98 Maf table runs out at 435gms/sec
04-20-2004, 10:54 PM
#1
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98 Maf table runs out at 435gms/sec The 97 and 98 Ls1s Maf table ends at 11,250Hz which is about 435gms/sec. My 382 all bore reaches peak HP at 5800 rpm and stays at that HP to 6700. All that time the Maf is maxed out at 435gms/sec, seemingly at the end of the PCMs Maf table. Is there a way to get the PCM to read data beyond 11,250Hz(435gms/sec) with Ls1 Edit with a 98 PCM. Thanks for any ideas.
04-21-2004, 12:11 AM
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I don't think you can get the MAF to read beyond the limit of the table in the PCM. It might be possible to get an aftermarket MAF that is calibrated for higher air flow. That option would require a new MAF calibration table in the PCM. My stock '03 truck MAF table maxes out at 437.34g/sec at 12000Hz.
04-21-2004, 12:51 AM
#3
Hey Dave, hope this thread helps you out... 
Trick PCM with MAFT
Trick PCM with MAFT
Originally posted by y2khawk
The 98's have a shorter MAF table than 99+, so you run into issues on extending the table. I don't recall if there is a flat lined portion of the table that can be moved up like the 99+ cars.
You can use a MAFT to shift the frequency from the sensor down, and shift the table in the PCM to match using LS1 Edit. That should let you get to the next limit of 67 lb/min and not hit the end of the table at 11250 kHz from the sensor.
To match the MAFT change, you need to scale the MAF table the other way. If you go -5% on the MAFT, increase the MAF table by the same. You want to shift everything up in the PCM to match what the MAFT is feeding the PCM. That way you will see the same airflow in the PCM but at a lower frequency than w/o the MAFT. Basically, the % change outside the PCM is offset by the % change in the opposite direction inside the PCM.
The 98's have a shorter MAF table than 99+, so you run into issues on extending the table. I don't recall if there is a flat lined portion of the table that can be moved up like the 99+ cars.
You can use a MAFT to shift the frequency from the sensor down, and shift the table in the PCM to match using LS1 Edit. That should let you get to the next limit of 67 lb/min and not hit the end of the table at 11250 kHz from the sensor.
To match the MAFT change, you need to scale the MAF table the other way. If you go -5% on the MAFT, increase the MAF table by the same. You want to shift everything up in the PCM to match what the MAFT is feeding the PCM. That way you will see the same airflow in the PCM but at a lower frequency than w/o the MAFT. Basically, the % change outside the PCM is offset by the % change in the opposite direction inside the PCM.
04-21-2004, 10:25 PM
#5
I think Deezel had another suggestion on LS1Tuning.com:
This also in the FI forum:
MAF range
For maxed out MAFs, I think most tuners add fuel via the PE vs RPM table. One rule of thumb I have seen is to add 3% more fuel to the cell in the PE table after the cell where the MAF maxes out. Then add 3% more than that to the next cell... (cell maxMAF+1 = cell maxMAF * 103% ; cell maxMAF+2 = cell maxMAF * 106% ; etc.)
MAF range
Last edited by JimMueller; 04-21-2004 at 10:36 PM.
04-22-2004, 04:59 AM
#6
Originally Posted by Caveman
The 97 and 98 Ls1s Maf table ends at 11,250Hz which is about 435gms/sec. My 382 all bore reaches peak HP at 5800 rpm and stays at that HP to 6700. All that time the Maf is maxed out at 435gms/sec, seemingly at the end of the PCMs Maf table. Is there a way to get the PCM to read data beyond 11,250Hz(435gms/sec) with Ls1 Edit with a 98 PCM. Thanks for any ideas.
I have an xls. that shows the conversions if you want it ( originally put together by Godspeed I think?)
joel