blown 944

Key word here.


Head bolt spacing, overall length, even larger bore in general (even a downsize of our current bore) are the drawbacks IMO.

In my experience, adding rpms is generally a recipe for breakage with a larger engine.

333pg333

Some good points raised although theoretically with a smaller bore / higher rpm motor you are reducing the peak cylinder pressures and the components are lighter and less likely to create ugly vibrations. Remember, we're not looking at going down to a 1.8lt motor, more around the 2.4-2.6ltr range. There will still be torque available. Also we're not running enduro events, but in reality it's like a qualifying format. We get 1-3 hotlaps per session and not even 10 sessions in a day with dual drivers.

We won't be pulling the trigger on anything without proper research and will be doing some direct comparisons to an Evo motor. We won't be running DSM type boost but feel that we can move beyond the normally accepted 18-22psi that the 944 turbo crowd use on the track.

Dave W.

OK here's a start. When I started rebuilding my engine a couple years ago I took a pic of a 4G63 head gasket on top of a 951 block. The Porsche engine is long.

Paulyy

Patrick are you looking at going smaller piston area or smaller stroke?

IMO i would go as large piston you can go and a stroke small enough to go to 2.4-2.6L like a 106mm bore with a ~70-73mm stroke

m42racer

From what I understand, this new engine will bring this 30 year old engine back into the modern age.

I cannot see alot of the development crossing over into the main stream as the costs will be too high for the average owner, but it will show what is capable of doing with these old engines.

From what I'm told, the engine in use to date was built as a street engine and the new engine was always destined to be the race engine.

Should be every interesting to see where this goes.

refresh951

Patrick - I look forward to what you guys come up with. Some interesting ideas for sure. I really like Dukes approach, a Hybrid Stroker with mild bore/stroke and a 16 valve head. The only thing I may do different is run a little lower CR, say 7.5-7.75 and make up the difference with a bit more boost to keep peak cylinder pressure down. I would also run a very short intake runner. The short runner along with rpm based control of the boost curve seems like a good approach for a high rpm track car. In this way you can manage peak cylinder pressure at peak torque and flatten the torque curve by increasing boost a bit after peak torque. Just my 2 cents.

333pg333

My assumption is that Neil will do some modelling on a few different options and see what the charts/numbers look like. We have to take a few things into account. Most of what has been covered in this thread of late. I don't see us making any rash decisions just for the sake of it. Basically we want to see over 700whp at not too crazy high boost. The 16v head will flow some serious numbers so we might have the advantage of running a bit more c/r without compromising on boost available. There's no point in making something that revs over 8000rpm if you're not making power up there. So we won't make it too linear or something that falls over up top like the previous motor. As for the intake, we have a few options. Duke is making something up for himself so we will see what he comes up with and of course we can knock something together ourselves. I haven't thought too much about that aspect just yet Shawn. We need to nut out some more basic details of this build first. As far as bore goes, it won't be too much smaller. Need to allow for large valves.

Interesting to see how much shorter the Evo motor is (thanks Dave). Wonder if they get any issues with hot spots between the cylinders?

Dave W.

The EVO/DSM engines have good cooling, almost even across the head. There's one common hotspot at the back of cyl #4 since that's where coolant exits the engine, so it's hottest there. Also, the EGR passage passes alongside the back of cyl#4, so it adds heat with less surface area for coolant to pull heat out. Otherwise the area between cylinders is trouble free. Are you thinking of doing a 4G63 swap?

Dutch944

333pg333

Ha, no...not at this stage. Just observing what they have compared to us as an example.

KSira

Altho there are many benefits to keeping the boost low and the peak cylinder pressure will off course wary with the engine configuration. Bacicaly cylinder pressure = torque. High or low boost will not make a difference to the cylinder pressure. If you want lower cylinder pressure and more hp, the only solution is more rpm.

Looking forward to see your new engine, it's for sure going to be a beast!

refresh951

Not sure how you arrive at this conclusion but it is incorrect.

KSira

Torque is the main component of cylinder pressure. High or low boost with same torque won't make much difference.

refresh951

At the same torque? Not sure I follow. Peak cylinder pressures can vary widely for a given torque value (at a given mean-effective pressure).

333pg333

Just found this short video to show one of the Evos that is in the next class up from us in the Time Attack competition. (Paul actually also drove the Orange one beside this car) While not a Porsche I think that you will agree that the attention to detail in this car is pretty amazing. Looks like something a factory would be proud of. Amazing stuff indeed.