3l GTV6 PRC project

[MD]

Greg,

My gut feeling is that the composite shaft wont create the hammering noises without a rubber coupler. At worst, the amplitude of the noise will probably just blend into the exhaust noise. As long as there was a fitting that allowed the engine to move about the mounts that's all you would likely need. Either a CV or a UV would do. Having said that, a rubber coupling would be much more gentle on the composite shaft and may help to prevent delamination. Just a thought.

[redalfaracing]

Apparently the equation to work out the dimensions of a tail shaft is torque x rpm x length or something like that. The rx8 is good for 12000 rpm at the engine. multiply that through the 6 speed ( i think 5th and 6th are both overdrives. technicaly it could be doing more than 12000 given a long enough piece of road.

carbon fibre is incredibly strong but brittle. put real hp thruogh it but dont hit it with a hammer!

[Jekyll and Hyde]

Apparently the equation to work out the dimensions of a tail shaft is torque x rpm x length or something like that. The rx8 is good for 12000 rpm at the engine. multiply that through the 6 speed ( i think 5th and 6th are both overdrives. technicaly it could be doing more than 12000 given a long enough piece of road.

carbon fibre is incredibly strong but brittle. put real hp thruogh it but dont hit it with a hammer!

When I had a look yesterday, Mazda USA's website stated 9,000rpm redline.....  In 6th gear the tailshaft will be doing 11300 rpm at redline.  BUT since that is 6th gear, effective peak torque (at 5,500 engine rpm, 7,000 shaft rpm) coming through the shaft is 811nm (and obviously dropping away somewhat from there).

A 3.0 litre alfa V6 has 250nm at 3,000rpm standard.  Ignoring the fact that you'll likely end up with hot cams etc, increasing your peak torque and the revs its found at, if we say that at 7,000 rpm its lost 100nm (Possible on a standard 3.0, but you'd have to check a dyno sheet).  In 3rd gear, with the gearbox you mentioned earlier, you are still putting 870nm through that tailshaft at 7,000rpm.  In 2nd, 1110nm, in first gear 1854nm - all at 7,000 rpm.

If you were to assume that you still have 200nm available at 7,000rpm (seems entirely possible with raised comp, big cams and headwork), then in 5th gear you are still putting more torque through at 7,000rpm than it will ever see in the RX-8 with those rpm (depending on actual torque in an RX-8 at 7,000rpm, 5th gear is 1:1 and may squeeze a bit more torque through at that point).

Don't get me wrong, I'm not saying its going to break - I'm sure that Mazda would have built an enormous safety factor into it.  Just making a point that just because the RX-8 spins fast, doesn't mean its tailshaft is necessarily transmitting any more torque when it reaches the speed of an Alfa tailshaft....

Although, your last comment sort of seems to be of concern considering its a rally car - is the tailshaft having a stone guard, and/or is the shaft any more likely to be buggered by a large chunk of rock striking it than a standard one?

Still interested to know the length of that tailshaft too, I'm wondering if I can fit it to one or two 'normal' rwd cars I'm involved in....

[MD]

About 5-6 years ago there was a guy in the US who was racing a GTV6 with a one piece carbon fibre drive shaft with complete success. Regrettably, I have lost the link. So yes it has been done before that's for sure.What should not be overlooked is the improved engine wind up rate due to less mass and some minor hp gains as well if combined with light flywheels etc.

For rally work, a guard would obviously make sense like it does for the sump.

Those numbers look interesting Jekyll.

BTW, the shaft I am referring to above was a one piece of the original length which from memory is around 1420-1430mm or thereabouts on the sedan whislt the coupe it's about 100mm or so shorter due to the wheelbase differences.

[Jekyll and Hyde]

About 5-6 years ago there was a guy in the US who was racing a GTV6 with a one piece carbon fibre drive shaft with complete success. Regrettably, I have lost the link. So yes it has been done before that's for sure.What should not be overlooked is the improved engine wind up rate due to less mass and some minor hp gains as well if combined with light flywheels etc.

If Greg can get it working with none of the typical uni joint rattle, I'll stick one in mine for sure - losing 7 more kilos out of my driveline would be quite nice, and save me replacing donuts... Although I haven't YET had one wear out, its only a matter of time...

[MD]

Here's the US company that makes 'em.

http://www.acpt.com/index.html

I should have mentioned this earlier but having a one piece shaft may necessitate the use of a modified shifter that is inside the cabin much like the one being installed in the car photos Jim supplied earlier.

The business end of the shifter could be one of these as per photo.

Obviously the application would generally only apply to race or rally cars.

[redalfaracing]

Yes, the stated red line is 9000, the engine is good to 12000 and the raceing rx8's regulary pull it. There is a supercharged rx8 in NSW that reportedly has 400 rwkw. Not sure if it runs the standard tailshaft though. These rx8's get flogged just like Alfas and i haven't come across any evidence that tail shafts give way.

The dimensions of the tail shaft is as follows; overal length 1270mm, centre of uni to center of uni 1078 mm, center of rear uni to face of rear flange 42mm, center of front uni to end of yoke 150. diameter of shaft 75 mm

I am thinking a shaft with the matching spline to the yoke, with a machined end to interference fit into the spigot hole in the end of the crank, with a triangular plate, bolted to the donut bolts ( would need to be shortened) also with the same spline. If there were a shoulder on the shaft in the appropriate place behind the plate, the three bolts would hold the plate and shaft in place and provide the drive as they do through the donut.

The shifter would have to be relocated from the tunnel obviously. I have been playing with a Magna shifter that uses 2 cables. One benefit of using cables and not rods is that the orientation of the shifter can be altered to favour right hand drive. How many people have hopped in an Alfa for the first time and gone from 1st to 4th? rotating the shifting gate will make it less difficult to find 2nd.

I do not have a sump guard yet, but it is definatly comming. extending it to cover the tail shaft is simple. It only needs to be 2.5 mm alloy to deflect the odd yonnie thrown by the front wheels. The sump guard will be 6 mm as some of the rally roads have lumps of rock sticking out. Having said that, i never had a sump guard on the 2l Alfetta, I have been pretty successful at driving around all the bitey things sticking out of the road so far.

One reason for going donut-less is to eliminate the risk of one giving way and causing a dnf. One giving way on a circuit car would be annoying, but you aren't far from the pitts and you can have it fixed b4 the next heat. Do one early in a rally and you miss 3 or 4 hrs of driving. I have dnf'ed early in a rally and immensly dislike sitting on the boot of the dead car, watching the procession of other competitors for hours.

Love to hear from a 105 owner re diff flange, Does it fit the transaxle. posts on other forums seem to indicate that some parts are interchangable between 105 and 116 drive lines.

[Sheldon McIntosh]

I think I can speak for many transaxle track drivers here and say that I am very interested in this tailshaft project.  As you say, it's only a matter of time till the donuts give way.....

As an aside, is that gear knob on the xtrac box up there one of those bungs they put on the side of racebikes to protect the fairings?  Probably not, but looks very similar.

[redalfaracing]

Here is a link to a crowd that supplies supercharger kits for rx8s.  Claim 100 more hp and 70lt/lb torque more with 5-8 psi boost. also plug and play.. no other mods ( inc tailshaft) 

http://www.pettitracing.co.uk/supercharger.html


There must be a lot of safety factor built in i think as you say Jekyll & Hyde

[redalfaracing]

Love to hear from a 105 owner re diff flange, Does it fit the transaxle. posts on other forums seem to indicate that some parts are interchangable between 105 and 116 drive lines.

Searching for 105 driveshafts got me this pdf file which shows Alfa driveshafts with uni's and donuts.
Can someone on this forum please enlighten me on what bit goes where on a 105, and if they are intechangable with a 116? never having looked under a 105 i have no idea what makes them tick.

Otherwise its off to hardy spicer to see if any one there knows about Alfa tailshafts.

[MD]

Greg,

It's been a long time since I have had the bean bag under the 105 chassis but from what I can remember the 105 tailshaft has the donut up front with the uni at the rear coupling up to the dif. I couldn't say if the PCD of the donut would fit an Alfetta. I doubt it. I know the tailshaft definitely will not as it is way too short.

[pep105]

Greg,
MDs on the ball, donut up front at the gearbox and uni at the diff end, Ive got a 105 2 lt complete tailshaft in the garage, if you want photos or PCD measurements of the flange or donut let me know, or if your local more than welcome to come and check it out. Im on the other side of the fence been a few years since ive been under a 116. 

[redalfaracing]

Pep, i am more interested if the diff flange will fit the clutch shaft on a 116. Also if the uni cups will fit the Mazda shaft. The Mazda uni cups appear to be 24mm diameter.

If i can use the rear diff flange and rear tail shaft flange off a 105 then all i have to work on is the front adapter.

There is mention of 8 mm and 9 mm bolt flanges. Is the difference just the bolt size, or is the flange beefier too?

[redalfaracing]

Ive got a 105 2 lt complete tailshaft in the garage, if you want photos or PCD measurements of the flange or donut let me know, or if your local more than welcome to come and check it out.

I called into Hardy Spicers today to talk tailshafts. I spoke to a guy named Matthew Pratt who appeared to know his stuff. They have the tooling to replace the staked uni joints, and claim better that oem strength. They have an Alfa uni joint kit in their catalogue part number K5-A532 that has 24 mm cups, but the catalogue doesn't have the model it comes from.

So where i am now, is i need to view a 105 tailshaft and diff flange. I am hoping that this K5-A532 uni is out of that joint and that that flange fits the GTV6 clutch shaft. I am in outer se melb . Anyone close that may have those bits out of a car?

I was thinking of bringing the GTV6 to the BBQ on Wednesday. Maybe some one attending that could bring one to look at? I will bring the RX8 shaft and a clutch shaft.

[pep105]

Greg,
Im in Maribyrnong so not near you but I work in Port Melb so if you like Ill bring the tailshaft to work and maybe you could swing past prior to the BBQ on Wednesday ? does that help ?
Sorry havent measured the uni cups yet been flat chat. Will try tommorrow
Let me know PM if you prefer or 0402 355 075