Carpokes Porsche Forum

It would be interesting to see what your 100-200kmh times are now although they may be negatively effected by the wheelspin!

What clutch are you using Thom?

Patrick, I will try, for the sake of science.

Tom, it is a KEP 2 pp with a later 930 disc with the larger 4 springs rather than 6 small ones on the earlier 930 disc.

Keep that up your sleeve for the Gendarmes.

Here is another log of interest, with boost peaking at 1.8 bar @4500 rpm and tapering to 1.5 bar @6700 rpm.
Flooring the throttle @2500 rpm sees 1.0 bar at 3700 rpm, with open loop boost control.
100-150 km/h in 2.5s
100-190 km/h in 6.9s
This is with losing traction when torque kicks in at 4300 rpm and again at around 5700 rpm.

Definitely a very fast car. I imagine that losing traction at such speed can be somewhat unsettling. Ever think about going with a stickier tyre?

Well, it was unsettling the first times and still is but somehow you get used to it. Obviously you are only going to try this on a deserted straight and turn the knobs of attention and focus to 11, but the car pulls straight, at least in the dry. I drive with headphones on to listen for knock but it is not easy to focus on your hearing when driving requires so much attention.
I may try stickier tyres depending on how the car drives after figuring out the settings for closed loop boost control which I find more difficult to tune as the turbo is much more responsive than on the 8V engine, but this is a car used in all weather and I need good all round tyres.

Ok dumb question. I’ve been mulling this over, if one builds a 16v turbo for street use would it be less “dangerous” to use a 2.5 block and crankshaft with a 944S head? You would still get the turbo adrenaline push but I’m assuming you would not lose traction (the less dangerous part). Also, would you be able to use less boost because better breathing due to 4 valves. Another plus would be better MPG, I think? (And yes I know you would need custom pistons to get the compression right and a standalone and everything else to make it work). Is my thinking on the right track?

I know a 3.0 would make more hp (more displacement) but is it to much for street. And yes I know many think what’s the point, but I’m just curious in regards to drivability between both flavors.

Too big is barely enough

The larger engine will always be nicer for street use thanks to the higher torque down low especially at light loads under vacuum, and you can always turn the boost down to keep traction under control yet enjoy an engine eager to rev up top thanks to the higher flow allowed by the 4V. It's better to have more than you can handle and keep the boost down than being haunted with "what if"s and a smaller engine that won't provide quite the same sense of occasion. However, what do you plan to use it for? For a full race car the excessive amount of torque will probably be counter productive and an engine revved high all day long should be more reliable with the shorter stroke.

An interesting configuration for track use would be an engine like mine but with the shorter stroke crank and a dry sump. Peak torque will be lower but should allow a nicely flat torque curve up top, especially with slightly longer duration cams, and probably more durable under intense use.

I concur with Thom's thoughts. If you're going to the trouble of putting a 16v engine together then why sacrifice capacity if it's going to cost pretty much the same amount? There are devices like these that you could implement. I have a feeling that Gustaf used something similar early on with his 3lt build/s? https://www.racetcs.com/ Also, of the three 16v heads, apparently the 2.5lt 4v is the weakest. It can be prone to cracking.

So Thom, for the track, are you talking about reducing the stroke and running longer rods? Or a traditional stroker style motor?