Testing and Teardown Jan 7, 2009
We took our LeGrand to the Ocala Gran Prix track last week to get some much needed seat time. The gearing on this car is still quite short—we were hitting the third gear redline at the end of the straight and shifting between second and third several times per lap. Despite this, we were turning our fastest laps ever at this track. Our runs landed in the low 35-second range, while a Street Modified Evo was in the high 36s.
The car felt great, but we did run into several problems. The timing pickup for the installed Dyna 2000 system came loose from the crankshaft; the car popped and missed to a halt after one session. We tracked down the issue and fixed it simply enough. The engine is a little buzzy, and we need to make sure that our fasteners are properly torqued and threadlocked.
The chain broke toward the end of the day, bringing our outing to a close. Upon inspection we discovered a red flag: The RK 530 chain had been stretching pretty regularly. Once we got the car back to our shop, it became clear that the front sprocket was only hand tight; the clutch cover was just barely keeping everything from spinning off into space. It sounds nasty, but it's all easy enough to fix. We even had a new spare Tsubaki Sigma chain that came with the car.
Since the car has been back in our shop, we've removed the five-piece fiberglass body and scuffed it down for some paint. We're not really big fans of blue, so we got an estimate of about $300 to paint the entire thing. We'll wait for it to get back from the paint shop to tell you what color it is. Hint: It's from a 1970s Porsche Carrera RS.
We also sourced a set of the original LeGrand magnesium wheels, which measure in at 13x7 for the front and 13x9.5 for the rear. These replaced the 13x6 and 13x8-inch wheels that came with the car. We're aiming to upgrade to 13x8 and 13x10-inch wheels later on, once we get a few other things taken care of. At least we now know that we've got the car back to its original rim widths.
Green Means Go Jan 12, 2009
We got our LeGrand bodywork back from the paint shop yesterday morning. The original estimate for the job was about $300 including tax, but this figure soon ballooned to $450. Why? Two reasons: We discovered a few small cracks in the wheel wells, and the shop found out our color choice.
The cracks took a few hours to fix, adding about a hundred bucks to the deal. Meanwhile, we chose to paint the car in Porsche Signal Green, a color that was made famous by the Carrera RS from early 1970s. The color choice required that the shop first paint the entire car white so that the color would come out in its correct hue.
It was worth it. The Signal Green absolutely pops, and the car looks stunning with its new paint.
Once we trailered the bodywork back from the shop, we started reassembly by laying the front and rear sections down onto the chassis. It's looking really good.
B-Modified Autocross Video Jan 12, 2009
We took our LeGrand to its second autocross this past weekend in Palm Bay, Florida. Despite the fact that it's still January, we were bathed in beautiful Florida weather.
The LeGrand took 10 runs between our two drivers, and it worked very well without issue. We posted the third-fastest time overall, just a few ticks behind a shifter kart and an A-Modified car.
While we know we still have to improve by a couple seconds to become nationally competitive, we're happy to note that at least we're in the ballpark for times.
We weren't clean on all of our runs. Luckily, our new carbon fiber splitter was up to the task of some cone carnage.
We're also posting video of our fastest run. You'll notice that there's quite a bit of vibration in the footage; that's due to the fact that we mounted the GoPro Hero camera to the rear wing, which has some play in the mounts. We'll add that to the list of things to work on.
Wheel and Tire Experimentation Jan 14, 2009
We started out using a 20-inch tall Hoosier R25a tire on the rear of our LeGrand. We soon discovered that this made our gearing way too short, allowing us to hit the top of third gear at nearly any autocross. We looked over the gearing charts for the KZ drivetrain and realized that we needed to go with a taller 22-inch diameter rear tire for now. We purchased a set of used R25b Hoosiers from USDRRT, and they should help us stay within our car's powerband in second gear.
As we mentioned in an earlier post, we were investigating wider wheel widths to really take advantage of our nearly wide-open rule set. We ordered a set of magnesium-centered Keizer wheels that had the exact backspace and bolt pattern that we needed. The 13x8-inch wheels weigh in at 8 pounds apiece, while the 13x10-inch rears weigh a pound more. While not inexpensive, the Keizers are exactly what we need—light and perfectly matched to our application.
We'll get these tires and wheels mounted up as our Solo season starts rolling.
Real Work Begins Feb 4, 2009
Like many older D Sports Racers, our LeGrand originally came with a locked rear axle, or "spool." This feature is simple, light and cheap. The downside is that it causes a lot of low-speed push. To solve this problem, modern sports racers use limited slip differentials mounted in custom housings.
We sourced a Wavetrac differential from Autotech Driveline. Meanwhile, we're having Bill Gendron of Small Fortune Racing make a custom housing for the differential that will be nearly a bolt-on. The housing will include a brake rotor, sprocket and a chain tension adjuster. This modification is the key to making a LeGrand (or any sports racer) turn at low autocross speeds. Bill stopped by our shop and chatted with us while taking measurements for our new rear end.
After our meeting with Bill, we put our car on our Longacre scales to see just how much this little beastie weighs. We were happy to see that we're at 823 pounds. With our approximately 200- to 220-pound drivers, we're in the ballpark for the SCCA Solo B Modified minimum weight of 1020 pounds with driver. We'll have to be careful once we start some modifications—we know we'll be losing 20 pounds when we change over to the lighter Keizer wheels.
We also played around with the car's current rear wing. Using a carpenter's angle finder, we cranked in a 15 degree angle of attack, then added a Gurney flap to the trailing edge. The Gurney flap will help the wing generate downforce at lower speeds and higher AoAs without stalling. Aerodynamics is a fascinating subject--we just ordered Simon McBeath's book "Competition Car Aerodynamics" to learn more.