Wednesday, June 10, 2015

Like LSD man...

Ok sorry for the goofy title, I couldn't resist. So after doing all the work of pulling out the transmission, it became very clear that I want to minimize the number of times I do this. It's sort of fun in a way, but it really does take a lot of time and effort. So besides replacing the tattered, clutch that was probably a hairs breadth from grendading like this one:

The flywheel, and the Limited Slip Differential (LSD) were also installed. Basically, as a consultant, my time can be converted to money fairly readily and long term it's cheaper to do it all at once.

The flywheel is the Fidanza Aluminum flywheel, which shaves 6.8lbs off (about 45%) the stock. The clutch plate itself is only an ounce or two lighter, but it has less mass near the edges, and the clutch plate cover and pressure plate is a pound less, so the total weight savings should be about 8lbs of rotational weight. 

The LSD will offset that somewhat, adding back a couple pounds or so, but the diameter of the added rotational parts will be small, so perhaps 5-6 lbs off the car, and even more reduction in rotational inertia. PLUS power will now be available in the corners!

Only one problem... with great power comes great responsibility. It turns out that a lot of the time I've not been very gentle with the throttle. The LSD exposes this flaw in my driving in 2 ways. First, if lateral grip is not at maximum, but the car is turning, when the LSD locks up, this results in power only on the outside wheel (since the axel has become solid the inside wheel with less weight and traveling a different radius must slip). That tends to torque steer the car into the turn. This is potentially useful, but also throws you off if you are not used to it. Second, if you are at the limit of lateral grip, adding power now causes the OUTSIDE rear wheel to slip... and that will tend to make the car want to spin.

So while the LSD unlocks a new level of potential speed, the open diff will tend to save you from yourself, and is slightly easier to drive. My first event on the new LSD was quite disappointing because I was discovering that my throttle work needed work. After about 5 events, now I'm getting used to it and learning to ease onto the throttle and not be on/off the throttle as violently, and may just be beginning to reap the benefits of the additional speed in the corners.

Other notes on the changes I made... the lighter flywheel seems to make it slightly harder to get the car to actually turn over, which puts my present battery solution right on the very hairy edge... I probably need to think about setting up a cold weather jump system to ease the wear and tear on my starter when I have to leave for a race in the early AM. Mostly I just need an easy way to get jumper pack clamps on the battery.... without risking a short. The present space is pretty tight.