de 730 Speedo re-cal

[Dave Zug]

While we're talking VSS / SPeedo / Calcs...

I just went thru an exercise over several days. I have my T56 trans (swap in
a 92 replacing a T-5) 40 pulse-per DS-rev signal dialed in for the ECM *AND*
for the 92 speedo, using NO aftermarket devices.. chip params only.

There is a hardware divider in there, uses the SCI. (axxc, and I'm sure
others) seperate scaler for the ECM and for the speedo.

I heavily searched the ECM and EFI archives and was suprised to find nothing
on this except "you have to buy a convertor"

Here's anyone's chance to splain the role of 8014h (8D), and why certain
values are BAD to be there.

If this is a big secret, do it private.. but I have it figgered out all by
myself and am going public ;-)

-Dave Z

89 Iroc - '730 - 383 large tube MAP TPI, ZZ3 cam ,dry NOS 50 shot.
12.79 @106 / 12.08 @ 112.   www.delanet.com/~tgp
92 25th annev convertible  305 / T56.  268 mph in a perfect vacuum.
----- Original Message -----
From: Bob Wooten <r71chevy at earthlink.net>
To: <gmecm at diy-efi.org>
Sent: Saturday, June 16, 2001 9:07 AM
Subject: RE: Mileage calcs


> Wow, this turned out to be one of those "Ah ha" moments.  I think that I
get
> it now.  I am going to stew on it for a while.
>
> As always, thanks gents.
>
> BW
>
> -----Original Message-----
> From: owner-gmecm at diy-efi.org [mailto:owner-gmecm at diy-efi.org]On Behalf
> Of Shannen Durphey
> Sent: Saturday, June 16, 2001 6:52 AM
> To: gmecm at diy-efi.org
> Subject: Re: Mileage calcs
>
>
> Bob Wooten wrote:
> >
> > So, let me see if I got this right.  On a TPI car the injector has a
> > different delta P across it @ idle vs. @ WOT,
> On any manifold in which the delivery end of the injector is not exposed
to
> constant pressure.
>
> > SO for a given fuel pressure
> > in the injector @ a constant IOT will give you different flow rates?
>
> Oh, yes.  The injector is not a pressure controlling device, it's a volume
> controlling devbice.  Injector flow rates are always given @ a
differential
> pressure, usually rail pressure relative to atmospheric pressure.  Change
> the
> pressure on either side of the injector, you change the differential
> pressure,
> and you've changed the volume of fuel delivered by the injector.
>
> >
> > BUT for a TBI car, as the injectors are above the throttle blades the
> delta
> > P across the injectors is the "same" @ WOT & Idle so they flow the same
> for
> > a given IOT?
>
> No change in differential pressure.
> >
> > If I am following then changing the Fuel pressure across the injector on
> the
> > TPI car keeps the volume of fuel the same for a given IOT?
>
> Well, yes, it can.  But I think with modified engines it often just
reduces
> the
> range of difference.  Using a fuel pressure regulator reduces the change
in
> IOT
> needed between lean and rich conditions.  Seems to me that the injector is
> the
> component getting special consideration here.  The ecm can handle IOT from
> zero
> to pintle lockup.  This has been proven in the past by list members who've
> tried
> to run undersized injectors.
>
> > if that is the
> > case then the SD formula for calculating the IOT remains linear & it
does
> > not have to have a log or ln function (or worse yet some odd ball curve
> that
> > has to be curve fit) for calculating IOT?
>
> Somebody want to pop in that can give us the TPI SD calculation?
>
> I'd definitaly say that the injector flow portion of the speed density
> calculation can be more accurately included as a constant with the
inclusion
> of
> a regulator.  What would be kewl would be to code injector flow as a
dynamic
> value based on differential pressure between measured rail pressure and
MAP.
>
> But speed density systems are curve fit anyway.  The data in the VE tables
> is
> (or at least was, in pre OBDII days) obtained by investing time and
> observations
> in driveability and emission tests.  Much of what we do here is modify the
> curve
> for a better fit, whether for a stock engine or for a different
> configuration.
>
> Shannen
>
> >
> > Yes? No?
> >
> > BW
> >
> > -----Original Message-----
> > From: owner-gmecm at diy-efi.org [mailto:owner-gmecm at diy-efi.org]On Behalf
> > Of Shannen Durphey
> > Sent: Friday, June 15, 2001 8:01 PM
> > To: gmecm at diy-efi.org
> > Subject: Re: Mileage calcs
> >
> > Ayup.
> > Shannen
> >
> > Bob Valentine wrote:
> > >
> > > Isn't the vacuum referenced FPR to account for the fact that the
> business
> > > end of the injector is exposed to intake vacuum, which would affect
the
> > > flow rating if not compensated for?  That's my understanding as to why
> TBI
> > > units don't have a vacuum referenced FPR.
> > >
> > > -> Bob Valentine
> > > -> bob at tecmark.com
> > >
>
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