Differential - Lap Time Difference?

[joeo]

Has anyone who has upgraded to an LSD experienced a significant drop in road course lap times?
If so - please share! Thank you!

-Joe

[chris_flies]

My times improved slightly, but I'm sure most of that was down to my improved confidence in the car. You'll probably reap more rewards since you have more power to put down.

It's wonderful, the difference it makes in how the car feels. It feels properly sporty and old-school.

Being back on an open diff (my LSD had a rapid unscheduled disassembly, my fault), I really miss the proper LSD.

[tsk94]

While my comparison is not directly relevant to your car I will provide my insight on my experience with my E92 M3 race car. The M3 stock comes with a clutch style, speed sensing, LSD from the factory. The unit is decent for what it is, albeit it locks up and unlocks slowly and the amount of lock is quite low. The diff was upgraded to a 2-way 8-clutch Drexler LSD (equal lock up on accel and decel). The difference is absolutely huge; predictability under power, confidence to put the power down, stability under braking are all massively improved compared to the stock unit (which was already a LSD, not an open diff). Lap time difference was estimated to be about ~3/4-1 second a lap from the diff alone around a 90 second track.

I know a lot of people preach the importance of a LSD, especially in the 1 series chassis as they come with an open diff. But not many people really emphasize the importance of a quality diff. Do not cheap out and get the cheapest LSD possible. If you have the means invest in the best diff you can. Clutch styles, for track use, will ALWAYS provide better performance. I'd recommend getting a unit that also locks up under decel for added stability under braking, and more confident trail braking characteristics.

[Ginger_Extract]

Get a clutch-type diff and send it. If I could do it again, I would have skipped the MFactory helical diff and gone for a clutch type, far superior for the torque-heavy power delivery of this platform. Helical doesn't lock hard enough, fast enough and drives like an open diff car. Works fine on an FRS with 200 horsepower, not so much with 400+ on a big heavy pig like a BMW.

[joeo]

Thanks all - sorry for the delay in responding. Price wise, M-Factory LSD is cheapest; bimmer world sells the wavetrac and clutch style (2 and 3) through diffsonline. Wavetrac is still a good bit less expensive than the clutch style and is basically maint free. While there is a lot of info on the Wavetrac, it's tough to say how well it will do on track.

[chris_flies]

Originally Posted by joeo

Thanks all - sorry for the delay in responding. Price wise, M-Factory LSD is cheapest; bimmer world sells the wavetrac and clutch style (2 and 3) through diffsonline. Wavetrac is still a good bit less expensive than the clutch style and is basically maint free. While there is a lot of info on the Wavetrac, it's tough to say how well it will do on track.

I was torn between the Wavetrac and DiffsOnline's own clutch-type, and I ended up going with the clutch-type diff again. I had an MFactory 1.5-way that I installed in a pumpkin myself, but the pumpkin was destroyed and I thought having a professionally-built diff would be a good idea after blowing up my second diff in two weeks...

Wavetrac has an unlimited mile lifetime warranty, regardless of usage, which is amazing, and it is maintenance-free (other than regular 50k-mile oil changes), so it's a great option for street-driven cars that need to remain refined. The design of their diff with the clutch puck means that it's mostly immune to the issues other helical differentials have when you lift a drive wheel off the ground.

What drew me to the clutch-type diff was the consistent and predictable performance I loved, and a very mechanical, old-school feel to it. It was such a joy to drive and always brought a smile to my face.

[cwlo]

Chris, how does the Mfactory 1.5-way compare to the diffsonline 1.5 way? I am considering an Mfactory or Cusco clutch type. Would also add OS Giken, but they seem to have some issues with their BMW unit.

[chris_flies]

Originally Posted by cwlo

Chris, how does the Mfactory 1.5-way compare to the diffsonline 1.5 way? I am considering an Mfactory or Cusco clutch type. Would also add OS Giken, but they seem to have some issues with their BMW unit.

I don't know yet, since I haven't gotten, let alone installed, my DiffsOnline diff. I loved my MFactory and had zero issues with it. Great value for money, especially if you can rebuild the differential yourself.

[spidertri]

For those of you with a real LSD and who have disabled E-diff, do your rear pads last considerably longer?

I'm amazed how much my rear pads (G-loc R12s) were used up after one track weekend. The fronts didn't have nearly as much wear. Not burning through rear track pads would probably help offset the LSD cost over time.

[chris_flies]

Originally Posted by spidertri

For those of you with a real LSD and who have disabled E-diff, do your rear pads last considerably longer?

I'm amazed how much my rear pads (G-loc R12s) were used up after one track weekend. The fronts didn't have nearly as much wear. Not burning through rear track pads would probably help offset the LSD cost over time.

Yes. Turn stability/traction control all the way off, and that'll fix it until you spring for an LSD. I went through an entire set of rear pads (Hawk HPS') in a single weekend when I first began HPDE-ing. I turned it all off and I could go almost a season on a set of pads.

[spidertri]

I had the traction control turned all the way off.

The car also has the nannies coded off except for e-diff and (I think) Dynamic Brake Control (DBC), I need to look and see if I can turn that down/off because I absolutely felt pedal pressure increase when braking for corners.

[joeo]

Did 3 days on track (Summit point - Main circuit) with the Wavetrac differential and 3.46 gears. The differential works. On corners where I was previously spinning the inside wheel in 3rd gear, that no longer happens. That was my main goal. When the rear end does start to slide out (a little), I can leave the power on and it feels much more progressive; if that makes sense.
Happy with the differential.
I don't know if the gearing helped or not. I'm certainly shifting more, which is more fun, but hard to say there. Lap times wise, it's harder to say. I was previously running consistently in the 1:25s, but now can run in the 1:24s - so I'd say I picked up ~0.5 second on average.
I can't comment on the difference between the Wavetrac and clutch style since I've never run a clutch style diff, but it is certainly much better than the factory and is a noticeable change. What I wanted fixed is fixed!

-Joe