Jon,
>From what I understand by talking to programmers, they actually change the
shape of the curve and fuel flow. The stock computer limits timing advance
under 3000 rpm, over that they throw the timing back in, but only for the
next 2000, then they pull a little out again at 5000. The fuel curve is
overly rich which limits heat and detonation problem as well as reducing
horsepower. These problems seem to be worse in the 97+ engines.
Aftermarket computer lean the fuel curve for more power and give plenty of
advance under 2400 rpms. They also give the sensors a wider set of
parameters for operation with higher lift cams. the 15 to 30 horsepower
gains depend on the level of modification, the more modified, the less power
gained. !5 to 20 hp seems more accurate for modified trucks.
Mark
-----Original Message-----
From: Jon Steiger <stei0302@cs.fredonia.edu>
To: dakota-truck@buffnet.net <dakota-truck@buffnet.net>
Date: Thursday, May 20, 1999 6:08 PM
Subject: DML: MP PCM - How do they do it?
I believe this has been discussed to some extent in past (I have even
answered variations of this question), but I'm wondering if anyone out
there knows exactly what MP does to put the "performance" in their
"performance computers"?
Here's the stuff I do know:
The WOT fuel maps are richer.
The timing is advanced. (I think I have heard 4 degrees?)
Of course, the rev limiter and speed governer are altered as well, but
they don't have any direct effect on the power output of the engine like
timing would.
Is the (supposed) 30hp gain from the computer merely from advancing the
timing and a richer mixture at WOT, or is there more? As far as the timing
goes, is it advanced X degress across the board, or did they actually alter
the shape of the timing curve?
Here is the reason I ask... I have been doing a lot of aftermarket
ignition research lately (trying to hash out a plan for a nitrous system),
and in my travels, I came across the Holley Pro Strip Annihilator. This
ignition actually lets you program your own timing curve. Here is a
snippet from their web site:
>>>>>>>>>>>>>>>>
Fully Programmable Timing Computer - Program a 32 point
timing curve from zero to 50° (in 1° increments) from 500 RPM
to 16,000 RPM (in 500 RPM increments). Max. timing span is 34°.
Timing is accurate to within ±1/4° from idle to 16,000 RPM.
<<<<<<<<<<<<<<<<
You can probably figure out where I'm going with this... If most of the
performance is merely from the timing, could you just slap this ignition on
there and program in a similar curve? (With this method, you could even
program in a custom curve to meet your unique requirements; you wouldn't be
stuck with the MP one.) Get a set of high flow injectors and now you've
got a richer WOT, just like the MP PCM...
What do you think? Is it that simple, or is there more? I was thinking
that if this would work, it might be an option for you '97+ folks that are
waiting for computers.
The one big drawback to this method is that, even *if* it does work, this
particular ignition is in the $500 neighborhood. (Jegs has it listed for
$559.99) Figure another $200 or so for the high flow injectors (for the
WOT fuel increase), and you're looking at almost $800 to simulate a $250
computer, but I guess if you're desperate enough... :-)
Any thoughts on this? Feasable, or is my brain running a few volts shy
of stoch? :-)
-Jon-
.--- stei0302@cs.fredonia.edu ------------------------------------.
| Affiliations: DoD, EAA, MP Race Team, NMA, SPA, USUA. RP-SEL |
| '96 Dodge Dakota v8 SLT CC (14.58@93.55), '96 Kolb FireFly 447 |
`----------------------- http://www.cs.fredonia.edu/~stei0302/ ---'
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