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spuggy spuggy is offline
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Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 2,825
Question Twin-plugging, C/R and boost levels on 930?


'78 RoW 930 motor, 8:1 compression ratio, SC cams, stock wastegate.

Motor is apart right now, with some upgrades (headers, K27, I/C, adjustable WUR) "while we're in there".

I have a fairly good idea of how much it'll cost me to twin-plug it, and I'm trying to decide if it's worth it - i.e. if there's better "bang-for-the-buck" elsewhere (like brakes, suspension, paint etc).

With adequate and correctly-tuned fueling as a given (as well as correctly timed ignition), what is likely to be a "safe" boost limit for 8:1 C/R, and how much would that be likely to increase when twin-plugged? 5%? 10%? Suck it and see?

Given a "safe" boost level, what sort of variance is there between that and a "higher, but still sane" boost level?

Just trying to get a feel for what the envelope looks like - not even necessarily going to run higher boost, but would like to know where the ragged edge actually is so I can factor some margin in for hot days/bad gas etc...


'77 S with '78 930 power and a few other things.
Old 03-08-2007, 11:20 AM
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