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Old 02-22-2008, 10:59 PM   #1
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Default better way to reach target afrs: adjust maf scaling or fuel map?

as tgui knows, my car runs rich...quite rich. he originally flashed my car to stage 2 last year, and since then i've installed a wideband and aps cai. i was also running IDCs in the range of 108% with just the installation of the cai, but scaling the maf for the aps cai brought IDCs down to 101%. i'm not worried about what my IDCs will be once my car is tuned to target afrs though.

while logging, the lc-1 was showing that i was running 9.5:1 afrs @ wot after installing the cai without any additional tuning to the stage 2 map. i consulted my friend who's a tuner out in colorado and he believes the best approach would be to continue scaling the maf until i reach target afrs. i thought the best way would be to adjust the fuel map.

i suppose either way doesn't really matter, but which is the preferred method?
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Old 02-23-2008, 01:06 AM   #2
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If the fuel map is calling for X, and the reality is that the car is running at Y, and you're on stock injectors, scaling the MAF to get it as close as possible is a good way to do it.

This presumes a couple of things. 1) You injector scaling and latency are correct 2) Your closed loop scaling is dialed in well enough that you don't have something crazy going on in AF Learning #1 D 3) You're missing your AFR targets in a predictable manner.
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Old 02-23-2008, 07:41 AM   #3
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Yes you need to rescale the MAF, dont just change the AFR table. Its not the better way, its the right way.

I was comtemplating doing this the other day since i just put a aps cai on my 02wrx. but then i remembered that the Air Fuel Learning A,B,C,D tables get set while you are in closed loop, but they still apply the correction when you are in open loop only now they are doing it blindly.
so if your maf table isnt scaled correctly then your corrections will be way off in open loop.

this should be pretty easy to do with the new MAF logger in enginuity with your wideband.
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Old 02-23-2008, 01:43 PM   #4
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Anyone ever encounter their AFR number's being off after they changed the AFR target? For instance my AFR targets for CA91oct are 11.0, my current scaling will be spot on with 91oct or even 100oct. But on my race gas map that calls for 12.0 the AFR for the most part never gets higher than 11.7-8ish. This is all in the same voltage range as well and AF learning D is at 0%.
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Old 02-23-2008, 02:25 PM   #5
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Originally Posted by Infamous1 View Post
Anyone ever encounter their AFR number's being off after they changed the AFR target? For instance my AFR targets for CA91oct are 11.0, my current scaling will be spot on with 91oct or even 100oct. But on my race gas map that calls for 12.0 the AFR for the most part never gets higher than 11.7-8ish. This is all in the same voltage range as well and AF learning D is at 0%.
couple questions here:

what are you measuring it with? do you have your ownn wideband? or was it tuned on a dyno with the sensor in the tailpipe? do you have any cats? were the pump and race gas maps made the same day? was the wideband actually used to tune the race gas map? <-- are you really sure it was? the tuner could have just set it to 12 for the race gas map assuming thats where it would go since he already scaled the maf on pump gas?

what was the mixture in your gas tank when it was tuned on 100octane?
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Old 02-23-2008, 03:34 PM   #6
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Quote:
Originally Posted by Phatron View Post
couple questions here:

what are you measuring it with? do you have your ownn wideband? or was it tuned on a dyno with the sensor in the tailpipe? do you have any cats? were the pump and race gas maps made the same day? was the wideband actually used to tune the race gas map? <-- are you really sure it was? the tuner could have just set it to 12 for the race gas map assuming thats where it would go since he already scaled the maf on pump gas?

what was the mixture in your gas tank when it was tuned on 100octane?
Measured with a Zeitronix wideband in the DP just after the turbo. No cats and on the street. Pump gas map was made on a different day but numbers were verified before the 100 octane was pumped in. Only thing done to fueling on the 100oct map was adjusting of the AFR targets, then logged with the wideband. The mixture was almost all 100oct. When I went bact to the 91 oct map even while running the 100oct the AFR was right on target. I am the tuner, I am just wondering what I should do to insure I hit my higher targets.
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Old 02-24-2008, 06:18 AM   #7
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sounds like you did everything right (as far as i know).

your maf is scaled
your corrections are all +-5
it reads right at 11:1 on pump

man i would just say to make your afr in the map 12.2:1

in all reality the #'s in the map are meaningless. its what your AF gauge says that really matters right? on my meth map my afr map calls for 13:1 for me to hit 12:1
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Old 02-24-2008, 06:19 AM   #8
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double cheese post
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Old 02-24-2008, 07:40 AM   #9
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Originally Posted by Phatron View Post
sounds like you did everything right (as far as i know).

your maf is scaled
your corrections are all +-5
it reads right at 11:1 on pump

man i would just say to make your afr in the map 12.2:1

in all reality the #'s in the map are meaningless. its what your AF gauge says that really matters right? on my meth map my afr map calls for 13:1 for me to hit 12:1
This is what I was told also, just wanted a 2nd opinion. I will do a little experimenting once the weather clears up.
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Old 02-24-2008, 10:05 AM   #10
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thanks for the advice.

Quote:
Originally Posted by Phatron View Post
sounds like you did everything right (as far as i know).

your maf is scaled
your corrections are all +-5
it reads right at 11:1 on pump

man i would just say to make your afr in the map 12.2:1

in all reality the #'s in the map are meaningless. its what your AF gauge says that really matters right? on my meth map my afr map calls for 13:1 for me to hit 12:1
so if my maf is already scaled for the intake and my fuel map calls for 11:1 @ wot, do you i continue to scale the maf or adjust the fuel map?
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Old 02-24-2008, 12:38 PM   #11
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Phatron is correct. If your closed look fueling is good, and your AFL's are all within 5%, I would just tune your fueling map so that your WB02 AFR's match what you're looking for.

On my car (06 WRX, stage 2, stock airbox), my AFR map calls for AFR's about 1.5 points above logged AFR's. The car runs great.
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Old 02-24-2008, 04:45 PM   #12
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Just wondering, why is it not a good idea to rescale the upper MAF to match the AFR on only the rom that is calling for 12:1?
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Old 02-24-2008, 05:13 PM   #13
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Quote:
Originally Posted by Infamous1 View Post
Anyone ever encounter their AFR number's being off after they changed the AFR target? For instance my AFR targets for CA91oct are 11.0, my current scaling will be spot on with 91oct or even 100oct. But on my race gas map that calls for 12.0 the AFR for the most part never gets higher than 11.7-8ish. This is all in the same voltage range as well and AF learning D is at 0%.
It's likely that you're racegas map is running in different load cells, which depending upon the map, could do this.
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Old 02-24-2008, 05:20 PM   #14
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Originally Posted by fujiillin View Post
It's likely that you're racegas map is running in different load cells, which depending upon the map, could do this.
That was the first thing I checked. It also isn't like a consistant .2 points richer it flucuates a bit as if the MAF needs to be rescaled.
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Old 02-24-2008, 05:26 PM   #15
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Quote:
Originally Posted by Infamous1 View Post
Just wondering, why is it not a good idea to rescale the upper MAF to match the AFR on only the rom that is calling for 12:1?
im not exectly sure. I believe its just easier to change the afr map because if its at 12:1 but your're only hitting 11.8, then you should be able to just change it to 12.2 to make it reach where you want. its much more tedioius to rescale the maf. wont it change your load so you would have to change a lot of other maps too?

dont forget there are other open loop enrichment maps that may because causing it too.
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Old 02-24-2008, 05:32 PM   #16
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Quote:
Originally Posted by Infamous1 View Post
Just wondering, why is it not a good idea to rescale the upper MAF to match the AFR on only the rom that is calling for 12:1?
I would change the MAF scaling first to get it as close as possible, then fix anything that can't be fixed with MAF scaling via changing the fueling target.
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Old 02-24-2008, 05:57 PM   #17
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Originally Posted by williaty View Post
I would change the MAF scaling first to get it as close as possible, then fix anything that can't be fixed with MAF scaling via changing the fueling target.
This is what I was thinking would be the safest option even though it would require the most time. Since the AFR isn't a steady 11.8 I just don't feel to comfortable with setting the value to 12.3 to get a 12:1 AFR with the occasional spike to 12:3. I guess the computer compensation isn't consistant and the MAF must be rescaled when the target varies a good amount.
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Old 02-24-2008, 06:25 PM   #18
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I would change the MAF scaling first to get it as close as possible, then fix anything that can't be fixed with MAF scaling via changing the fueling target.
i'm guessing this applies to me as well? maf is scaled to what the wideband sees only i'm still running 1pt too rich. fuel map asks for 11:1 @ wot but i'm seeing 10:1.
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Old 02-24-2008, 08:01 PM   #19
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interesting convo... i'm noticing the same thing from my tune.
closed loop corrections are all pretty good. the maf was rescaled up to 1.8 load, then above that it looks like the fueling changes were all just adjusted in the target AFR map which is mostly calling for about 11.7 when i'm actually running about 11.0.
any other negatives to this, or should the maf scaling be adjusted slightly to get these numbers closer together?
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Old 02-24-2008, 08:20 PM   #20
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If your other things are right (injector scaling/latency, fuel pressure, enough fuel to do the job, etc etc) and you're largely missing your OL fueling targets, the most logical conclusion is that the MAF is mis-calculating the amount of air entering the engine. This messes up fueling, obviously, but also timing other things as well. Anything that references airflow or engine load will be screwed up if your MAF scaling is wrong. This is why you want your MAF scaling as close to right as possible.

However, when you dial in your MAF scaling in Open Loop, you'll find that while you can get it to hit the called-for target AFR is MOST cells, you won't be able to get it to do it in ALL the cells. At WOT, there will be changes in the MAFv to actual airflow calibration that change more quickly than the points in the MAF scaling table. In other words, you might be both +10 and -12 between 4.22 and 4.34 MAFv. Obviously, you can't do anything about that will MAF scaling. It's at that point you have to start altering the OL Fueling A/B table to get it to hit the target.

For example, this is the WOT column of my OL Fueling A/B Map:
Code:
	RPM	1000	1200	1400	1600	1800	2000	2400	2800	3200	3600	4000	4400	4800	5200	5600	6000	6400
Target AFR	12.46	12.46	12.46	12.46	12.46	11.98	11.98	11.98	12.46	11.98	11.98	12.46	11.76	11.76	11.98	12.46	12.98
That map makes me run between 12.3 and 12.8 all the way up a WOT pull. The only reason it's that close is because the MAF scaling is as close as possible. Prior to MAF scaling, to hit the 12.5 target just by altering the fueling values, I was having to enter values between 9.0 and 14.5 into the OL Fueling AB map.
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Old 02-25-2008, 02:13 AM   #21
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Originally Posted by Phatron View Post
but then i remembered that the Air Fuel Learning A,B,C,D tables get set while you are in closed loop, but they still apply the correction when you are in open loop only now they are doing it blindly.
so if your maf table isnt scaled correctly then your corrections will be way off in open loop.

this should be pretty easy to do with the new MAF logger in enginuity with your wideband.
can you explain this more?
i thought that the ecu applied afr corrections in closed loop mode, but was hands off in open loop.
also, are you saying its easy to scale open loop with the maf logger, or just closed loop?

and also, can someone list the areas of the map that will be affected if the maf scaling is changed? want to make sure i'm not missing anything on my mental checklist here...
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Old 02-25-2008, 02:20 AM   #22
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Originally Posted by Wrinkleboi View Post
can you explain this more?
i thought that the ecu applied afr corrections in closed loop mode, but was hands off in open loop.
also, are you saying its easy to scale open loop with the maf logger, or just closed loop?

and also, can someone list the areas of the map that will be affected if the maf scaling is changed? want to make sure i'm not missing anything on my mental checklist here...
The ECU learns the values for AF Learning #1 A through D while in Closed Loop. However, when it transitions to Open Loop, it continues to apply AF Learning #1 D, though without any possibility of changes to the value (no learning).

The 785 MAF tool can only scale closed loop.

MAF scaling doesn't change any particular area of any map. MAF scaling determines how the ECU estimates actual airflow from MAF Sensor Voltage. From this estimation of the actual air entering the engine, the ECU calculates everything that depends on airflow or engine load (fueling, timing, CL/OL, and on, and on).
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Old 02-25-2008, 06:12 AM   #23
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Quote:
Originally Posted by williaty View Post
The ECU learns the values for AF Learning #1 A through D while in Closed Loop. However, when it transitions to Open Loop, it continues to apply AF Learning #1 D, though without any possibility of changes to the value (no learning).

The 785 MAF tool can only scale closed loop.

MAF scaling doesn't change any particular area of any map. MAF scaling determines how the ECU estimates actual airflow from MAF Sensor Voltage. From this estimation of the actual air entering the engine, the ECU calculates everything that depends on airflow or engine load (fueling, timing, CL/OL, and on, and on).
so now this can be done on romraider w/o necessarily needing a wideband connected? (to more or less get a general idea for us people that dont have a wideband)
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Old 02-25-2008, 07:32 AM   #24
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Yes the MAF scaling can be done with romraider BUT ONLY THE CLOSED LOOP PORTION OF THE MAP.

This is about the first 1/3 of the MAF table. 0-100 grams/sec. You can change the ranges it will collect data in. Its quite a knifty tool. you just drive around and it collects all the data within the parameters you specify, then when you feel you have enough data just hit the interpolate button and it will show you the interpolation over all the dots. Then it will even rewrite the table into enginuity if you have the rom open.

Anything above that you need a wideband for.
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Old 02-25-2008, 01:56 PM   #25
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The ECU learns the values for AF Learning #1 A through D while in Closed Loop. However, when it transitions to Open Loop, it continues to apply AF Learning #1 D, though without any possibility of changes to the value (no learning).
Thanks for the response. Do you know how AF Learning #1 D is calculated? Not sure what the difference between A, B, C, D are.

And another thing I'm trying to crunch in my head but don't full grasp is...
When the MAF is scaled perfectly in Open Loop Fueling vs. when its off to the point that the difference between your Target AFR and Actual AFR is 1.0, for example.
How would AF Learning #1 D be different for these two situations? Wouldn't it affect both equally?
So... if you nail all of your closed loop MAF adjustments, will AF Learning #1 D be very small, and as a result not make any noticeable changes to Open Loop Fueling? Meaning that the Open Loop AFR Targets can be off by a bit without any ill effects?
Lastly, can I still make minor changes in my Closed Loop MAF scaling without it affecting other areas of my tune, or is that a big no no?
Thanks for the help, just trying to process all of this so I understand how it works completely.
Bryan
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