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Scorpio
Joined: 05 Jul 2007
Posts: 1957
Location: Brisbane, Australia
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 Posted: Mon Dec 15, 2008 5:42 pm Post subject: forgot the magic power number |
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whats the max safe power (bhp and engine horse power) the 924 drivetrain/torquetube/gearbox etc can handle before bang? i think it was 250 at the crank?
my little Garrett T25 is good to 235hp....19% drive train loss?
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1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT
Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!! |
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Mon Dec 22, 2008 6:01 am Post subject: |
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250hp is so-so on 924 na gearbox and clutch. Clutch will slip a bit for sure and gearbox will fail with hard launches. Torque tube seems to have endless power reserve.
200 flywheel hp is ok for both gearbox and clutch assuming they are in very good condition.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold 
'84 924, turbocharged, sold.
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Scorpio
Joined: 05 Jul 2007
Posts: 1957
Location: Brisbane, Australia
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| Posted: Mon Dec 22, 2008 7:53 am Post subject: |
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200 at the crank ...oh yeah forgot to mention i have a upgraded clutch..i think its from a audi 200 turbo.... mmm might need to jump on that gearbok buy with RC...Thanks Raceboy!!
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT
Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!! |
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Martijnus
Joined: 29 Dec 2006
Posts: 2019
Location: Netherlands
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| Posted: Mon Dec 22, 2008 8:35 am Post subject: |
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| Raceboy wrote: | 250hp is so-so on 924 na gearbox and clutch. Clutch will slip a bit for sure and gearbox will fail with hard launches. Torque tube seems to have endless power reserve.
200 flywheel hp is ok for both gearbox and clutch assuming they are in very good condition. |
wow, I'm really surprised that the gearbox dies before the torquetube.
The torque tube isn't that large in diameter and long enough to warp... the longer a shaft is, the easier it is to deform/warp it....
interesting 
I thought I read somewhere that the gearbox was able to withstand 300+ horsepower... or are those the turbo boxes (I know the 951 box can withstand most...)
what gearbox was in the carrera gt/gtr/gts?
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)
924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Mon Dec 22, 2008 8:49 am Post subject: |
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CGT had a modified snailshell.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Martijnus
Joined: 29 Dec 2006
Posts: 2019
Location: Netherlands
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| Posted: Mon Dec 22, 2008 8:53 am Post subject: |
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| Rasta Monsta wrote: | | CGT had a modified snailshell. |
any idea what exactly was modified? The shafts? the gears themselves? what's the weakest link in the system?
I guess cgt trannies are muy expensivo 
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)
924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Mon Dec 22, 2008 9:28 am Post subject: |
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You can check part numbers in PET. My understanding is that gears were hardened, and HD synchros were used.
Many of the parts are still available. . .it seems you could rebuild a G31 with CGT parts, although it probably would be a bit spendy.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Mon Dec 22, 2008 6:05 pm Post subject: |
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| Scorpio wrote: | | 200 at the crank ...oh yeah forgot to mention i have a upgraded clutch..i think its from a audi 200 turbo.... mmm might need to jump on that gearbok buy with RC...Thanks Raceboy!! |
Uprated clutch kills gearbox sooner.
I have Spec Stage 3 and after installing that I got rid of two boxes immediately when making burnouts and few drag-races. With a bit slipping clutch the old gearbox held for a year and a half of hard driving.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Mon Dec 22, 2008 6:58 pm Post subject: |
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| Raceboy wrote: | | Scorpio wrote: | | 200 at the crank ...oh yeah forgot to mention i have a upgraded clutch..i think its from a audi 200 turbo.... mmm might need to jump on that gearbok buy with RC...Thanks Raceboy!! |
Uprated clutch kills gearbox sooner.
I have Spec Stage 3 and after installing that I got rid of two boxes immediately when making burnouts and few drag-races. With a bit slipping clutch the old gearbox held for a year and a half of hard driving. |
hold on...i dont understand....you have a CGT box and it didnt hold or?
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Supercharger and EFI kits
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Tue Dec 23, 2008 2:38 am Post subject: |
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Where did I say that? I have regular 924 4spd or 5spd audi type box.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche |
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Tue Dec 23, 2008 3:40 am Post subject: |
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nah..sorry i didnt read corectly
now i get it
However..if we are into gearboxes now...how about the audi A4 gearbox...some say it could fit the 924
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Martijnus
Joined: 29 Dec 2006
Posts: 2019
Location: Netherlands
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| Posted: Tue Dec 23, 2008 5:07 am Post subject: |
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| morghen wrote: | nah..sorry i didnt read corectly
now i get it
However..if we are into gearboxes now...how about the audi A4 gearbox...some say it could fit the 924 |
With enough effort, everything will fit.
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)
924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment |
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leadfoot
Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia
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| Posted: Tue Dec 23, 2008 11:16 am Post subject: |
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Weakest link is the teeth on gears. I would rate the n/a clutch and torque tube at 225hp. It would also depend on how much you car weighs and what tyre size you are running.
If you were not fussed about noise you could go to dog cut gears or have new gears cut without syncros therefore getting more metal in the contact area for strength. You might do this for 1st and 2nd gears only.
Hollinger quoted me around $3K ~$3.5K to modify the stock gearbox by nitriding and shotpeening the gears. I'm sure a good machine shop would do it cheaper though if you stripped the gearbox down first. You could also get the torque tube nitrided.
Stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress... |
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Scorpio
Joined: 05 Jul 2007
Posts: 1957
Location: Brisbane, Australia
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| Posted: Tue Dec 23, 2008 5:34 pm Post subject: |
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| Quote: | | Hollinger quoted me around $3K ~$3.5K to modify the stock gearbox by nitriding and shotpeening the gears |
ouch..almost worth buying a 931..or that 944 turbo on ebay :s
| Quote: | Raceboy
Joined: 01 Mar 2004
Posts: 1371
Location: Estonia, Europe
Posted: Mon Dec 22, 2008 6:05 pm Post subject:
Uprated clutch kills gearbox sooner.
I have Spec Stage 3 and after installing that I got rid of two boxes immediately when making burnouts and few drag-races. With a bit slipping clutch the old gearbox held for a year and a half of hard driving.
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hey was just reading through maximum boost and Corky Bell states (pg13)( in regards to adding a turbo to NA engine)
"WILL THE TRANSMISSION AND DRIVETRAIN BE ADVERSELY AFFECTED?
Very Unlikely. Consider that the drivetrain endures more torque in first gear from the stock engine than almost any turbo can produce in second gear. Occasionaly a clutch comes along that wont do the extra duty. Most clutch problems are going to crop up when shifting habits are less than acceptable. Not to worry."
Is the 924 an anomily whereby drivetrain IS adversely affected by a small turbo?? im confused... 
dont think my 245 wheels are gonna help
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT
Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!! |
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Andrew NZ
Joined: 22 Jun 2004
Posts: 744
Location: New Zealand
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| Posted: Tue Dec 23, 2008 6:01 pm Post subject: |
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I'm now upgrading to a 944 torque tube, as for me the 924 one was the weak link. I estimate that I have just over 200hp, but with an 8000rpm red line the driveshaft bent like a banana. Not sure if it was the rpm, hp or possibly dodgey bearings, but it didn't last.
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Andrew
1977 RX924 race car
12a bridgeport supercharged
www.race4-dcup.co.nz |
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924 FAQ (Technical)
