The C4S, How'd They Squeeze The Extra HP

[DeAd-EyE]

What is the difference between the engines, is it just the timing or the camshafts? How come the other engines are derated? It is the same basic engine afterall isn't it?

[ar38070]

The last year of the 996 C2, C4, C4S (2004) all had the same hp, 320.

From and engineering perspective, you never operate anything at 100% rating if you are looking for reliability. The m96 motor is probably good for 350-400 hp if you were to tweek everything. And it would probably blow up after 20-50K miles.

[poppies]

wow! impressing...do you mean the engine could blow-up so quickly, if tweaked to the 400 hp?

[DeAd-EyE]

^ probably, i mean even the cup car engines which are based on the much more durable GT engines, need a rebuild after what? 30 Hrs? 40 at most? During that thime they'll probably see 20-30,000 Kms.

[ar38070]

^ probably, i mean even the cup car engines which are based on the much more durable GT engines, need a rebuild after what? 30 Hrs? 40 at most? During that thime they'll probably see 20-30,000 Kms.

<{POST_SNAPBACK}>

Not even. I believe a GT3-RS motor needs a minor rebuild at 25-30 hours and a major at 50. This is hours not miles. This is less than 5000 miles.

When an engineer builds something, if they are smart, they build in safety margins. Typically 20-50%. Applied to an M96 motor that means 360-450hp. Now the GT3-RS motor puts out 425hp with a stronger block, better connecting rods, no exhaust or catalytic converters, race gas etc. so 400hp for a M96 motor is probably about it.

I am no motor engineer but to do something like that probably means getting more fuel/air into the cylinders. That means free flowing intake and exhaust manifolds, free flowing exhaust, high lift camshafts, remapped ecu, etc. Assuming that this results in the wanted HP gain in all liklihood the idle is shot and it probably makes too much noise for the street.

Now with that much power we now have to worry about whether or not the connecting rods and pins are going to hold everything together because one way to make power is more rpm (from remapped ecu). If they hold on will the transmission? Will the clutch? Will the radiators be able to cope with the added heat?

Now will the entire drivetrain last 100,000 miles? Or are you going to ask Porsche to warranty it if it breaks?

:D

Lastly whether it breaks or not is also a function of how it is used. A GT3-RS motor needs to be rebuilt often as it is run nears it maximum output for most of the time between rebuilds. If you were to take a M96 motor, tweak it to 360+hp, but then just took in on the highway and cruised in 6th gear at 70mph, it would probably last for 100K miles. If you took it to the track every weekend and put 200-300 track miles on it that way every weekend, it probably would not last anywhere near as long. I can guarantee you that if the cooling system were not up to the task that the motor would blow up pretty fast.