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i have a k 29 turbo and ruf motor 3.4 l twin plug enfine b&b exhaust and headers kokelin intercooler and my factory dreadful 4 spd transmission last night i was racing my friends zo6 he took me out with all gears and i looked pretty stupid i guess what it is what it is i have old technology i hace to face reality i hace an 20 year old car now my 2003 996 gt2 is a different animal how do i convert my 88 into a beast please help me out there i hate the 4 spd in this car it sucks
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Roughly speaking the curb weight of your 930 is 2850 lbs. and your engine produces in excess of 420 hp. So, you should be at a Power to weight ratio of 6.6 lbs/hp. While the Z06 is 505 hp and 3132 lbs. for a Power to Weight ratio of 6.2 lbs/hp.
How old is your build and how many miles are on the motor? When was the car last tuned?
I think you need to look at your Ring and Pinion selection. Is it stock? The 930 was geared for high fuel mileage and top speed. If you swap out the ring and pinion with lower gears your acceleration will be increased. Additionally, you can close the gap between gears to keep the car in boost. Or, you can install a shortened 5 speed, which is still plenty strong, and has a more usable curve. You should also look into getting a Quaife Differential.
Finally, what wheels and tires are you running. You can really reduce your unsprung weight with the right options.
915 would also work. i know everyone loves the g50 but the 915 has better feel to it when it's properly adjusted. Also the 915 can handle more torque than most people think. Keep it under 400ft pounds and you should be fine.
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1983 911SC steel widebody, 1994 Supra 6spd 827rwhp, 1979 Benz 300SD, 1969 Fiat Dino coupe, 1993 Jeep GC limited
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I have a 1978 Porsche 930 which had a 915 tranny in it when I purchased it. Shortly after I purchased it the tranny started sounding like nuts and bolts were flying around in a washing machine. When we got it apart it was not worth rebuilding. I ended up converting a G50 [shortened case, steel synchros, plumbed for external cooler and oil spray nozzles over gear stack and pinion, G50\50 LSD] to go with the motor which I converted to 3.4 with EFI using a DTA engine management ECU. The 915, even if you strengthen the innards will not be able to handle the increased torque and HP.
If you're going through the trouble I'd stick with the G50... No sense in using something that "will work" when there's a much better tool for the job and you are going through the time/expense of swapping out anyhow. You might look for a HighFlow series K27 Turbo instead of the K29 to reduce lag, and other than that brokentrackbar has given you some good advice. What wastegate are you running? If you're still on a stock wastegate even the smallest hairline crack in the diaphram can leak off boost - With the build up you have I'd definately look into a TiAL billet unit if you aren't already running one.
When I was considering rebuilding the 915 box that was in my 930 when I got it the consensus was that if I left the motor bone stock the 915, if I did not beat it up or stand on it, would probably hold together, but I would need to pause between shifts and be nice to it. The motor I built has over 560 ft\lb of torque and approx 500hp so the 915 was out of the question. It has one of Kevin's high flow K27 turbo's, EFI w\3.2 carrera intake manifold, custom throttle body, twin plugged, custom intercooler, Tial wastegate, GHL headers and a DTA engine management system. A G50 conversion is expensive-figure on the cost of the box, rebuild, steel synchros, billet shift forks, plumbing for external cooler, gear stack etc ...$7k and more. The other alternative is to have your 930 box re-geared with a taller first gear and then close ratio gearing which could do the trick.
An 80’s 930 would not be my first choice for drag racing the Z06. But, I do think that altering the ring and pinion selection is a relatively inexpensive way to really transform the 88 car. The factory ratios were just way too long. The G50, will take the car to an entirely new level. I also agree that the k27 is a really nice option, one I personally prefer to the k29.
I assume that with a properly tuned and 3.4L twin plug and k29s he would be over the edge of what a built 915 could handle. In my mind, it would not make sense to invest the dollars in building one with the possibility of grenading box only a stones throw away.
The OP has received some good advice in this thread, but it looks like it may be a hit and run post. Perhaps someone else will find the information useful.
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