12200411 PCM swap for 1996 to 2000 GMT400 trucks

[L31MaxExpress]

Here's the 1500 MAF cal.

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And the dually.

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You'll notice bumps in both. It's where the new cal is merging with the old cal. Takes about a jillion hits to really smooth it out. They were bigger before. If you're a glutton for punishment I can post the values, but it would blow up the page pretty bad. I will say for the stuff I couldn't reach I just extrapolated the last corrective value all the way to the top. The dually was done down at 2500' elevation and the 1500 here at 6500'+. Both have Whipples, but the 1500 still uses a stock airbox whereas the dually got its own airbox and intake setup from Whipple. That one bypasses the fender but still ultimately draws from the same spot at the core support.

If you have time at some point, throw the 350s up or screenshots of the table. When it comes to tuning I am a glutton for punishment to have a good tune. I forget your 1500 has a Whipple though too.

 

[Supercharged111]

If you have time at some point, throw the 350s up or screenshots of the table. When it comes to tuning I am a glutton for punishment to have a good tune. I forget your 1500 has a Whipple though too.

The 1500 is the 350. Closest thing I'll have to bolt on in the nearish future is when I slap a 411 into the plow truck (454/4L80). I think I'll start with the 1500's MAF cal and a black box VE paired with the 350 van timing table to start off.

 

[L31MaxExpress]

I had a chance to mess with the MAF curves. The L31 van 0411 reaches a peak of about 7.5% lower than a GMT400. Which means at WOT, will be about 7.5% leaner.

 

[L31MaxExpress]

Attached is a 5.7L/4L60E 0411 HPT file with the GMT400 MAF curve and GM MPFI upgrade injector data. Also has a fairly hot high octane spark timing map. It might have knock retard on 87, it is what I ran the Express van on 91 with a 170F thermostat with. Total timing at WOT in the van was 29-31*.

 

[AK49BWL]

I'll have to compare the MAF table to what I spent weeks setting mine to several years ago lol. I'm curious if it'll be close.

 

[L31MaxExpress]

For those not using HP Tuners.

Disclaimer here not that it will really matter to anyone here because I doubt their engine moves enough airflow for it to matter. The BlackBox has a 400 gms/sec limit, which the stock MAF curve reaches at a little less than the highest 11,000 hz entry. From 10,875, the MAF curve is a linear extrapolation from the trend of the data between the GMT400 and Express van. The last 3-4 entries before that were a 5.2% difference between GMT400 and Express. I thus multiplied the Express van entries starting at 11,000 hz through 12,000 hz and multiplied them by 1.052 and allowed HPT software to cap the value at its highest value of 511.992 for the last two entries. Not like any L31 truck is really going to run up there anyway. Most are not going to break 300 gms/sec much less 400 gms/sec. 1 gm/sec is pretty close to 1.2 hp at the crank or 1 hp at the wheels. Thus rough math, a truck moving 300 gms/sec is making about 360 crank hp or 300 wheel HP.

MAF HZ and Flow GM/Sec

1,500---2.508
1,625---2.898
1,750---3.367
1,875---3.859
2,000---4.422
2,125---5.039
2,250---5.734
2,375---6.508
2,500---7.336
2,625---8.211
2,750---9.180
2,875---10.203
3,000---11.289
3,125---12.445
3,250---13.680
3,375---15.023
3,500---16.438
3,625---18.008
3,750---19.680
3,875---21.430
4,000---23.297
4,125---25.289
4,250---27.367
4,375---29.555
4,500---31.852
4,625---34.234
4,750---36.727
4,875---37.695
5,000---40.375
5,125---43.195
5,250---46.180
5,375---49.313
5,500---52.609
5,625---56.102
5,750---59.781
5,875---63.641
6,000---67.672
6,125---71.867
6,250---76.250
6,375---80.773
6,500---85.477
6,625---90.313
6,750---95.336
6,875---100.539
7,000---105.930
7,125---111.516
7,250---117.281
7,375---123.227
7,500---129.367
7,625----135.703
7,750----142.234
7,875----148.922
8,000----155.898
8,125----163.102
8,250----170.516
8,375----178.117
8,500----186.094
8,750----202.875
8,875----211.688
9,000----220.805
9,125----230.234
9,250----239.969
9,375----250.016
9,500----260.367
9,625----271.063
9,750----282.063
9,875----293.398
10,000---305.055
10,125---317.039
10,250---329.367
10,375---342.000
10,500---354.969
10,625---368.266
10,750---381.875
10,875---395.797
End of GMT400 Factory MAF Data

Start of extrapolated data
11,000---409.523---cut to 400 in the blackbox
11,125---424.109
11,250---439.039
11,375---454.313
11,500---469.922
11,625---485.875
11,750---502.148
11,875---511.992
12,000---511.992

 

[Scottm]

Cool! How many grams is 32 lb/minute?

 

[L31MaxExpress]

Cool! How many grams is 32 lb/minute?

Had to google it since I never use lbs.

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[Scottm]

Thanks! So 1.2 x 242 is only 290 crank hp at 4900, a little disappointing, since that's the stock L29 rating.

 

[L31MaxExpress]

Thanks! So 1.2 x 242 is only 290 crank hp at 4900, a little disappointing, since that's the stock L29 rating.

Probably an indication injector data is off or the MAF curve has been monkeyed with or both. Tuning around bad injector data causes all kinds of problems.