SloMo228

Just daydreaming a bit and thinking about building up my 2.5 DOHC motor in the far future.

It's got a 6800 RPM redline from the factory. That's good, but it could be more gooder. I imagine it could probably handle 7000 RPM without much fuss, but what would it take to reliably touch 7200 RPM? 7500 RPM? I'm assuming lightened crank and pistons are a must, and some kind of valve train improvement. Are solid lifters necessary? Lighter valves? Stiffer valve springs?

Has anyone built a 16V engine for high-RPM NA power? I've seen a few S2 and 968-based large-displacement builds that have made big numbers, but I've not come across very many people doing anything with the smaller 16V cousin.

A build like this wouldn't be cost-effective compared to swapping a 968 motor or a V8, of course, but it's fun to think about the possibilities anyway.

Arominus

Due to oil pump cavitation issues i'd probably stay under 7100. My 968 engine is chipped at 7100 but i really try to shift at 6900 or so in first. Pistons, rods and a lighter flywheel seem like a good idea for it and i'd have the cams re-ground for more umph. This would let it spin up a little faster, that said i don't know that it would be worth the investment for the rods/pistons. I'd start with cams and supporting breathing mods and see how it does. That motor already rev's pretty well over 4k. My 968 engine revs up *much* faster than my 944S did, but its also more powerful and i'm at 6,000ft which hurts both of them.

SloMo228

Hmm, I didn't think about the oil pump, although I guess that's kind of a weak spot for all 944 engine variants. Maybe a dry sump with a remote oil pump would help that issue.

Arominus

It would but, damn, thats some money usually. I'd want to get into cams/intake/exhaust before i hit that. Mostly because there is more power there than just spinning it up. If you're going for a race motor it could be worth it, but i'd also think that valve float could be a problem. 7k is pretty good and the S already feels pretty good at that point. Fresh motor, cams, intake (s2? needs to be dyno'd vs S intake), better header/exhaust, MAF and tune (MS or rogue if he gets it out) and you could have a bitchin', still streetable motor i think.

SloMo228

Oh yeah, for sure. There's no way I'd be spending that much money on a S motor, just thinking about what it might take if money were no object.

I do plan on a rebuild/upgrade of my engine in a year or so, but I won't be going farther than a general refresh with hotter cams and maybe lightened internals.

Paulyy

bottom end bearings will take a beating too.

ramius665

The Firestone Firehawk S2s were rev-limited to 7200 and could run there without significant improvements to the valve train. That being said, the S cams are already the most aggressive variant from the factory and the motor is very anemic below 4k or so. At the same time, the Firehawk cars also suffered vibration-related issues due to their high rev limiters, specifically the power steering pumps had a tendency to fail or separate from their mounts.

JustinL

I would agree with this. I run my 968 engine to 7000 on occasion, but I prefer to shift around 6800. I do have a hot set of cams and forged rods and pistons, so it could probably handle more, but I'm not going to push it out of mechanical sympathy. I worry about the oiling as well.

It's got a manual rack so power steering pump is not an issue, but I wonder about spinning the alternator that fast.