... yeah, I think it was calculated out closer to 1105cc @ 43.5 base fuel pressure. I'm hoping that will be enough for a red at ~28psi on E85, but that may have to wait until next summer if I can get into a house with a garage soon

I hadn't logged the IDC yet since I was just getting the WOT fuel dialed back in. I'll grab some and report back once it is a little closer. Either way it has to be better than 110%. I think I'll stop calling those 780cc's PTE and start calling them spinal tap

 

Ok guys, someone really needs to slap me and set me straight here because I'm starting to over think things. After dropping in my FIC 750cc's the other day and getting the scaling/latency's set and doing some idle logging I finally went for a drive today to log my LTFT Mid. Now just a few details, I did two back to back runs with a 5 min idle inbetween, each was 20min long crusing at a steady 55mph on flat highway. At the end of the second run my LTFT Mid was @ +1.080... great! Now I look at my STFT, and it's everywhere. It jumped around from -9 to +5 randomly. I used Microsoft Spreadsheet and calculated my STFT average and it came out to +0.0340, but is that an accurate figure to use to say was my STFT? I'm lost when people say "my STFT is -2" or "my STFT after a cruise was -3", how do they come up with these solid figures? Is my STFT the only one that jumps around randomly? Any help would be highly appreciated.

 

STFT will jump around...it is completly normal. As long as the LTFTs are + / - 5% then you are golden. Sounds to me like you have it licked. If I were you I would call the scaling good and move on to fuel and timing WOT tuning.

 

Yeah I knew the LTFT Mid was in good shape, better than I thought, but I was unsure about the STFT. I knew they jumped around, but didnt realize how much and if I was more than usual. I'm still not clear on how people come up with a solid figure as their STFT, do you have a formula you use? I'm just wondering for future refrence if I have problems and need to post them I want to know what to use as my figure.

 

I think how most people get the STFT number your are speaking about is after the car cycles 4 times, they usually take the last number it settled on. I ususally let it cycle a few more times and if your car is happy, it will come right back to the number that it landed on on the 4th cycle. My STFT does move, but it also does not go out side the +/- 5. Both the LTFT and STFT have to stay in that range. I was have in the problem of getting the LTFT to be right on, but the STFT was always way out side the range. I left the scaling the way it was, and only made a small adjustement to the 11v latencey. Understand ever car idles different and my idle voltage is around 13.4-13.8 volts. So I am assuming that the car is interplolating the number between the 11v and 14v latency. At any rate it fixed it along with MAF scaling..Hope this helps.

 

I understand what your saying. Looking over my 2 logs, at the end of that fourth cycle my STFT did not fluctuate outside that +/-5 range either time. I was getting those really crazy numbers before that when I first started logging. My LTFT's are pefect and land basically in the same spot after every log whether it's the Low's at idle or my Mid's at cruise, so I think I'm pretty much set for now. I think after a day or two I'll do the same type of log's just to make sure everything stay's where it is. I do understand now where the STFT number comes from now, it's not a solid reading it's just at the end of the cycle seeing where it basically is. Thanks alot man.

 

Basically don't pay any attention to stft. It is an "instantaneous" fuel trim. The only time I even use it is the first or second time I'm flashing to see if I"m wayyy off (and fine tuning the MAF Scaling). If you start out in the +/- 5% LTFT low/mid you shouldn't even need to pay attention to STFT.

Make sure you are in each range for at least 16 minutes. The long term trims cycle every 4 minutes, and the more cycles you have, the more "accurate" your long term trims are for all driving conditions.

 

Oh yeah I make sure I do atleast 16min cycles. I did back to back 20 min cycles yesterday while driving, and after comparing the 2 logs my Mid was actually better after my second cycle and settled at +1.080 as compared to +3.24 after my first cycle. I'll prob do 2 more driving logs saturday just to verify that everything is still in check and start my WOT tuning.

 

I still have to take a ton of fuel out of the WOT tune, but today I was running 71% @4500 RPM and 79% @ 7K with 11.1 -> 10.7 AFR I am going to be able to take out a ton more fuel though

I am a little surprised, it bought me alot of head room but still not a ton if I go red. Does anyone know a typical % or ratio of increase in going from a IX turbo to a red?

 

the problem with long cycles is you get radiator fans turn on which screws up the voltage or something...

 

I just order some PTE 880 and have been reading about scaling. So far my understanding is as follows:
STFT – Gives the real time difference from the fuel map compared to what the ECU is fueling at closed loop using the front O2.
The LTFT are values that the ECU learn to add or substract from the actual value to get it closer to 0 (in EvoScan a 0 is a 100%).

But what does the Low Med and High Trim means? Does low refers to low RPMs, mid to mid RPMs and High to High RPMs? If not what exactly Low, Med and High refers to?

 

Low, mid and high refer to the MAF swithcing levels based on air flow. Basically when airflow is below a certain level (undetermined as of now) then the LTFT low kicks in. From what I have tesed the switching point is somewhere around 40Hz. When the airflow is lower than this Hz value (usally at idle) the LTFT Low is the responsible trim. Above it is the LTFT Mid. I have never seen my LTFT High ever adjust.

 

Why is airflow measure in Hz? What is the reasoning for that? Trim levels are somehow related to RPM also since the higher the RPM the higher the airflow (assuming boost is the same). Is that true?

 

I agree... I guess you can be from 1 of two camps on that:

1) The fans and higher load idle is a natural state of the car, so the ltft low should be the average of all of the natural states of idle for that driver/car/setup. (This assumes you don't just turn the car on and let it sit in the garage for 16 min, but actually drive around for a couple of days)

2) The car should be set to idle in the ideal situation and allowed to adjust for the other. The car may run slightly better when things are perfect, and slightly worse when they are not.

I think I fit in camp 1, but mostly just because its easier

Airflow is measured in Hz because it is a digital signal sent to the ECU. Read about how a Karmann vortex generator MAF works for a more specific description.

The levels are only related to airflow. It is just a natural relation that at higher RPMs it will be easier to attain higher airflow levels.

 

Here is mine for the Precision 780cc that I used to achieve -2 and -3 in the LTFT Low and Mid. I have been driving the car almost 100 miles with in the last 3 days. Can it be better?

597

4.6875 3.504
7.03125 2.184
9.375 1.320
11.7188 0.912
14.0625 0.696
16.4062 0.360
18.6768 0.240