Ok, sorry, pardon my ignorance. What I said before is not entirely true. I
know, Steven, you hate it when I do that. Let me respond before you figure
it out or at least before you can respond. E-mail server's from @home still
suck so timing is not always correct on these responses.
"Open loop" occurs during the following times:
1) Ignition switch (key-on) mode
2) Engine start-up mode
3) Engine warm-up mode
4) Acceleration mode
5) Deceleration mode
6) Wide open throttle mode
"Closed loop" occurs during the following times:
1) Idle mode
2) Cruise mode
It is true that there are fixed tables in the PCM for air/fuel ratios and
emission controls. There are also engine timing tables. These tables are
used in both open and closed loops in different ways. In all cases, there
are many input sensors that supply information to the PCM. The only sensors
that are ignored in "open loop" are the O2 sensors. That's because the
emission controls are not used during this time because enriched mixtures
are generally needed. This means that the data tables and programming is
used in all cases based on input from a lot of sensors, O2 just being two or
three of them depending on the engine you're running. When in "closed loop"
the PCM attempts to adjust your air/fuel ratio to 14.7/1. This is supposed
to be ideal for emissions. The assumption by the automotive engineers is
that you're in "closed loop" most of the time. This is probably not the
case with DML people.
This is getting long, huh? Well, I'm not done yet because it's not fair to
just tell part of the story. Each of the six "open loop" modes causes
different things to happen. It's not just "open or closed" Those different
modes in the "open loop" have different effects on your engine and the PCM
responds accordingly. Since not too many people are interested in any mode
that doesn't have to do with performance I will only go into that detail.
Acceleration mode: The PCM recognizes this by an abrupt increase in MAP
pressure or throttle position. Injector pulse width is increased in
response to this condition.
WOT mode: The PCM receives input from the following:
1) Battery voltage
2) Crankshaft Position Sensor
3) Engine coolant temp
4) Intake manifold air temp sensor
5) MAP sensor
6) TPS
7) Camshaft position sensor
The PCM increases the amount of fuel by adjusting the pulse width ignoring
the O2 sensor readings. Timing adjustments are made by the PCM at this time
also.
Basically, what all this boils down to is this. The PCM tables are still
used, Jet or no Jet. It seems the Jet or Hypertech, fools the PCM by
presenting different or false sensor inputs to the PCM. Based on the
instructions for the Jet module, it is installed on the plug that has the
inputs to the PCM.
In my quest for information I am trying to get a hold of the timing tables
that are in the PCM, both stock and HP. I will let you know when I get it.
Great reading, huh?!
Ron
00 SLT QC 4X2 5.9 46RE 3.92 LSD
For modifications see my DML Profile
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net]On Behalf Of Jack Hilton
Sent: Tuesday, October 24, 2000 2:04 PM
To: dakota-truck@buffnet.net
Subject: Re: DML: Re: Re: Jet Chip Group Buy
Well, all the JET does is intercept and modify readings from the sensors.
When the truck is at WOT it goes into Closed-Loop and reverts back to the
static data tables burned into the SBEC , so it doesn't even look at the
sensors.
Jack
"Steven T. Ekstrand" wrote:
> | Yeah, but the biggest problem with a JET module is that it only effects
> | Part-Throttle performance , *not* WOT.
>
> Jack-
>
> I didn't know about this one? It only works in "open loop" operation???
>
> -STE
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