The introduction of our Project 996TT (“Introducing the Budget Supercar,” Aug. ’11) created a good deal of interest and questions from our readers. Many encouraged and cheered the initiation of such a project, admitting that this was just what they were waiting for. While others disputed the ultra-low purchase price of our project car. Well, we got what we paid for, because at the track event where we planned to collect the baseline data for our “cheap” $32,000 ’01 Porsche 911 Turbo it began billowing huge plumes of white smoke. Yee-freakin-ha!
Let’s step back in time and start at the beginning. The first necessary upgrade for our Project 996TT was a new set of tires. In fact, the tires that came on our 996TT when it was purchased had barely enough rubber to roll home on, thus contributing to (among other things) the ultra-low negotiated purchase price. We selected the Toyo Proxes 1, Toyo’s new flagship tire. It was engineered from conception with a focus on high-speed performance, high-load cornering and extreme braking, in both wet and dry conditions. All of the qualities true enthusiasts look for in a maximum performance summer street tire. They were an excellent choice, because when you are starting from scratch on a new project, it is advisable to use a consistent tire for baseline through chassis modifications. Also, by choosing a performance street tire instead of an R-compound it is easier to notice and quantify deficiencies and/or improvements in your project’s handling progress during the course of your buildup.
The Toyo Proxes 1 is loaded with modern features and technology. It has a straight blocked non-directional asymmetric tread design that allows for excellent water evacuation, multi-compound rubber construction and easy rotation for cars with staggered size specifications. Other features include interlocking tread blocks that improve directional stability in high-speed, straight-line driving and slanted grooves that close during cornering for increased stability. A multi-function taper is also applied to the inside of specific tread blocks to obtain uniform contact pressure during cornering and to provide a wider channel along the circumferential groove to resist hydroplaning. One additional feature is the Silent Wall technology in the tread design that decreases noise transmission by reducing pipe resonance when traveling on today’s varying road surfaces. In addition, the Proxes 1 utilizes the latest in tire construction methods by means of a wider, high-rigidity belt package developed through TruForm technology. The result is better uniformity and improved handling performance because the contact patch is consistently maintained from low to high speeds. It has a highly rigid casing, sidewall and bead design for greater directional stability and for quick and linear steering response. Overall, this combination results in excellent all-round performance and a reasonable UTQG tire wear rating of 240, so you won’t have to replace them every year like you would with most maximum performance tires.
For Project 996TT we decided to slightly upsize the tires to improve the contact patch, selecting 255/35 and 305/30 for the front and rear, respectively. This sizing does make the speedometer read a few percent lower, but it does not affect the AWD, ABS or PSM systems because the front-to-rear size ratio remains the same, nor does it cause any rubbing issues provided that your wheel offsets are chosen wisely. I found the Proxes 1 to be extremely quiet under all road conditions with a smooth and velvety ride quality. Grip levels were excellent for a non-R-compound, exhibiting a progressive breakaway, even in bitter cold conditions. Feedback through the steering wheel is very good too, as one can truly feel the tires working under high-g corners.
In Part 1, we noted that the 996TT would benefit greatly by installing a limited-slip differential in the rearend. After scanning the market, we decided on a less expensive Torsen-type LSD. Geared LSDs, like the Torsen, use worm gears rather than clutches of the friction type of LSD unit, and work by moving the torque from the slowest moving wheel to the fastest, rather than actively controlling slip. The main reasons for this purchase were we didn’t really need the most sophisticated or expensive unit, we just needed something to do the job of getting more power to the pavement in the rear that would work in combination with the older 996TT four-wheel-drive system. Also, we didn’t want the additional maintenance required by a friction-type LSD nor did we want the extra heat generation. The install of a new LSD unit is a black art requiring the removal of the transaxle and R&R of the differential by a skilled Porsche technician. The new LSD unit is fitted first with shims to set bearing preload. Next, the ring gear can be bolted up and then the whole unit installed using a procedure that arranges the aforementioned shims to center and set the precise meshing specification (backlash, 0.005 inch) to the pinion gear.
OK, so we thought we were finally ready to begin baseline testing now that everything had been given a once-over and the new LSD and Proxes 1 tires were installed. We were wrong. As mentioned at the beginning of this article, our 996TT began billowing huge plumes of white smoke. The cause was a small split or tear in one of the main coolant line elbow hoses. This piece (PN 996 106 502 74, superseded by PN 997 106 502 00) can be a problem if the vehicle has had the transaxle removed without dropping the engine at the same time (on a clutch repair for example). In cases such as described above the engine is haphazardly dangled by, you guessed it, two of these elbow hoses (not an official Porsche procedure by the way) leading to a billowing white smoke event down the road. Fortunately, it is an easy fix and not very hard on the wallet. Regardless, an older car is always going to have some unexpected issues, especially when one takes their machine to the track for a good thrashing.
Next time we will cover our brake upgrades and obtain baseline numbers. There’s a great deal of potential here so the performance delta will be significant.