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Old 05-19-2008, 01:33 AM   #1
07wrx4life
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Default need help with scaling the MAF

Hey, some of you may have seen my other thread some may not, basically I have a 07 wrx protuned stg 2 and I recently installed a perrin Turbo inlet tube. since the install the car will not idle when it gets to operating temp. I received my tatrix cable the other day and I just logged the car, but have no idea what to look for. Some people have been telling me I need to rescale my MAF since I installed the turbo inlet. If someone could take a look at my log and let me know how to change it or even correct it for me that would be sweet.

Let me know if you would like to help by PMing me your email addy and ill send you a copy of the log I saved, or just post it here. I dont think I can attach the file to this thread > : (

Edit: If you pay attention to the RPM's you'll notice where the Idle starts to jump around.
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Old 05-19-2008, 01:48 AM   #2
Phatron
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you can read this....
HOWTO: One Man's Way of Scaling a MAF

To do it right you need a wideband to be able to do the open loop portion of the MAF table, basically anything above 55 g/s.....the lower close loop portion you can do by logging AF Corrections A-D and adjusting your MAF accordingly....

Here is how i rescaled mine after installing a APS 65mm intake....i started with a stock rom, then broke it into the appropriate sections in excel A=0-5g/s B=5-10g/s C=10-50g/s D= >50g/s.....logged the AF Corrections along with my AFR from the wideband.....corrected the MAF appropriately based on the corrections and AFR data collected.
You set your AFR table in the rom where you want it to be (11.3:1) then adjust the maf until your wideband matches the table in the rom. It only took me 3 runs to do this on my WRX. The first log i found i had been running 12:1 with values of 11.3 in my AFR table. After the first run i decided to be conservative and change the AFR targets to 10.8...and since i was at 12.0 with 11.33 targets i increased the MAF by 8% to add more fuel to the car. Increase MAF adds fuel cause you are telling the car more air is going in, decreasing the MAF takes out fuel. You are pretty much screwed without a wideband...i'd pay the $240 and get one ASAP. its well worth it.

As for the tables below....the top one is the one i started with....i believe its a stock s203 maf table....I chose to start with that since i am running STi pinks and the APS CAI. The %INC is the percent increase i multiplied the s203 MAF table by to come up with the second MAF table.

Code:
[Table2D]																																															
MAFV      0.94	0.98	1.02	1.05	1.09	1.13	1.17	1.21	1.25	1.29	1.33	1.37	1.41	1.48	1.56	1.64	1.72	1.8	1.87	1.95	2.03	2.11	2.19	2.27	2.34	2.42	2.54	2.66	2.77	2.89	3.01	3.12	3.24	3.36	3.48	3.59	3.71	3.83	3.95	4.06	4.18	4.3	4.41	4.49	4.57	4.61	4.65	4.69
MAF       1.31	1.5	1.71	1.93	2.19	2.47	2.78	3.12	3.49	3.88	4.31	4.75	5.27	6.31	7.49	8.8	10.21	11.79	13.51	15.41	17.55	19.95	22.63	25.62	28.92	32.47	38.34	44.93	52.2	60.07	68.57	77.68	87.56	98.37	110.08	122.69	136.19	150.67	166.2	182.83	200.63	219.7	240.02	254.21	269.09	276.81	284.69	292.74
[Table2D]																																															
MAFV      0.94	0.98	1.02	1.05	1.09	1.13	1.17	1.21	1.25	1.29	1.33	1.37	1.41	1.48	1.56	1.64	1.72	1.8	1.87	1.95	2.03	2.11	2.19	2.27	2.34	2.42	2.54	2.66	2.77	2.89	3.01	3.12	3.24	3.36	3.48	3.59	3.71	3.83	3.95	4.06	4.18	4.3	4.41	4.49	4.57	4.61	4.65	4.69
MAFg      1.41	1.62	1.85	2.07	2.34	2.64	2.95	3.31	3.70	4.07	4.53	4.99	5.53	6.56	7.79	9.15	10.62	12.97	14.86	16.95	19.31	21.95	24.89	28.18	31.81	35.72	42.17	49.42	56.90	65.48	74.74	83.89	94.56	105.26	117.79	131.28	145.72	161.22	177.83	195.63	214.67	235.08	256.82	272.00	287.93	296.19	304.62	313.23
%INC      1.08	1.08	1.08	1.07	1.07	1.07	1.06	1.06	1.06	1.05	1.05	1.05	1.05	1.04	1.04	1.04	1.04	1.1	1.1	1.1	1.1	1.1	1.1	1.1	1.1	1.1	1.1	1.1	1.09	1.09	1.09	1.08	1.08	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07	1.07
this is what it looks like graphically

Last edited by Phatron; 05-19-2008 at 06:23 PM.
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Old 05-19-2008, 01:56 AM   #3
07wrx4life
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Default

I wish i understood how to change all this stuff lol, I guess i needa save my ROM and hopefully someone on here will help changing it. In the mean time im going to read that one link that you just sent me, looks like there is alot of good info in there. Thanks!
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Old 05-19-2008, 02:37 AM   #4
Phatron
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The thing is no one will be able to help you unless you have a wideband....otherwise they are just guessing at the AFR....
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Old 05-19-2008, 02:56 PM   #5
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good thread. just what i needed since i have an aps 65mm cai i need to tune for.

thanks for the info ron!
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Old 05-19-2008, 06:24 PM   #6
Phatron
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I just added this to above...forgot to explain what i actually did...

The top MAF table in the code is the one i started with....i believe its a stock s203 maf table....I chose to start with that since i am running STi pinks and the APS CAI. The %INC is the percent increase i multiplied the s203 MAF table by to come up with the second/rescaled MAF table.
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Old 05-21-2008, 10:10 AM   #7
nhat
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so if i'm running rich, i want to lower the maf reading to lean it out.

any idea why my mafv tops out at ~280g/s?
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Old 05-21-2008, 11:38 AM   #8
Phatron
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Yes, lower the MAF scaling to lean it out......

If you tell the ECU you are putting 500g/s of air in at 2.0v and your target afr is 11.33 its gonna throw enough fuel in for 500g/s of air to hit 11.33
If you tell the ECU you are putting 200g/s of air in at 2.0v and your target afr is 11.33 its gonna throw enough fuel in for 200g/s of air to hit 11.33, which is a lot less fuel than the first example.

lower g/s = leaner

higher g/s = richer

Your g/s is topping out at 280g/s in a log....or in your ROM?

my 06STi goes out to 348.45g/s at 4.92 mafv in the stock ROM.
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Old 05-21-2008, 11:47 AM   #9
fujiillin
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For the OP, are you using the stock airbox?

The turbo inlet tube will have no effect on CL fueling, and only a slight effect on OL depending on the VE changes.

Sounds like the issue here is a boost/vac leak from the install, provided you're still on the stock airbox.

nhat, for CL maf tuning, I find the RomRaider Maf Tab to work really well. Open your rom and check your AF correction, AF learned, Maf g/s, Front o2 sensor AF, Maf V, coolant temp, Intake temp, and RPM in the data tab . Set the filter properly and drive the car for a few hours at a variety of temperatures, interpolate a good curve, and update. Rinse & repeat until the interpolation is all near zero.

For OL maf tuning, I log RPM, Load (direct), Maf V, Maf g/s, and wideband AFR. Plug that into Airboy's spreadsheet along with your fueling table, and interpolate the AFR. The spreadsheet will give you a nice % error in the afr plotted along the maf voltage. Apply the necessary corrections to the maf table, rinse & repeat until your wideband is within a couple % of the target. Before each log, be sure fuel learning is zero, reset the ecu as needed. Also, I like to get the IAM up to 1 before logging, and set the fuel table relatively rich & flat, but it isn't a necessity for this.

Last edited by fujiillin; 05-21-2008 at 12:00 PM.
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Old 05-21-2008, 12:01 PM   #10
Phatron
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Just another tip if you are gonna use a % increase like i did.....

Remember that it varies as the g/s go up.....10% increase of 50 = 5g/s increase

10% increase of 250 = 25 g/s.....

So you cant use a blanket % over the whole range.

I also noticed that 1% g/s seemed to move the AFR about 0.1. So if your AFR is hitting 10.5 but your targets are 11.0, then decrease the MAF ~5% to get the AFR to 11.....its probably different on every car and i may have been drunk so use that at your own risk
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Old 05-21-2008, 01:51 PM   #11
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Quote:
Originally Posted by 07wrx4life View Post
since the install the car will not idle when it gets to operating temp.
Sounds like a problem with the install, and not with your MAF scaling.
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Old 05-21-2008, 02:21 PM   #12
Phatron
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hook up your laptop, log AFR and the corrections, and let your car idle in the driveway then spray some brake cleaner or wd-40 around the turbo inlet.....if the AFR's go whacky then you have a leak
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