HJK. Don't let any of these "Nay sayers" give you a hard time. Nothing wrong with being the so called "underdog" I love challenges, and it seems you do to!
I'm watching with interest, but I can tell you that building high hp small displacement motors are not a myth. Many have done exactly this when trying to stay within class/spec racing sanctioning bodies rules. It is however not a bang for your buck endevour, but then we are all driving 25yr old cars that are not exactly the best bang for your buck now are we?

Good luck!

What do you want?
Fast
Reliable
Cheap.... Pick two

 

The motor we are speaking of was damaged by metal contaminates from a bad balance shaft bearing - it had to be torn into and rebuilt anyways. So to clarify - all those mods I mentioned cost me less than $500 because I did all the work myself and scrounged the junkyards for used parts off of different models. It was time-practical because the motor had to be stripped down and rebuild regardless.

 

Thanks for the tip on the cage. I'll look into that one when the time comes.

Read the Raetech article on flow a while back, and it is interesting. Particularly the pressure wave diagram which spikes as the exhaust gas leaves the cylinder.

I've got a different solution to the intake problem on the drawingboard - a variable intake much like the mazda r26b le mans entrant.



Much simpler and less bulky, though. Will post about it when my CAD model looks right - basically the idea is that you can spread the resonant charging effect over the entire RPM range.

The exhaust side is, as far as I can see, impossible to make "varied volume". If anyone knows a way of progressively changing runner or collector volume in a hot exhaust then they are pretty smart

At the moment, the key bit in the middle is the intake and exhaust port flow. I'm looking into the theory there, rather than anecdotal evidence.

Would be good to compare a detailed visual on those ports with the actual performance on dyno day.

Glad that someone with deep pockets is opening up this area - unfortunately for you it's going to be cheaper for those following you

 

What kind of analytical work have you done? Man, 400 horse is a VERY tall order. I did some design work with a guy who owns a racing outfit on a 3.0L BMW. We got this kind of power out of his (I think we're at 356 to the wheels), but it had a lot more things going for it. It was a 13.0:1 CR engine, but the bore size was only 84mm. Trying to get taht kind of CR out of a 105-106 (forget what you did) bore is going to be a lot harder. I guess you can do it, and just retard the snot out of it until over 6000 RPM to avoid detonation, but that is still a huge CR number for such a monstrous bore and AvGas ain't gonna cut it. It has variable valve timing. It is also a 6 cylinder. You'd need 42mm intake valves and 37mm exhaust valves to have the equivalent flow area you'd need. If they can even fit in the head, valves that big are going to be HEAVY, and harder to get the same kind of cam profile out of. The runners on his intake were very, very short (which you could no doubt do). I designed it to hit peak torque at 7500 RPM. We're over 130% VE at peak power, closer to 140% at peak torque. It was dry sumped, I assume yours will be, too. There is only one thing I can think of that may help you over him, and that is that your oversquare engine will have lower FMEP than his undersquare one. But those numbers are in the weeds.

I don't mean to come across as a nay-sayer, but from what I've read (and I note that I may be misreading some of this), it looks like you are just bolting on parts and hoping for the best. You really need to take a very, very hard look at all aspects of it, as a complete system. What kind of ISAC can you best hope for? What kind of FMEP curve do you think you can achieve? And with those constraints, what kind of VE versus RPM target curve will you have? Once you have that, what kind of valve size and cam events are you going to need?

 

I'm not bolting on anything, don't worry. Michael Mount is building a new engine within the confines of the S2 housing, there's an awful lot going on inside and he's been able to get over 320 out of a streetable engine, we're doing additional intake stuff, a lot more rpm and everything it takes to make that work. The aim is 400+ But we don't know till we run it....
H

 

Very cool project. At first I assumed it would be some dreamer who was trying to get attention but this is obviously very well planned. I hope it succeeds, if it doesn't then all of us who love Porsche and 944s will learn something and enjoy the process with you anyway.

Maybe not the Chevrolet engine people though, they may not enjoy it or learn anything. I like V8s, I have one in my boat. I think I could enjoy one in a Cayenne even. Has anybody dropped an actual Porsche V8 into a 944?

But I jest, this thread should be about your project. Please attach a vid of your dyno run so we can hear the engine when it is finally together.

 

Thanks, will do !

 

okay, here we go, the following post originate from Michael Mount, I just do the copying and pasting, enjoy the ride....

 

This dialog is to document the hunt for >400hp in a naturally aspirated 944S2 engine. This horsepower level is new territory, but recent developments utilizing FEA, CFD and virtual engine modeling show potential for huge power gains over previous cut and try approaches. We’re going for it! The foundation for this effort is a 944S2 core engine provided by Henk. Our goal is to achieve a reasonable maintenance and rebuild interval along with huge power. Since the best available fuel in Henk’s neighborhood is 100Avgas, compression will be limited to a conservative 12.5:1. RPM limit will be 8000.


BLOCK PREPARATION
The S2 and 968 (3.0) block is structurally superior to the 2.5 block in a racing environment. The cylinders are far more effectively supported since the water jacket is very shallow and the cylinders are tied together at the deck surface.

 

Preparation involves disassembly, inspection, and stripping the block of head studs and the oil galley plugs so that machine work can begin. Although reconditioning worn cylinders with a Nikasil coating process is an excellent alternative, custom iron sleeves are being used in this build. With sleeves, repairs can be made in relatively short order by replacing a single cylinder, and cylinder freshen-ups can be handled be any well equipped race engine shop. The sleeves are flanged at the top and seat into a ledge machined in the deck surface. Bores are 4.155” (105.5mm).

 

The main housing casting at the bottom of the cylinders is radiused to provide some improvement in internal windage. This old 911 trick has application in the 944.

 

Main and rod bearing oil clearances are measured using a bore gauge and a micrometer. PlastiGauge is not nearly accurate enough. The main bore housing is also checked for straight. Corrections are made as required.
Piston to cylinder wall clearance is set after measuring each piston to ensure they meet spec. The clearance is based on cylinder wall material, piston design, and race application. The final cylinder size is achieved with a Sunnen CK-10 machine or similar, which also provides the proper finish (determined by the ring material) and a consistent size top to bottom. Getting the cylinders round and straight with the correct finish and size is a complex juggling act. It takes an expensive machine and a very skilled operator.

 

CRANKSHAFT

The core used is a 968 crank since it’s pounds lighter than the S2. Counterweights were not machined/lightened to avoid rigidity issues and maintain the endurance approach. The rod journals are offset ground by .100” and the diameter reduced to 1.888”. Poof: The stroke is now 3.564”. The revised stroke and big bore gives us 3.2L. Note the additional oil holes in the rod journals to ensure full pressure during the highest cylinder loading. Clevite coated race bearings (ala NASCAR) are used for the rods.

 

RODS

Brian Pauter supplied custom billet rods (on the left) to accommodate the power level and the revised configuration. The big end is Honda size, and the pin bore is .866” (22mm). They’re 6.150” center to center (+ .250” over stock). Oil clearance of .0025” was achieved by stroking the big ends in the Sunnen rod machine.

 

PISTONS

The box supported skirt design originated in F1 and is now available to us mere mortals. The design provides a very strong and extremely lightweight piston. Weight is 425g. These were custom built by JE who also provided the short 22mm diameter straight wall pins. A special feature to provide additional ring seal is incorporated, and hand radius work on the intake valve pockets improves the low-lift air flow.


RINGS

A very narrow conventional ring set was provided by Total-Seal. Thicknesses are .043”/.043”/.078”. The top ring is ductile-moly, the cast second ring is Napier cut, and the oil ring is low drag. Multiple oil ring expanders were tested for tension in the finished bores and the one selected is tailored to the crankcase vacuum provided by the dry-sump oil pump.