924Board.org

[Robert Hooper]

Team,

I have a race car with a fully balanced race motor, bottom end etc... that has done very low race miles, I also have a 924 turbo road car, im thinking, can I stick these together and make them work by sticking the turbo head etc on the NA block.............

So...

Will the 924 turbo head work fine on the 924 NA block without lowering the compresson too much

Will the differnt pistons casue problems, and the rings associated

Has this been done ???

I want to get around 200-230 hp, for racing and im trying to do it as cheap as possible....

Thanks team

Robert
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1982 924 Race Car
1981 931 Road Car

[jpab924]

This has been covered here....>>>>>>
http://www.924board.org/viewtopic.php?t=11973

[john h]

[Robert Hooper]

John,

I know derek i raced with him a few years back, but he has spent a heap on his engine and only got around 145hp, NOT ENOUGH, i want to build a car i can club race but also race in the bridgestone in a few years time when i get some more money together.

My original question was, if i put the 924 turbo head and turbo etc on the NA block with this work reliably ? or is it better to just rebuild the 924 turbo engine and jam in in my race car,

I have already planned to change the brakes and roll bars over, as these arent really up to scratch

I really want a 200-250 hp car, i belive that this would stick me mid pack and with a low race weight and the good handling of the 924 should make for fun racing...

Any advice ????

PS - Do you still race your GT

Cheers

Robert
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1982 924 Race Car
1981 931 Road Car

[Lizard]

Robert,

you can bolt the 931 head right onto the 924 block, however the 931 head has a combustion chamber in it where the 924 has NONE, so this means that you are going to be adding alot of space into the combustion chamber, doing the calculations it works out to about w/ 8.5:1 (us) pistons you will end up with about 6.7:1 cr and with the 9.3:1 (euro) pistons you will result with roughly 7.5:1 cr with the turbo head on the NA block,

so if you wish to use the 931 head with the better combustion chamber design and better flow that is great but you are going to need to get custom pistons, and for the 924 2.0L engine in order to get over the 200bhp mark you are pretty much going to need either a new head with DOHC w/ excellent flow characteristics, and probably going to need to stroke it, there was a 2.4L stoking kit avalible at one time however it required modifications to the block and oil pan for clearance.

there is talk about using a VW TDI crank which would give you roughly 2.3L displacement however no one has verified it will bolt in and you will need custom rods and pistons, and you will also have to fabricate a custom flywheel which would have to be able to accept a 931 pilot bearing or you will just fry clutches. even with all that you will be pushing it getting to the 200bhp mark, you will have to have converted to EFI with extremely short intake runners giving you all top end and probably individual throttle bodies. on top of this you will also need a new camshaft if you stick with the 931 head and it will have to be pretty wild and if you want reliability you will have to go with a billet camshaft.

in other words if you really want about 200bhp or more out of the 924 engine without a turbo or supercharger you are going to spend ALOT of money on the car and you are also going to have to do alot of trial and error with testing different parts.
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3 928s,

[Robert Hooper]

yes i want to turbo the engine, but will the bottom end of the NA including the NA pistons hold up to the added heat etc ????
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1982 924 Race Car
1981 931 Road Car

[numbbers]

To the best of my knowledge, the bottom end is the same. Only the pistons and head are different on the turbo.
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1980 924 Turbo

[Lizard]

[Khal]

Fellow Hooper,

I found a link (in the "Links" section of this board) to the Technical Specifications of the 924 series (inc. Turbo)
It's in MS Word format. It's very detailed but I can't vouch for its correctness (although I have no reason to doubt it).

I can't remember where the link is, but I have the Word doc and will happily e-mail it to you (just PM your e-mail address).

EDIT: Found the link;

http://www.porsche-club.ru/Tech_info/spec/924TECH.ZIP

A quick perusal of the specs suggests that the block on the NA and Turbo are all but identical (at least in major dimensions such as bore, stroke, etc...) And I think it's accepted that you haven't got any problems physically fitting the Turbo head.

[Smoothie]

According to my copy of the factory parts list, the following are the same between 924na and 924t: crankshaft, main bearings, connecting rod bearings, connecting rods, and connecting rod to piston bushings. They don't list the block seperately without pistons, but I know the block is the same between na and turbo. The pistons are of course different, but they're both cast. I don't know if there are any differences other than shape - maybe the turbo pistons are thicker in places.. I don't know. The 924 Carrera GT and other race versions of the turbo got forged pistons as you probably know, but both the regular 924na and 924T got cast.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Khal]

Here's the link re: alternator placement.

On my '81 Turbo the alternator is on the opposite side...
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'80 924 Turbo

[john h]