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spuggy spuggy is online now
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Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 3,414
Sam,

You're really not gonna get very valuable help until you help us help you. Post a full description of

a) What you started with

b) What was changed/fitted/done

c) What you have now.

Even your sig says it's a 77 targa, but you now have a forced induction 3.0. Was that a 3.0 Carrera? An SC transplant? A 3.0 930?

What compression ratio? What turbo? What injection system? What ignition? What's the 411?

Mark's right - 10 PSI could be way too much boost for a high C/R motor - like an SC, for example. What's it supposed to be set to boost to? Is there an overboost sensor in place?

Frankly, I wouldn't even run it into boost until you know what's going on.

Seems to me you have at least two different car-related problems. The overheating could be ignition related, the sputtering sounds like AFR/mixture related and the idle sounds like a leak.

What oil cooling do you have? Fender mount carrera? Trombone? Front mount? Engine oil cooler only? Does it run hot if you're not in boost at all? How do the plugs look? Running lean (air leak) will also make it run hot, even off boost.

I don't think you can get away with no external oil coolers if boost is involved, even on a cold day.

When you say it sputters - when? All the time? Just on boost? Only when cold? I'd incline towards "massively lean from air leak" if it were the first. Which might also explain overheating. Heck, mine sputters badly pulling away cold with too much throttle as soon as the weather gets cold until I adjust the idle mixture to get CO2 in the right range. Then it runs too rich in the spring.

As far as a $3K bill from the shop goes, that doesn't go very far at a good independent Porsche shop. And not all independent Porsche shops are the same. Folks who work on factory 930's aren't necessarily qualified to work on modified 930's or custom installs.

Just for information, my factory single '77 fuel pump supported a mild 930 install for 310 FWHP just fine. But you should baseline the fuel flow, along with everything else.

Sounds to me as though you're either going to have to do it yourself, pay your mechanic an hourly rate to sort it, or get another mechanic (and pay them).
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'77 S with '78 930 power and a few other things.
Old 01-23-2009, 05:52 PM
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