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Preparing a 964 for Track Usage Authored by: Bill Gregory (sansho@rennlist.com), CVR |
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This article focuses on what can be done to improve a Porsche 964's performance at the track. Please note that because the 964 we are using as our example is a daily driver. So while this vehicle also logs track time, modifications that would be used for track-only, or racing applications are not included in the discussion First, let's look at the interior: Rollbar, seats, harnesses, and floor. For the rollbar, I used one from Doughterty (DAS), which is a removable bar, i.e., bolted in, not welded. What's nice about this bar, which fits both 964's and 993's, is that it has a base support bar that attaches to each side of the body at the stock seat belt take-up spool locations. I like to think this adds some amount stiffness to the body, and it's a good place to mount your fire extinguisher. Stock seats were replaced with Recaro SRD's, which include holes for the shoulder harness and sub belt. Both 964's and 993's share a body made for all wheel drive, so we have to deal with large center tunnels and limited-to-no space to install the seats. However, with a dremel tool and some Brey Krause parts, it can be done. Rear harnesses are run through the seat, over the rollbar, and down to eyebolts at the rear seat belt mounts. Lastly, floors. In a 964, there is a thick bundle of wires running off
center on both the drivers and passengers floors. To prevent the
insulation being chewed up at the track (with floor mats removed), I
used some 2'x2' ribbed .032" aluminum sheets and cut out pieces
shaped essentially like floor mats, which are secured by a few screws.
Others use thin plywood, like the Factory, as an alternative. Next, mechanicals: suspension, brakes, engine. The stock suspension is marginal for track usage. Alternatives abound, from various lowering and stiffening springs to heavy duty shocks to spring/shock combinations to adjustable sway bars. I chose to stick with a mostly Porsche solution, and installed the suspension used on the non-US Carrera RS. You can read an article discussing the installation, with pictures, at www.porsche964.co.uk. The only non-Porsche part was a larger rear adjustable anti-sway bar (21mm vs Porsche 18mm). A Brey Krause strut brace is used. ---------------------- Note:
this article was originally prepared by the author as a two-part piece
for a PCA regional publication. Copyright 2002 (C), CVR. |
Brakes are quite good on the 92-94 C2's and all C4's.
90-91 C2's used a dual piston rear caliper, versus the C4's quad piston
caliper. So, on the brakes,
the front and rear brake backing plates were removed,
cryogenically-treated front (also slotted) and rear rotors are used,
with Pagid Orange brake pads. I also added a Porsche brake cooling kit
(an available Tequipment part) which routes air from cutouts in the fog
lamps via a hose to the wheel well. Mike Shaw, as well as others, also
makes a similar brake cooling kit. The brake bias valve was upgraded to
the Turbo 60 bar valve, which adds to stability under heavy braking.
Minimal changes were made to the engine. First, holes were drilled in
the air cover. The factory originally claimed an additional 7 hp from
this, however tests since then suggest that may be a stretch. What it
does do is add a marvelous growl from the exhaust under full tilt boogie
conditions. Primary muffler was exchanged for a cup bypass pipe.
Catalytic converter and final muffler remain in place. To
protect the exterior, Armourfend was applied to the hood, front bumper,
front lights, rear view mirrors, side sills, and rear panel in front of
the wheel well. Finally, 225/45x17 and 275/40x17 Kumho Ecsta V700 DOT
"R" rated tires are used on track wheels. The flat oil line in
the right wheel well was made a bit flatter, for tire clearance. And
how is it on the track? Nice. With the adjustable sway bars, the general
balance is tuned towards a neutral position. The progressive springs,
however, are a compromise for dual purpose usage. On the street they are
fine, firmer than stock, but not harsh.
At the track, on the plus side,
progressive springs can help your driving, as they respond to
smooth transitions. A downside is that, in high load turns, the
suspension has to move through the progressive part of the coil before
it gets to the more rigid part of the spring, for the chassis to take a
set in the turn. Brakes are fine. Aerodynamics
can use a little help, so a rear RS America/Carrera-style wing and front
valance extension are next on the improvements list. If
there are any questions, I can be reached at sansho@rennlist.com.
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