View Full Version : How different are S15 HLSDs from Quaife?

05-09-2005, 07:09 PM
Anybody know internal differences? Do they act basically the same?

05-09-2005, 10:06 PM
Same operation(i.e. acts like an open diff when you lift a wheel or aren't applying power) - but the torque biasing characteristics and when it starts to bias the torque will be different based on the geometry of the helical gears used inside.

My S15 HLSD feels good though - plenty of corner exit rotation when I get on the loud pedal. Just need to tweak the suspension a bit and get that same rotation on corner entry.

05-09-2005, 10:56 PM
Alright, thanks. I knew they wouldn't be identical, was just curious if the S15 was as good. Post it up if you figure out a better suspension setup for it.

05-10-2005, 09:24 PM
I have a 30mm tire stagger(245 frt 275 rear), and I think going to some 255's would cure a little bit of that. Plus I *barely* get the 275s up to temp just beating the absolute crap out of the car on the track. You can feel that they're almost stone cold for the first 10 mins - so they're really too big for a fairly light car(S13 hatch - 2560lbs full fuel).

Speaking of that, I've heard of a 17mm rear bar that came stock on some S13s. I have a 15mm rear bar, and I think that a 2mm step up would help the car rotate a bit but not get to that "crazy inside tire lifting" size.

I will tell you that the car spun the inside wheel BAD on T5 at Road Atlanta - which is an uphill off camber turn. Like lay on the power 10 ft before the apex(really late apex, can get on the power early if you line up right) and the car would just smoke the inside wheel through 3rd gear. My car was only running about 9 psi on the stock SMIC, otherwise it's an SR with bolt-ons. I dyno'd it at 205rwhp in that configuration, so not huge power, but it'd still spin the tire until I got out of the throttle.

With the S15 HLSD, I was running about 1-2 psi more boost on a FMIC and I could nail the throttle all day long in the corner and didn't get one peep of wheelspin. Car just rotated beautifully. Definitely the biggest results were seen in T7(very slow decreasing radius turn, like 40mph at the apex) where the car definitely "tucked-in" with throttle much more than with the open diff. Also in T12(VERY fast corner at the bottom of a 50 ft hill, good stuffs), where getting on the throttle close to the limit would make the car want to rotate TOO MUCH due to the aerodynamic lift the S13 hatch makes at high speed(I was tracking out in the 110mph range here). So the diff works great, just think I need to add a hair of rear roll stiffness with a slightly larger bar and then get some front and rear downforce to balance the car out at speed and it'll be sweet. It's already nipping at the 1:49's at RA with street tires, so I think with a bit more balance and some downforce it'll lap in the high 1:40's on street tires(which is my current goal). For comparison, a REALLY fast driver in a stock E46 M3 can pull a ~1:46-1:47 out - that's like low-level professional driver like Speed World Challenge cars. So I imagine there's still a few seconds I don't have the skill to wring out of the car. As it stands, I usually only get passed by the high dollar cars(Vipers, Porsche GT3's an 996 TT's, and the very well prepared E36 M3 cars) - so the lil' S13 is doing ok on street tires for now. It'd be nice to crack off a mid 1:30 in the car far in the future, that's pretty scary fast to experience, so I can't imagine how fun it is to actually DRIVE that fast. http://forums.freshalloy.com/images/graemlins/grin.gif

Sorry for the rambling, there's nothing on TV tonight. http://forums.freshalloy.com/images/graemlins/tongue.gif

05-11-2005, 02:13 AM
Good stuff. I'm just getting into BMW track days up here in the Northwest. I'm looking at going with a 225/245 stagger. I already have whiteline adjustable sway bars, so we'll have to see how much I need to play with it to get it to handle like I want. I was considering 245s all the way around, but I'm pushing around 240-250whp (S15 T28) right now, and more like 280+ in the future, so a stagger might be a better idea. I'm going to have to look at your posts again about fitting those tires under there..

Very impressive times by the way, you've only been doing this for about a year or two, haven't you?