Stock maf = perfect idle. Big maf = unstable idle. Any tuning suggestions?

[onfire]

Stock maf idles at 12.5g/s....fluctuates +-0.5 g/s.

Big MAF idles at 8.5 to 14.0 g/s fluctuates +- 5.5g/s.

I've moved the hertz curve up and down....no changes....car starts hunting for the idle.

[Tordne]

Have you scaled the MAF table for the new MAF. It would appear to me that at idle the airflow requirements of the car will not have changed, and that there will be no benefit of the larger MAF it idle (as you would hope). Therefore I would expect the value at the idle Hz range to be the same as what you are seeing on the stable smaller MAF.

For example (and these numbers are completely made up) say the small MAF has 50Hz which equals your 12.5 grams/s, maybe the big MAF has 20Hz which equals 12.5 grams/s.

All getting too confusing now :(

Basically, I would expect that you would require a new MAF table for this new beastie.

[joecar]

Auto Tune VE table first, then Auto Tune MAF table.

[onfire]

It came with this maf hertz vs gps from a flow bench:


Hertz GPS
1500 3.18
1625 3.58
1750 4.04
1875 4.57
2000 5.18
2125 5.86
2250 6.63
2375 7.49
2500 8.44
2625 9.50
2750 10.65
2875 11.92
3000 13.31
3125 14.81
3250 16.44
3375 18.21
3500 20.10
3625 22.14
3750 24.33
3875 26.66
4000 29.15
4125 31.81
4250 34.63
4375 37.62
4500 40.79
4625 44.14
4750 47.68
4875 51.41
5000 55.33
5125 59.46
5250 63.80
5375 68.35
5500 73.12
5625 78.11
5750 83.33
5875 88.78
6000 94.47
6125 100.41
6250 106.59
6375 113.02
6500 119.72
6625 126.68
6750 133.91
6875 141.41
7000 149.19
7125 157.25
7250 165.61
7375 174.26
7500 183.21
7625 192.46
7750 202.03
7875 211.91
8000 222.10
8125 232.63
8250 243.48
8375 254.68
8500 266.21
8625 278.08
8750 290.31
8875 302.90
9000 315.84
9125 329.15
9250 342.84
9375 356.90
9500 371.34
9625 386.17
9750 401.39
9875 417.00
10000 433.02
10125 449.45
10250 466.29
10375 483.55
10500 501.23
10625 511.99
10750 511.99
10875 511.99
11000 511.99
11125 511.99
11250 511.99
11375 511.99
11500 511.99
11625 511.99
11750 511.99
11875 511.99
12000 511.99


I plugged that in and the AF went to 19:1 at idle....hacked and coughed....I plugged the factory scale in and it went to 10.1:1 AF at idle. So I made a zillion logs and recurved the lower area up to 16gps (max for my idle flow)...compared DYNAIR to MAF AIR and compared COMMANDED AF to ACTUAL AF on a wideband in open loop to zero the ltrims.....biggest problem is the wide range of gps at an 850rpm idle...stock only move up/down around 0.5gps.....this new maf jumps around +-5.5gps which is huge and is causing problems....I hope I just got a bad one.....

Tune is fine with the stock maf....any other suggestions is appreciated.

[onfire]

BTW, how do you autotune a maf table?

[Tordne]

Like 'joecar' says the best thing for you to do is perform the AutoVE procedure and get your VE table dialled in. Then calibrate the MAF on your car with know good values. Without doing this you will always be pissing in the wind.

[Tordne]

OK.. So basically what you will need to do is perform the AutoVE procedure. This will have you running in Speed Density mode, without MAF input.

It is best to do this, and any tuning really with a Wideband O2 controller BTW.

Once you have your fuel trims pretty much spot on then you can tune the MAF with sort of a % error approach, as the AutoVE procedure is.

Basically what you do is plug the MAF back in and log the Hz value and the matching airflow values. This essentially will generate a new MAF table to plug back into the Tune Tool.

Hope that makes sense.. There are a few threads on this site about it, and probably over on LS1TECH also.

Cheers,

[Tordne]

In a way tuning a MAF is almost harder than running MAFless, cause you have to tune twice essentially
Could you just run MAFless? I have a nice shiny new SLP 85mm MAF sitting in my garage never to be used again

If you own EFILive Commercial (or Workshop) you could use a Custom OS and still retain the dual spark maps.
Just a thought...