blade7

In terms of useability and cost. Seems to me it's 400 bhp.

Penguinracer

Is the figure at the flywheel (fwhp) or the wheels (whp)?

Tim

Penguinracer

Cost - I'd have thought 400 - 420 fwhp would be the best bang for your buck - as a well tuned 2.5 litre should be able to get there.

V2Rocket

might also be subjective to what sort of driving you are doing/when you want the power to be there.

if you do a lot of motorways you might want 400hp to be able to fly in 4th/5th gear with ease.

in my car i have a ~250hp n/a V6 (which makes 250lbft peak, 200 of which is available off idle) and it can be scary in 1st/2nd gear and is a real delight on the highway in 3rd. 4th/5th it can overtake other cars with ease but certainly not "fast" in those gears.

Penguinracer

I'd include torque in that sweet spot - so for 90% road & 10% track at sensible value for money (otherwise you might as well go & buy a 997.1 turbo manual which is similar money to really good 951 build) :

Power: 400 - 420 FWHP;
Torque: 400+ lb/ft

blade7

A healthy 2.5 8v engine. A decent exhaust, turbo, standalone ecu with suitable injectors. cold air feed to a big air filter. Should get close to 400 crank bhp at 18 psi boost. Add a bigger intercooler, better cam and run 20 psi boost and get another 30-40 bhp. Plenty for twisty roads, and still within the capabilities of the 30+ year old chassis. And way short of 996/7 turbo money.

Voith

600whp.

Porsche-noob-91

Well I drove a 350 hp car in France and it was great.
My car is stock, and I haven't driven it much yet (just a test drive).

blade7

I'd say torque is important, it's what makes cars feel fast, especially on twisty roads. Plus I've got used to AWD, big brakes and traction control in my everyday car, so trying to use much more than 400 bhp in a road going 944, sounds like hard work to me.

968to986

My car has a refreshed (but not rebuilt) 2.5, K26-8, Tial wastegate, A-Tune and 18 psi. So maybe 280-300 WHP? When I don’t drive it much, it feels fast and it surprises/scares most passengers. When I drive it often, I think I’d be quite happy with another 100 HP. Yes, I’d say 400 would be a real sweet spot.

blade7

It's been quite a while since I bought the parts that could make 400, but I'd guess $1000 for a decent exhaust, $1500 for a modern turbo, $1500 for a standalone ecu, $500 for a DP wastegate, say another $1000 for injectors and air filter/ cold air intake. So say around $5500. Not cheap by any means, but way less than some have spent to go further.

Penguinracer

I think the issue is that if you have a motor with 130,000+ miles, tuning it to 400+ fwhp could potentially be the straw which breaks the camel's back, unless you use full power very sparingly.
It's having to refresh a higher mileage motor to future proof it for 400+ which gets expensive.
You'll initially question your rods, then pistons, then you'll get to thinking about perhaps having a different bore & before you know it you're into full tear down, upgrade and rebuild because quite sensibly you were concerned about turning a 150,000 mile 250 bhp motor into a 400 bhp one.

blade7

It's a fair point about the rods, most unopened turbos are probably running on cast rods. And while they can take a fair amount more power, I expect they're borderline unless the engine has a good tune. I've seen pictures of rods that have twisted or bent slightly and the engine has still run. There seem to be some mystery about the standard pistons too, they're strong, but don't expand anything like aftermarket forged pistons. I purposely titled the thread about road cars, because I think a car used hard on the track would find any weaknesses at 400 bhp sooner.

968to986

So assuming all the bolt-ons needed to potentially put out 400whp, what kind of boost levels are we talking about? It seems to me that high boost level, rather than the components themselves, is where engine internals really start to become stressed. When I refreshed my engine, I replaced the rod bearings, confirmed clean, unmarred bores, and replaced the head gasket. Could I produce 400 whp at 16psi with the right parts? I’m running 18 psi now and it feels good, but it make me nervous. AFRs are in the low 11 range at full boost.

333pg333

400whp and 16psi don't mix. Not with an 8v anyway. Without significant mods I'd say for a 2.5lt 8v you'd need well over 20psi for 400whp.