pfi & 747's

[rr]

Yes, good thoughts at that, very much the voice of reason. . . I always
figured the best way would be p&h's with a driver module. That is
a bit of electronics just to stay with a '747. The other side is the
knowledge base I have in the tbi ecm. At this point I'm actually
considering staying with the tbi with bigger butterflies.

BobR.

Bruce Plecan wrote:

> Very early in the DIY was a guy (Dale Ulan(?)) that posted, the recommended
> operating times of the P+Hs is 1-5 Msec, and 2-10 Msec for Sat..
> I have yet to be able to disprove anything he wrote.
> You can do alot of things, and kludge many things to get a system to work,
> but injectors types, and stategies don't seem to be one of them.
> Like the ongoing 4 P+Hs in series parr. wiring.  Some guys claim it works
> just fine, yet when I run them thata way on the ecmbench you can hear them
> starting to lose sync, sound funny.
>   You want to run P+Hs in a saturated strategy that seems to work, but
> drivers are an issue.
> Jus some thoughts
> Bruce
>
> > Now this is interesting, 30# injectors are rather large for the
> > power these engines make. Seems as though they are making up
> > for lack of pw with a larger injector.
> > The 17ohms makes them saturated, the slow to open type.
> > Yes, 4-1/4 ohms per bank, 3.2A @ 13.8v, should work. . .
> > BobR.
> > Shannen Durphey wrote:
> > > rr wrote:
> > > > I wouldn't be too quick to dismiss the '747 for a port
> > > > injected engine. Edelbrock sells a pfi conversion kit to
> > > > convert '747 powered trucks over to port.
> > > > In the tables they change the injector constant to 112, and
> > > > the pump shot stuff to smaller values. The most interesting is
> > > > that they leave the injector bias, min bpw, max bpw and the
> > > > 'switch to async' mode pulse widths the same.
> > > > The key is to find out if they are using saturated or p&h
> > > > injectors. Anybody know about this? Other thing in their
> > > > favor is that these trucks are not revving too high. Although
> > > > they add fuel fuel right up to the end of the ve table.
> > > Here's what I have:
> > > > They are 17 ohms DC resistance.  There is no other part number
> > > > that
> > > > Edelbrock gives for them except their house number of #3598.  They are
> > > > pintle-type, they flow 30 lbs./hr at 50 psi, 20 degree spray cone.
> > > Looks like 4 1/4 Ohms/bank of 4, yes?  Compared to around 2 Ohms for
> > > traditional tbi injectors.
> > > > I'd bet they are using p&h injetors. As the pfi p&h's are
> > > > twice the impedence as the tbi p&h's, you could drive
> > > > four from one driver, in a parallel/series configuration.
> > > > BobR.
> > > > p.s. still working on an iac writeup, I'm knee-deep in school
> > > > work, bit more off than I could chew. . . or is that grabbing
> > > > a hot iron by the end opposite the handle <g>
> > > Definitely the latter.
> > > Shannen
>
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