Clutch,Ring gear, Starter Q's

[milesallen]

Hello all,

I am in the process of mating a BMW v12 (450bhp) to a Porsche G50.21 6 speed gearbox, the gearbox coming from a 993. The starter motor will be mounted to the gearbox, in its original position. A bespoke flywheel and adapter plate will be made by my self. In order to progress however I could use some help on my starter, ring gear and clutch selection.
Due to the 993 being available in an RS version and having a similar performance to the proposed vehicle, I feel using its clutch and detachable flywheel would be a good match, any opinions? However when sliding the ring gear into the box it will only go in about an inch and a half before it hits the edge. Other posts have said that grinding the inside of the box is needed, I don’t understand this as if the old duel mass flywheel with its integral ring gear fitted surly this should!? If the detachable ring gear has effectively a bigger out side diameter surly it will not engage with the starter if the box is grinded out and ring gear fitted?
Also does any one have any experience of the RS clutch? I believe it’s an organic plate so should not be too bad in stop start traffic, any opinions?
I do not have a starter as yet and want to get as big and powerful one as possible, is the standard 993 unit recommended? Is the spline detail of the starter the same from vehicle to vehicle, what are the options?

I thank you in advance to any info given…..cheers guys

[andygtt]

I've made an adapter plate to fit the BMW V12 to my porsche box which has the same dimensions as the G50.... However I am using a triple plate clutch with the starter on the gearbox side.

I am yet to have the flywheel made as I havn't desided what starter to use yet.... my last car used the std Porsche starter (largest one) and I really rate it. However its not an option for me this time as I have to use a special porsche item which is extremelly expensive... you won't have the same problem on the G50.

there is a pic of mine adapter here.


[url]http://hometown.aol.co.uk/andycanam/p[/url]


>> Edited by andygtt on Wednesday 26th October 22:09

>> Edited by andygtt on Thursday 27th October 09:02

[steve_d]

I have no knowledge of how the original Porsche flywheel/starter arrangement works nor the RS clutch.
What I do know now is.
1. The bell housing has to be machined/ground out on the G50/20 6 speed from a 993 (this is what I have).
2. The clutch is Porsche and the starter ring bolts onto the clutch pressure plate body.
3. The ring gear is Porsche.
4. I am using the high torque, but physically small, starter supplied by the Ultima factory and custom made for them.
5. The starter mounts on the gearbox and the pinion drives forward to engage. Perhaps the original Porsche starter was longer and the ring gear further away.

What I don’t know.
1. The flywheel may be custom Ultima putting the ring further into the bell but that would cause clutch release issues.
2. The 993 may have a smaller clutch/ring gear with larger pinion.
3. The 993 may have the ring gear on the flywheel and the starter fitted from the engine side.

Not much help i'm affraid.

Steve

[milesallen]

Thanks for the replies;
I spoke to Kennedy engineering who said that the G50 87-89 ring gear is dimensionally the same as the 993 unit so im happy I have the correct ring gear. Steve d can you tell me if you have any experience of the standard 993 starter, is this what you started with? If so did you have the 10 or 9 tooth unit? Also andygtt are you dry sumping your v12? If so what’s the spec, (Number of scavenge sizes, pump etc)?

Cheers

[steve_d]

I have only had the factory starter which is 10 tooth.

Steve

[andygtt]

I have two options for my dry sump package, either a 5 stage barns or a 3 stage peterson.... I'm favouring the Peterson due to not really requiring any more than 3 stages as I beleive the oiling is quite efficient (ie I do not need to add additional oiling to the head etc).
Also the Barns has an additional power steering pump attached that I will now not be using.
The pipe sizes are -10 and -12.

[milesallen]

andygtt ive just been on your link page and am very impressed with your project and set up, i have a few questions if you don’t mind;
1. Is that the Getragg 6 speed you are using?
2. What steering rack are you using?
3. What is the turn to turn ratio of your rack,2.7?
4. Can you tell me how much total travel this rack gives you?
5. What percentage Ackerman are you running on your design?
6. What material is your adapter plate made from? I am concidering Ally HE30.
7. Are you positioning your rack through a CAD or geometry program? if not i have Hans suspension geometry which may of be interest to you. As used by Van demond and other high profile race car constructors. I would be lost with out it, let me know.

Many thanks

[polus]

andygtt said:

I've made an adapter plate to fit the BMW V12 to my porsche box which has the same dimensions as the G50.... However I am using a triple plate clutch with the starter on the gearbox side. I am yet to have the flywheel made as I havn't desided what starter to use yet.... my last car used the std Porsche starter (largest one) and I really rate it. However its not an option for me this time as I have to use a special porsche item which is extremelly expensive... you won't have the same problem on the G50. there is a pic of mine adapter here. [url]http://hometown.aol.co.uk/andycanam/p[/url] >> Edited by andygtt on Wednesday 26th October 22:09 >> Edited by andygtt on Thursday 27th October 09:02

Is the correct page, interesting stuff

http://hometown.aol.co.uk/andycanam/GttPage2.html