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Evil_Dr_Fish

Uprated Clutch good for 300+bhp

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Hi guys,

A zillion years ago I got an uprated clutch from AP Racing. I always said I wouldn't post the information until I had it up and running but this is now a billion years later and now I think it's best just to get this information out in the public domain so it's 'safe' and so others can potentially make use of it :D

So the magic numbers are:

The CP2394-46 Pressure plate and CPCP2583-15 friction plate

I've had the gearbox out and the pressure plate fits fine on the gearbox spline and the pressure plate / housing bolts happily to the flywheel. It also all fits just fine beneath the bell housing...

BUT!!!

This is as far as it has got so far... There is a metal plate on the back of the pressure plate's 'fingers' that is not present on the OEM clutch so I can't say how it will all interact with the clutch actuator fork.

If you call AP and ask them for an Esprit clutch they will think you're mental! I simply, painstakingly went through their entire parts catalogue back in the day and compared all the fitments etc and took a huge great gamble! Just order those parts and they should fit as far as I've been able to test :D

At least the part data is now 'out there' and safe for longevity! haha


Just for what it's worth (and these are purely for illustrative purposes)

This is what the clutch that came out of my car looks like:

Volvo-Clutch-Pressure-Plate-1340758.jpg

 


...and this is what the AP one looks like:

0032509104.jpg

 

 

It's going back a fair bit now but if I recall correctly, it's rated for 350bhp! that would be one hell of a lot on G-car! haha

REMEMBER - THIS IS A TURBO CAR! I've no idea if the S3 clutch / flywheel were the same, my gut recollection is that they're not, you'd need a turbo flywheel.

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Upgrade today to remove Google ads and support TLF.

Nice, use this set up with the standard open differential and your gearbox will be toast in no time:)

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It's fine, I've got it covered thanks. I've been following Garry Kemp's advice.

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Take a brand new, unused gearbox, get it stripped and take the parts and casing to these 2 places in turn

http://www.frozensolid.co.uk/

for cryongenic treatment 

and they will then ship it all on to:

http://www.remchem.com/services/isf-process/

For isotropic superfinishing process.

I won't bore you all with the details / science of what goes on you can google that / read up on it on their websites :D

Then after all that hope for the best as no one has done this before so we have no idea how well it would work - so hang on to your old box just in case! ;)

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The AP Twin plate clutches look nice bits of kit. Im fitting the standard twin plate one for the Renault gearbox to a flywheel for someone on here.

 

Buddsy

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Nice one! 

This is just a single plate clutch but it's a big step up powerwise from stock.

DSVitesse is right to point out that there's not a lot of headroom powerwise on an OEM gearbox before they lunch themselves, iirc lotus would run thing to within either 10 or 15% of tolerance...

That said I knew people who were running over 260bhp through them in the past but I've been 'out of touch' for so long, I've no idea how they fared over time

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There are a few people that seem to run the standard Citroen box with V8 engines of various powers. Mostly despite our dire warnings they seem to stand up to the raised power and torque.

 

Buddsy

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That's comforting to know! I'm hoping with all the work I've had done on the box it will take a few more ponies through it! ;) I'm aiming for around 300 ideally but who knows.

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I think there are some changes Harry^^ can recommend that you can make to the standard box in the way of the internals that are most common to fail.

 

Also I guess it depends how you drive the car too.

 

Buddsy

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F**k me it's Fishy!....sorry....carry on with your topic which is technical so can't add to whatsoever....... :welcome:

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Hello old chap! :)

I figured I ought to get the part numbers as a matter of 'public record' before I lost the info!

How have you been?


Ah yes... also on the technicals... I've had all the gearbox's Eastern European, milk chocolate bearings replaced by nice German ones made of metal to higher tolerances :)

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Do they really make bits out of chocolate? Frankly I wouldn't know!

 

I'm fine mate, hope you are well.

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Yeah! True story! ;) Not even the nice, Belgian stuff either but that really cheap, nasty, plasticy stuff you get on market stalls! ;)

The used to make our pistons out of the same stuff too! ;)

Life is starting to come back together, thanks :D

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Quaife ATB differential makes a lot of difference. No more sudden movements inside the diff. Protect the ring and pinion.

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I had the crown ring and pinion go in my Diablo! Was told it was pretty rare to happen and must have been a manufacturing fault! haha These things happen! :)

I'll give some thought to the quaife though, cheers

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Also I guess it depends how you drive the car too.

 

Buddsy

 

That is the most accurate statement..

 

 People bolt all sorts of G/box's onto to all sorts of engines.. If they drive them with respect of the

shortfalls then they will have no problems..  But you can not get past the fact that G/boxs have their

limits.. This does not just apply to the shafts, bearings and gears, but also the casings.  In a lot of

failures the casing flexing is the root cause why other components let go..  Good look with yours..

 

On the clutch you listed and pictured.. cp2394-46

Are you aware that it has a clamp load of 3600 lbs and a set up hight of over 50mm with the relief plate fitted..

Not only will you struggle to get it to fit with enough clearance for ware out. (6mm)  but you will need to be a weight lifter

to depress the peddle..  If you manage to gear the peddle to actuate, then the strain on the 180' crank's thrust bearing

will be more than you should apply.. then the clutch fork may also break.

I have the -60 fitted which was the Cosworth 500 spec into the UN1 set up. but this needed major re-engineering to 

accommodate.. I have put 450 ft lbs torque though this set up which is way over your needs and lower spec..

 

I think you will find the S4s / Sport 300 set up will more than meet you requirements for a bit over 300BHP. Failing that

I previously listed somewhere a Helix clutch which bolts straight in and holds 425 BHP 409 torque.

I would look at these options as best value, anything else is OTT.

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Robin,

 

Great to to see you're back on board!

Edited by MrDangerUS

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Thanks John! :D

Dave - hmmm definitely food for thought... It 'fits' beneath the bell housing just fine so far but we've not attempted to put it all together yet... there is a 'plate' on the pressure plate's fingers as mentioned in my first post which I will remove if necessary.

As for actuation force... I guess we'll find out! hahaha

As mentioned above, the entire casing was cryo treated at the same time as everything else. It's all a bit of a voyage of discovery and I guess I'll find out as it goes along what actually made a difference or not! Until then, I'm keeping my old box and clutch etc!

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CP2394-60 has "only" 2400 lbs of clamp load, which may be easier on the crank thrust bearing.

It is good up to 339 lb/ft and its set up height is 45.9mm

If pedal effort is a problem, perhaps CP2394-20 will suffice, 1900lbs clamp force, 270 lb/ft torque capacity.

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