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Old 01-30-2021, 01:03 PM   #197
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Originally Posted by Compelica View Post
I've been looking around for the answer to a question that doesn't seem to come up. If getting fuel trims laid out correctly is so important, which the car needs driving for some time to learn at four rev ranges in CL - how does any OFT tuner accomplish any work within an acceptable time? For example, if I was working on ignition for 98 RON I would have to:

1. Make change in tune.
2. Flash tune to car.
3. Wait for AVCS to turn on.
4. Wait for LTFTs.
5. Do pull, monitor IAM and knock parameters.
6. Rinse and repeat.

Even if a person is on a dyno, he/she wouldn't have all day for step 3 and 4 - I know LTFTs can be turned off but you wouldn't be testing in the proper scenario eventually.

Is there something that I'm missing here?
On a dyno you have realtime AFR and you use the fuel trims in closed loop and fuel error in open loop to get the system setup correctly. You can hold the car in certain load scenarios. Thing is, on a dyno if only an hour you would spend that setting up the power range and probably just checking some closed loops regions so it was close enough to not change the open loop portions of the map.

You should still do road testing as the final part of any mapping session.
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Old 01-30-2021, 10:13 PM   #198
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Quote:
Originally Posted by Kodename47 View Post
On a dyno you have realtime AFR and you use the fuel trims in closed loop and fuel error in open loop to get the system setup correctly. You can hold the car in certain load scenarios. Thing is, on a dyno if only an hour you would spend that setting up the power range and probably just checking some closed loops regions so it was close enough to not change the open loop portions of the map.

You should still do road testing as the final part of any mapping session.
I'm not sure if I follow...

Even if the dyno has realtime AFR readings and I could tune based on them, that wouldn't necessarily be the AFRs that I would end up with after the ECU learns up the fuel trims, would it? AFRs would affect how much ignition I can run, it may look good on dyno day but it won't necessarily be a few days after the ECU settles in?

..
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Old 01-31-2021, 04:40 AM   #199
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I'm not sure if I follow...

Even if the dyno has realtime AFR readings and I could tune based on them, that wouldn't necessarily be the AFRs that I would end up with after the ECU learns up the fuel trims, would it? AFRs would affect how much ignition I can run, it may look good on dyno day but it won't necessarily be a few days after the ECU settles in?

..
If there is no error in the fuelling, then there will be little to no fuel trims. Minor changes to AFR will make little difference to a tune and fuel trims should bring the AFR back to target if the setup is done right.
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Old 01-31-2021, 06:38 AM   #200
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If there is no error in the fuelling, then there will be little to no fuel trims. Minor changes to AFR will make little difference to a tune and fuel trims should bring the AFR back to target if the setup is done right.
Thanks - but the strange thing is that my actual AFRs and AFR commanded are straying way off from each other... which brought me to my initial tuning question.

As a background I'm on Wayno's tune, only with a decatted OEM header and I'm trying to understand why the actual AFRs are not doing anything to 'catch up' to the commanded. Now @Wayno himself has stated that the actuals does not need to follow commanded, but to see it run off 0.4 points is unsettling.

The car has also done at least 1000kms since the flash, and I'm seeing a constant LTFT of 2.93 throughout 5500 to redline, so I'm assuming the trims are fine.

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Old 01-31-2021, 05:49 PM   #201
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Quote:
Originally Posted by Compelica View Post
Thanks - but the strange thing is that my actual AFRs and AFR commanded are straying way off from each other... which brought me to my initial tuning question.

As a background I'm on Wayno's tune, only with a decatted OEM header and I'm trying to understand why the actual AFRs are not doing anything to 'catch up' to the commanded. Now @Wayno himself has stated that the actuals does not need to follow commanded, but to see it run off 0.4 points is unsettling.

The car has also done at least 1000kms since the flash, and I'm seeing a constant LTFT of 2.93 throughout 5500 to redline, so I'm assuming the trims are fine.
Many points to consider here:
1. It's richer so will be safer and won't cost you any real power.
2. Do you trust the AFR output? Have you verified it?
3. Wayno is correct that the 2 do not need to align. Helpful for mapping but otherwise not actually necessary. It might be that the AFR you have is what is wanted and that the fuel map is setup to achieve that. Not saying that it is, but I know that is a method of tuning.
5. The LTFT is set in buckets, as such, based on load and RPM. This is definable in maps. LTFT is set by the STFT so all the time the STFT is 0, as is the case in open loop, then the LTFT will not adjust. I can't remember where the upper threshold starts but IIRC it's in the mid to low 4k RPM range.

At the end of the day, fuel error and fuel trims are essentially the same. If the STFT and LTFT combined at any given point are +10% then your fuel error is that. If trims aren't active or not set, then you can calculate the error simply by using the input and output AFR. All my log systems use a calculation based on combined fuel trims and pure error, so I can make corrections within seconds of getting data and immediately after flashing.
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Old 02-01-2021, 02:29 AM   #202
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Quote:
Originally Posted by Kodename47 View Post
2. Do you trust the AFR output? Have you verified it?
3. Wayno is correct that the 2 do not need to align. Helpful for mapping but otherwise not actually necessary. It might be that the AFR you have is what is wanted and that the fuel map is setup to achieve that. Not saying that it is, but I know that is a method of tuning.
Point taken. I pulled out a dyno reading done previously on the same tune and AFRs were reading about low 12s. But that leads to another question - is there a limitation to the OEM O2 sensors that we can't scale them to closer accuracy? After all, the sensor feeds values to the ECU, and the ECU reacts appropriately to those values.

It's like setting up everything with a non-linear offset instead of placing actual values, which makes me wonder how on the road tuning would be possible...

I have another question - what is the purpose of the load limiter tables from a tuning standpoint for NA? What I can think of, it's only used to prevent the engine from getting into a low RPM high load state, and subsequently preventing LSPI. Apologies for the out of order questions, there's lots I'm picking up but there's a few pieces that I find it difficult to fit into the bigger picture.
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Old 02-01-2021, 05:05 AM   #203
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Point taken. I pulled out a dyno reading done previously on the same tune and AFRs were reading about low 12s. But that leads to another question - is there a limitation to the OEM O2 sensors that we can't scale them to closer accuracy? After all, the sensor feeds values to the ECU, and the ECU reacts appropriately to those values.

It's like setting up everything with a non-linear offset instead of placing actual values, which makes me wonder how on the road tuning would be possible...

I have another question - what is the purpose of the load limiter tables from a tuning standpoint for NA? What I can think of, it's only used to prevent the engine from getting into a low RPM high load state, and subsequently preventing LSPI. Apologies for the out of order questions, there's lots I'm picking up but there's a few pieces that I find it difficult to fit into the bigger picture.
O2 sensor can be scaled but it's only as accurate as the settings and I've tried off the shelf ones and it wasn't totally accurate on my car vs when I verified and adjusted using a dyno. Also, the car is only in closed loop around when the AFR target is set to 14.7. ANy richer than that (unless you're a MY17) and the ECU moves to open loop and therefore doesn't use the AFR output.

LSPI is not an issue for NA, the load limiters are there to aid ignition timing and fuel delivery limits and that's about it. The ECU will read over the specified limits but cap the maps at those limits.

Let's be clear, AFR tuning is not going to be accurate. You have 1 AFR sensor taking an average of 4 cylinders. Unless you put a Wideband in each runner, you're tuning will only be as good as a fair guess as you have no idea what the actual AFR is anyway. So long as it's not knocking and too rich or too lean to make power, then it doesn't matter. Those are your goals under WOT; Make power, while not knocking.

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Old 02-17-2021, 11:48 PM   #204
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Great link and thx for the info Kodename47
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Old 07-20-2021, 02:19 PM   #205
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@Kodename47 @Wayno @steve99 @tomm.brz

I understand that with pump gas the engine is knock limited, but does this knock limit apply to the higher RPM ranges only, or otherwise?

As a background - I am slowly increasing ignition only at WOT loads to a point I start to see significant FLKC at > 5k RPM. But anything below 5k RPM there evidently isn't any knock at all. With your experiences - are we knock limited at WOT loads in lower RPMs (<5k)?

I am only optimizing WOT as I am aware it is possible to advance past MBT in partial throttle loads.
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Old 07-21-2021, 06:04 PM   #206
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@Kodename47 @Wayno @steve99 @tomm.brz

I understand that with pump gas the engine is knock limited, but does this knock limit apply to the higher RPM ranges only, or otherwise?

As a background - I am slowly increasing ignition only at WOT loads to a point I start to see significant FLKC at > 5k RPM. But anything below 5k RPM there evidently isn't any knock at all. With your experiences - are we knock limited at WOT loads in lower RPMs (<5k)?

I am only optimizing WOT as I am aware it is possible to advance past MBT in partial throttle loads.
Are you seeing FBKC at all? High load low RPM does seem knock limited. Are you over your load limits values at all, which will mean your changes may have limited impact.
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Old 07-21-2021, 10:11 PM   #207
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Hi guys,
Trying to learn more about the ecu program and was wondering why in closed loop at cruise eng loads , .5, I am seeing a commanded AFR of 14.2 - 14.4 on a flat road with no throttle change. Actual AFR tracks it pretty close. I under stand how the CL compensation fuel additive tables addition of - numbers works but that would then give me around 14.48 - 14.57 commanded or higher at the same rpm and eng load. Is there another table some where that I cant find. Was thinking of reflashing factory tune to see if its the same as Waynes roms or OFT for that matter. Not wanting to change anything just wanting to understand whats going on. Cheers
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Old 07-21-2021, 10:32 PM   #208
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Are you seeing FBKC at all? High load low RPM does seem knock limited. Are you over your load limits values at all, which will mean your changes may have limited impact.
No FBKC at all, and loads are well under the load limits. Here's the log if it helps illustrate things:

https://datazap.me/u/compelica/knock...?log=0&data=20
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Old 07-22-2021, 06:55 PM   #209
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@Kodename47 @Wayno @steve99 @tomm.brz

I understand that with pump gas the engine is knock limited, but does this knock limit apply to the higher RPM ranges only, or otherwise?

As a background - I am slowly increasing ignition only at WOT loads to a point I start to see significant FLKC at > 5k RPM. But anything below 5k RPM there evidently isn't any knock at all. With your experiences - are we knock limited at WOT loads in lower RPMs (<5k)?

I am only optimizing WOT as I am aware it is possible to advance past MBT in partial throttle loads.

no likely you will advance past mbt on petrol unless its very high grade but you would rearly need a dyno to prove that. Not possible on our local petrol here but its pretty crap
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Old 07-22-2021, 06:59 PM   #210
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Hi guys,
Trying to learn more about the ecu program and was wondering why in closed loop at cruise eng loads , .5, I am seeing a commanded AFR of 14.2 - 14.4 on a flat road with no throttle change. Actual AFR tracks it pretty close. I under stand how the CL compensation fuel additive tables addition of - numbers works but that would then give me around 14.48 - 14.57 commanded or higher at the same rpm and eng load. Is there another table some where that I cant find. Was thinking of reflashing factory tune to see if its the same as Waynes roms or OFT for that matter. Not wanting to change anything just wanting to understand whats going on. Cheers

The values in fuel tables is the values your asking for, the afr value is the measured value from the afr sensor its never going to be exact especially atfluctuating rpm and loads. at light loads light throttle the ecu will use long and sgort term fuel trims to try to match those up


If iam is lass than 1 the fueling compensation table comes into play and may slightly richen fueling depending on value s in that table
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