944kid

First of all, this is purely a discussion for my amusement/education.

Second, the question! As I understand, one big drawback of the turbocharged 944 is it's displacement. Because of the large rotating mass, higher rpms cannot be reached, and therefore epic horsepower numbers aren't seen by more than a few.

I've seen a few kits for bored and stroked 951 motors, but in my quick search, I couldn't find info on smaller displacement motors. So I ask, would a smaller displacement 951 generate more power than the stock, or even a bigger displacement motor?


Remember, keep it simple. I don't have a 951 either, so my knowledge of the car is limited at best.

'Splain.

evil 944t

Its possible to extract more hp from a small cc but you will need to go to a higher RPM to move the same amount of air.

There is a 951 turbo in my area that has a 2.1 16v motor. They run it up to 10k rpms and high boost. It makes around 480-500rwhp. They had to do a custom gearbox to keep it revving all the time.

944kid

I'd expect higher rpms, but I'd also expect much higher HP.


Digging through my brain, isn't another drawback of the 951 it's turbocharger placement? What if something was done like the 9ff car, where the engine was tilted fully upright, or even more towards the right of the engine bay? In addition to smaller displacement, would this be a better setup?

Driftomagnifico

The 944's problem isn't it's stroke or bore it's simply keeping the engine lubricated and cool, and getting air in and out.

Nissan's KA24DE engine has a rod length of 165mm with a 96mm stroke, the piston is relatively lighter being that it is 89mm in diameter, but it has MUCH higher piston speeds compared to the 944. They routinely rev out to 7000 RPM on stock rods and bearings. I've seen as high as 7500 RPM but that is dancing on thin ice. To add fuel to the fire they have huge bearing surfaces and 4cw cranks.

The main issue I've seen with the 944 is that the engine simply does not make top end power with the 8v head setup. Reducing the displacement will only shift the same amount of airflow upwards, as noted before, and you will run into the exact same problems as the 2.5L at a lower RPM. The 8v head's design is so archaic that it's just going to flat out choke at elevated flow levels.

The 16v head on the other hand... would be much better suited at higher RPMs. However, getting the 2.5L running gear up to the task of sustaining 9000 - 9500 RPM is very costly.

Cory9584

With the right mods our engines can rev pretty high aswell

944kid

The right mods being?


Lighter valve springs, valves, sure. What else equals higher rpms?

evil 944t

Crank, rods, pistons, dry sump, cam, valves, springs etc.. the list goes on.. Depends on what your trying to do.

Cory9584

Lightened and balanced crank, titanium co rods, lighter pistons and valves, light flywheel and pp, solid lifters, stiffer titanium valve springs, then you need to have everything flowing well for response

evil 944t

Ti rods are nice but not needed, even up to 10k rpm. Factory lightened/balanced turbo rods do well. Ti valve springs?

Tms951

The problem with the engine and reving is the way the displacement is created. The problem is the stroke, and such big pistons also cause other power related problems. Simplely put there are not enough cylinders, I would asume this was done to place it below the 911s in marketing. If the engine was a 6 cylinder it would have more vales and it could have smaller diameter pistons and the important part for high reving less stroke and still maintain the same displacement. If porsche had used Audis 5 cylinder engine these would have been much better cars, but they wanted to use thier own engine and took half of a big V8, IMO not the best chioce but they were trying to get away from how un porsche these cars are.

944kid

Let's say that all of that is done, could a 951 block handle power over say, the 600 number? Would it have to be reinforced?

Dave, I'm trying to reach 1000 hp Supra territory. (In my mind.) So, let's build the ultimate motor here. I've got another week I take it off of school before they'll let me back in, at the least. I'm trying to keep my mind occupied. I might as well learn about something during my "break!"

Cory9584

the reason i mentioned the titanium parts wasnt necessaraly because the strength is needed, but because of its weight savings.

evil 944t

You can use custom pistons and longer rods. That helps take some stress out of the engine.

Porschefile

Hmm, lets see. 1000hp? You are talking a Gt42r or something similar around the ~74mm T4 range. That's some manly lag you're talking about there. ;-) If you could do it, you'd have to build the motor to rev to like 9k rpm just so you could have a 2k powerband. ;-) Doing it just to do it is a perfectly good reason IMO, however you are talking about some serious money to acheive something like that, so I'd be honest with yourself and ask yourself exactly what it is you want. The only real purpose one could have with a 1000hp 951 would be for serious drag racing. Other than that, it would be useless on the street. To be vague, you are looking at roughly $15-20k+ for a motor, $14-18k for a transaxle, $2-4k for a multi plate clutch, $1k for axles..........and that doesn't even cover all of the supporting mods, suspension, brakes, etc. Hell, you could probably buy a Mk4 Supra, and build it to sustain at least one 1000hp dyno pull for less than it would cost to make a 951 do it. ;-)

944kid

That's the point, Porschefile. Do it to DO IT! What about running 2 turbos, ala (oh god, memory!) the GTI Polo? Or is that one turbo and one supercharger? What I mean is, one turbo for down low, and one for up high in the rpm range. Could that be done?

For me, 9k rpms is not a big deal, in theory. I like what Corleones did with his car, and from now on, I think I'll spend a lot more time in the 951 forum. All of this is completely foreign to this N/A guy!