Adjusting MAF with Open Loop Fuelling

[Tor]

A tip from @Kodename47 in this thread:
http://www.ft86club.com/forums/showt...=114760&page=3

Splitting this topic out in its own separate thread.

My MAF is pretty well scaled and produces consistently low fuel trims. However, I had some curls in the critical 3-volt section that I couldn't get rid off, presumably because of AVCS.

My MAF looked like this:



After a bit of fiddling with the OL fuel table (moving a row and rescaling + adjustments), off I went for a drive:



I had brought my laptop. Pulled over, uploaded to datazap, did some adjustments in RomRaider, flashed, and did another pull:



The OL fueling table looks like this:



I'll sacrifice another row and move things a bit around, so I can put in another point to make the first part of AFR command more pointy to counter the dip.

It was a bit scary to flash the car while pulled over some random place. And moving rows around in OL fueling I preferred to do at home. So I am not done yet.

Before anyone says it's too lean, keep in mind this is without learning - just flash and go. The entire AFR curve moves down where it should be once the ECU learns the fuel trims. Usualy I end up with +1-2 after very little driving.

I just wanted to share my experience for anyone wanting to take this route too. I'm done messing with MAF. As long as it's a nice exponential curve and produces low LTFTs I think this is an easier way to bring AFR into line.

[Vin]

This is a really nice result! Can you post the table when you are done? Our AFR curve looks 100% the same on stock Wayno STG2.

[Tor]

Originally Posted by Vin

This is a really nice result! Can you post the table when you are done? Our AFR curve looks 100% the same on stock Wayno STG2.

Yes, sure. I'm just working on it now.

I'm changing OL fueling, so AFR command will look like the red line to get AFR to hopefully follow the target blue (green was actual and made it too lean at 3200 rpm):



OL fuel looks like this (note different rpm scaling!!!). Also this is what I just made and haven't been flashed yet:

[Tor]

Don't know if you can copy paste this. Try (be sure to copy it all, it scrolls horisontally):

[Table3D]
0.30000001192092896	0.4000000059604645	0.5	0.6000000238418579	0.699999988079071	0.800000011920929	0.8500000238418579	0.8999999761581421	1.0	1.100000023841858	1.2000000476837158	1.2999999523162842	1.399999976158142
800.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.937777777777777	13.066666666666666	12.799999999999999	12.628187919463087	12.543999999999999	12.543999999999999	12.543999999999999	12.543999999999999
1000.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.937777777777777	13.066666666666666	12.799999999999999	12.628187919463087	12.543999999999999	12.543999999999999	12.543999999999999	12.543999999999999
2000.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.937777777777777	13.066666666666666	12.799999999999999	12.628187919463087	12.543999999999999	12.543999999999999	12.543999999999999	12.543999999999999
2200.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	12.97655172413793	12.713513513513513	12.543999999999999	12.46092715231788	12.46092715231788	12.46092715231788	12.46092715231788
2400.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	12.887671232876711	12.628187919463087	12.46092715231788	12.378947368421052	12.378947368421052	12.378947368421052	12.378947368421052
2600.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	12.799999999999999	12.543999999999999	12.378947368421052	12.298039215686273	12.298039215686273	12.298039215686273	12.298039215686273
3200.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	12.799999999999999	12.543999999999999	12.378947368421052	12.298039215686273	12.298039215686273	12.298039215686273	12.298039215686273
3400.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	12.799999999999999	12.628187919463087	12.628187919463087	12.628187919463087	12.628187919463087	12.543999999999999	12.378947368421052
3650.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	13.158041958041958	12.97655172413793	12.97655172413793	12.97655172413793	12.887671232876711	12.543999999999999	12.378947368421052
3950.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	13.158041958041958	12.97655172413793	12.97655172413793	12.97655172413793	12.887671232876711	12.543999999999999	12.378947368421052
4000.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	12.713513513513513	12.298039215686273	12.061538461538461	11.90886075949367	11.90886075949367	11.90886075949367	11.90886075949367
4400.0	14.7	14.7	14.7	14.586046511627906	14.254545454545454	13.835294117647058	12.713513513513513	12.298039215686273	12.061538461538461	11.90886075949367	11.90886075949367	11.90886075949367	11.90886075949367
4450.0	14.7	14.7	14.7	14.586046511627906	14.147368421052631	13.734306569343065	12.713513513513513	12.378947368421052	12.218181818181817	12.139354838709677	12.139354838709677	12.139354838709677	12.139354838709677
4600.0	14.7	14.7	14.7	14.473846153846154	14.041791044776119	13.634782608695652	12.628187919463087	12.298039215686273	12.139354838709677	12.139354838709677	12.139354838709677	12.139354838709677	12.139354838709677
4800.0	14.7	14.7	14.7	14.363358778625953	13.937777777777777	13.536690647482013	12.543999999999999	12.218181818181817	12.061538461538461	11.984713375796177	11.984713375796177	11.984713375796177	11.984713375796177
5200.0	14.7	14.586046511627906	14.473846153846154	14.147368421052631	13.734306569343065	13.34468085106383	12.378947368421052	12.061538461538461	11.90886075949367	11.833962264150943	11.833962264150943	11.833962264150943	11.833962264150943
5600.0	14.586046511627906	14.473846153846154	14.254545454545454	13.937777777777777	13.536690647482013	13.158041958041958	12.298039215686273	12.061538461538461	11.90886075949367	11.833962264150943	11.833962264150943	11.833962264150943	11.833962264150943
6000.0	14.473846153846154	14.254545454545454	14.041791044776119	13.734306569343065	13.34468085106383	12.97655172413793	12.218181818181817	12.061538461538461	11.90886075949367	11.833962264150943	11.833962264150943	11.833962264150943	11.833962264150943
6400.0	14.254545454545454	14.041791044776119	13.835294117647058	13.536690647482013	13.158041958041958	12.799999999999999	12.139354838709677	11.984713375796177	11.833962264150943	11.76	11.76	11.76	11.76
6800.0	14.041791044776119	13.835294117647058	13.634782608695652	13.34468085106383	12.97655172413793	12.628187919463087	12.139354838709677	11.984713375796177	11.833962264150943	11.76	11.76	11.76	11.76
7000.0	13.937777777777777	13.734306569343065	13.536690647482013	13.250704225352113	12.887671232876711	12.543999999999999	12.139354838709677	11.984713375796177	11.833962264150943	11.76	11.76	11.76	11.76
7200.0	13.835294117647058	13.634782608695652	13.44	13.158041958041958	12.799999999999999	12.46092715231788	12.139354838709677	11.984713375796177	11.833962264150943	11.76	11.76	11.76	11.76
7400.0	13.734306569343065	13.536690647482013	13.34468085106383	13.066666666666666	12.713513513513513	12.378947368421052	12.139354838709677	11.984713375796177	11.833962264150943	11.76	11.76	11.76	11.76

(changed 3900 to 3950)

[Vin]

Unfortunately copy pasting that doesn't work. Maybe you could send me your tune when you are finished with it (I'll PM you my details ), then I'll just copy paste it over.

[Tor]

I tried copy pasting from here too. It worked for me, are you sure you select the whole text before copying? You need Table 3D too.

[Vin]

Yes, now it works, I had to change my Windows settings (decimal and point for numbers) ! Or maybe I did it wrong the first time .. one way or another, it works

Edit: Which Wayno MAF scale do you use? The default one (+2%) or the lean one ?

[Tor]

Originally Posted by Vin

Yes, now it works, I had to change my Windows settings (decimal and point for numbers) ! Or maybe I did it wrong the first time .. one way or another, it works

Edit: Which Wayno MAF scale do you use? The default one (+2%) or the lean one ?

Wayno used logs from my car (among others I presume) as a test subject when making the new MAF scales for the tunes with the new injector ratios. So I have one from those tests.

I tried the +1.5 and it gave a really nice result too (still stg 1):
http://datazap.me/u/tor/stg1-102-v12...zoom=9515-9631

As you can see I had +2 LTFT with the +1.5, and near perfect AFR. LTFT doesn't matter diddly squat with the new injector ratios because there is no split at 5000 rpm which usually messed up AFR if the LTFT were off on either side. The only thing that matters is that AFR is correct in OL, which can be adjusted easily by adjusting the MAF above 3.20 volt.

Even though LTFT of +2 doesn't matter, I decided to use the custom MAF that came from testing on my car for another reason. The benefit for me is that it practically doesn't have to learn anything (see, the last log screenshot - +0.28 LTFT and the AFR is where it should be). So I can pretty much "flash and drive" without thinking about learning. I don't drive that much and disconnect the battery a lot so it has value to me.

Anyway, I don't think that it will have an influence on the adjustment made in OL fueling here which scale you use. Since it's more of an adjustment for the AVCS (or whatever is causing the bumps).

[Tor]

P.s.
I use German Shell V-Power 100 octane. It contains a whopping 5% additives, which may be the reason that there was never a "ready made" MAF that really suited my ECU completely (only 95 percent fuel injected where assumed 100%).

[aagun]

that rich area is a fake rich . keep ur eyes on any activity knock

[Tor]

This turns out to be more complicated than I thought - as usual.

Yes, something funky is going on. I tried out the last version that I pasted in the previous post and it doesn't work the way intended. It apparently wants to make a dip shape there no matter what. And now it makes a lean problem instead. No knock though. But another problem that becomes apparent is the influence on load:


http://datazap.me/u/tor/tor-204?log=...zoom=2636-2742

Compared to the normal OL fueling (that flat spot between 3600 and 3900 rpm).


http://datazap.me/u/tor/tor-201-1-ia...zoom=5894-5985

It looks like there is some benefit to correct the lean spot above 4000 rpm. This was the more moderate first attempt:


http://datazap.me/u/tor/tor-202?log=...7&zoom=627-725

So as usual, it's probably better to keep it smooth. I am going to revert this and forget about the (perhaps fake) rich dip below 4k and only concentrate on smoothening the lean spot above 4k, which seems to give better load values.

Maybe this dip shape is more to do with load limits?

[aagun]

http://datazap.me/u/tor/tor-204?log=...mark=2657-2661


smooth avcs ext to correct afr . otsv3

[Tor]

It's definitively load related. Curiosity got the better of me, so I changed went back to the normal OL fuelling and tried to change the load scaling instead. Changed 3700 to 1.25. Both stock and OTS has 1.3 already at 3200 rpm so I thought it would be okay.

Oh boy! It felt like the engine was running at half power. Never has the car felt so sluggish!:



It did however, correct the dip. It used to be between the two yellow lines. Obviously it throws the whole MAF scale off as well and now it's running insanely rich.

http://datazap.me/u/tor/205?log=0&da...mark=3487-3510

To top it off, I heard for the first time real audible knock. Didn't sound like "ping" though, rather a sizzling sound. Ptjuzzzz combined with a noticeable bogging down. And this was under light load as can be seen in the log:



Next up: Reverting to standard loads and OL fuelling and forgetting about the dip. I am going to have to go with Wayno and aagun on this one, that dip is probably just somehow a wrong representation of what is actually going on in the combustion chamber.

But hey, learning by doing... It was an interesting experience.

[Tor]

Okay I shouldn't be posting here late at night, let alone mess with flashing and logging.

The load change log I posted above is totally messed up. The AVCS is not active at all. I don't understand why. I followed my usual procedure. After flash:
- Ignition on, wait 20 secs, then off again.
- Ignition on, wait 20 secs, start engine.
- Without touching anything let the car idle for 1 minute.

I even timed the one minute yesterday because it was late and I didn't want to let the car idle for too long unnecessarily (neighbors bedroom facing my driveway).

Anyway the log shows AVCS is not active at all:
http://datazap.me/u/tor/205?log=0&data=22-33-34-35-36

So I suppose 1 min wasn't enough for the calibration to complete?

If AVCS stayed at 0 during the drive, I suppose that would throw everything off including MAF?

P.s.
The load change is the only thing changed (OL fuelling back to normal).