and speed, just used a video camera on a tripod stuck behind me on the left. i will get the video put together when i get home. hopefully you will be able to see everything.

 

the video didnt turn out too well, too dark, i'll do another one when it's dark outside so you can see the gauges. on another note. is it possible that with the colder air im getting into boost eariler and the fuel map on the r4 isn't tunned for that ?