7747 tuning again

[Walter Sherwin]

What are your scan tool commanded BPW magnitudes like, at above say 3000
thru to wherever you shift?  Have you done anything physical to actually set
your TBI pressure to 18psig?   Or, have you just read the gage at idle?

18psig TBI pressure, while under load on the road, **usually** requires
either an intentional regulator P/N change (to something like 17113186 with
the vac line disconnected) or the addition of a grafted external return line
regulator downstream of your existing OE regulator.  You theoretically will
have enough injector capacity for 250'ish HP in your case (using base '60
pounders tweeked up to 18psig), **if** your BPW's are truly max'd and **if**
your pressure is truly 18psig.  Don't worry about your pressures causing
injector delivery/failure problems, because you are no where near that
danger threshold yet.  Can you post the engraved numbers from your TBI
injectors?

TBI fueling is a big balancing act between pressure, delivery, BPW headroom,
and VE table headroom.  Sometimes you have to get creative with the base
pulse constant (and associated scalars) to get what you want, even if the
software values are a bit non-sensical at a cursory glance.  I think in your
case, there's something else underlying your delivery problems, and no I
would not think that you should need to step up to the next larger TBI
injector for your application.


Walt.



>
> I raised the BPW constant to 140 since the engine has 10 more cubic inches
> than a 350. I used Tunercats equation with a 5.9L vs. 5.7L engine. As for
> EGR, I raised the TPS% EGR ON to 99.9% and the EGR OFF to 99.2%, or
something
> real close to that. I realized after I sent this post that I haven't
checked
> the fuel pressure under load, only at idle. I figured that idle was the
worst
> case for the regulator to handle since it is bypassing the most fuel at
this
> condition, but I realized that I could have a stuck regulator bypassing
too
> much fuel under load. Its a stock regulator and the PSI is too high so
maybe
> there is something wrong with it.

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