Using MAP to determine intake restriction
Thread Starter
Joined: Apr 2007
Posts: 9,711
Likes: 999
From: Evansville,IN
Using MAP to determine intake restriction I've always heard about people using the MAP at WOT to determine if the intake is a restriction.
I've read about people comparing a stock LS1 intake to a FAST but never understood what to look for.
Thanks for any help.
J
I've read about people comparing a stock LS1 intake to a FAST but never understood what to look for.
Thanks for any help.
J
TECH Regular
Joined: Jun 2012
Posts: 414
Likes: 5
From: SV, AZ
Compare your MAP koeo to your MAP at WOT. If it decreases more than 10 Kpa I would say you have some restriction. Min is like 102kpa koeo and like 99 at WOT with a ported fast 102 and 102mm tb and 4" tubing to lid no maf.
MAP sensors read in KPA and KPA is a measure of pressure. At sea level 101 KPA is the atmospheric pressure and varies with altitude. I'm going to use sea level as the example here. Anything under 101 KPA is a vacuum. At wide open throttle you want to be as close to 101 KPA (NA motor) as you can because anything under that would represent a restriction on the intake side. You can read this through a scanner like HP tuners you just log a run and check the histogram to see what your max KPA is at WOT. So a fast is just a bigger hole with less restriction compared to a stock intake.
On my Vortec van with a screened 75mm MAF, MAP drops
from 100kPa at 2000RPM WOT to 95kPa at 5000RPM. That
is 5% left on the table.
The Camaro with descreened 85mm and 85mm intake,
goes from 100kPa to 98kPa at 6500RPM despite also
having a better cam & exhaust & intake & higher max
RPM (pulling down harder against the inlet tract).
The next question after "how much?" is "which piece
or pieces?". You could have yourself some fun with
a few MAP sensors and log various points along the
way simultaneously, or you could make yourself a
cheap manometer out of Tygon tubing and water
(as I did for my ancient flow/pressure drop posting).
Of course either one of those would require you to
poke holes in stuff.
from 100kPa at 2000RPM WOT to 95kPa at 5000RPM. That
is 5% left on the table.
The Camaro with descreened 85mm and 85mm intake,
goes from 100kPa to 98kPa at 6500RPM despite also
having a better cam & exhaust & intake & higher max
RPM (pulling down harder against the inlet tract).
The next question after "how much?" is "which piece
or pieces?". You could have yourself some fun with
a few MAP sensors and log various points along the
way simultaneously, or you could make yourself a
cheap manometer out of Tygon tubing and water
(as I did for my ancient flow/pressure drop posting).
Of course either one of those would require you to
poke holes in stuff.
