To keep this post somewhat short (whew!)...
The 30.8" is what two different MAP sensors (original and a brand new one) were
registering on my truck under boost. That's not where it should be for boost
conditions...more like 1-2" on a 1-BAR MAP.
As for the lean condition (pinging)...we had seen 15.7-16.2:1 on an A/F meter
on the local Dyno. That's under part-3/4 throttle. Under WOT, it went down to
about 13.8 but creeped up back to 14.7-15.0 after 3800rpm...in 4th gear at
WOT! (You can blame Dodge for that one...4th gear forces the computer to try
to get back into Closed-Loop.)
Will it help...sure will. I've hooked up a bread-board version of the system
on my truck already and it's much "peppier" under WOT now. Since i'm tricking
the computer by changing the MAP signal to something more "normal" (1-3"hg
instead of 30.8"), it's keeping the fuel at a more useable level (richer).
I've also had to swap out my FMU plate back down to the 10:1 since this mod...I
was running the 12:1 to compensate for the 9# pulley.
I'm going to be setting up some extensive dyno time in the next few weeks to
really get this thing down. In the mean time, i'm using out lab at work to
check all the POTS on the box and recording all of the voltage ranges that they
can adjust to (marking them on the board as well). The nice thing about the
lab is that we can simulate the driving conditions with our programs to be able
to test different TPS and MAP signals. (And...the actual schematics and the
bread-board box have been verified on a Computer Simulation Program and it's
running without any problems.)
- Bernd
> I've had similiar results. Basically I'm guessing the MAP has the ability to
> read in a range of approx 1"hg to approx 30"hg. But as you mentioned the PCM
> takes a snapshot of the MAP at engine start time to get a baseline
or "ambient"
> pressure. It then uses this baseline in determining load. I've found that
> based on what the outside or "ambient" pressure is, I'm reading ranges of
either
> 1-9"hg or 8-30"hg from my scan tool. Maybe on days where ambient is already
> kinda high it uses the higher scale (or vice-versa). It might be a method of
> dealing with only 1Bar of resolution (response characteristics) on the MAP
> sensor itself. I ran into this issue several months ago when trying to
> determine if a MAP sensor was bad. I went into my directory of saved scans
> covering about 2 years and discovered 2 different sets of values coming out.
I
> can only assume this is because of the changing outside or ambient pressure.
> Whaddya think?
>
> These are pretty interesting also - from this data its easy to see why turbos
> and huffers use 2 and 3-Bar MAP sensors - for the greater resolution on the
top
> end. Do you think it would help your situation?
>
> That makes sense - when you say "leans the engine enough to ping" - are you
> seeing this also in you A/F gauge?
>
> I think that faking the O2 signal could provide good results if you could
> somehow make it hover around 12.5 to 1 instead of 14.7 - I'm sure this would
> eat cats but I wonder how much power it could unleash. Unfortunately the
> electronics aren't trivial due to the frequency response and sensitivity of
> those sensors. You would even need an expensive Wide-Band O2 sensor to dial
it
> in initially - not to mention dyno time. May as well go to an aftermarket EFI
> at that point.
>
> This is cool stuff for sure!
>
> Latr,
>
> Shane
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:57:47 EDT