Monday, August 20, 2007

SCX Pro Audi-work continues


Tuning on the SCX Pro Audi is continuing here at the garages of Slot Car News. Large diameter Pro wheels have been added to the front of the car, not to produce a speed increase but to get the car closer to a more proper LMP look. The small wheels that come on the car on the front just didn't have the look I was after. I stretched the stock front tires over the large diameter wheels (photo of the new wheels above). Now the car looks a bit better, still they look too small...but better. I adjusted the front axle with the screws under the front axle, the axle is now adjusted with nearly no up and down travel. It still spins smoothly (and quite well because it's riding on the tips of the grub screws), but no doesn't float.

Under full acceleration out of the corners the car seemed to want to lift up at the front a bit. So a "suitcase" of lead was added, a small slug of 7 grams of lead was glued in place just behind the front axle.

No other mods have been made to the chassis. The pod float is excellent and I couldn't figure out and improvements to make.... so since it wasn't "broke" I didn't fix it.

Since the original track testing for the review I changed the tires to SuperTires silicones form the SuperTires "Yellowdog" urethane tires. Lap times dropped quite a bit, more on that later.

The most important change was to the gearing on the car. The stock gear was changed to a SCX Pro 24-tooth gear. On the straights (on the East New York Raceway) the car seemed to not have enough "legs" and ran out of speed about half way down the straight away. The 19k Pro Motor needs to be geared much higher than the 26 tooth crown. The next experiment will be to the pinion to see if even higher gearing gets me anywhere.



A small screw was added to hold the stock Pro motor in place. The pod doesn't really allow the motor to twist, but I figured it was good to screw the motor down anyway.

So lap times..... in stock form with Yellowdog urethane tires the car was doing mid 5 second laps on the East New York Raceway, which isn't all that fast. After the tuning described above the lap times dropped to fastest laps under 5 seconds. A fastest lap of 4.980 was done and several laps followed at nearly the same speed. The quick laps came after many laps had been done. With the stock motor on a large track this car really takes quite a bit of driving to find the speed. Lap times under 5 seconds are the benchmark for what we consider "fast". For comparison, modified and heavily tuned Slot It, Spirit, etc, cars do sub-5-second laps. So this car is certainly in respectable company...with the stock motor!

The Pro Motor isn't overpowering in this this car, and in fact, it's a bit too mild IMO for an LMP car. But I love trying to get the most out of these SCX motors and it feels like I've gotten close to the end of the speed I can get out of the motor.

The wheels and gear used in this test were provided by Fantasy World Hobbies, thanks for their continued support of Slot Car News!!!!!!!!

DaveK
Publisher, Slot Car News

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