Using MAP readings to measure LS6 intake restriction
05-19-2004, 01:42 PM
#1
Using MAP readings to measure LS6 intake restriction Does anyone have any MAP value comparisons using ATAP or EFIlive between the LS6 and the FAST or sheetmetal intakes? I noticed that when I logged my WOT runs at the track for my LS6 intake that my max MAP drops to 27.4 hg or 94Kpa at high RPM. Anyone else see this?
05-19-2004, 08:29 PM
#2
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You will see a MAP drop. However it may or may not pertain to
the LS6 itself. You lose some every step of the way, airbox slot
to back end of the intake. I see 14.5-14.6 PSI MAP readings on
my car at 6KRPM upshift, off a 14.7-14.8 ambient, with all inlet
pieces better than stock but no cam/heads/exhaust.
MAP is not the whole deal. It does not comprehend any of the
action in the runners. But it does indicate whether you have
any gain to be found in the MAF, TB, etc.
With a better breathing motor you should be drawing more
airflow hence dropping more pressure in the intake tract. A
stock-internals car with your intake pieces would see less
drop because it's not drawing the same.
Have you descreened the GM MAF? That would probably
be the best inlet pressure drop reliever, if no. From my
limited flow testing it does not cause any great error in
frequency (two tandem units in the same pipe have the
same frequency, one screened truck MAF and one de-
screened truck MAF).
the LS6 itself. You lose some every step of the way, airbox slot
to back end of the intake. I see 14.5-14.6 PSI MAP readings on
my car at 6KRPM upshift, off a 14.7-14.8 ambient, with all inlet
pieces better than stock but no cam/heads/exhaust.
MAP is not the whole deal. It does not comprehend any of the
action in the runners. But it does indicate whether you have
any gain to be found in the MAF, TB, etc.
With a better breathing motor you should be drawing more
airflow hence dropping more pressure in the intake tract. A
stock-internals car with your intake pieces would see less
drop because it's not drawing the same.
Have you descreened the GM MAF? That would probably
be the best inlet pressure drop reliever, if no. From my
limited flow testing it does not cause any great error in
frequency (two tandem units in the same pipe have the
same frequency, one screened truck MAF and one de-
screened truck MAF).
05-19-2004, 08:53 PM
#3
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Yeah, what jimmy said makes sense. The MAP sensor in the intake really doesn't tell you much about the way the manifold flows, just the pressure drop from ambient to manifold.
Camshaft design can come into play, allowing manifold pressure to bleed through the exhaust. But MAP data probably tells you more about the cam overlap than the flow of the intake.
Camshaft design can come into play, allowing manifold pressure to bleed through the exhaust. But MAP data probably tells you more about the cam overlap than the flow of the intake.
