Ok so as I said I would, here is the feedback on having a Quaife Diff (non Alfa Q2) fitted into the gearbox of my GQV.
Lots of debate on this forum about the E-Diff fitted to the G, which uses software and sensors on the car to analyse each wheels speed, throttle, engine settings and sideways motion (G forces) etc to give electronic stability by braking of an inside wheel as required to assist with keeping a tight line through a corner when driving the car hard, but it slows the car by doing so and on a twisty road or track can cause excessive heat to build up in your brakes. Would the E-Diff counteract any mechanical diff? Would having both cause any other issues or, would the Qaife diff provide everything that was needed before the E-Diff got round to thinking that it was needed?
Alfa produced the Q2 some time ago for specific gearboxes as fitted to Busso V6's and 1.9 diesels predominantly. The Q2 diff was Alfas own cheaper and slighlty less able version of a Quaife diff, designed specifically for those Alfa gearboxes, and anyone who has driven one will know the difference it makes to the cars handling.
I have had my Quaife diff fitted now for a week and had time to play with it, throw the car around a bit and attack a few corners I am familiar with to compare the handling before and after and can say that it most ceratinly makes a difference as follows:
Fire the car up after having the work done, put it in gear, turn the wheel to pull out and as you move the first thing you notice is the steering feels a bit heavier, not worse just meatier as drive is now going directly to both wheels simultaneously rather than just one at a time as the steering and drivetrain loads up.
On the road when driving straight it feels much more planted and solid, as if someone has fitted different suspension, grippier tyres and put a big weight on the nose. Very noticable. that suprised me and I did'nt expect that.
Pre Quaife diff, if you attacked a corner with any type of aggression, as you turned in all seemed normal, a touch of understeer, you clip the apex, put the power down hard and the wheel will normally weigh up and try to start to straighten out slightly as the car powers away due to the torque and inertia of the driven wheels pulling on the steering or, if you really threw it at the corner the E-Diff kicked in and the car could be felt tightening its line and slowing as it tracked through the corner with virtually no understeer. All very normal for a FWD car where drive is only ever going to to be spun away on the inside wheel and drive through a corner is dependant upon mechanical tyre grip and one driven wheel.
With the Quaife diff two things are different straight away. One is that you can put the power down earlier, and secondly the steering wheel stays turned with no tugging and trying to self centre or torque steering evident whilst the car just tracks around the corner as you accelerate hard.
The faster you go the more evident this piece of hardware becomes and it really is so much more apparent on mid and high speed corners than at lower speed. Confident inspiring and a definate must if you want to go faster from A to B in your GQV.
Any negatives......following a 20mph slow moving vehicle I dropped it into 2nd, floored the throttle and a split second later just as I went to swing the wheel to the right to pull out from behind it, the wheel tugged left for a second as the power delivery settled itself and spread across both wheels, oops, not an issue really as I felt it pull and caught it easily but it could catch out an unwary driver I guess. A Quaife diff is what all racing cars have essentially, and many of them can react in much the same way. Its a trade off.
This diff will not rewrite the law of physics. if you drive faster and faster around a corner until you car is on the verge of throwing itself off the road, then fitting a Quaife diff will not prevent that happening at the same speed. Physics! Simples. It will however ensure your drive right up to the point at which it slides into the hedge is much more controllable. I have now had tyre squeel and understeer going hard into a corner at a speed where the E-Diff would have been fighting hard to keep the car going round the corner. The difference is that I still got around the corner but exited it much faster rather than had the E-Diff braking the car to slow it and twist it around the corner. And to date I have not felt the E-Diff cutting in. That may come driving on snow and Ice which in a way I am looking forwards to now.
So, the painful bit, the cost, from AutoLusso in Dunstable £1000.
Couple this to some mapping to give you a bit more power, say to around the 260 - 270bhp mark as don't forget, the achilles heel of these cars is the gearbox which is nearly on its safe limit for power already, and on a twisty road a GQV with 300bhp will not keep up with you without eventually overheating its brakes and stressing itself out. But that is extreme driving and not really for public roads. The feel of the car and the way it now sits and holds the road ticks my box, and the first high speed corner you throw the car into will put a smile right across your face.
Would I recomend this mod, yes if you have a GQV, 159 or 4C with this engine & gearbox combo and you have any interest in making the car handle better. It's something which makes the car faster point to point without mapping or boosting power in any way, and I mean that on normal twisty roads or a track not in a drag race. Why didn't Alfa do it then, cost in all probability. It would have added at least another £600 to the cost of a GQV which was high enough in the first place against its competitors. Am I happy