Ecoboost Speed Density tuning

[metroplex]

I have not tried the correction but feel the STFT data on a histogram paints a better picture

[cyruss]

ok thanks. Is there a way like it use to have on GM to reset the LTFT before logging and do the correction with newer LTFT+STFT ?

[metroplex]

Has anyone made any more progress on this? I've noticed a trend where STFT drops a lot above 5700 RPM with stock boost, and above 5400 RPM. My lambda also happens to go really rich at those RPM ranges above well.

I know Bugasu has the correct methodology but I'm wondering how Blown383 was able to resolve it just by correcting the slope?

[Blown383]

I added methanol to my car and tuned it via the slope. At WOT, the car runs a constant -4 STFT across the RPM range, which is accurate enough for me. Certainly works well enough for WOT but isn't too good for part throttle adjustments from what I have seen.

[metroplex]

What if we just tuned it for high RPMs like 4k and above?

I also found STFT to be inconsistent. I'd have it hovering near 0%, -5%, or +8% at WOT depending on the color of the moon. But it drops really negative above 5400 RPM.

But the lambda stays consistent until above 5400 rpm when it goes rich.

[Blown383]

I haven't had a problem using STFT as the basis for fueling adjustments on several cars at WOT. As long as you make the adjustments in the proper mapped point, it's pretty straight forward.

[metroplex]

My point was that my STFT isn't consistent. At WOT when STFT stays flat up until 5400 RPM, it can stay flat at either of those values I posted above. Which do I choose? Lambda error seems to be consistent

[Blown383]

Do you have a log of it doing that? I haven't encountered an Ecoboost with that much inconsistency. The problem I have using lambda error is that lambda error is calculated after the current fuel trim is added. So you can have lambda error read +/- 2% through an entire pull but the fuel trims could be adding 10%.

[metroplex]

I have a few logs, the STFT differs from day to day or hour to hour. I will try tuning the slope values above 5k RPM to see how it works out.

[metroplex]

First datalog I was running a tad lower boost, but the last 2 datalogs were the same boost levels. That being said, I've encountered similar STFT trends with the same settings on different day/conditions.

The first 2 were on the street, so I wasn't starting from 0 mph. But you can see how the STFT dips down (around 5500 RPM) with the minimum around 6000 RPM. But you can see how the STFT trends at around -5.5%, 0%, or +5.5% depending on some unknown variables. But regardless of how it trends, it dips negative above 5500 RPM. The red line is actual lambda, and you can see how it goes rich around the same time STFT goes negative. Otherwise, actual lambda very closely matches commanded lambda.

One website said this is an indication the turbo is choking (out of efficiency) but I ran it around 11-12 psi and it did the same thing, albeit the STFT wasn't this negative above 5500 RPM but it still dips down a little.

[Blown383]

Is the other line throttle angle? To me it looks like depending on how open your throttle is changes what the STFT is. I tune Ecoboost to keep the throttle open 100% when at WOT. I don't see any fluctuations such as this when I do.

[metroplex]

The cyan/light blue and white lines are what the throttle plate is actually doing. The purple is my gas pedal. You can see how the STFT dips down at times when it is pure WOT above 5400 RPM. If I put my cursor to where the STFT first starts to dip in any of those datalogs, it is about 5400-5500 RPM. I actually lined the logs up based on WOT 1-2 and 2-3 shifts.

But I was trying to show how the STFT trends at different percentages (ignore the dipping into negative for now). It could be +5.5%, 0%, or -5.5%. Usually if I run it at stock boost, it will be very positive. If I run it at higher boost, it could hover around 0 or like at the track, it trends negative and dips even more negative... Yet actual lambda is matching commanded lambda until above 5400 RPM.

[Higgs Boson]

why don't you disable closed loop for tuning and use lambda error?

[metroplex]

I tried tweaking the slope values but couldn't see any substantial changes to the STFT / actual lambda. The STFT still drops sharply after 5400 RPM with actual lambda going rich around the same region. The good news is that the knock retard I was seeing wasn't false knock, it had a lot to do with fuel quality.

As for the STFT drop above 5400 RPM, it's either the turbos are out of efficiency or the stock airbox/paper filter is causing a pressure drop/restriction. If I run stock boost levels, the STFT drops at about 5400 RPM but is only flowing 38 lb/min (well between surge and choke lines and stock flow rate). If I run higher boost levels, the drop occurs at the same RPM but is flowing 44+ lb/min. Granted, the stock boost doesn't causing the manifold to heat up much and the STFT drop isn't as much.

I'd have to run an Airaid/Windstorm to see if this changes the STFT data - or perhaps someone with those CAIs could actually perform a datalog. If the STFT continues to dip at above 5400 RPM, then the stock airbox isn't really a restriction. I expect the STFT dip would occur at a higher RPM with an aftermarket intake.

[tbrtuning]

Changing only the slope will add or remove fuel at all boost levels. Slope and offset both need changed to add more fuel at lower boost and less at higher.

[metroplex]

I only changed the slope values for 5000+ RPM cells in MP 0-3 (the ones that actually activate with the SHO at WOT). Any changes that were present seemed to be the usual variances in STFT I've observed.