ECU tuning: was; The whole 1.8T puny injector debacle

[jdbubb@ix.netcom.com (Dan Bubb)]

A normal FPR maintains a constant fuel pressure above manifold pressure i.e.
the  if you have a 4bar FPR then if manifold pressure is 1 bar absolute then
the fuel pressure is 4 bar. If the manifold pressure is 2 bar absolute (15
psi boost) then the fuel pressure is 5 bar.
A rising rate FPR increases the fuel pressure faster than an increase in
manifold pressure. So, a 2:1 rising rate would give 6 bar at 15 psi boost in
the above example.
If you've actually programmed an ECU then you would know that programming
for a regular FPR is relatively straight forward. Programming for a rising
rate throws another curve into the equation that makes it more difficult to
intuitively see what the map needs to look like.
Rising rate FPR's allow more power from smaller injectors. OEM's may use
them since with a smaller injector they will have better fueling control at
idle and low load conditions for cleaner emissions, longer CAT life, less
expensive injectors......


----- Original Message -----
From: Allyn <amalventano1@comcast.net>
To: Joe Doty <rocco2nr@hotmail.com>
Cc: <scirocco-l@scirocco.org>
Sent: Saturday, June 15, 2002 10:36 PM
Subject: Re: ECU tuning: was; The whole 1.8T puny injector debacle


> eagle talon tsi as well as alot of audi models come with rising rate fpr's
(where do you think us
> cheapasses get em from?). yes, some factory turbo cars come with rising
rate fpr's (i doubt they are
> taking any kind of 'cheap route' there..
> i misspoke there on taking map out of the equation, it doesnt do that, but
it does let you get more
> boost ran on lower flow injectors. a rising rate fpr compensates for
change in manifold pressure,
> thus keeping a constant d/p across the injectors in all conditions
(normally the d/p drops as boost
> rises, effectively lowering the flow rate of your injectors). this
compensation makes tuning easier
> as it turns one of the variables into a constant. it also makes the range
of the fuel map smaller in
> the end (doesnt have to go way up to compensate for increassed manifold
pressure).
> Al
>
> ----- Original Message -----
> From: "Joe Doty" <rocco2nr@hotmail.com>
> To: <amalventano1@comcast.net>
> Cc: <scirocco-l@scirocco.org>
> Sent: Saturday, June 15, 2002 9:23 PM
> Subject: Re: ECU tuning: was; The whole 1.8T puny injector debacle
>
>
> > I would disagree with you there.  A rising rate FPR a cheap way to get
more
> > fuel without touching the fuel injectors or fuel maps.  Most kits that
use
> > rising rate FPRs max out at 8-9 psi.  It's an enrichment device.
> >
> > I believe the best way would be an adjustable FPR.  If you are able to
> > adjust the mappings via a chip or standalone management, tuning it
properly
> > there would be the best idea.
> >
> > >yea, rising rate fpr is a good move on turbo cars. it takes manifold
> > >pressure changes out of the
> > >equation
> >
> > Most fuel maps ARE based on manifold pressure changes.  It's probably
better
> > to tune the car there rather than futzing with the fuel pressure.
> >
> > Joe
> >
> >
> >
> >
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