Fuel Trims? Options

[BudmannG]

What Fuel trim do you guys usualy run on your logger? I read some where to try and get them as close to 100% as I could.
Right now my fuel trims are L=139.5 M=127.9 H=134.2

On saturday when I went to Nates, My knock was off the wall 42 was the highest and I think we got it down to 21. Did we do something wrong, or is this right. Not that I don't trust Nates tuning, I just want a second opinion on this. Because I still have knock and my fuel trims are all showing I'm running lean. Unless I'm reading it wrong.

[natedogg]

Your fuel trims are closed loop controlled and dependent on the 02 sensor output. The tuning we were doing was WOT open loop and is independent of the fuel trims. The appropriate feedback for WOT open loop is knock and timing. If you want to bring your trims down you'll want to pay attention to what RPM's you cruise and idle at and adjust accordingly. I tune mostly for WOT, because the ECU takes care of the cruising trims for me. Of course, I'm not as concerned about fuel mileage, whereas you probably are.

Starting from a knock count of 43 and bringing her down to 20 is a good start, but if you want to try richening her up more in your mids you may be able to bring that count down more. If your boost is spiking at all it can bring that count up and then it will slowly come down during the run. Also keep in mind that knock can come from warm air just as well as a lean condition. I'd try richening her up some more and see what happens. Its not always easy for me to tell how it feels vs. what the numbers tell me if I'm not in the driver's seat.

[turbohcar]

Well, on my drive home, my fuel trims remained a constant 81.2% on the FTRL, FTRM, and the FTRH. My O2 voltage remained a constant 2.03V as well (not sure what's up with that) and I'm knocking at cruising speeds. Knocking quite a bit actually, up to 24 counts at times but when you accelerate or let off it will stop. It only does it from time to time so I can't really tell what's causing it.

Mods to intake: 2G TBE, HKS upper IC pipe, K&N filter. That's it, no hacking of the MAS.

[ncgalant]

Looks like now you have added to much fuel(on the low end). The ECU is taking out all that it can with the long term trims. If the O2 trim doesn't even have enough room to lean it out then you will run more than 14.7:1 all of the time. What you are seeing may even be part throttle rich knock.

[BudmannG]

Looks like now you have added to much fuel(on the low end). The ECU is taking out all that it can with the long term trims. If the O2 trim doesn't even have enough room to lean it out then you will run more than 14.7:1 all of the time. What you are seeing may even be part throttle rich knock.

Who was this for me or Turbohcar?

[black92_tsi_awd]

I think ncgalant post was for turbocar.

BudmannG your situation is the opposite, you need more fuel accross the board. What's your FP set at? Didn't you get an adjustable FPR?

[BudmannG]

I set the pressure at 37 psi when I was at Nates. When I got there I was running 70 psi .

[turbohcar]

Sorry, didn't mean to steal your post Budmann. But, I figured since we're on the topic, I'd try and get some advice.

Now, I've got a MAS Translator that I can put on (provided I've got a working logger), would something like that help or would I be adding too much air?

[BudmannG]

No stealing done here it was for everyone. If it helps you, me, and someone else I have done my part.

[natedogg]

Well, on my drive home, my fuel trims remained a constant 81.2% on the FTRL, FTRM, and the FTRH. My O2 voltage remained a constant 2.03V as well (not sure what's up with that) and I'm knocking at cruising speeds. Knocking quite a bit actually, up to 24 counts at times but when you accelerate or let off it will stop. It only does it from time to time so I can't really tell what's causing it.

Mods to intake: 2G TBE, HKS upper IC pipe, K&N filter. That's it, no hacking of the MAS.

Could be as NCgalant describes. Here's another possibility in your other thread:

http://www.dsmcentral.com/invision/index.p...pic=3564&st=105

[ncgalant]

sorry about that, yes my post was for turbohcar. If its taking out that much fuel, you might want to try some hacking. At a minimum you can back the adjustment screw out.

[turbohcar]

Now, I've got a MAS Translator that I can put on, would something like that help or would I be adding too much air?

I'd probably get a new knock sensor as well to aid in the logging portion too.

BTW, I did a WOT run tonight and found that the car was bucking in the 5000rpm + range. I don't know how else to describe it other than it was like stabbing on the brakes for a split second. What should I be logging to verify fuel cut? It looked like it was happening in fourth gear only (didn't get to fifth) and when knock was the highest. I'm hoping something in the drivetrain isn't binding up while it's got heavy load on it and at high speed.

[black92_tsi_awd]

Fuel cut should show up as an open throttle, no injector pulse and a 1600hz airflow count.

[turbohcar]

I'll have to do a log of airflow but there are spots in this log where it shows 0.0ms of injector pulse during the WOT run. Mind you, this car still retains the stock fuel system and the fuel pump has not been rewired yet.

[JMoushon]

I'll have to do a log of airflow but there are spots in this log where it shows 0.0ms of injector pulse during the WOT run. Mind you, this car still retains the stock fuel system and the fuel pump has not been rewired yet.

Have you ever had the fuel rail off? Check the injector sheets and rings. Bad seals at the rail will cause a high end miss.

Fuel cut is loud, or at least it was in every DSM I've ever driven. Usually makes an interesting cloud behind you for a second. Feels more like hitting a wall than tapping the brakes. Not really, but my point is that it is not gentle.

[turbohcar]

This isn't gentle either. I meant to relate it to burying the brake pedal in the fire wall for a second. I've had the rail off, recently in fact. I couldn't see any leaks while it was off, but I wasn't looking at it in particular either. I'll have to check for the cloud you speak of.

[black92_tsi_awd]

If your getting 0.0ms of injector pulse and it matches up with a "slamming the wall" incident, I'd say its fuel cut.

The way I understand it, is that the fuel system doesn't matter, it's strictly air flow related. Increase airflow with the stock ECM programming, and you're going to get fuel cut. I've got a rewired 190 in mine, and I hit cut at around 3500 under WOT. Curiously, at the strip I don't get fuel cut...I think because my RPMs never drop below 4000 all the way down the track.

MAF translators delay the onset of fuel cut by the way they modify the air flow signal to control fuel.

My understanding the only way to eliminate fuel cut is to have the ECM reprogrammed.

[natedogg]

You can also tune around fuel cut by using the translator to lean out a bit at WOT. Sounds like you may be running rich anyway. This way the signal reaching the ECU is never high enough to trigger fuel cut.