Upgrades advice

[pete a]

Thinking of doing a few mods to my 997.1 GT3, namely fitting the GT3RS lightweight flywheel and clutch and a GT3 shorter final drive.

Has anyone done the above and can give some advice as to the pros and cons so I don't go and make an expensive mistake.

[arcamalpha]

I have no experience of swapping the flywheel, but would be inclined to change gear ratios rather than the final drive. Lowering the final drive will mean you're at 4000rpm on any motorway cruise which may be a nuisance.

[jackwood]

Changing crow wheel and pinion is a relatively easy and cheap job. Changing the gear ratios is neither.

I think Cunno on here has done these mods on his 997.1

Jack

[IMIA]

You should speak to Mike at Sport and Classic. He owns a 6 GT3 and carried out a gearbox refresh on his own car inc changing ratios etc. Well worth a chat and the fellow is a GT3 junkie!

[pete a]

Looking at this final drive

http://www.carnewal.com/products/P97GT3/p96198/GT3...

And this lightweight flywheel kit, which I believe includes a new clutch as well.

http://www.carnewal.com/products/P97GT3/p96174/GT3...

[thegoose]

IMIA said:

You should speak to Mike at Sport and Classic. He owns a 6 GT3 and carried out a gearbox refresh on his own car inc changing ratios etc. Well worth a chat and the fellow is a GT3 junkie!

I though it was the final drive he changed, certainly felt like that when I drove it round Silverstone with him, had to get used to being one gear higher on a few bends.

[IMIA]

thegoose said:

IMIA said:

You should speak to Mike at Sport and Classic. He owns a 6 GT3 and carried out a gearbox refresh on his own car inc changing ratios etc. Well worth a chat and the fellow is a GT3 junkie!

I though it was the final drive he changed, certainly felt like that when I drove it round Silverstone with him, had to get used to being one gear higher on a few bends.

you may be right

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[pete a]

Anyone tell me the effects and pros and cons of the upgrades, if it makes the thread more popular you can mention the effects on value and or if you think I should just get a PDK instead

[captainblakk]

I've researched the final drive swap, some threads reckon it hasn't got the longevity of the OE part for various reasons, looks like an interesting modification though, be good to hear of any real world experiences

[Slippydiff]

pete a said:

Anyone tell me the effects and pros and cons of the upgrades, if it makes the thread more popular you can mention the effects on value and or if you think I should just get a PDK instead

Good insight into the effects of a crown wheel and pinion swap from Matt at GT (Guard Transmission) here :

http://www.6speedonline.com/forums/gt3-gt2/208748-...

Fitting a lightweight/RS flywheel package to the car will make it rev more quickly (less rotating mass to accelerate) your engine will feel more responsive, especially in the lower gears at low revs.H & T downshifts will need some recalibrating on your part due to the revs falling away more quickly.
The trade off will be a noisier transmission, especially when the gearbox/diff are hot. The dual mass flywheel smooths out the resonant frequencies which would normally make the the transmission gears rattle. Without the DMF, the gears will rattle at tickover and under load (ie when you accelerate in a high gear from low road speed.

Both mods will make the car more responsive and "busy".

[pete a]

Yes that's what I'm looking for, some real life experience.

I understand that the shorter final drive reduces top speed, but improves acceleration through the gears, what I don't understand is by how much top speed is lowered and how it affects the lower gears?

Where's Neil or Steve when you need them?

[Slippydiff]

pete a said:

Yes that's what I'm looking for, some real life experience.

I understand that the shorter final drive reduces top speed, but improves acceleration through the gears, what I don't understand is by how much top speed is lowered and how it affects the lower gears?

Where's Neil or Steve when you need them?

I reckon you'll lose 25-30mph of the top speed, so motorway cruising revs will increase itro 500 rpm (it doesn't sound much, but could grate on long runs) Fuel consumption will also suffer.

As an example (not actual figures) of what it does to the lower gears (it will affect all the gears, it'll just be more noticeable in 1st, 2nd,3rd) If first used to run out (on the rev limiter) at 50mph, it'll now run out at 40mph (Neil will crunch the figures for you I'm sure) and where second would have been good for 95mph, it'll now be good for 80mph etc etc.

[pete a]

Thanks Slippydiff, that's interesting , I'll have read through that link.

Thanks for the advice

[Slippydiff]

pete a said:

Thanks Slippydiff, that's interesting , I'll have read through that link.

Thanks for the advice

You're very welcome. Do read the thread I've linked to, most of what you need to know (pros and cons) can be found within it.
Matt Monson is a top bloke and supplies Porsche Motorsport .........

Here's a quote from the thread I've linked to :

I would only be guessing here, but I would say that changing the R/P ratio like this will accelerate wear somewhere in the neighborhood of 20%. Though I don't think this at all is "pushing the gearbox too much". Porsche made a 5.00 R/P set for these gearboxes. We haven't gone even close to that short with it.

The reason that the 997.2 RS with 3.89 has comparible speeds and RPM drops to a 996 GT3 when using our 4.125 R/P set is because of the individual gear ratios themselves. If you look at the charts posted earlier in the thread you'll see that the gearing is a bit different between the two boxes, in addition to the final drive ratios being different.

However, if you put this R/P into a 997.1 or a non-RS I would expect your car to probably accelerate more quickly than the RS. It would be shorter in every gear position, including 6th, which is already a shorter gear than the RS uses, and the only gear of the stack that is actually a different ratio.

So pros and cons aplenty

[pete a]

Not as straightforward as I thought, I'll read that link in full, cheers mate