PI : DI Ratio Discussion

[ztan]

Originally Posted by thambu19

Okay. The engines Ive looked at not (FA20) the last row of load in CL is what gets used in OL. Are our engines using Wide band O2 sensors/AFR sensors or jus regular switching O2 sensors?

Front O2 is Denso Planar
Rear O2 is standard switching type

http://www.ft86club.com/forums/showthread.php?t=82875

[Kodename47]

Originally Posted by thambu19

Okay. The engines Ive looked at not (FA20) the last row of load in CL is what gets used in OL. Are our engines using Wide band O2 sensors/AFR sensors or jus regular switching O2 sensors?

Historically it seems to be MAF boundaries, in Romraider these are "A/F learning airflow ranges." I also think there is a 2nd set of ranges, the table looks close enough to the one that is mainly defined but how it's used or if at all yet has to be ascertained.

The last g/s boundary should be the one that is used in open loop and in theory if you raise the last range lower limit then then nothing can be set in the last range, however this doesn't seem to be the case.

[solidONE]

Originally Posted by thambu19

Id think 4-6% LFTF isnt a concern at CL but at OL yes maybe. Some ppl tried going 100% DI at loads above 0.7 for knock relief they also said their fuel trims went up. I am wondering if it is because at 100% DI vs earlier 50% DI the charge cooling is increasing the VE and hence the LTFT. If that is the case the engine should run the same AFR at OL as before. Since you said the LFTF increased and made the engine run Rich in OL id suspect that the LTFT was not supposed to go positive but did due to PW not scaling appropriately with PFI/DI ratio change.

Those who have had this issue can you chime in?
Did you see higher LTFT in areas where you increased PFI or in areas where you increased DI?
The LTFT learnt at low loads should not affect OL. Usually it is the LTFT just below OL that gets carried into OL. So if the idle LTFT is off nothing to worry there, atleast not so much

While running 100% Pi after having dialed my MAF for full DI I've found that at the lower MAF ranges 0~1.7v fuel trims will go up about 7~8% on average. AT 1.9~2.0 it fule trims go up about 4%. Then 2.1~3.0v, fuel trim ramp up to +10% with my scaling. I ended up subtracting 5% from the port injector scale value and find this is a good compromise. I may try to subtract 6% if I'm not happy with the result (being anal), but so far I think this works well.

[freerunner]

Originally Posted by thambu19

Since you said the LFTF increased and made the engine run Rich in OL id suspect that the LTFT was not supposed to go positive but did due to PW not scaling appropriately with PFI/DI ratio change.

Those who have had this issue can you chime in?
Did you see higher LTFT in areas where you increased PFI or in areas where you increased DI?
The LTFT learnt at low loads should not affect OL. Usually it is the LTFT just below OL that gets carried into OL. So if the idle LTFT is off nothing to worry there, atleast not so much

I'm investigating this now. LTFT went up to +3.2 in the 0.2x-0.3x load area. Haven't
had the chance to perform a WOT run due to traffic, but OL at 1.0 load LTFT went into the opposite direction (-3.9).

I'm going to lower the port scaling a bit (to get it running
richer in CL) and try again.

Log link

edit: car's running thambu19's pi/di ratio table

[solidONE]

Originally Posted by freerunner

I'm investigating this now. LTFT went up to +3.2 in the 0.2x-0.3x load area. Haven't
had the chance to perform a WOT run due to traffic, but OL at 1.0 load LTFT went into the opposite direction (-3.9).

I'm going to lower the port scaling a bit (to get it running
richer in CL) and try again.

Log link

edit: car's running thambu19's pi/di ratio table

The cold IAT might have something to say about LTFT subtracting fuel. You could try doing some pulls in warmer temps and I wouldn't be surprised if your LTFT go up slightly.

[freerunner]

Originally Posted by solidONE

The cold IAT might have something to say about LTFT subtracting fuel. You could try doing some pulls in warmer temps and I wouldn't be surprised if your LTFT go up slightly.

That would only make sense to me if the iat compensation table exaggerates in its current form. Else the ecu should add fuel to compensate for higher air density, if it's cold.
Nevertheless, comparing the actual log to an older one with similar ambient temps (where ltft was zero nearly all the time), I'm pretty much certain that adding the 70% pfi at low loads exposed the pi<>di proportion is off.

I didn't care about going full di when I calibrated the maf scale back then. :-/

[solidONE]

Originally Posted by freerunner

That would only make sense to me if the iat compensation table exaggerates in its current form. Else the ecu should add fuel to compensate for higher air density, if it's cold.
Nevertheless, comparing the actual log to an older one with similar ambient temps (where ltft was zero nearly all the time), I'm pretty much certain that adding the 70% pfi at low loads exposed the pi<>di proportion is off.

I didn't care about going full di when I calibrated the maf scale back then. :-/

Interesting. Perhaps fuel quality may have something to say about this as well. I'd like to know how much difference your PI will end up compared to a maf scale dialed to 20*c (68*F) in full DI where the IAT compensation is 0 on the stock temp compensation table for the entire range. That's if you want to be as anal as I am with this thing. My previous MAF scale was dialed to much warmer (also varying temps. higher on the lower end of the scale. particularly idle, and off idle speeds) temps since the average ambient temperature around here is pretty high compared to where you're at, I'm assuming. I was seeing about a 6% average difference in fuel trims in CL between DI and PI. Of course the difference was not linear, though predictable.

Edit: after changing the Port injector flow scaler to -6% from stock fuel trims have gone too far in the negative above 2.0v and also below 1.7v MAF. Will go back to a higher number for the port injector flow scaler. May have to look into getting something that will log the PI and DI injector quantity and adjust there as @Kodename47 suggested to really nail this down.

This was the amount of error with -5% value from stock


This is after changing the value to -6% along with small changes to IAT compensation. (214.xx vs 216.xx)


I think I'm probably spending too much time trying to "fix" things and it's backfiring.

[freerunner]

Small update: After casual driving for a couple of days, I decided to go back to full-DI in the 0.2 load column. It doesn't feel very well.
My assumption is that the intake air suction at low rpms is too weak to get the mixture dispersed enough.
That's my only concern for now, else the car feels great! 👍

[Wayno]

Originally Posted by freerunner

I'm investigating this now. LTFT went up to +3.2 in the 0.2x-0.3x load area. Haven't
had the chance to perform a WOT run due to traffic, but OL at 1.0 load LTFT went into the opposite direction (-3.9).

I'm going to lower the port scaling a bit (to get it running
richer in CL) and try again.

Log link

edit: car's running thambu19's pi/di ratio table

Richer in closed loop?

I think you need to google "closed loop" again.

[freerunner]

Sorry, English is not my native tongue. Of course AFR is always around ~14.7 in closed loop. What I meant was getting the injectors to inject (lol) more gasoline, thus getting trims back to zero.

[steve99]

After a couple of tests settled on ratios as below. Made the 3200 line 100% DI as this is arround where the last ltft correction is done (maf arround 3V) and after that your using DI exclusively anyway

Needed to adjust the Port Injector BRZ scalar down 3% to balance up the PI with DI.

Now getting pretty well 0 ltft (+/- 1%) except for the first couple near idle about 3% variation with large changes in intake air temps.

[Yobiwan]

Originally Posted by thambu19

When you get a chance can you try something like this? At WOT I have gone 100% DI. This means you need to a degree or so more spark there to use the full potential. If you do not then it will feel sluggish compared to stock calibration.

I logged after changing PI/DI ratio.

http://www.datazap.me/u/yobiwan/sc11...zoom=4683-5433

CL AFR target become leaner. always shows 15~16

today I switched to original PI/DI table . and CL AFR is steady on 14.7


HKS V2 supercharger with 41.5mm restrictor
Tomei UEL header
Stock intake with KN filter
OFT tune.

[solidONE]

Originally Posted by Yobiwan

I logged after changing PI/DI ratio.

http://www.datazap.me/u/yobiwan/sc11...zoom=4683-5433

CL AFR target become leaner. always shows 15~16

today I switched to original PI/DI table . and CL AFR is steady on 14.7


HKS V2 supercharger with 41.5mm restrictor
Tomei UEL header
Stock intake with KN filter
OFT tune.

Wow... that that is really strange. It should not have an effect on target AFR unless you changed the base fuel mapping. Something is really wrong.

I'm sure running this lean is not very good for your engine. Revert to your old rom until you figure out what it going on with this one.

[Kodename47]

Originally Posted by Yobiwan

I logged after changing PI/DI ratio.

http://www.datazap.me/u/yobiwan/sc11...zoom=4683-5433

CL AFR target become leaner. always shows 15~16

today I switched to original PI/DI table . and CL AFR is steady on 14.7


HKS V2 supercharger with 41.5mm restrictor
Tomei UEL header
Stock intake with KN filter
OFT tune.

If it's only just during cruising then I'd leave it, better fuel economy and all that. Your actual AFR doesn't quite go that lean anyway. I haven't seen that on mine though so I'm not sure why it's happening especially as in CL is should be targeting 14.7.