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spuggy spuggy is offline
Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 3,523
Originally Posted by parasailsam View Post
Looks like I don't have a second fuel pump, but Spuggy says he runs ok on mild turbo upgrade...
Yup, single 'S' factory pump (original AFAIK) made good flow/pressure figures and AFR's were fine flat out when checked by PO, and when dyno'd by me. I think it's a myth that you need two fuel pumps.

(Later fitted an 044 motorsport pump because the original pump was noisy/just for the heck of it/cheap insurance when I uprated the turbo. The brand new Bosch 044 pump made exactly the same noise as the old factory pump.)

Flow and pressure are the only things that count. What system pressure does it make? How much does it flow?

Yes, the car runs well up to 10psi where the boost limit is, then it sputters and the boost guage goes up and down rapidly from 5 to 15 as it cuts out, sputters, looses power and basicly worries the heck out of me.
Shouldn't the wastergate limit the boost a 10psi but not dump all the boost?
Yes, the wastegate should regulate the boost at the maximum setting.

The factory two-pump setup cuts the rear pump when the overboost sensor triggers (range 1.1-1.4 bar, IIRC), and folks here describe it as like hitting a wall (head bouncing off the steering wheel effect). Rear pump failure is "limp home" mode.

I don't have one fitted, and my car doesn't overboost anyway. Can't tell you how it might behave with a single pump - but the symptoms might well be different.

Are you sure you have an overboost sensor? And the relay? What's it wired to - the front pump circuit?

Sure you're not hitting the rev limiter?

Are you running the 930 CDI box (with a built-in rev limiter) or a rev limiting distributor rotor?

I don't know never having had a turbo before.

The mechanic who worked on it said I should get 2 or 4 prong plugs and a high enery ignition system... would that really help?
I'm pretty sure the stock 930's didn't have that stuff in the late 70's.
They ran single prong Bosch Platinum plugs from the factory. They're very, very, cold (so they don't melt your pistons) - but they don't foul in town.

The Bosch CDI ignition IS a high-energy ignition system. You don't want to get a belt from that sucker.
'77 S with '78 930 power and a few other things.
Old 01-24-2009, 05:09 PM
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