Re: Turbo MAP & MAT interaction

["Jeff M" <tystorm@email.msn.com>]

Brucester wrote:

> I'll take you word about all you say.

I quote from seen GM docs on this, and apply it to use, and add what has
been learned from others too ;-).

>, but, there are some critical areas
> that need addressed in my opinion.

Opinions are when we all learn, least you don't flat out say I am wrong
(your too professional and mature for that), we don't learn well then ;-)
and nobody is really  impressed at that point.

>  The stock senders are so slow in
> responding to temp changes, that while the ecm might be making changes
based
> on what the sensors tell the ecm are, they change so much from a heat sink
> at idle staging to 4-5 PSI boost (Brakes Locked, car still), to 20 PSI at
> 5,500 rpm, and this can happen in 5-10 sec, the ecm can't forecast what
the
> operating conditions will be, so it has to have at least quick responding
> sensors, again in my opinion.

Very true, then I wonder if it was that bad (it sure seems to be) then how
does the fuel and timing values work making power in a safe manner?  I am
sure these areas are still out there and if others want to add, here:


>    Personally, I want full time baro, and instant CTS, and MAT
corrections.
>    Why they have such good MAP sensors, and then drop the ball on the temp
> stuff makes no real sense to me, other then it's not an EPA requirement,
so
> they got it close, and it feels good seat of the pants and they just left
it
> there.

Costs vrs returns I would imagine.

>    I just dug it out but I'll be ordering a 12160855  transmission temp
> sensor to see how it compares to a normal MAT/IAT/CTS sender.  This one is
a
> pipe thread,  there is one other one I got in my notes to try.
>    Other thing is that you can fail safe the calibration much better.
i.e.,
> sudden spike in CTS, and kill the timing, and you reduce the power and the
> damage from say a blown headgasket.
> Grumpy

There are a number of companies (Alnor. Fluke, Extech, TIF. Checkit etc) and
suppliers (Omega etc) that make and sell sensors such as K-Type, T-Type,
J-Type, E-Type, U-Type, S-Type, R-Type, Platinum RTD, and others.  With each
having it's best working range: with good resolution, accuracy, linearity
and signal feed type to select from, and I am sure you would be more
successful at getting all these true values (linearity etc) from the
suppliers instead of GM ;-).

Jeff M


> > > I have been monitoring the ALDL data on my car for over a week now,
and
> > > have noticed that the Manifold Air Pressure (MAP) sensor reading is
> > > varying from about 1 bar with the engine off, to 0.25 bar at idle &
> > > overrun to about 1.7 bar at full whack. This seems correct from the
> > > documentation I have. However the Manifold Air Temp (MAT) sensor
output
> > > hardly changes, only rising by a few degrees in a few minutes, and
that
> > > appears to be more to do with the engine warming up than anything
else.
> > > There is no short term, MAP related temperature change.
> >
> > You are inquiring about monitoring MAT temp changes as far as the direct
> > effects of air temp increase related to boost pressure increase? OK.
But
> > your MAT does elevate in temps as the engine warms to normal temps
right?
> > Assuming these then yes (and you have an intercooler I assume?), you
would
> > expect the temp to rise accordingly as boost pressure was raised but not
> as
> > much as we can expect with these sensors and the layout of your system.
> > This is not uncommon and efforts (I say efforts, not absolute
resolution)
> > are addressed in the ECM by code working with tables to give a more
> > meaningful and usable strategy to provide good values for the SD
equation.
> > In the chip there are calc variables such as tables that provide
simulated
> > linearized MAT that take the raw A/D MAT reading using a 1K ohm pull-up
> > resistor to provide more true values for those MAT sensors.  Then there
> are
> > also offsets that compare the CTS to the MAT and scale this out to
> > represent a more true reading.  Then you can consider that a fully
warmed
> > engine will already have hot intake runners warming the incoming air,
and
> > now these calcs make more sense.  There is some more massaging but I
think
> I
> > explained it enough here for it to not look so off to you.   Now, I
would
> > hesitate to relocate the MAT to try to avoid the heat soaked effected
MAT
> > temp as you would then need to completely rework the above mentioned
calcs
> > and, would no longer have proper readings of the air temps as they ARE
> > heated by the engine, and this would then make for a cold (perceived)
MAT
> > reading making your calc offset towards the rich side of fueling, and
then
> > your oxygen sensor would wonder why the mix is so rich and would be
> working
> > to try to resolve this in closed loop.  There are so many details worked
> out
> > in the chip that one would spend a lot of time trying to come up with a
> much
> > better approach, but for those who want the challenge, and to what
> > gains???? go for it.  With this type of setup as it is, I have yet to
see
> > one that is THAT far off to warrant a total revamp of the system, though
> as
> > with this list, we know we can always tune it a little better and look
for
> > those challenges ;-).  Now if someone really wanted to do this, there
are
> a
> > host of sensors that are faster acting and accurate, but all the
sections
> in
> > the chip would need to be told this to work properly.
> >
> > Jeff M








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