If you had a Cayman, what engine would you build?

[Porschekid962]

To Mr. Turboteener. The GT3 RSR motor is a 3.8 litre flat 6, breathing through two 29.2mm restrictors. I know how much power they make. The Grand Am DP motors are the same save for the fact the intake manifold is slightly different to accomodate an "open" intake. E.G. there is no intake restriction. These motors were just updated to rev to 9,250rpm and make a prodigious amount of power. Is the end result 600bhp? I cannot tell you as I promised the dyno operator I would not, is it impressive, very much so. That being said these motors have a 40 hour shelf life between builds. They use Ti rods, Ti valves, pistons, rods and cylinder liners are 40 hour replaceable pieces.

If you really think you can squeeze more power out of that motor while having a decent turnaround time I would be impressed. Bumping the displacement has been tried, they made impressive numbers but never lasted very long at all. One engine literally ate itself into bits. I have never seen a piston weld itself to a head before. The rod was a lump about the size of a large grape.

Sure you could spend 60k. You can start with hollow stem Ferrera Ti valves, dont bother trying to get lighter rods, you might possibly find lighter pistons in the aftermarket from Cosworth or Accralite. Chambon might make you a lighter slightly longer stroke one off crank. Straight cut intermediate gears could be used to claw back some windage losses, go with Ti while your at it. Then you can spend weeks detailing the inside of the case, polishing it, boattailing the mains, polishing the oil pump etc. Then get custom coated main bearings, coated rod bearings, coat the valve faces too. Dont forget to pick up a stock GT3 RSR header since its inconel already. Then you can polish up the intake and exhaust ports on the heads a little bit. After that is all done call up the kids that built the "spike throttle body" for their college FSAE car and have them fab you a set for your 600+ na porsche motor. This is probably the best throttle body you can find. Then call up TAG/McLaren electronics and set yourself up with their motorsport injectors which are more powerful than any Porsche MFI pump and pickup their engine management system as well. Run two sets of injectors, direct and in the throttle spike. Now set yourself up with some Ti valves and Ti retainers, Ti lashcaps and you are almost there. Still need that custom cam. Better yet call up DelWest engineering and have them build you a one of pneumatic valvetrain so you can spin it to hell and back just like an F1 motor.

A motor like that would make fantastic power numbers, I seriously doubt that it would last any longer than a GT3 RSR or DP motor in terms of being able to rebuild it at a reasonable cost. Sure Cargraphic built a 4.0 litre flat six but you start to press your luck at this point. The updated 964RS/GT3/DP case can handle things to a certain point but one way or another when you go that big something has to give. You almost might be better off spending money on a custom crank, case, heads, cylinders and building yourself a flat 8 at that point.

Either way I wish you the best in your endeavours. Ryder

[Lukesportsman]

Just to be clear. I'm not some mullet wearing muscle car touting man in anger. I hadn't the least anger. I rarely post on Ford racing forums and even less to Mustang Forums. I really have no reason to be angry in that Ford made a less efficient air pump than Porsche or XYZ. I still haven't forgiven them for not making a deep skirt block till recently

I was just playing devil's advocate. I didn't mean that it couldn't possibly done, only that for the funds of a team short of Lemans aspirations would seem quite difficult.

I may not be an engineer, but I don't lack all knowledge of physics. AGAIN NO ANGER here. I didn't design either engine. I've worked on both....even a SBC but don't tell anyone.

All's good for a debate. Actually, I've never been that impressed with specific outputs of 3.2 NA engines. Though some of the new head designs may change my views.

[turboteener]

Dang, I had a super nice post earlier today and the server dropped it somewhere between my computer and the forum. Oh well it was probably for the good.

Luke, I still don't forgive Ford for the 4.6 debacle. That engine is a waste of good engineering talent. You can't make much power from it in NA form. Bore is to small. I guess they made up for the eighties and 90s when they had Chevy on power with the 5.0. Now it is all Chevy. Give me an LSX over any kind of Ford.

Anyway.

Pkid? What kind of turn around do you need. The engine needs to last 25hours max for the shorter sprint races. Since Most guys don't race every weekend, turnaround would not be a problem.

Cams and heads would hardly resemble the stock pieces. Plenty of welding and reshaping will bring out the best of the top end. I have many secrets to apply to the bottom end, that I can see are not being done right now.

600 can be done with lots of development. It will probably be the upper limit but it can be done.

This is an unlimited engine there are no rules. SO whatever it takes to get it. This engine could live a whole season in club racing with proper maintenance and good driver behavior.

[Porschekid962]

What kind of turnaround? None at all but just to let you know all DP and RSR motors are built and rebuild on a 40 hour scale. Reason being is the small end of the Ti rods begin to elongate, the pistons go out of shape and the cylinders get wrecked. Keep in mind these are not 600 hp motors and are monitored very closely.

A 600hp 25 hour motor "might" be possible but you are talking about needing pro drivers to look after its well being. To be totally honest there really isnt a whole lot you can do with the bottom end to free up enough hp to breach 600. Boattailing is overrated and really cannot be done to the 3.6/3.8 964rs based RSR's and DP's due to vibration harmonics. Doing a "true" knife edge to the crank, not just the bs shaping of the bottom of the counterweight still wont bring the peak hp that high.

The heads on those engines are pretty much at the limit. Yes you could polish them up a bit by hand but what would you get, 5hp max? I am not saying it cannot be done I am just saying it might be foolish to invest the time and effort in order to do so.

If you started with a DP 3.8 motor, upped the compression slightly, had custom cams ground, swapped the injectors for TAG/McLaren parts, swapped the Bosch MS (which has thousands of maps) for a TAG/McLaren unit, had custom F1 style inconel merge collector headers made by an F1 or NHRA drag team, spent months hand detailing the heads and case, swapping out the large intake for single runners, you might get a 600hp engine.

The problem becomes service intervals. I seriously doubt that a motor built to those specs would survive over 25 hours of club racing. Shifts are harder for one adding undue stress to the entire drivetrain, adrenaline often impedes sound judgement, it has happened to us all myself included. I truly believe a sub 4.0 litre 6 cylinder porsche motor NA could be built to make over 600 hp I just would not want to deal with the rebuild intervals.

At that point it might become more cost efficient on a dollar per hp basis to build a very highly tuned twin turbo motor. Jurgen Alzen owned the ring with his gt2 DP composites widebody turbo until he wrote it off into a wall. Two twin scroll or two sequential turbos running inline with a very finely tuned engine management system could make a very reliable 800hp without resorting to very costly internals that would be needed in an NA motor.

That being said I still wish you all the luck in seeing your motor to fruition. If you would like and inside tips let me know.

[turboteener]

Its not my engine. The OP ask what you would do. I agree you could boost the motor and make well above the goal without too much trouble.

Sorry those are not the internal mods I am referring to. I chose not to share what I know, but trust me it will make more power. I could make the same power level with steel rods. I know a manufacture that makes a steel rod that is very close to the weight of a comparable to a Ti rod.

Durability will go down as HP goes up. There are people that don't mind spending that kind of money on a motor like this. I can find 40+hp in the heads. A properly designed plenum will make more power than ITBs. ITBs have a nice "drivability".

All of the things you have listed are normal "bolt on" type approaches that will hit the limits you have seen. I prefer to look beyond that.