Geoffrey,
0"hg should read 0" vacuum (confusing and not quite accurate wording).
At idle, you have (on the average) 16-18" vacuum. The more you press
the throttle, the less vacuum you have...works on a linear scale. WOT =
0" vacuum (again, slightly wrong wording on the website).
What the MAP charger does (not the Map/Boost Bypass - they're two
different things) is simple:
At WOT, you have approximately the same voltage at Key ON/Engine OFF ("0
Setting"). When you're under boost, the 1-BAR MAP doesn't understand
the positive pressure and continues past the "0 Setting" (also the same
at WOT)...literally "freaking out" the PCM and it leans out slightly.
Now what the MAP Charger does is override the out of range MAP reading
and set it to the "0 Setting" or slightly below. It's activated by TPS
position and you can adjust the ON/OFF (bypass voltage as well) to
whatever you want.
It works and has been working on a test truck for the last several
months (about 6 I believe).
- Bernd
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net] On Behalf Of Geoffrey Hausheer
Sent: Tuesday, October 23, 2001 12:41 PM
To: dakota-truck@buffnet.net
Subject: DML: ATTN Bernd: MAP Charger/Bypass
I have a question about how the MAP Charger/MAP Boost
Bypass work. According to everything I've seen in my
truck using the OBDII reader, 0"Hg is absolute vacuum,
and 29.2inHg is about atmospheric pressure (at 0ft above
sea level). So at idle, i see about 11inHg (OBDII
reader) which corresponds (as per my boost gauge) to
about 20"Hg vacuum. When I go to 20% throttle, this goes
to about 20"-Hg (via the OBDII reader) which is about 10"
of vacuum (as per the boost gauge). SO at 31"-HG (which
the sensor maxes out at), I'm at about atmospheric, which
is right where I should be. Now at 6-lbs boost, I should
really see about 42"-Hg on the computer, which I don't,
but it seems tlike it is doing the right thing already.
So what does the MAP charger/ MAP Boost bypass do? If it
sets the pressure to 0" (as per the web page at
speedtweaks), then you effectively just closed the
throttle, (though the tps will still indicate wide open),
which should royally confuse the computer. Am I missing
something?
Thanks,
.Geoff
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