COBB AP/ATR Beta Fuel Scaling

[Enki]

Originally Posted by silvapain A very basic primer on how the ECU determines injector pulse width: 1. The ECU gets a voltage signal from the MAF, and using the MAF scale, turns that into mass airflow (g/s) 2. The ECU determines RPM and calculates load 3. Based on RPM and load, the ECU determines spark advance, VVT, and AFR target 4. Using mass airflow and AFR target, the ECU calculates fuel requirement in mass rate (g/s, lb/hr, whatever) 5. Using a scalar that represents injector size (lb/hr; on DI this would also incorporate fuel rail pressure), the ECU determines required injector pulse width (in milliseconds) It's the scalar in item 5 that COBB is adjusting I believe.

That still doesn't quite add up; step 5 amounts to a linear change, which we know doesn't work based on MAF scaling alone. What Finkle said about fuel mass makes more sense; more e = more oxygen getting into the cylinder (aside from the expected airflow) = higher scaled MAF value to equal the same AFR (if that makes sense).

If this is the way it is being done, it's pretty fucking smart. If not, please correct my understanding.

[Cobb Tuning]

Originally Posted by rfinkle2 No. LOL.... "changes to your injector dwell time and mass of fuel scalar" are being changed. If dwell time = latency than yes, if dwell time does not = latency than no, I'm not sure. Bolded type is what is being tweaked.

To clarify, what I'm looking to do is change the flow rate table of the injectors in the ECU - what some people call its scalar. Now what that does in turn is tell the ECU the injectors are either smaller or larger (in flow). From that, it calculates IPW to hit the AFR target you ask of it. In the case of E85, you say the flow rate is LESS so it INCREASES open inj. time to accommodate the additional mass needed to meet stoic. If you have bigger injectors, you'll say it has more flow rate so it'll cut down on the IPW.

This is the "correct" way of changing the injector routines from a fundamental level - or else it'll be correct for only certain RPM/Loads and won't scale with your car's different pressure/RPM/load.

And as I said before, still in development. For those of you that have maps, give me the final LTFT's off (and be sure to include +/- on those LTFT) so I can remake them with a final adjustment.

-David@COBB

[Evan@COBB]

Also, if any of you guys are still waiting for us to get you your maps, please send me an e-mail or PM. I was dealing with a pretty decent group of you yesterday and may have missed a couple.

The 'tweaked' maps that David is sending out are just estimates as to what "scalar" is needed for your fuel blend. I've been testing these for awhile now but we don't have it down to a science yet. We're still trying to figure out a good formula. The goal of having you guys see how it reacts on your cars is to try to figure out a formula that will work for any blend you have.

If you know your MAF scale is dead on for 93 and we sent you a scalar but now your trims are coming at -5 or so, that's because the scalar we gave you is really just our best guess as to what you need and may need some tweaking. Once these tables are released in ATR, you'll be able to go crazy with them to get yourself dialed in perfectly.

[djuosnteisn]

Originally Posted by David@COBB To clarify, what I'm looking to do is change the flow rate table of the injectors in the ECU - what some people call its scalar. Now what that does in turn is tell the ECU the injectors are either smaller or larger (in flow). From that, it calculates IPW to hit the AFR target you ask of it. In the case of E85, you say the flow rate is LESS so it INCREASES open inj. time to accommodate the additional mass needed to meet stoic. If you have bigger injectors, you'll say it has more flow rate so it'll cut down on the IPW.... -David@COBB

David, have you seen any tables or logic that look like it may control the injector opening position? Basically a way for us to start spraying fuel earlier?

[Fobio]

even if I can't directly benefit from the E85 scaling, it appears that the fueling discussion here will have wider implications for everyone.

[Lex]

The benefit of this is several fold:

1. MAF will no longer need to be scaled artificially for different fuel blends meaning that going E85 etc will just be a scalar away - easier to tune.

2. Larger injector fuel potential again without messing with the MAF when and if injectors are available.

3. People hitting load caps because of MAF scaling have this issue resolved. **Here's something interesting ** Just like you can scale up for E85 you can also scale DOWN. If we have an unkown load cap/table at say ... 2.0 load - scaled your MAF DOWN so that you are at stockish loads and use this multiplier to get the correct AFR. This is called tricking the trick And it's a hack in the opposite direction to deal with an uncovered table or cap.

In terms of VVT. Increasing VVT even on the K04 results in higher flow but lower power at high RPMs. However, increasing it on a big boy turbo should allow more fuel and more power. Increasing timing also decreases the amount of fuel available so pick your battles

[silvapain]

Originally Posted by Fobio even if I can't directly benefit from the E85 scaling, it appears that the fueling discussion here will have wider implications for everyone.

Ansolutely. What David is doing will be needed if/when we have larger injectors available to us. The ECU will need to adjust the dwell time for the higher-flowing injectors.


I noticed there was a discussion about injector latency and dwell times earlier. They are not the same:

Dwell time = how long the injector is 100% open, usually defined in milliseconds. If you take dwell time and divide it by the total available time that the injector can be open, you get duty cycle, measured in %.

Latency = how long it takes the injector to go from one position to the other; either from closed to open when the ECU commands it to open, or from open to closed when the ECU commands it to close.

[Enki]

Actually, you can benefit, Fobio. Get a bigger MAF housing.

[Cobb Tuning]

Originally Posted by silvapain Ansolutely. What David is doing will be needed if/when we have larger injectors available to us. The ECU will need to adjust the dwell time for the higher-flowing injectors. I noticed there was a discussion about injector latency and dwell times earlier. They are not the same: Dwell time = how long the injector is 100% open, usually defined in milliseconds. If you take dwell time and divide it by the total available time that the injector can be open, you get duty cycle, measured in %. Latency = how long it takes the injector to go from one position to the other; either from closed to open when the ECU commands it to open, or from open to closed when the ECU commands it to close.

To latch onto one of the topics - Injector duty cycle is calculated by a lot of things:

1) Crank Angle\RPM\VVT
2) Spark timing/advance
3) Load and airflow
4) Injector startup/duration/close time
5) HPFP pressure
6) Injector Flow rate size

This is why you can get 140-150% when using the old way of MAF scaling to run E85. Remember that it is an approximation.

As for opening injectors earlier, we need to find out if it actually moves the injection earlier for more time or just starts in the same place. This will ultimately determine if the stock injectors can run 100% E85 correctly.

-David@COBB

[Fobio]

Originally Posted by Enki Actually, you can benefit, Fobio. Get a bigger MAF housing.

I am already running a bigger maf. But there's BlueStreak with the forged motor and aiming for 26psi+. He will likely benefit from the refined fueling control. This is exciting stuff guys!

[rfinkle2]

I love to read the nitty gritty from all of you guys. I'm glad to have everyone contributing, and to have Cobb so involved in what was once an otherwise overlooked platform (@ least compared to other, more popular aftermarket platforms).

Thanks guys for the technical info, and David and Evan for working out some of the technical "stuff". (I'm particularly glad Evan has an ms3 and he and Phate are all about e85 LOL).

With companies like Deutchwerkes, Cobb and EFR working on shit for our cars, it opens up a whole new can of worms, imo.

[djuosnteisn]

Originally Posted by David@COBB As for opening injectors earlier, we need to find out if it actually moves the injection earlier for more time or just starts in the same place. This will ultimately determine if the stock injectors can run 100% E85 correctly. -David@COBB

[Alpha]

Originally Posted by rfinkle2 With companies like Deutchwerkes, Cobb and EFR working on shit for our cars, it opens up a whole new can of worms, imo.

Can of worms for the other platforms on the road.

[Nataphen]

If we can get larger injectors, control the injector open/close, and get fuel and injector scalars in the next few months, I see even more breakthroughs for 2012 than we saw in 2011. This is exciting stuff. 500-600whp without pouring in meth by the gallon may be closer than we think.

[laxplayermjd]

this thread is win, someday when im not so cheap i can buy alot of go fast parts, all this work from you guys would make tuning easier. Sure am starting to wish i had some e 85 around here.

[mrmonk7663]

Subd.

[themytb]

I hope all you fuckers have tiny dicks to make up for your super huge brains-----I'm so confused-----so much to learn yet. And I didnt even get a big dick.

[silvapain]

Originally Posted by themytb I hope all you fuckers have tiny dicks to make up for your super huge brains-----I'm so confused-----so much to learn yet. And I didnt even get a big dick.

If you really want to know, pictures of my meat sword are conveniently located in the cock thread in VIP.










You're welcome.

[themytb]

ehh dont really wanna know, just jelly of the knowledge. Hard to catch up with you guys.

also sorry for fuckin up a good thread Ill stfu now

[silvapain]

@David@COBB @Evan@COBB

I got DTC P2096 - Target A/F feedback system too lean today. I cleared the code, and after a couple key cycles I got it again. I flashed a new map to clear the LTFT's and did a datalog; it appears my STFT's are maxing out at +25 at very light throttle in 5th and 6th. See attached datalog.

[Enki]

If it was fine just after flashing the map, the issue is either due to a vacuum leak or an injector sticking shut.

[silvapain]

Originally Posted by Enki If it was fine just after flashing the map, the issue is either due to a vacuum leak or an injector sticking shut.

The log is from just after flashing the map. It was also happening before flashing the map.

It only started after going to the COBB beta map.

[Lex]

Originally Posted by silvapain @David@COBB @Evan@COBB I got DTC P2096 - Target A/F feedback system too lean today. I cleared the code, and after a couple key cycles I got it again. I flashed a new map to clear the LTFT's and did a datalog; it appears my STFT's are maxing out at +25 at very light throttle in 5th and 6th. See attached datalog.

Silva throw in injector PW in the log.

I am suspecting this is due to the poor resolution of the MAF at that low airflow. The MAF reading is almost the same as at idle.

For shits and giggles multiply the 1.37 to 1.60 V region by 1.1 in the MAF table and smooth the 1.60 to 1.76V and 1.29 to 1.37V regions.

[silvapain]

Originally Posted by Lex Silva throw in injector PW in the log. I am suspecting this is due to the poor resolution of the MAF at that low airflow. The MAF reading is almost the same as at idle. For shits and giggles multiply the 1.37 to 1.60 V region by 1.1 in the MAF table and smooth the 1.60 to 1.76V and 1.29 to 1.37V regions.

Will do for the next log.

I wanted to get input from COBB before I did any MAF corrections, to see if there was any more information they needed from me.

[Evan@COBB]

Originally Posted by silvapain @David@COBB @Evan@COBB I got DTC P2096 - Target A/F feedback system too lean today. I cleared the code, and after a couple key cycles I got it again. I flashed a new map to clear the LTFT's and did a datalog; it appears my STFT's are maxing out at +25 at very light throttle in 5th and 6th. See attached datalog.

Have you loaded up your 45% fuel map yet?

[Cobb Tuning]

Originally Posted by silvapain @David@COBB @Evan@COBB I got DTC P2096 - Target A/F feedback system too lean today. I cleared the code, and after a couple key cycles I got it again. I flashed a new map to clear the LTFT's and did a datalog; it appears my STFT's are maxing out at +25 at very light throttle in 5th and 6th. See attached datalog.

You need more fuel - the STFT's are at their max allowed error correction, so we need to up the amount.

Try the 45% and see if it helps. We might need to go higher if your STFT's are still too far.

-David@COBB

[silvapain]

Originally Posted by David@COBB You need more fuel - the STFT's are at their max allowed error correction, so we need to up the amount. Try the 45% and see if it helps. We might need to go higher if your STFT's are still too far. -David@COBB

I know the max trims allowed are +/- 25%. My question was why is it only at this specific point? My LTFTs are within +/- 8% otherwise; not ideal by any means, but well within the CL adjustment range if the ECU.


Tapadatass

[Lex]

Originally Posted by David@COBB You need more fuel - the STFT's are at their max allowed error correction, so we need to up the amount. Try the 45% and see if it helps. We might need to go higher if your STFT's are still too far. -David@COBB

Dave, take a look at my comment a few lines above. His STFTs are only high at very low airflow values.

[silvapain]

For reference, here's an Excel file of my pump gas MAF scale and my E85-adjusted MAF scale to show the percentage difference.

My averaged percent difference is 41%; hence the reason I'm using the 40% scalar

[Cobb Tuning]

Originally Posted by silvapain I know the max trims allowed are +/- 25%. My question was why is it only at this specific point? My LTFTs are within +/- 8% otherwise; not ideal by any means, but well within the CL adjustment range if the ECU. Tapadatass

Never seen that before. Your car seems to be the only one that is having this issue.

are the LTFT's you are having typically positive or negative?

EDIT: One of our calibrator's looked at your logs, and said that it is most likely a MAF scaling issue - so try to change it and give it a shot.

-David@COBB

[Lex]

Could also be a slight air/vacuum leak past the MAF but less likely because it wasn't there prior to the calibration change.

[djuosnteisn]

Originally Posted by silvapain The log is from just after flashing the map. It was also happening before flashing the map. It only started after going to the COBB beta map.

Originally Posted by silvapain I know the max trims allowed are +/- 25%. My question was why is it only at this specific point? My LTFTs are within +/- 8% otherwise; not ideal by any means, but well within the CL adjustment range if the ECU.

Is your fuel pressure still all fucked up below 3k rpm?

[silvapain]

Originally Posted by David@COBB Never seen that before. Your car seems to be the only one that is having this issue. are the LTFT's you are having typically positive or negative? EDIT: One of our calibrator's looked at your logs, and said that it is most likely a MAF scaling issue - so try to change it and give it a shot. -David@COBB

I have both positive and negative LTFT's. That's the primary reason I don't think I need to go to the 45% scaled map.

Dustin, My HPFP issues have been resolved (at least temporarily) by cleaning the spill valve thoroughly. You can see in the datalog I posted earlier that I'm maintaining fuel pressure throughout the log.

[Fobio]

the one time my LTFT kept worsening, was when I had a leak at the manifold/turbo gasket.

[Lex]

To test this parameter why even jump directly to 40%? Why not use a smaller step size that you can monitor directly without even having to use E85 in the car - just use the same fuel (same tank) and make small changes that can be tracked through trims and commanded PW changes as well as AFRs under WOT. This way there are less variables to consider.

Dustin also made a very good suggestion of making smaller increments such as 10, 20% and then scaling the MAF back by those same percentages. Then observing trims and WOT AFRs. No need to ACTUALLY use E85 and many map variations to test a fuel scalar.

[silvapain]

Originally Posted by Lex To test this parameter why even jump directly to 40%? Why not use a smaller step size that you can monitor directly without even having to use E85 in the car - just use the same fuel (same tank) and make small changes that can be tracked through trims and commanded PW changes as well as AFRs under WOT. This way there are less variables to consider. Dustin also made a very good suggestion of making smaller increments such as 10, 20% and then scaling the MAF back by those same percentages. Then observing trims and WOT AFRs. No need to ACTUALLY use E85 and many map variations to test a fuel scalar.

If I was going from pump gas to E85 just now, that's how I would do it.

I don't know if the data table COBB uncovered is 0-D or 1-D, but if it's 1-D I'd get my MAF dead-on with pump gas, then incrementally increase E85 concentration and use the new table to adjust the MAF accordingly. That way I'd know my mass airflow readings are 'actual', and not skewed due to recalibration for E85.

I could easily fix any LTFT errors I'm having now by simply rescaling the MAF; but then I might be back where I started with mass airflow and load values that don't mean anything because they've been skewed too much.

[Lex]

Just change one variable at a time and don't let it be the gas since that's hard to control.

Slowly increment the scalar and scale down the MAF to maintain the same AFR under WOT and trims.

[silvapain]

Originally Posted by Lex Just change one variable at a time and don't let it be the gas since that's hard to control. Slowly increment the scalar and scale down the MAF to maintain the same AFR under WOT and trims.

What I'm saying is that if the point is to maintain legitimate mass airflow values in the MAF table when going from pump gas to E85, you would want to adjust the fuel scalar table instead of the MAF table to hit AFR targets.

[djuosnteisn]

I think right now David's just looking for "proof of concept", and trying to establish how much of a tweak is required to get X percentage increase. From that data, he'll be able to wrap it all up nice and cute for ATR, and all we'll have to do is plug in a simple scalar.

[phate]

Look at the correlation between boost (vacuum) and the STFT's. You have very high STFT's as vacuum increases. That looks like a very small vacuum leak, to me.

This is obvious, but: To check, just flash back to your other map and see if it does the same thing. If STFT's go crazy, it's a vac leak. If all is peachy, then it's the scalar.