Re: New Member, LT1 Questions

[Ken Kelly <kenkelly@lucent.com>]

Comments In line

Dave Zug wrote:
> 
> ok, its been long enough and no one is responding.... now its amateur answer
> time - be warned ;-)
> 
> ----- Original Message -----
> From: Dave Plummer <davepl@MICROSOFT.com>
> To: <gmecm@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.

	Actually the stock LT1 injectors are 24# and Dave suggested
he will run 50#. These are huge injectors. I would not worry
about running at 100%, but I really would worry about the
minimum injector pulse width at idle. Also for Doubling the
Fuel flow with these injectors you will need to get a better
fuel pump. Many people are running 30# injectors, I don't
know anyone running 50# on the LT1, but at 15 lbs of boost
it may be necessary, I assume that your current system with
the FMU is not running 50# injectors.

> 
> 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?

	AT WOT the PCM runs in open loop, so the O2 sensors aren't
really used.

> >
> 
> 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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> >
> 
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