MAF's and their CFM rating VS Hz
11-02-2006, 11:09 AM
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MAF's and their CFM rating VS Hz I have and aplication where I need a MAF that flows the most CFM @ 11500Hz.
Does anyone know what these MAF's flow CFM or # wise @ 11500Hz?
Stock LT1 MAF
Stock LS1
SLP MAF
Does anyone know what these MAF's flow CFM or # wise @ 11500Hz?
Stock LT1 MAF
Stock LS1
SLP MAF
11-02-2006, 01:12 PM
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Originally Posted by CollinsAutomotive
How much CFM do you need?
11-02-2006, 02:39 PM
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Left stock, the LS-1 / Holden 75mm MAF has
the highest indicated mass airflow at any given
frequency. That would be 512g/sec at 12000Hz.
The 85mm are less, 450-460g/sec at 12000.
If you want to calibrate your own, then "porting"
any of these will produce more air per Hz. This
is very little due to raw airflow qualities and
mostly from changing the true to sensed area
ratio. You could hog out an 85mm and get it to
the same g/sec:Hz at the big end as the smaller
units. Or more. But with a LSx PCM more would
not help because of internal PCM limitations for
the MAF data, 512 g/sec. Some other engine
management system, though, might let you use
a higher data value.
the highest indicated mass airflow at any given
frequency. That would be 512g/sec at 12000Hz.
The 85mm are less, 450-460g/sec at 12000.
If you want to calibrate your own, then "porting"
any of these will produce more air per Hz. This
is very little due to raw airflow qualities and
mostly from changing the true to sensed area
ratio. You could hog out an 85mm and get it to
the same g/sec:Hz at the big end as the smaller
units. Or more. But with a LSx PCM more would
not help because of internal PCM limitations for
the MAF data, 512 g/sec. Some other engine
management system, though, might let you use
a higher data value.
11-02-2006, 04:45 PM
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Originally Posted by jimmyblue
Left stock, the LS-1 / Holden 75mm MAF has
the highest indicated mass airflow at any given
frequency. That would be 512g/sec at 12000Hz.
The 85mm are less, 450-460g/sec at 12000.
If you want to calibrate your own, then "porting"
any of these will produce more air per Hz. This
is very little due to raw airflow qualities and
mostly from changing the true to sensed area
ratio. You could hog out an 85mm and get it to
the same g/sec:Hz at the big end as the smaller
units. Or more. But with a LSx PCM more would
not help because of internal PCM limitations for
the MAF data, 512 g/sec. Some other engine
management system, though, might let you use
a higher data value.
the highest indicated mass airflow at any given
frequency. That would be 512g/sec at 12000Hz.
The 85mm are less, 450-460g/sec at 12000.
If you want to calibrate your own, then "porting"
any of these will produce more air per Hz. This
is very little due to raw airflow qualities and
mostly from changing the true to sensed area
ratio. You could hog out an 85mm and get it to
the same g/sec:Hz at the big end as the smaller
units. Or more. But with a LSx PCM more would
not help because of internal PCM limitations for
the MAF data, 512 g/sec. Some other engine
management system, though, might let you use
a higher data value.
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11-02-2006, 05:12 PM
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Due to lack of time and at the risk of not having completely thought this thru yet, I'll continue anyway, would this work? Example, lets say that you have a MAF that really moves 1024 when the PCM thinks it has 512 G/S. Then you 1/2 the cubic inches to double the fuel, should work, right? What am I missing, too simple.
11-03-2006, 08:44 AM
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Originally Posted by dynocar
Due to lack of time and at the risk of not having completely thought this thru yet, I'll continue anyway, would this work? Example, lets say that you have a MAF that really moves 1024 when the PCM thinks it has 512 G/S. Then you 1/2 the cubic inches to double the fuel, should work, right? What am I missing, too simple.
Interesting idea to get around the 512K MAF limitation, BTW. This idea crossed my mind also (after a few beers) but then I started thinking, what other tables do we not have access to that could be affected by this....
11-03-2006, 09:36 AM
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Originally Posted by muncie21
What about the other airflow tables such as VE or idle? I'm guessing these would have to be doubled to account for the extra fuel. I'm also thinking the fuel adders/multipliers would have to be changed also.
Interesting idea to get around the 512K MAF limitation, BTW. This idea crossed my mind also (after a few beers) but then I started thinking, what other tables do we not have access to that could be affected by this....
Interesting idea to get around the 512K MAF limitation, BTW. This idea crossed my mind also (after a few beers) but then I started thinking, what other tables do we not have access to that could be affected by this....
11-03-2006, 03:57 PM
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Originally Posted by muncie21
What about the other airflow tables such as VE or idle? I'm guessing these would have to be doubled to account for the extra fuel. I'm also thinking the fuel adders/multipliers would have to be changed also.
Interesting idea to get around the 512K MAF limitation, BTW. This idea crossed my mind also (after a few beers) but then I started thinking, what other tables do we not have access to that could be affected by this....
Interesting idea to get around the 512K MAF limitation, BTW. This idea crossed my mind also (after a few beers) but then I started thinking, what other tables do we not have access to that could be affected by this....
I figure that the Pcm computes inj pulse width based off of a long algebraic formula, of which airflow, cubic inch, VE, RPM and Inj size are the main factors. So if you 2X the actual air and you 1/2 the actual cubic inch, the VE table should take care of itself. I haven't thought thru the spark table yet, but I noticed with 2 or 3 bar speed density systems, it still comes up with an air volume scale. I'm mentally handicapped for this kind of thinking because I quit drinking couple years ago.
11-03-2006, 04:05 PM
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Originally Posted by dynocar
I figure that the Pcm computes inj pulse width based off of a long algebraic formula, of which airflow, cubic inch, VE, RPM and Inj size are the main factors. So if you 2X the actual air and you 1/2 the actual cubic inch, the VE table should take care of itself. I haven't thought thru the spark table yet, but I noticed with 2 or 3 bar speed density systems, it still comes up with an air volume scale. I'm mentally handicapped for this kind of thinking because I quit drinking couple years ago.
Mis-statement, "So if you 2X the actual air", should have stated, "So if you actually have 2X the measured air". As someone pointed out, you could accomplish the same thing with injector sizing Vs engine sizing.
