CIS fuel pumps, how much HP?

[JShadzi at aol.com]

BTDT many times on Audi applications with 2 pumps, never any problem you describe, though I could see how it can happen.

Javad

>I would add one caveat. You can get too much fuel volume for your fuel
>pressure regulator to handle at idle. Since the engine does not use much
>fuel at idle most of what your pumps will be doing is recirculation the fuel
>through the system and back to the tank. We ran into this on a 911 turbo
>project car (428 hp on an engine dyno). MoTec fuel/ignition running 2 fuel
>pumps to insure enough fuel under full load at high rpm. The fuel pressure
>would creep up at idle causing and overly rich condition. We had to add a
>second pressure regulator and return line to control it. Maybe we went a
>little over board on fuel pump sizes but we never had a lack of fuel.
>Jim
>1984 4kq
>1985 4kq
>
>-----Original Message-----
>From: JShadzi at aol.com [mailto:JShadzi at aol.com]
>Sent: Tuesday, November 26, 2002 11:28 AM
>To: jeg1976 at yahoo.com; quattro at audifans.com
>Subject: Re: CIS fuel pumps, how much HP?
>
>
>IME, the CIS3 pump is good to 400hp safely, I just replaced my 15 year old
>CIS3 pump recently because I was getting some fuel cut out at 20psi and race
>gas (350+hp I'd say no problem, considering I have about 300 at 15psi),
>swapping in a S. African CIS truck (Eurovan) pump seemed to do the trick,
>its the same diameter as the CIS3 pump, but 1" longer, a real hog, got it at
>Eurospec a way back, no more cutting out.
>
>Anyway, you can't go wrong with 2 pumps, maybe a little overkill for 350hp,
>just keep an eye on your fuel pressure, if it drops at max power, you know
>you need more pump.
>
>Javad
>80tq.com
>
>>In preparation for some obscene HP, I've been
>>wondering how much HP the CIS-III fuel pumps are good
>>for?  I'm planning on trying for 350 hp after the
>>header and new IM go in.  Should I pipe in a second
>>pump in parallel just to be safe?  It's already
>>sitting right there from the first stage of the
>>project.  As far as the header goes, it just went to a
>>new welder as the first one was just to backed up to
>>do it anytime soon.  He said maybe Friday!  I can't
>>wait to get my car back..
>>
>>TIA,
>>
>>=====
>>Jim Green
>>'89 90tq 034EFI, Haltech IG5
>>http://www.geocities.com/jeg1976/car_home.html
>>
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>