[octane]

fs: alpine sbr-102cr 10" sub/enclosure

Autocrossers and track drivers:

How many of you find the steering response of the STi a little unpredictable at the limit? I have trouble holding a line if I ever need to make a throttle correction. The torque-sensing front diff just makes things feel strange.

If I were to speculate, I'd say the STi would handle better if the front diff were replaced with a conventional, clutch-type LSD. Maybe one from an earlier STi.

I'm considering this mod, and I'm just wondering if anyone else is. While the tranny is out, I'd also put in a lighter flywheel. With such low compression, it takes forever for the revs to fall with the stock flywheel.

 

[hatchy]

Why would you want the revs to fall quicker? And wouldn't a lighter flywheel make the "problem" worst?

Autocrossers and track drivers:
I'm considering this mod, and I'm just wondering if anyone else is. While the tranny is out, I'd also put in a lighter flywheel. With such low compression, it takes forever for the revs to fall with the stock flywheel.

 

[WRX_Mundi]

I'm neither octane nor an expert, but my understanding is that the flywheel is acting as a spinning weight (kind of like a, um, flywheel). A heavier flywheel will take more energy to get spinning (hence revs go up slower), but also keeps spinning longer given no more energy (hence takes longer for the revs to come down). A lightweight flywheel will improve performance by sucking less energy out of the system -- revs go up and down quicker (listen to the F1 cars do quick revs while tuning -- they go up and back down super fast). Similarly, when you push in the clutch, the revs will drop quicker, and if you have the clutch in and step on the throttle the revs will go up quicker. Whether you want this or not is another question -- most people do the lightweight flywheel just to avoid the extra energy used to spin it (hence more to the ground).

Why would one want revs to fall quicker? To better rev match or make double declutching faster. I'll ignore the whole double declutching stuff and just talk about my experience with matching revs. If I am upshifting (say 2nd to 3rd in a fast set of gates), I am really high in 2nd gear and I push in the clutch and abck off the throttle. Hand shifts to third moving quickly as soon as the left foot has pushed the clutch pedal past the disengagement point. In a car with a real short shift this is really fast. Barring revs, we just let the clutch out and get back on the gas. The problem is that if the revs aren't matched right, you're going to cause stress to the system and unbalance the car, perhaps losing traction in your tires as well. So instead we're hanging around twiddling our thumbs waiting for the dang revs to drop so the clutch can be let out.

Sort of similar on a rev-matching downshift (heel-toe or not). Clutch in, throttle down as soon as the clutch has just passed the disengagement point meanwhile shifting with hand, then we're waiting for the revs to go up... and then the clutch is engaged again. Faster revs up/down, caused by a lighter flywheel, makes this process faster.


Anyway, sorry octane -- I'm in Idaho and none of our dealers have an STi yet. Hence nothing for me. Every autocross for the last month I've been getting 10-20 people asking me when my car is coming, or why I'm not driving it, etc. I keep telling them that I don't know when, the dealers just say "soon", and if it were up to me it would be here by now. Not good hearing about unpredictable throttle steering -- when I get things right in a sweeper in the Miata it is an absolute blast to rotate the car either direction with little throttle adjustments.