fuel pump adapt

[r lane]

Good morning. we are installing a 3.2 Motronic engine into a 3.0 CIS car. I haven't bothered to look up the different specs on fuel pressure and delivery for the specific pumps, and will do that at some time today, but will a Motronic engine run correctly off of a CIS pump. Thanks, Bob

[Discseven]

R... here's CIS and Mo links I recently looked at. Not saying they're right. Is cross ref to whatever you find.

CIS - 911 CIS Primer - Fuel Pressures

Mo - https://www.porscherepair.us/porsche-911-1984-1989/fuel-supply.html (Fuel pressures are noted about half way down document.)

[r lane]

The volume is approximatley the same, but 5.2 bar for CIS and 2.5 bar for Motronic. Concerns that the additional pressure from the CIS pump will present a problem for the fuel regulator/damper on the Motronic, but with the return, maybe not. Any one with having tried this? Bob

[spuggy]

Originally Posted by r lane

The volume is approximatley the same, but 5.2 bar for CIS and 2.5 bar for Motronic. Concerns that the additional pressure from the CIS pump will present a problem for the fuel regulator/damper on the Motronic, but with the return, maybe not. Any one with having tried this? Bob

From the Bosch Motorsport Fuel Pump document

Modern electric fuel pumps are “Positive Displacement” type pumps, this
means that the pump cannot produce pressure unless it is acting upon a
restriction. The only restriction in the system should be the fuel pressure reg-
ulator. The regulator controls the system pressure; the pressure ability or
flow volume capacity of the fuel pump will not alter the system pressure.

With CIS, there's a pressure regulator in the fuel distributor. With EFI, the fuel pressure regulator is typically somewhere on the fuel rail. This is what determines the pressure the system runs at, nothing to do with the pump.

After I converted my 930 to Motec, I continued to use the same 044 pump as I ran with CIS. Any pump that can achieve satisfactory flow at CIS pressures will be yawning and loafing with EFI - and will achieve at least the same flow (if not considerably better) with EFI, for lower current draw. It's not an issue.

[Flat6pac]

I’ve done conversions 3.0 to 3.2 since the late 80s Many times and never had a problem or concern of using the SC pump. I recall questioning the install in the 80s an out the pressures and told the regulators on the rails controlled the pressures for motronic.
Bruce