RE: Injector Pressure - (The new guy )

From: Mok, Alan (AMok@spbank.com)
Date: Thu Oct 08 1998 - 18:15:14 EDT


I'm talking about full-time, street driven applications. If you have an
adjustable FPR that has enough range it will delivery more or less the
same pressure at idle or part throttle. FPRs have a vaccum port
connected to the intake manifold. At part throttle/idle there is a
vaccum condition causing the FPR to open the return port to the fuel
tank and therefore less pressure. AT WOT (N/A engines) there is no
vaccum in the manifold so the FPR will close shutting off the return and
therefore more pressure.

You set the pressure to what you want to see at WOT, with the vaccum
hose disconnected.

FMUs are basically boost sensitive FPRs. When pressure from boost goes
from the intake through the hose to the FMU it will raise (shut off
return) the FP.

Alan

'98 Dakota R/T (Headers, FABM & waiting for Shift kit)
'89 Mustang GT (347, Griggs, S-trim...)
Ducati 916 (someday)

                -----Original Message-----
                From: Wisotzkey, Rich
[mailto:Rich.Wisotzkey@gsc.gte.com]
                Sent: Thursday, October 08, 1998 2:38 PM
                To: 'dakota-truck@buffnet.net'
                Subject: RE: DML: Injector Pressure - (The new
guy )

                Alan,
                I see what your getting at. Crank up the pressure for
the track, then turn
                it back down for the street. Is this correct? I was
viewing this from a
                full-time perspective. (I'm into permanent mods. Do it
once then forget
                about it.) By the way, what are "FMU's"?
                Rich

                -----Original Message-----
                From: Mok, Alan (SPB Brentwood) [mailto:AMok@spbank.com]
                Sent: Thursday, October 08, 1998 4:47 PM
                To: dakota-truck@buffnet.net
                Subject: RE: DML: Injector Pressure - (The new guy )

                As far as raising the fuel pressure you can do so up to
a point without
                breaking your injectors. We boost loving folks with FMUs
run pressures
                up to 80# for short periods during peak boost with no
harm done to the
                injectors. Depends on the design. Pintle valve design
can withstand 80 -
                90lb (during WOT). "Disk" types can't really withstand
more than 60lb.
                You don't want your injector to seize up. Just think
what would happen
                if they are stuck open or closed. Not pretty.

                What will kill an injector is by exceeding 80-90
percent of injector
                cycle for extended periods of time. My injectors go
static (100%) on
                extended WOT runs but since it only does so for short
periods they
                continue to work fine after 3 years.

                I think Ford and CC use about 36 - 40lb or pressure at
static (vaccum
                disconnected=WOT).

                I was wonder why the guys who are running a BIT on the
lean side (with
                proper mods) don't use an adjustable FPR instead of
buying new
                injectors.

                Alan

                '98 Dakota R/T (Headers, FABM & waiting for Shift kit)
                '89 Mustang GT (347, Griggs, S-trim...)
                Ducati 916 (someday)

                                -----Original Message-----
                                From: Wisotzkey, Rich
                [mailto:Rich.Wisotzkey@gsc.gte.com]
                                Sent: Thursday, October 08, 1998 12:48
PM
                                To: 'dakota-truck@buffnet.net'
                                Subject: RE: DML: Injector
Pressure - (The new
                guy )

                                Bill,
                                Maybe this will help in your decision
making equation.
                Jacking the pressure
                                up through the usage of an adjustable
pressure regulator
                alone will shorten
                                the life of the injectors. What happens
is this:
                                Driving the pressure up on the stock
injectors will
                indeed deliver more fuel
                                into the cylinder. This additional
pressure takes its
                toll on the internal
                                components of the injector and will
shorten its useful
                life. Also, the
                                proportional return on the pressure
increase in
                non-linear. Another words,
                                if you double the fuel pressure, you
will not get double
                the fuel delivery.
                                It will be a diminished percentage.
                                Increasing the size of the injector will
give you more
                fuel delivery without
                                decreasing its life expectance. But you
don't want to
                large of an injector.
                                If to large an injector is selected, the
fuel will not
                properly atomize
                                exiting the nozzle, and your performance
will suffer
                from a poor burn rate.
                                (Standard formula for this: .5 pounds
per hour per
                horsepower.)
                                Also, at WOT you will more that likely
suffer from fuel
                starvation if the
                                fuel pump cannot deliver an adequate
supply of fuel to
                the injectors. In
                                this case, you will also want to
consider a higher
                pressure fuel pump. Keep
                                in mind also that over time, the fuel
pump delivery rate
                is going to
                                decrease over time due to wear. This
will further add
                to the fuel
                                starvation dilemma.
                                Increasing one or maybe two injector
sizes will probably
                work fine, but
                                anymore than this really warrants
upgrading of the
                entire system. I hope
                                this helps.

                                Rich - Ashburn, VA

                                ----Original Message-----
                                From: Bridges, Bruce
[mailto:bbridges@alarismed.com]
                                Sent: Thursday, October 08, 1998 1:46 PM
                                To: 'dakota-truck@buffnet.net'
                                Subject: RE: DML: The new guy

                                Bill,
                                Dont jump too fast. You only get a lean
condition with
                the 52mm 700+cfm TB,
                                not the Stage 1s or the home style port
and polish
                units. I dont think you
                                can increase the FI pressure to get a
richer mixture
                though (I could be
                                wrong...) We should have some good data
for DML review
                by the end of next
                                week/ week after if you can wait so you
can make a more
                informed decision.
                                BKB

                                -----Original Message-----
                                From: William Blount Arthur
                [mailto:m990198@nadn.navy.mil]
                                Sent: Wednesday, October 07, 1998 9:53
PM
                                To: dakota-truck@buffnet.net
                                Subject: Re: DML: The new guy

                                Yeh, especially if I dont have all that
crap in the
                truck. I am thinking
                                maybe I want to get some 24 lb
injectors. that guy said
                the Jet leaned it
                                out too much. Maybe I should just try
to get an
                adjustable pressure
                                regulator like the 5.0 guys use? Later

                                Bill

                                On Wed, 7 Oct 1998 Boog318@aol.com
wrote:

> Bill
> I was running in 68deg. with 95 %
humidity. Search
                the archives for
                                "Boogs
> Racing Times" Yeah you have to run
up at Cecil Cty.
                You will probably
                                run
> faster.
> Oct 23rd.
> Boog
>



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