View Single Post
spuggy spuggy is online now
Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 3,523
Originally Posted by beepbeep View Post
First: CIS works with fairly high system pressure. When used with turbocharger fuel demand can be quite high,
No question.

thus 930 needs two pumps in series to satisfy fueling needs. Using a single SC pump (or even worse, a single EFI pump tailored to lower fuel pressure) is probably not safe for anything but mild boost.
With respect, this doesn't necessarily follow from the earlier statement, in my limited (sample size == 1) experience.

The AFR's sustained on a mild 3.3 930/60 by the single, stock, possibly-original (in which case it would have had 237,000+ miles on it) factory pump in my '77 were assessed by the PO.

With an LM-1 at speeds up to and including the rev-limited top speed. Multiple runs. They checked out.

He tracked the car. More than once. He drove the car on 1,500 mile road trips, including through the desert. More than once. Didn't blow up.

I took the car to a reputable 930/MOTEC tuner to have AFR's checked. They were not a concern and nothing was adjusted. Car made 310 FWHP.

I'm not saying AFR's, fuel flow and fuel pressure (and ignition) aren't critical.

I'm saying you don't need two pumps simply because the factory fitted two. What the pump delivers to the fuel system - flow & pressure - and the AFR's "seen" by the motor - is what matters.
'77 S with '78 930 power and a few other things.
Old 01-25-2009, 09:13 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #28 (permalink)