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BARknucklehead BARknucklehead is offline
Corrupted by power
Join Date: May 2009
Posts: 55
Damn, jackpot! 911ST, I was hoping you'd chime in, too.

Originally Posted by 911st View Post
Not an expert but here are some thoughts.

7R case starts reaching its limit at about 270hp. At the heat of a turbo with severly increased combustion pressures and you might be taking a risk. Might be better to find an early sand cast aluminum case if durability is important. Steve Weiner assured me that a properly prepped small bore 7R's threshold is far above 300HP. The baby RSR was mag cased.

Small displacement, short stroke, low compression, cams that will support a usable power band up to 8000rpm -- and I suspect low end power and response is not going to be in the cards. See the dyno sheet above...depends on your point of refernce, but the inferior spec on that sheet still made as much power down lows as a 2.4S, which is enough for me - I just want it even better

For example, a K27-7200 turbo supports 320 hp. Boost starts to come on at 2500 with full boost at about 3200rpm on a 3.3. Put in on a 2.2 and boost will start at about 3700 rpm with full boost at 4500rpm. The K27 is dinosaur tech compared to Tial housed Garrett ball bearing turbos. A journal bearing GT25 Garrett will make 400HP in a MUCH smaller package, with better A/R and a modern ball bearing mechanism. My point is to find the right small turbo to make that power and spool up fast. The K27 ain't it.
Further, you will not likely get low overlap cams to work well at the rpm you want to reach. Thus, boost will come on later with the same turbo. I trust John Dougherty and he says these cams will tear your face off. The dyno above is damned impressive IMO and my cam spec is far superior - this is from John who specced both cams: mine and the ones in the dyno above

Also, you may need a larger lower restriction hot side for less back pressure so there is less hot gasses being pushed back in through the exhaust valve and past intake valve up into the intake manifold. Cool - My headers are 1.5"/38mm, which is pretty favorable by my calcs. What are you thinking in terms of specs?

Think a step beyond a 911S 2.2 (906?) in terms of power band and throttle response. You will probably want the turbo and cams to come in at about 6k to work right. No reason to go twin turbo that adds complexity and weight and you will be looking for turbos that make about 160hp each. This was my plan, but it seems from some other correspondence that a T3 works really well as a single for this config, so a more modern and efficient turbo might fit the billbetter than a twin.

What would be fun would be to run an MFI set up with your 2.3 turbo set up. I have one that would work, but like the progrmability and the extensibility of computer controlling everything - you and Burn Bros should form an MFI turbo cheer club; you might convince me

The best.
Old 05-26-2009, 09:22 PM
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