Engine rebuild - Converting to 4 throttle bodies

[Fara]

Hi,

I'm going to be starting an engine rebuild on my '83 944 in January and am starting to gather the parts at the moment.

The car is being built up to run road rally's here in Australia under the classic car class - I'm only just starting my venture into road racing. It has to stay close to stock, but can have performance modifications within limits. (No Displacement changes etc.)

I'm considering changing the car over to 4 throttle bodies to help get the most out of my little 2.5L - Combining this with a custom ECU should help me drag every last bit out of the cars engine without making any major changes.

Has anyone done this? Sourcing the parts isn't too hard and I've got a really good contact to configure the ECU to be compatible.

I need the car to be almost bulletproof - I'm not looking for a big power increase, just a little bit more power to offset the additional weight of the roll cage that I'm having fitted. Additionally, the car has to remain road legal as getting the car transported to races doesn't interest me

[speedracing944]

Go for it. I was going to do Suzuki Hayabusa throttle bodies with Mega Squirt on my "S" engine I have mothballed.

[fiat22turbo]

Make sure to pay attention to the total inlet length to tune the power curve to match the rev range of the motor.

To give you an idea of what I'm talking about:

Tuned Intake

Good luck with the project!

[Fara]

Hey Fiat,

Thanks for the heads up on that. I've been doing some research into intake lengths and that gives me more motivation to do it right the first time

[porschetub]

You should see reasonable gains in power if set up is right,there a outfit in your country that does nice throttle bodies based the Weber 48 IDA ? spacing (you probably have seen them) but due to the relative lack of performance parts for these cars the inlet manifold may need to be custom made.
So you would be looking @ a crank fire ignition also?, I think Patrick Motosports do a good setup from memory.
Have you thought about fitting the 2.7 head with the larger valves?.

Depend on your funds really "horsepower isn't cheap"as the saying goes.

[fiat22turbo]

Can you lighten the bottom end components?

A lightened or aluminum flywheel, lightened rods and knife-edged crank could help wake the motor up a bit as its a big motor that doesn't exactly rev like a smaller 4 might.

Otherwise I like the idea of getting a little more flow into the cylinders through slightly larger valves.

[Fara]

It's definitely worth considering the lightened flywheel - it's a fairly minor modification and will make the engine feel a bit more "perky"

Depending on the condition of the crank/cam, I may have to re-machine or replace it either way.

With regards to the new head, it's a great idea, but I'll have to confirm with the regulations as to the "legality" of the change.

[seafeye]

Try extrudabody.com

For ITB's.

[porschetub]

Originally Posted by Fara

It's definitely worth considering the lightened flywheel - it's a fairly minor modification and will make the engine feel a bit more "perky"

Depending on the condition of the crank/cam, I may have to re-machine or replace it either way.

With regards to the new head, it's a great idea, but I'll have to confirm with the regulations as to the "legality" of the change.

Most people won't know.

[962porsche]

i have doen this to 3 of my own cars . my 1988 countach , my suzuki gsx-r 1000 powered car i race in DSR . and my 944 8V hill climb car . you will spend many hours doing R and D to get the 944 set up right with a total cost of about 5k if you do most of the work your self . you will need to fab up the intake . if you have to tools and know how the material cost will be about 200 dollars and it took just over 40 hours to do the fab work on the intake alone . you will not see any big HP or tork numbers from this swap you will really only get more tuneability . the internals of the motor were all change using non porsche parts but the crank .the motor went from about 150 to just over 210 HP with 192 tork . the total cost of the motor build came out to be just under 26k and that was with me doing 99% of the work my self . was it worth the money spent HELL NO ! you say you want to run in a classic car class . i don't know were you are but here in the states you will not be able to do that . you can only run things on the car that were offered in the year that your car was built . if you want to off set the weight of the cage you have to remove any thing not needed in the car . one of my 944 V8 powered cars started life with a static weight of 2700 LBS with a full 8 point cage it is now at 2100 LBS putting out 478 HP . just by changing out the rear glass for lexan you will off set the weight of a full cage with a total cost of about 1500 dollars .so power to weight to power to dollars spent your best bet is to lose the cars weight than try to add more power to off set the added weight . most of the time its cheapper with bigger gains .