1st AutoX in turbo SE-R, ? on time improvement with R-Compounds

Tim Rogers timrogers at charter.net
Tue Jun 1 23:59:07 CDT 2004

Tyler Clark wrote:
> it was a handful trying to keep the cars power on tap
> since there is inherently some lag in a turbo car. I struggled with
> whether to stay in first in the tighter areas or move to second and deal
> the lag coming out of a turn and only getting a second or 2 of raw
> acceleration under boost.
I'm not an active autocrosser (but I play one on TV.)
Actually, I used to auto-X my '83 Mitsubishi Starion Turbo before I took up
road racing in a Datsun 510.  One of the tricks that I would use to build
boost in a turn would be to "brake torque" the motor after the apex.  This
involves using your left foot to lightly step on the brake as you get on the
gas.  You get on the gas harder than you normally would and this helps to
build boost sooner as you are loading the turbo sooner and harder.   You use
the brakes to control what would be wheel spin, so doing this effectively
takes some getting used to and plenty of practice.  Since this is a track
only car, its hard to practice on the street if your regular ride is N/A.

> I would want a R-Compound tire for sure. I really believe this now but I'm
> wondering how much time I can look to pick up over a 60 second autoX

I think they are worth 2 to 3 seconds per run, but that is _old_ info.

>  I just needed 5 mph more in the turns to keep the cars boost level in a
range that would
> make it available on exiting the turns.

R-compound tires will increase your cornering speed...
Also, if you switch to a smaller diameter tire, like a 45 or 50 series on 14
X 6.5" lightweight rims, you will reduce:  your car's overall weight,
unsprung weight, weight that the engine must try to rotate and your car's
effective gearing (effectively putting in a shorter final drive ratio.)

> Any comments on tires would be appreciated as well as other mods making a
> significant difference. I know the biggest difference will be in the
> having more seat time but I'm just struggling with traction right now.

E.S. control arm and engine torque mount bushings.
An alignment that is Auto-X friendly (check out SE-R.net).
Ground Control camber plates (lets you play with spring rates, maybe 400
front and 350 rear?
Lower front control arm brace (from ShigSpeed?)
Rear STB and ShigSpeed Pillow Ball Mounts.
Softer front sway bar and a stiffer rear bar to get more traction from the
front and more car rotation from the rear.
Tires?  Start with some affordable Kumhos or similar, then graduate to
You would probably need some wheel spacers to keep 225's from hitting the

Also, have you checked out the autocrossing section on the sr20forums?

Who else has some (better) ideas?

Tim Rogers
'93 NX2K- Sapphire Blue, CAT Back, JWT S4's & ECU, Tokico/Eibach, JUN
Flywheel, P/R CAI, 15X7 Borbet Type H's.
'91 NX2K- White, SCCA ITA racecar-to-be
'91 NX2K- Black, parts car

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