New Member, LT1 Questions

[Dave Zug]

ok, its been long enough and no one is responding.... now its amateur answer
time - be warned ;-)


----- Original Message -----
From: Dave Plummer <davepl at MICROSOFT.com>
To: <gmecm at lists.diy-efi.org>
Sent: Monday, January 31, 2000 3:53 PM
Subject: New Member, LT1 Questions


> Hi!  I've spent a good deal of time reading the archives and pouring over
> PROM dumps, and I've got a few questions that I didn't find answers for.
> First, the scenario:
>
> '94 Corvette 350LT1 w/6psi Vortech
> ...and under construction:
> 396LT1 w/50# injectors, 12-15psi boost, 2 core intercooler
>
> My first goal, under the heading of "learn on the old motor first", is to
> eliminate the FMU and alter the spark tables to be better suited to the
> blown application.

to eliminate the FMU your (assumed) stock injectors are going to need some
more fuel pressure, an adjustment to the injector constant to accomodate the
pressure, and will run closer to 100% dc and may even be short after all
that.  Idle may suffer a bit from the PW having to be lowered for the
increased FP - something about the time it takes the injector coil to pull
the pintle open being close to the amount of time the injector is required
to be open.  I fell asleep in injectors 301.

spark is easier and cleaner. watch out if your application has spark
weaks  - the main table may not be the appropriate one to modify if there is
a supplimental one more suited to WOT or PE or ?

come on people someone tell this guy where I'm wrong so I dont ruin his car
;-P

>
> My big question is about the WOT Enrichment vs. RPM table.  It's described
> in some places as specifying a desired AF ratio, in others as a percentage
> of extra fuel to add during WOT.  Which is more accurate?  How does the O2
> sensor get figured into this blanket enrichment at WOT?
>

the percentage line is more accurate - ....I dont know the LT1 ecm at all -
I'm an old timer '165 MAF groupie. in 165 it is an approximation to target
the desired AF ratio - but even slight mods like air filters can change its
accuracy. (did I pass on that one?)

> My second question relates more specifically to accomodating boost.  Since
> the VE tables are limited to 100%, what's the best way to program for
boost?
> I'm thinking this:
>

the common answers are "convert to MAP" - I'll say given what you have, the
FMU may be best, but upping the RPM based fuel addition may help given
nothing else. I'd keep the FMU. the reason I personally would try to make
the ecm handle it by itself is that I would not like to spend the $ for the
FMU ;-)

> 1) In the RPM range where boost is present, in the 100kPa column, set VE
to
> 100%

VE may be 105+, and rpm that 100kPa is present depends on alot and will
shift.

> 2) Get the extra fuel to accomodate the true >100% VE by upping the WOT
> enrichment table entries

the RPM based fueling too i'm thinking. - may be the same thing

>
> I can't really do #2 without understanding that table a little better,
hence
> the original question.  Any feedback on how I should go about programming
> the LT1 controller for boost would be greatly appreciated!
>

I dont even have any misguiding advice there, thats specific to the LT1 - I
almost had a LT1 car but I wrecked my trade-in :-{

> Thanks,
> Dave
>
your welcome,
Dave www.delanet.com/~tgp

take all I said knowing I have changed exactly 4 things on 2 cars ever. 8-P

...um - and one was a turbo and I popped the head gasket in it (no, not the
buick bruce)

>
>
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