Looking to pic your brain on MAFS for FI cars
01-19-2006, 01:23 AM
#1
Staging Lane
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Looking to pic your brain on MAFS for FI cars ok, here we go!
has anyone ever thought about or tried to use a maf from another vehicle on an FI car? what i'm getting at is we are generally stuck with SD tunes on FI cars! i know that there are mafs that do not peg out on FI cars of other makes. in my ealier tuning days with fords (no flames please!) we had a wide choice of mafs. some better at be sucked through, others better at being blown through. the point being that there has to be an answer to not having to do SD only tunes for these cars that are FI.
so lets do some looking and talking on the subject! a few HUNDRED heads have got to be better than ONE!!!!!!!!!
has anyone ever thought about or tried to use a maf from another vehicle on an FI car? what i'm getting at is we are generally stuck with SD tunes on FI cars! i know that there are mafs that do not peg out on FI cars of other makes. in my ealier tuning days with fords (no flames please!) we had a wide choice of mafs. some better at be sucked through, others better at being blown through. the point being that there has to be an answer to not having to do SD only tunes for these cars that are FI.
so lets do some looking and talking on the subject! a few HUNDRED heads have got to be better than ONE!!!!!!!!!
01-19-2006, 06:48 AM
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The more basic problem is that the PCM has a 511
g/sec MAF limit that's pretty hard to get around
(custom OS?). That, and the 12kHz input frequency
max. The LS1 / Holden MAF "just happens" to be a
straight fit-up to both limits. The truck / 'vette
MAF reads less airflow at the 12kHz limit.
Once you get past 511g/sec you have to fake it
or punt. Hardware really is not the problem, other
than the PCM perhaps having the 12kHz input
limit for a reason (e.g. how well can you measure
frequency above 12kHz, at the clock rate / code
main loop rate you've got?).
This is prime "custom OS" motivation but the percentage
of dudes who really need to be above 511 g/sec is not
that large. Hell, on my car I am still seeing less than
300 peak, so figure you'd have to be up past 600HP
before it becomes even a nuisance, maybe700-800HP
before it's not "cheatable" with just PE/RPM. By the
time you've bought all of that grade of plumbing and
foundation, and ripped it up, maybe it's just time to
walk away from Mr. stock computer. You don't see
NASA flying Gateway PCs, right? Maybe you need
launch grade hardware on a wider scale than just the
MAF, by the time the MAF runs out of room.
g/sec MAF limit that's pretty hard to get around
(custom OS?). That, and the 12kHz input frequency
max. The LS1 / Holden MAF "just happens" to be a
straight fit-up to both limits. The truck / 'vette
MAF reads less airflow at the 12kHz limit.
Once you get past 511g/sec you have to fake it
or punt. Hardware really is not the problem, other
than the PCM perhaps having the 12kHz input
limit for a reason (e.g. how well can you measure
frequency above 12kHz, at the clock rate / code
main loop rate you've got?).
This is prime "custom OS" motivation but the percentage
of dudes who really need to be above 511 g/sec is not
that large. Hell, on my car I am still seeing less than
300 peak, so figure you'd have to be up past 600HP
before it becomes even a nuisance, maybe700-800HP
before it's not "cheatable" with just PE/RPM. By the
time you've bought all of that grade of plumbing and
foundation, and ripped it up, maybe it's just time to
walk away from Mr. stock computer. You don't see
NASA flying Gateway PCs, right? Maybe you need
launch grade hardware on a wider scale than just the
MAF, by the time the MAF runs out of room.
01-20-2006, 03:44 AM
#3
Staging Lane
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jimmyblue,
ok, so lets say you stick what weve got! so if i understand you correctly, you can set PE map enable, and PE tps (hot and Cold) enable at a point that begins just before you reach boost. so in doing that you can enter PE (eliminating the maf input) in order to tune an FI car? in doing so i am assuming that you can tune an FI car making up to 800 HP (given that all thing support this HP level, fuel pump, inj., and so on)!
i know i've seen somone tune one that made 897 crank HP without an SD only tune, is this how? if i'm missing something PLEASE jump in and let me know!!!!!!
ok, so lets say you stick what weve got! so if i understand you correctly, you can set PE map enable, and PE tps (hot and Cold) enable at a point that begins just before you reach boost. so in doing that you can enter PE (eliminating the maf input) in order to tune an FI car? in doing so i am assuming that you can tune an FI car making up to 800 HP (given that all thing support this HP level, fuel pump, inj., and so on)!
i know i've seen somone tune one that made 897 crank HP without an SD only tune, is this how? if i'm missing something PLEASE jump in and let me know!!!!!!
01-20-2006, 07:29 AM
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You'd use the PE just as usual, but the deal is
that once the MAF flatlines, your PE value has
to now break away from a fairly flat EQ ratio
(say, 1.3 1.3 1.3 1.3 1.3 ... for a 11:1 AFR)
to a rising line that keeps up with RPM (airflow
following RPM, until the air path starts to limit).
You'd taper up the PE in the outlying RPM to
get the desired enrichment result, despite the
MAF data (or speed density airflow data for
that matter, waiting to see the answer on that
511g/sec question) being clipped.
Basically it's almost an alpha-N scheme with
a whole lot of baggage, at the end of it all.
that once the MAF flatlines, your PE value has
to now break away from a fairly flat EQ ratio
(say, 1.3 1.3 1.3 1.3 1.3 ... for a 11:1 AFR)
to a rising line that keeps up with RPM (airflow
following RPM, until the air path starts to limit).
You'd taper up the PE in the outlying RPM to
get the desired enrichment result, despite the
MAF data (or speed density airflow data for
that matter, waiting to see the answer on that
511g/sec question) being clipped.
Basically it's almost an alpha-N scheme with
a whole lot of baggage, at the end of it all.
