924Board.org

[Dave]

Hi

I’m new here - so hi all,

I'm from Australia and love Tarmac Rallys. As you can see from my avatar I currently drive a ***cough*** Subaru ***Cough****, but what is happening over here is, that there are 2 governing bodies fighting for control and they are making a bit of a mess of the rules in the modern class, so I would like to enter in the classic competition (pre 1982 cars) where things are a bit more stable. The idea is to build a car capable of winning rallys outright in the pre 1982 car class.

Doing some research I find the cars that dominate the classic competition are the 911 RSR's but then hidden away in the rules is the inclusion of the 924 GTR as eligible in this class and no one runs one. There is a GT but he's not in it to win. I did some more research and found that the GTR should be a good thing. Especially with the rules which allow 2.5 litres and unlimited boost with the cylinder head, turbo (period style), exhaust, engine internals, and the entire inlet is free it should comfortably make 450+hp and only weigh 945kgs - sounds a bit like a rocket . The Subaru makes around 400hp and weighs about 1400kgs. (by the way replica’s are allowed, in case you thought I was going to throw a $300k car at the country side).

Do you think I’m headed in the right direction with a GTR or are the guys with 911’s (same rules) always going to be in front.

For those that are interested here are the rules... Page 15 - 18 is the guts of it.

http://www.camsmanual.com.au/pdf/road/1112_Tarmac_Rally_TechRegs-Classic_Q408.pdf

My problem converting a standard 924 to a GTR would firstly be knowing the engineering differences between them and secondly the bodywork.

Is there much information out there on these and does anyone make a body kit for them ?

Here is a bit of a look at the racing I do, this is not me though as I don't want any evidence of my driving out there.

http://www.youtube.com/watch?v=R8gb21NzEsw

Thanks all
Dave

[Peter_in_AU]

Welcome aboard.

One thing that might make your project easier or harder is that there is not a whole lot of information available about the GTRs. There were 17 of them (I think), they were hand-built, some had 2 litre engines others 2.5 litre. Probably safe to say that no two were the same which probably will make it easier to get a replica accepted.

Does the 2.5 litre rule include the 1.4 multiplier for forced induction? That is, can you run a 2.5 litre with a turbo or are you restricted to 1785cc with a turbo?

The 2.5 litre engine was not the 944 engine although the guys checking the car won't know that so you might be ok with a 944 block.

What about fuel injection and engine management? If you're forced to run period injection and management that could be a real challenge.

Transaxles are interchangeable so you're looking at a 5-speed LSD from a 944 Turbo or a 6-speed from a 968 (if the rules allow).

Body kits are available in fibreglass and carbon-fibre. A search will bring up the players.

Potentially you may be better starting with a 924S (the 2.5 litre car) than a 924 or 924 Turbo (931). Rare here in Oz but a few in WA and over in NZ.

And everyone knows that a 924 only needs 75% of the power of any 911 to use the 911 for toilet paper.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[Dave]

Hi, Thanks Peter.

If some of them were sold from the factory with a 2.5 litre engine then I am allowed to go to 2.93lt, it's a formula that they came up with, but that is the actual displacement. To pidgin hole us in a class they then multiply that swept volume by 1.7 for having a turbo, so if I can start with almost 3lt then I will be in the over 5lt class which doesn't worry me because I want to compete for outright in Classic anyway.

If it has fuel injection originally I can replace that with a different type of injection (I'll have to check but if it is a mechanical injection I think I can change to an ECU driven system). If it has an ECU then the ECU is free providing it was available at the time. Was Motec around then ?

If the original 2.5lt blocks are not available I can probably get approval to use a close cousin - i.e. the 944 block.

Transaxle is free provided it has only 5 forward gears. Do they have clutch / plated LSD's?

Dave

[arx]

So if i understood correctly you want to enter group C3 with 924GTR produced before year 1982?

All pre 1982 924GTRs were 2.0 liter, turbocharged, mechanical injection, motor code M 31/70, a close relative to 924 turbo engine 17 cars were built.
The 2.5 liter 16 valve engine was installed in 924 GTP cars which of only 2 cars were built to enter LeMans 24 hours race in 1981.

So, according to the rules you are restricted to use 2.0 liter 924 or 931 steel block and mechanical injection. You can´t use 924s/944 derived 2.5 liter aluminum block and EFI.

Good news is that gearbox is free so you can use instead of Getrag G31 an Audi derived gearbox where were gears and differentials are more easily available.

If they will accept 924 GTP cars and you can prove they built at least 5 cars, then its all different story. With 944 2.5 liter and 16 valves turbocharged 400hp+ shuld be easy to obtain, although 945kg of weight requires quite radical weight reduction measures.

[924RACR]

[arx]

Here are the 80, 81 and 82 entry lists and results
http://www.racingsportscars.com/photo/Le_Mans-1980-06-15-photo.html
http://www.racingsportscars.com/photo/Le_Mans-1981-06-14-photo.html
http://www.racingsportscars.com/photo/Le_Mans-1982-06-20-photo.html

notice that the only 2.5 liter turbo car (or 3500cc) participated only once - in 1981 - and was listed as Porsche 924 G.T.P LM or
944 LM #006 – Porsche L4 2476cc Single-Turbo in GTP+3.0 class
2.0 liter turbo engined cars (or 2777 cc) were listed as Porsche 924 Carrera GTR – Porsche 924 t/c L4 1983cc KKK in GT class

But it would be still interesting to see another 924 GTR replica built and racing. Why not even in this # 74 cars Shell/PORSCHE CARS AUSTRALIA/Spirit of Australia disguise
http://www.racingsportscars.com/photo/1981/Le_Mans-1981-06-14-074a.jpg

[emoore924]

Sorry for the hijack but those period pics of the old cars are sooooo kewl to look through.

I'm almost positive I've seen that 1980 race-winning rondeau in person at Watkins Glen for the Zippo GP vintage race...

[arx]

Chassis no5.






Just a thought -
If Porsche produced 6 of these prototypes with chassis # 001 to #004 having 2liter M31/70 steel lump and chassis # 005 and 006 had 2.5 16V alu engine,
wouldn’t it still be possible to use the latter alu engine and EFI, because basically, still all these 6 prototypes were from the “same batch” of chassis’s - # 001 to #006

[morghen]

did the 2.5L ones have EFI ?!
_________________
Supercharger and EFI kits
https://www.the924.com

[emoore924]

I think so. I have pickies someplace. Now if I could just remember where they were...

^^^^^Where are these cars being shown?

[Rasta Monsta]

[Chrenan]

[RC]

[morghen]

yep..it says there it used Motronic.
Cool stuff !
_________________
Supercharger and EFI kits
https://www.the924.com

[ideola]