Best way to determine intake manifold leak with Hptuners?
04-17-2006, 08:43 AM
#7
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MAP readings would be funky (different) since that constitutes a pressure leak. If you want to see it first hand, scan a buddy's car, then pull a vacuum line and watch what happens.
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04-17-2006, 10:05 AM
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If the leak is small then you may see it only as a high
idle, low IAC counts relative to "normal". If the leak
elevates MAP the speed density side will see it and
fuel it, SD accounts for most of the idle fueling if not
all (looked close enough to 1:1 to me, last I messed
with idle fueling & VE table low RPM). If SD handles
the air as it should, trims will show nothing.
Since IAC is its own closed-loop deal you may need
to unplug the servo to keep the PCM from hiding any
effect from shooting fuel. I recommend an unlit propane
torch (tape off the air venturi holes for pure propane)
rather than wet fuels as propane won't make a puddle
to flare all at once if something flashes it. Plus gas
will go around corners that a stream won't.
Don't forget the backside of the manifold where the
MAP sensor sits in its grommet, and vacuum lines
are taken off for accessories & AIR system.
idle, low IAC counts relative to "normal". If the leak
elevates MAP the speed density side will see it and
fuel it, SD accounts for most of the idle fueling if not
all (looked close enough to 1:1 to me, last I messed
with idle fueling & VE table low RPM). If SD handles
the air as it should, trims will show nothing.
Since IAC is its own closed-loop deal you may need
to unplug the servo to keep the PCM from hiding any
effect from shooting fuel. I recommend an unlit propane
torch (tape off the air venturi holes for pure propane)
rather than wet fuels as propane won't make a puddle
to flare all at once if something flashes it. Plus gas
will go around corners that a stream won't.
Don't forget the backside of the manifold where the
MAP sensor sits in its grommet, and vacuum lines
are taken off for accessories & AIR system.
04-17-2006, 01:16 PM
#10
Originally Posted by RedHardSupra
i have some general methodologies for spotting leaks at the end of this article:
http://redhardsupra.blogspot.com/200...every-car.html
http://redhardsupra.blogspot.com/200...every-car.html
04-17-2006, 01:30 PM
#12
Originally Posted by RedHardSupra
map will drop usually on intake leak, but O2s are much better indicators for header leaks
So would it be OK to compare WOT MAP values from a previous log from my stock 346 to now a 408?
04-17-2006, 01:51 PM
#13
two different engines, so nothing to compare, on the most basic principles of science.
what you wanna look for is either abnomally low MAP (most people should see 98-103kPa, which depends on altitude, baro pressure, etc, although i've seen logs from denver and west virginia that were more like 92-93kPa). so if your MAP never goes past 80, you know you're screwed somewhere.
another great indicator of compression gone wrong is dynamic cylinder air. most stockish NA cars work in 0.76-0.80 range. nice big h/c combos create usually up to 0.95-1.04. turbos vary depending on target boost levels, but they all should produce way past 1.20.
what you wanna look for is either abnomally low MAP (most people should see 98-103kPa, which depends on altitude, baro pressure, etc, although i've seen logs from denver and west virginia that were more like 92-93kPa). so if your MAP never goes past 80, you know you're screwed somewhere.
another great indicator of compression gone wrong is dynamic cylinder air. most stockish NA cars work in 0.76-0.80 range. nice big h/c combos create usually up to 0.95-1.04. turbos vary depending on target boost levels, but they all should produce way past 1.20.
04-17-2006, 01:59 PM
#14
Originally Posted by RedHardSupra
two different engines, so nothing to compare, on the most basic principles of science.
what you wanna look for is either abnomally low MAP (most people should see 98-103kPa, which depends on altitude, baro pressure, etc, although i've seen logs from denver and west virginia that were more like 92-93kPa). so if your MAP never goes past 80, you know you're screwed somewhere.
another great indicator of compression gone wrong is dynamic cylinder air. most stockish NA cars work in 0.76-0.80 range. nice big h/c combos create usually up to 0.95-1.04. turbos vary depending on target boost levels, but they all should produce way past 1.20.
what you wanna look for is either abnomally low MAP (most people should see 98-103kPa, which depends on altitude, baro pressure, etc, although i've seen logs from denver and west virginia that were more like 92-93kPa). so if your MAP never goes past 80, you know you're screwed somewhere.
another great indicator of compression gone wrong is dynamic cylinder air. most stockish NA cars work in 0.76-0.80 range. nice big h/c combos create usually up to 0.95-1.04. turbos vary depending on target boost levels, but they all should produce way past 1.20.
04-17-2006, 04:39 PM
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Originally Posted by black_z
Youssif, fog around the intake with propane, if the idle drops when you spray it you have found your leak.
But, aren't you worried about blowing up?
Don't do it while smoking!
04-18-2006, 11:24 AM
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Originally Posted by silverTA2002
I've heard something like that before.....
But, aren't you worried about blowing up?
Don't do it while smoking!
But, aren't you worried about blowing up?
Don't do it while smoking!
I am an auto engineering major and we focus heavily on emissions, we use propane for a lot of different tests/lab experiments. 