As part of the 2.5S engine rebuild, I'm doing a few things to try increase the output of the engine in the hopes it can get to the levels of the standard S2 - 208hp. Modest yes - but perhaps in reach with a modest budget. In fact I'd love to see 220bhp which will be the same as the series one turbo...
While rodders might say there's "no replacement for displacement", the japanese have been eaking out more BHP from their engines by lightening the internals and spinning them at higher revs. Legend has it that even within the 944 family range, the 968 is reputed to have a much lighter crankshaft. As I'm not opening up the bottom end, the crank will stay stock - for now...
While there is a lot of debate about the actual gains of lightening engine internals - reducing rotating mass helps you accelerate faster and releases power because the engine has less weight to throw around blah blah blah. Racers do it so it has to be good right?
After chatting to a couple of engine builders and engineers, on their advice I decided to lighten the 944S flywheel and clutch pressure plate - balancing them at the same time if needed. Interestingly, the engineer who lightened my components was very surprised to find that after lightening, the two parts were not only lighter but also virtually perfectly balanced.
Here are a couple of before and after comparisons - unfortunately in my enthusiasm I forgot to weigh them before I charged off to the engineer!
While rodders might say there's "no replacement for displacement", the japanese have been eaking out more BHP from their engines by lightening the internals and spinning them at higher revs. Legend has it that even within the 944 family range, the 968 is reputed to have a much lighter crankshaft. As I'm not opening up the bottom end, the crank will stay stock - for now...
While there is a lot of debate about the actual gains of lightening engine internals - reducing rotating mass helps you accelerate faster and releases power because the engine has less weight to throw around blah blah blah. Racers do it so it has to be good right?
After chatting to a couple of engine builders and engineers, on their advice I decided to lighten the 944S flywheel and clutch pressure plate - balancing them at the same time if needed. Interestingly, the engineer who lightened my components was very surprised to find that after lightening, the two parts were not only lighter but also virtually perfectly balanced.
Here are a couple of before and after comparisons - unfortunately in my enthusiasm I forgot to weigh them before I charged off to the engineer!
While the 8v 2.5 flywheel can be lightened significantly by skimming virtually all of the back of the flywheel, the 16v flywheel cannot be lightened near as much. If you compare the pic above it's obvious that the back of the flywheel has had a good few mm removed without compromising the integrity or effecting the grub screws for the sensors.
The engineer removed material from the outer ring face and the inner recessed section. The front face of the flywheel has been skimmed ever so slightly to prepare it for the new clutch friction plate (which I've yet to source).
If you've ever handled a flywheel and clutch pressure plate you'll know that they are HEAVY bits of kit. I can gladly say that they feel significantly lighter than before. I'm happy about that and it will be interesting see the end results on the dyno when compared to stock.
All in all a good modest 'mod' for not much money - hopefully.
Nice little writeup! Looks like you've had this on for 2 and a half years...what's your opinion on it now? How has driveability on the street changed? I'm doing my clutch in my 87 NA in a week or so and I'm trying to weigh (ha!) the pros and cons of doing this myself.
ReplyDelete