UTEC fuel question...

[ScoobieSnaX]

I've generated several datalogs with my wide-band o2 sensor (FJO) and have the following results with my stg4 kit:

RPM a/f
3500 10.3
3750 10.3
4000 10.2<---------way too rich
4250 10.2<---------way too rich
4500 10.1<---------way too rich
4750 10.0<---------way too rich
5000 10.2<---------way too rich
5250 10.3
5500 10.5
5750 10.8
6000 10.8
6250 10.9
6500 10.5
6750 10.2<---------way too rich
7000 10.0<---------way too rich

So lets say I want my a/f to be at 10.6 and its at 10.2, how much fuel would I add as a "rule of thumb" to achieve this? For example, for every +0.2 points of fuel you will yeild ~+0.1 a/f.

Or is it even possible to draw such a conclusion?

Thanks,

ScoobieSnaX

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[paul99se]

Maybe you mistyped (it's late), but subtracting fuel will increase your air/fuel ratio (leaner).

With Stage 4 you are making the maf voltage adjustment less negative (adding + maf voltage correction) to richen things, opposite to lean them out. This can be sort of confusing as adding maf voltage correction = less negative correction = more fuel injected. Subtacting voltage correction = more negative correction = less fuel injected.

Try -0.1, to start, across the range that you're shooting for higher a/f (leaner).

I don't think you can draw any direct correlation between the two values (maf voltage and a/f). There are too many other factors involved... (ecu's base fuel map at each rpm/load point that's being modified by your modified maf voltage. for example)

-Paul
Edit: It was late, I got my signs reversed to. Fixed now.

[ScoobieSnaX]

woops! Ya, that's what I meant....I want to lean things out a bit. It is late!

I'll give the -0.1 a try and see what I get.

Thanks!

[motoxphil]

ScoobieSnaX,

Please don't assume those air/fuel ratios are too rich until you take timing and boost into context. These are critical variables in tuning and the AFR doesn't tell all.

We however run more fuel there to compensate for those who like to mash the pedal to the floor in 5th at low rpms since the car will sit at there for substantially more time with high boost levels.

A general rule of thumb is too run the car rich at or around peak torque, as this is where the car is most susceptible to "knock."

There are many schools of thought when it comes to tuning and if you prefer to run the car leaner you should pull some timing out in those areas.

Happy Tuning,
Phil
TurboXS

[ScoobieSnaX]

Thanks Phil,

Are you saying that I would get different a/f numbers doing a 5th gear WOT run than I would in 3rd or 4th?

I've spent quite a bit of time last night and today working on my software and tuning the car. I just can't seem to get rid of these knock events at 5500rpm though

I can hear a slight ping along with a CEL flash, followed by timing being pulled (as seen in the datalogs). I'm running 92 octane fuel (which is now 'winterized'). I've pulled out 2 degrees and added 0.4 points of fuel. Should I be adding more? My a/f at 5500 appears to be fine (suggested 10:7).

Thanks,

Jason

[motoxphil]

Yes, speed and air/flow across the intercooler will have an effect on air/fuel ratio. The biggest difference is the time spent at each rpm point in the upper gears.

I believe my current STG4 map only runs about 22 degrees of advance at 5500 rpm due to the reformulated gasoline we are seeing now. Timing has a greater impact on "knock" than fuel (this is greatly generalized). Try dropping timing to around what i'm using. Add fuel if needed by monitoring your egts.

We will continue testing on this reformulated gas so we will update the maps if needed.

Thanks,
Phil
TurboXS