Petrol or Diesel??

500bhp! Thats mental, especially for a front-wheel-drive..

Can the Q2 diff be fitted to any of the Coupe gearboxes? You'd need summat like that for 500bhp, an open diff would be useless.

I am pretty sure the Q2 diff does fit the 6 speed gearbox, although I am not sure whether it fits the 5 speed.
Funnily enough the earliest 5 speed is a stronger box than the 6 speed and handles that level of power better.

I still think the Q2 would even struggle to get 500bhp down through the front wheels. Great though the Q2 is there is only a certain amount of grip.

I think the most powerful coupe that has been made is well over 600bhp BTW.

Originally Posted by Pud237

Can you use the 2.4 bottom end on a 2.0 20VT to make a 2.4 20VT? Sure I've read about it on FCCUK..

From what I recall talking to John many years ago the 2.4 Stilo block is too tall to fit in the coupe, they have to mod the 2.0.

Coupe has a fergeson coupling so its not too bad with coping with a fair amount of power, there were a couple of 500bhp coupes long before the 2.4, they were based on the 16v and I'm sure one was conveted to 4wd, risi tuning springs tomind.

Originally Posted by symonh2000

I am pretty sure the Q2 diff does fit the 6 speed gearbox, although I am not sure whether it fits the 5 speed.
Funnily enough the earliest 5 speed is a stronger box than the 6 speed and handles that level of power better.

I still think the Q2 would even struggle to get 500bhp down through the front wheels. Great though the Q2 is there is only a certain amount of grip.

I think the most powerful coupe that has been made is well over 600bhp BTW.

I can well imagine the 5-speed is the better box for a big power car, having longer ratios would help it maintain some sort of decorum.. Is the 6-speed the same box as the 156 V6?

As for the Q2, you're right, it would just mean both wheels spin up rather than one, I think Pablos's is approaching its limits now he's had his 147 GTA supercharged.. For 500bhp you really need RWD, or 4WD. Has anyone ever done anything other than FWD with a Coupe? Someone on here has a RWD Alfa 33, so I suppose it could be done with a Coupe. Would certainly be interesting!

I think people usually convert the Coupe to 4wd by using parts off a 155 Q4.

Sandy, I didn't realise the 2.4 block was taller than the 2 litre.
Also the standard visco coupleing works ok, but isn't as good as the Q2 diff.

I am pretty sure the 6 speed box is similar to the 3 litre GTV and 166, but with different ratio's.

The actaul gears themself are not as strong as the 5 speed IIRC. However there are 2 types of 5 speed box, early 20VT's had a lift reverse and later 5 speeds didn't. The earlier lift reverse is the stronger box.

I used a Q2 temporarily in my car for a year, and then reverted to a clutch type diff.
The Q2 was excellent value but there are clear limits as to how suitable it is to very high powered FWD cars that also have a lot of torque. Standard GTAs are fine though, where it perfroms excellently!

Unlike a plate (aka clutch type) diffs the Q2 will still definitely spinup a single wheel, just later than normal obviously. - its not really able to spinup both unfortunately, so its not as effective for very high powered GTAs.
Its still very good of course, but as the torque of the car its applied to increases (modified etc) it becomes less effective.

The reason that it still spins up a single wheel under duress is simply that it can only limit the split of power to the unloaded wheel to a certain proportion of the torque, and if that more than the available grip - well ..thats it your goose is very suddenly cooked, and cue sudden and spectacular torque steer!

The Q2 doesn't have any pre-loaded plates to limit this type of wheelspin in a similar fashion to a clutch type diff (although a racing version of the Torsen diff for RWD cars does have this feature, but its currently too "wild" for FWD cars).

With a clutch type diff you do have to apply enough power to cause both wheels to spin-up, and importantly when the spinup happens its very undramatic and a slight breath on the throttle will instantly correct it.
With a Q2 or any torque sensing diff you have to back the throttle right down to reestablish a working torque bias..
Some folks can use left foot braking under accelerataion to provide preload here in certain situations.

Originally Posted by symonh2000

I still think the Q2 would even struggle to get 500bhp down through the front wheels. Great though the Q2 is there is only a certain amount of grip.

I think the most powerful coupe that has been made is well over 600bhp BTW.