Changing turbo motor to high comp NA

[Mukilteo911]

I was thinking of taking a nice turbo motor and replacing the pistons with 10/1 comp JE pistons, and installing in my 86 944. Turbos are cool, but my car is really not setup for all that, but a nice bump in HP with a better motor might be the trick. Anyone done this before, have any thoughts on it?

I suppose getting the turbo dme rechipped mit be a pain?

[Slam]

How about an S2 motor instead of a rebuild? Pretty much the same HP as a 951 and a bolt-in conversion.

[nynor]

if you do what you are planning, you won't need the turbo DME. your 86 DME will work just fine with a chip. in fact, using the turbo DME might not work at all.

why not go 10.2 or even 10.5 on the compression? someone correct me if i am wrong, but i think the ROW early 944's were 10.2:1 compression.

[Catamax944]

All 2.5 ROW n/a have 10.6:1 compression ,10.2:1 are '88 US models.

[nynor]

there ya go. so bump that ratio to 11:1, get 944max to burn you a custom chip to handle that compression ration on 91 or 92 octane fuel (you'll need a richer mixture) and you are off to the races.

[KEV951]

You will get severe detonation with that much compression ratio on street gas reguardless of the tune, and collapse your piston ring walls if you race it, I GUARANTEE IT, no matter how rich you make the mixture. You would actually have to detune the crap out of the timing to play it safe , and the car will feel sluggish. you need higher octane or leades gas, but with leaded gas, your cat will deteriorate and get plugged and your o2 sensor will foul up often. Get some sunoco 100 or 104 unleaded, if you don't want catastrophy. just my 2 bits with 14 years of building and racing these cars,

[nynor]

i ran 11:1 in my air cooled triumph motorcycle twin without problems. but i am definitely not an expert. that 750 ran like a bat out of hell, too.

[Rogue_Ant]

If you use the turbo flywheel/PP then the turbo DME will work fine. You will definitely want it chipped, or go the DIY route.

That said, 11:1 on the 8-valve head on pump gas is too high; a 16-valve head will work though...

A motorcycle has a significantly smaller bore than the 944, and much less load - thus motorcycles can get away with quite a bit of compression compared to a car. 13:1 is the norm for new sport-bikes.