A check of the tire temperatures showed that the fronts were getting a little overheated at 220F. The rears showed a 205F average across the tires, so we decided to increase the pressures to try and compensate. We added 4 psi to the front tires and 2 psi to the rears, and Jeff headed back out onto the track.
Once more, a couple of slow laps preceded a flying lap of 1:30.11. I was getting excited now as a sub-1:30 lap was looking inevitable. The next time around Jeff stopped the clocks at 1:30.03. Damn, so close! On the third lap we hit pay dirt as the timers stopped at 1:29.97 with an average speed of 68.02 mph.
Jeff wasn't finished yet. Without the problematic brake fade that plagued our earlier sessions he was able to stay out on the track and nibble away at the lap times. In fact, the brakes worked perfectly until the car made seven or eight laps, by which time Jeff had logged the best time yet of 1:29.70 sec., averaging 68.22 mph. Harrison was obviously having fun now, but I signaled him in and asked him for his feedback.
"The tire pressure adjustment definitely helped eliminate the understeer. When I turn the car in now it settles immediately and holds the line perfectly all the way through the turn. It's very neutral and easy to drive.
"The suspension is working perfectly and the tires are well up to the abuse. They are very consistent and predictable for a DOT tire. The brakes worked great overall. I would think that the only gain to be had from a larger four- or six-pot setup would be a little more resistance to fade during an extended track session or race.
"The chassis feels very good for a street car. It's still got a little flex in it, but nothing that a welded-in rollcage and a little extra bracing wouldn't cure. At this point, what this car really needs is about 150 more horsepower. This chassis is vastly underpowered. As I exit the turns and get on the gas it feels like I'm going backwards. More power would also help me to balance the car on the throttle. The cornering speeds are so high now that we're beyond the power range of the engine in any given gear. Give me some horsepower and we'll really rock!"
With our KA24DE-powered S14 still in pretty much stock configuration with less than 140 wheel hp, our chassis is now hugely underpowered. The ongoing program of modifications we have planned should correct this situation (turbo kit, etc.), and we will, naturally, return to the Motorsports Ranch on a regular basis and let "Hound Dog" Harrison do his thing.
Our final test results were impressive. Our modifications picked up almost 6 sec. over the 1.7-mile track with an increase in average speed of more than 5 mph. To put this into perspective, our 240SX in the hands of Harrison lapped the road-course within two-tenths of a well-driven 350-hp Subaru WRX on similar DOT rubber and road-race suspension. Not bad for an underpowered, 6-year-old veteran.
Our project car now handles better than we could have hoped for and is an absolute blast to drive on my favorite Texas back-roads. The brakes are great and the car looks awesome with its lowered stance and wider wheels and tires. I just know we can get a 1:27 lap with some more power-now where did I put that turbo kit catalog?
Autocross / Road-Racing SpecsFront Toe-In: 0 degreesFront Caster: 5.5 degrees positiveFront Camber: 2.5 degrees negativeRear Toe-In: 2mm both sidesRear Camber: 1.5 degrees Negative
Idiots Guide To Skidpad (Math)Properly testing a car on the skid pad is one of the best ways to maximize your car's cornering potential and is also an essential benchmark for monitoring the effects of chassis modifications.
First of all, you need a large, flat and smooth-surfaced area to mark out a 200- to 300-ft diameter circle (our tests were done using a 200-ft diameter pad). Use cones, empty plastic cups (use tape to prevent them from blowing away) or paint to outline the circle.