Have been running some high intake AVCS values (45) but was getting knock at cruising speeds (2800-3000 rpm, at 0.9-1.5 g/rev) even full DI with IAM dropping.
I've just re-reduced the AVCS intake cam to 40 which has settled the knock signal and about to add in ignition.
I'm not sure if it was true knock or just intake AVCS noise too close to the cam advance limits, but the engine is behaving much better with a bit less cam, more PI lower down, full DI up top.

Too much intake advance means intake is opening when piston is travelling up in exhaust stroke. This can send exh gas up intake runner and re breathe increasing residuals and knock. So there is always a fine balance.

Sent from my HTC One_M8 using Tapatalk

This is more so at lower speeds

Sent from my HTC One_M8 using Tapatalk

Flashed your PI/DI map yesterday. Added 3 degrees ignition advance at
load > 0.90 up until 3,8k rpm or so. And there's still headroom for more spark left.

Feels better than before. Seems worth to play around with these tables.

Be careful adding too much spark at engine speed making peak torque. Up to 3800rpm should be okay. Some engines I have worked on goes straight to pre-ignition. Don't want thatone

Sent from my HTC One_M8 using Tapatalk

I'm not too active on this forum lately but I did get caught up with this thread, as these things tend to die and suddenly get revived.

The AVCS intake side has the negative values @thambu19 and others were talking about because it is a mid lockpin AVCS. That means the intake side can retard, not just advance. The retard is a fuel economy thing. It's the same type of AVCS that's on the FA20DIT. In fact, it's the BorgWarner phaser technology that Ford uses on the 5.0 Mustangs. On those FA20DIT engines when you delete the tumble generator valves you need to advance the AVCS or it runs like crap without all that tumble motion in the combustion chamber.

http://www.ft86club.com/forums/attac...1&d=1449028139

more details (mostly relevant to FA20DIT) here http://forums.nasioc.com/forums/show....php?t=2687550

Any one else notice the fuel trims go crazy after loading these tables? How are you guys dealing with it?

http://www.ft86club.com/forums/attac...1&d=1448249234

Could it be because now engine is scavenging with pure air instead of air fuel mix

Sent from my HTC One_M8 using Tapatalk

That probably means your port and direct injection is not scaled correctly.

Assuming your maf scaling is ok and its not due to wide temp variation at lower rpm due heat soak.

I am assuming its gone all one way ie plus or negitive at the lower load rpm ranges where the big shift from direct to port was done

If your kean you could adjust the "injector flow scaling BRZ" (port injection) parameter up/down slightly to correct the imbalance between port and direct that easier than messing with direct injection pressure mutipliers. althout ztan did discover what he has called Multiplier C an overall direct injection multiplier

To do it correctly you would rearly need to go 100% port and correct that then go 100% direct and correct again.

You're right, fuel trims pretty much have all gone positive during low load CL operation. This end up increasing the LTFT in OL causing it to run rich in OL. So I'd assume I'd need to increase the "injector flow scaling BRZ" value?

OK if trims gone positive then its adding fuel to compensate when we switched in heaps more port , so we assume the port injectors were not adding as much fuel as the directs did.

So I think we need to make ports add more fuel.

In a petrol tune Inj scale BRZ (port) is 228
In a E85 tune its 171

So looks like lower number means more fuel.
Shiv added roughly 30% more fuel in E85 tunes so it looks like if we moved the injector scalar 2 it would equate to roughly 1% change in port fueling.

So if we want to add more fuel as the trims have gone up say +4% we need to move scalar down roughly 8. Its not going to be exact as we did not go from 0 port to 100% port but should be in the ballpark.

I would not go wildly adjusting the scalar though.

To do it correctly you would have to go 100% direct (whole map) make sure trims are good, then switch to 100% port and adjust scalar to get it as close as possible to what you got trim wise with 100% direct.

Why do they not react appropriately when we change ratios. With more pfi the ecu should have added the right amount of pulse width I would assume

Sent from my HTC One_M8 using Tapatalk

What's weird is that the LTFT seems to want to go positive, but if you subtract the amount of stft it's actually not that far off. It seems the afr will fluctuate pretty drastically under certain circumstances and somehow cause the ltft to go positive. While with ltft positive beyond a couple percent or so the stft will be just about the same amount negative canceling out the positive ltft. But once you go into OL operation the ltft just sticks at the positive trim causing it to run rich. Does that make sense? Lol

I think this is what I'll have to do. Since the previous di/pi ratio table I had it set to fully Di in the first 3 columns (.10, .20, .30 load) Whereas the new table has it set to 70% PI from .20~.40 at low rpms. This is the area I'm getting the most trouble I think.

I would avoid going for the big multipliers as it's unlikely the whole lot is off.

If you can log fuel quantity, I have a way to tie in the fuel between injectors. If not then you can try running 100% DI, 100% PI or 50% and then compare the trims. I would then adjust the DI Flow Scalar as it is the most adjustable of the lot without affecting large areas unnecessarily .

Yes you would think it should. but others have found it not always so.

their was a heap of discussion on it here

http://www.ft86club.com/forums/showthread.php?t=53064

http://www.ft86club.com/forums/showp...5&postcount=12

http://www.ft86club.com/forums/showthread.php?t=3172


jamesm who is a tuner, no longer on this forums suggested this proceedure

http://www.ft86club.com/forums/showp...&postcount=195


ztan found some pi/di fueling error
http://www.ft86club.com/forums/showp...1&postcount=37

You would think, but the PI and DI fuelling algorithms are not dead on. There are differences with the scaling in both systems which mean that if you alter stock settings, the balance between PI and DI may change final fuelling quantity. There is also the issue of port fuelling running out the exhaust in high overlap areas which should not happen as much with DI fuelling. We are reliant on our lambda sensors to give us information of what is happening just after the cylinder, but don't have the ability to find out what is actually happening in the cylinder...

I set the car at 100% DI and got the MAF rescaled to flat, then set to 100% PI and set PI scalar and latency to get the PI fuelling in line - made everything run much smoother. You can work it any way you want.

There is something in the fuelling algorithms that makes OL operation much richer than we would expect - I have not been able to unpick it and the logic is very complex, but there is much written on NASIOC and RomRaider on "rich dip" on throttle application or CL/OL tranistion. A lot of people have tried to get rid of it and have ended up accepting it or deciding to run full time OL. I've partially addressed it by applying more CL fuelling using the EL Comp table at the higher MAP cells - this smooths the transition a bit, but is a bit of a messy band-aid fix.

I had done quite a bit of work to try to balance my DI and PI systems prior to loading a similar table - found my trims got slightly better clustering if anything.

Are your ratios similar in the .10 (0% pi) and .20 (70% pi) columns? Since idle loads after the engine is up to operating temps tend to float between .14~.20 g/s, I noticed this is where AFR will fluctuate quite a bit. I'm assuming the fluctuation in the di/pi % has a lot to stay about the fluctuating AFR thus the fluctuation in the fuel trims.



fluctuating fluctuations have fluctuated...

I run 0% up to 0.3 load and 70% at 0.4. Full DI at low load for me stops a bit of erratic behaviour when AC cuts in and out. I also have bigger port injectors which have a larger non-linear region than stock which accentuates the split fuelling problems at low pulsewidths.

I do see quite wide variations in AFR trims at idle speeds but not at low load whilst cruising - there is a lot of intake temp variation under the hood when the car is not moving and I largely ignore these now.

Same here, but the change in AFR and fuel trims due to IAT change is predictable and not quite as drastic for me while running 0% Pi up to .30 load. At most my LTFT will go up to +4% previously, but after changing the table to the one I posted above it will go up to as much at 8~9% varying from 0%~9% at idle speeds depending on load and temps. I think the more Pi you run, then more LTFT will vary due to IAT change versus DI.

I'm going to scale my MAF as close to 68* as I can the entire range in 100% DI then take it from there. Good thing it's getting colder in socal, so I shouldn't have too much trouble doing this.

I get idle speed trim variation of +/- 11 at times. I have chased this in the past and have given up on getting them stable as long as my fuelling is good whilst the car is moving. Seemed to me to be quite weather dependent and I have put it down to temp/humidity shifts whist the car is stationary and the oven under the hood heats up (I also have the Greddy Turbo intake which sits in the engine bay consuming the hot air).

So the way we get around is by scaling the MAF to reduce fuel trims? Does not look like the most straightforward approach to me. Maybe this is the only way to get fuel trims right until someone discovers a table or something that should be changed that will make the ECU adjust fuel pulsewidths appropriately when PFI/DI ratio is changed.

@arghx7 would you know anything about this?

There's a lot of discussion here among different people and scenarios that I'm trying to unravel.

First question: is this a matter of the fuel trims moving around more than would be ideal or is there an actual driveability, knock, etc problem?

Second: Are we talking about stock port injectors, obviously stock DI injectors, and stock MAF scaling or scaling that has been judged ok before the PI and DI balance was changed?

I suspect there's a bunch of wall wetting compensation, gas flow model, or injector flow compensation that is poorly understood because we don't have actual block diagrams of how the software works, just whatever has been reverse engineered.

My position is, generally speaking and subject to case by case revision--if the fuel trims are just moving around more who cares? That's their job. They're compensating for some inscrutable fuel calculation that hasn't been unraveled, or more likely, production tolerances in injectors, given that the stock values were for some mean spec part most likely.

:sigh:Is there an actual problem with the car here or are we just trying to make the fuel trim lines on an excel graph look pretty

@arghx7 @solidONE @steve99 @Kodename47 @ztan

My concern is if the fuel trims go up or down too much say more than 10% it will take the estimated load along with it. Estimated load = Originally assumed load through MAF signal +- corrections from fuel trim. This means the cam and spark lookup will move around unnecessarily?

I dont know how exactly it works on the FA20 so this is just my assumption. This is assuming that most OEMs trust their fuel modeling more than air flow modeling. So when fuel trim moves the load estimation moves as well.

My other concern is how is MAF scaling going to fix this? For example say if by going 100%PFI at low loads causes the LFTF there to go 10% +ve causing a load estimation to go up 10%. The MAF there would be moved up 10% at the same Voltage to bring the LTFT to 0% but we still have the same problem because now the MAF readings are higher (artificially) causing a higher load estimation and hence spark/cam lookup = bad combustion or knock depending on which direction we go in load lookup

You're giving Subaru too much credit. It's not that smart, or at least, not that anyone has proven. Unless someone here wants to link to somewhere showing the load estimation being related to fuel trims. It certainly never did that on the EJ engines.

The code is really not that sophisticated. There's no combustion model based spark control either--or if there is, it doesn't matter enough that anyone has bothered trying to understand it. Have you seen the cooled EGR spark controls on the FA20DIT? It's just a dumb look up compensation table, or at least the one that has been found so far seems that way. No residual gas model aspect to it.

MAF scaling has always been strategic tail-chasing in this context.

I have a totally different theory. I think the rich condition in CL is caused by sudden "Tip-in" enrichment, which affects STFT, becoming LTFT. This is then passed on to OL. I think Tip-in should have a lower threshold, and smoother transitions, so it wouldn't adversely affect fuel trims in CL, and then corrupting OL. It doesn't require any mysterious ECU reverse engineering, and it is a fuel source outside of usual channels unaffected by the MAF or MAP sensors. What do you think @thambu19?

Here are my current Tip-in thresholds above, compared to the OFT OTS map thresholds below. As well as my current Tip-in Enrichment A, and B tables, above, compared to the OFT OTS A and B tables below. I have tried smoothing out the transition between throttle angles 5.86%, and 7.81%, because there is such a jump there, but it didn't work as well when I drove it. So, I just stuck with smoothing the transitions under 5.86% and lowering the thresholds. Do you think the stock configuration of the Tip-in Enrichment and Thresholds could be the source of the problem?

1. Aside from increased LTFT causing the car to run richer than desired OL operation under certain conditions (average to cooler temps) there is not much perceptible drivability issues or increase in knock that I've noticed.

2. I don't think the stock MAF scale has been very good for anyone that I can remember. For my case, it's a maf scale that worked well while running less PI (more like the table below), but experienced a good amount of increase in fuel trims in areas where Port injector ratio was increased. This somehow led to an increase in LTFT in OL operation causing it to run even more rich than before the changes to the port injector ratio tables.

https://scontent-lax3-1.xx.fbcdn.net...7e&oe=56E28828

One would suspect one would spend less time "chasing one's tail" if I simply modified the port ratio table to run 100% DI at .20 load and lower, but where is the fun in that right? lol

It's seems that many of the guys that have already done some "tail chasing" had pretty good success balancing the port injectors to the direct injectors after dialing their MAF scale while running 100% DI. This is what I've decided to do now, but I will take it one step further by taking the IAT compensation into account. I've dialed my MAF while running 100% DI at IAT of 66~70*f by making sure my IAT don't go below 66*f throughout the entire range and not using any of the data with intake temps above 70*f. I think this will give me a good base before making changes to the IAT compensation and port injector scaling.

https://scontent-lax3-1.xx.fbcdn.net...db&oe=56EE32CF

Fuel trims, on my car, has not increased beyond 9% (idle LTFT) after changing the port injection ratios. I'd say at most +4%~6% LTFT in the "problem" areas aside from idle speeds. My main concern it the fluctuations in fuel trims seems to be bumping up the LTFT in OL operation causing it to run a bit richer than before. I wouldn't call it a 'huge' concern, but it is something I think I'd address. If anything, I just want to mess with it and see how close I can get it to requested AFRs as I can.

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

At this point in time we aren't sure quite how the LTFT ranges work. There are definitely bands but the standard defined ones don't seem to quite tie in. I think @solidONE has been testing something but nothing conclusive.

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?

First: Getting DI and PI systems balanced made a driveability difference to my car - just went smoother.

Second: You would think that the Subaru engineers would be quite close with their stock MAF scales and fuelling algorithms. Some cars seem to be close to the mark, others not so. I was happy leaving the DI system stock on the hope that the engineers did their job, scale the MAF to that, then dial in PI system. I had planned to upsize my port injectors so it made sense for me to do it in that order to have a stable base to calibrate my port injectors to.

Third: I agree, there is a huge amount in the code that is not defined. I did disassemble the Tau transient fuelling tables, but have not been able to make sense of how to change them logically, so I've left them alone.

Finally: I'm happy to let the trims to their work and I have given up trying to control them around idle speeds, but I also like a pretty graph, even if the information it gives me is erroneous.

I haven't been able to find exactly where fuel trims get applied, but engine load calculation comes quite close to the beginning and all the trim calculations that I have seen seem to be calculated referencing a figure that has already been finalized. I suspect the trims do get applied to fuelling only and do not affect load.

Changing MAF scale does shift load cell - this should be finalized (or stock values accepted as a reference) first before anything else is touched, as most of the other values reference load. Changing MAF scale later in the process screws around with everything under it in the code.

Front O2 is Denso Planar
Rear O2 is standard switching type

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

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.

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.

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