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Ordered Quaife today

9K views 67 replies 17 participants last post by  Dean_S 
#1 ·
I finally got tired of DSC interrupting my spirited accelerations and ordered a Quaife from VAC motorsports. THe one on my old race car was/is fantastic, so I'm looking forward putting the d's power to the ground with a real TBD. Next up is Evolve ECU reprogramming. I'm waiting on that due to the BMW recall to reprogram the ECU. No point getting it and having it wiped almost immediately.
 
#4 ·
Now that is some COJONES my friend. Another ****** in the crowd like a FEW of us to make changes w/o worrying about the wartanty, keep us posted ok

Sent from my SPH-L710 using Bimmer App
 
#5 ·
I have the ability to change it myself, a shop, a lift and the tools, but I also have a friend in the indy BMW repair business that I trade computer work for car work. I'll have to figure out which way I go. Warranty expired today, BTW. I've swapped the chunk on a e28 and an e46 and it wasn't too difficult.
 
#11 ·
I'd be interested in doing the same come spring time. Please keep us posted.
 
#13 ·
Damn... I want that too. I said I will not add any mods to my d till I get LSD. I will talk to VAC again and plan trip to PA for install.
 
#17 ·
Car is back. Quaife works quite well. I can pull out in front of folks without DSC killing the engine. It seems DSC will allow a little wheelspin as long as both are spinning. I haven't tried it with DTC, but can't imagine it would be an different. THe car has a lot more traction in DSC mode in any event.
 
#21 ·
SHipping BTW was $98 from VAC (UPS) and $68 (FedEx) to ship the core back.

Here's my seat of the pants take on how the Quaife improves the driving experience.

On dry pavement with DSC fully on, ANY wheelspin led to an abrupt cut of engine power. I believe this is because in DSC the brakes aren't used to create a pseudo LSD. I can't prove this and can't find it in the literature. With the quaife it is harder to spin a wheel, so DSC throttle intervention is raised. It will still happen if you light the tires up. DSC allows some wheelspin as long as both rear tires are spinning at the same speed and aren't spinning much faster than the fronts. THis is why I believe the LSD function of DTC is off in DSC.

I still haven't driven the car in DTC mode, primarily because there isn't a need to. Before the quaife, if I was going to accelerate hard, I enabled DTC to avoid DSC throttle intervention.
 
#22 ·
Thanks for your input ChasR, it is greatly appreciated.
It seems like BMW should have put this thing on from the factory! I could see not in the 335i if they didn't want to steal M sales, but the d seems to really need this even with my 265 wide rear tires. I can't imagine how bad traction is on the non sports with 225s!
 
#25 ·
Quaife LSD

I am planning to have the Quaife LSD installed by VAC as soon as I can contact them and schedule. At the same time I will have them install M3 Rear Subframe Bushings and M3 Rear Sway Bar. Still considering the H&E Rear Sway instead, but kinda want to stick with mostly BMW parts.
 
#27 · (Edited)
It's been raining for days in Atlanta, so the Quaife has gotten a pretty good workout. It makes a dramatic difference in the way DSC behaves. It's obvious the DSC logic is written to accommodate a LSD (or TBD in the case of a Quaife). With the Quaife you can lacceletate rapidly, straight or turning, without DSC engine intervention kicking in until you spin the rears too fast or start to slide. It's much safer to drive as there isn't the virtual stall if you apply a little too much throttle.
The fact that the quaife works so well, and so much better than DSCs automatic brake differential (ABD) has led me to research what the DSC system logic really is. I haven't found it yet, but my seat of the pants take is that in DSC if one wheel spins the first step is to cut torque through engine intervention, if it continues to spin, DSC invokes ABD, If you turn on DTC, by pressing the button, this logic is reversed, ABD is invoked on one wheel spinning and if both wheels spin past the limit (which is higher than the DSC limit) engine intervention kicks in. DSC will allow some wheel spin as long as both wheels are spinning, which is where the Quaife come in, doubling traction and spinning both wheels if too much throttle is applied.

If you live in a snowy/icy climate and are concerned about the Quaife not working with one wheel on ice or off the ground, punch the DSC/DTC button and ABD will brake the spinning wheel and off you go.
 
#31 ·
Mileage is unaffected. Tire wear may be affected now that DSC allows some wheelspin. I'm going to have to do a track day soon.
 
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