At the 2017 Solo National Championships, several of the STU competitors got together for a rather special test. We had the fastest 350Z in the class, the fastest STi in the class, and the Borg Motorsports Corvette (the fastest Corvette in the class). We put Bryan Heitkotter and Dave Ogburn into all three cars to see where they sorted out and what the advantages (or disadvantages) of each car were. Below is the report Dave and I compiled.
STU Vehicle Shootout
2017 Solo National Championship, Lincoln, NE
September 5, 2017 (17:30-18:30)
Nationals Test and Tune Course (NTNT)
Test Participants and Organizers
Dave Ogburn III
Report complied by Lane Borg (Borg Motorsports) and Dave Ogburn (Yaw Moment Racing), 10/25/2017
Test Outline and Procedure
The objective of this test was to see what differences, if any, exist between various STU cars. Course variability was minimized by using the standard NTNT course, which all drivers involved in the testing had driven prior to the test. Using two professional drivers with multiple Solo National Championships minimized driver variability. The two drivers were Bryan Heitkotter (professional race driver) and Dave Ogburn (tire industry test driver).
Each driver put a maximum of three laps on each car with a control rerun at the end of the session. Bryan’s control car was the 350Z. Dave’s control car was the C5. The NTNT session was mostly private, minimizing any variation in the course due to changes in the condition of the rubbered in racing line and/or changes in the clag/marbles off line.
There were three cars used in the test. A multi-time Solo National Championship winning Nissan 350Z (provided by Bryan Heitkotter), a multi-time Solo National Championship winning Chevrolet Corvette (provided by Lane Borg), and a multi-time National event winning Subaru STi (provided by John Hale). Each of these specific cars has been the fastest of its make/model in STU at both the 2016 and 2017 Solo National Championships.
Bryan obviously drives his own car regularly at events and is familiar with its capabilities, but has not driven either of the other test cars. Dave has driven the Borg Motorsports C5 before, but not on the tires, differential, or suspension combination used at Nationals. Table 1 outlines the details of each car.
Results of the test are provided below in two sections: Objective Results and Subjective Results. However first, the caveats of the test must be discussed.
YOU MUST READ THIS PART!!!
The course was a lower average speed than most Nationals courses. This caused a lack of separation in the cars and likely gave the STi an advantage (only needed one shift, not in the C5’s power band).
While two cars were on the BFG’s, the 350Z was on Nexen’s. Do your own research to determine if there is an advantage in Lincoln, but this likely skewed the results somewhat.
Data was taken for both drivers, however there were GPS issues on Bryan’s data rendering it unusable. Video was taken for Dave’s runs and is available on his YouTube channel (Dave Ogburn).
The subjective results/comments are the result of the following:
- Bryan and Dave’s discussion after driving each car
- Dave’s testing notes taken after each run
- Dave and Lane’s analysis of Dave’s video
- Dave and Lane’s analysis of Dave’s SoloStorm data
Objective Test Results
Table 2 includes the lap times run by each of the drivers in each car, as well as the average and best run. Please note that shifting was an issue in the STi on the NTNT course. Bryan did not shift on his first run, but did shift on his second and third runs. Dave shifted on his second run, but did not shift on his first or his third. Note that the run order is different for each driver. The data is presented in the order the cars were run for each driver. Table 2 has been color coded to clarify which car each driver ran at which time: Yellow for the C5, white for the STi, and blue for the 350Z based on the actual color of the test cars. An entry of “N/A” indicated that the driver decided not to take further runs as they felt they achieved the maximum the car had to offer.
Table 2. Lap times of the STU shootout.
Subjective Test Results and Comments
Subjectively, the 350Z was softer than the other cars, but this seemed to result in more mechanical grip. It was also very easy to put power down, allowing for a tighter line choice and thus, a shorter distance. The steering response was a bit slow and the platform had a disconnected feel between the front and rear axles. In second gear, the 350Z had a slight acceleration advantage to the C5 at the speeds seen on the NTNT course. The 350Z was not stellar at anything, but it didn’t do anything wrong. It was easy to drive a tight line (shortest distance), apply power on exit, and had the highest slalom speed (50.0 MPH) even though it had a higher amount of body roll than the other cars.
The C5 was the best at high speed sweepers, but had more trouble putting power down than the 350Z. Because of this, it favored more of a late apex line to better manage the power application center-off. The C5 has very good response and the best turn in of the three cars. Despite this, the C5 suffers in tight corners from its large size, favoring a larger more open course where the vehicle width and long wheelbase aren’t as detrimental to its performance. The Corvette had the second place slalom speed of 49.4 MPH. The poor gearing of the base C5 transitions to being an advantage as the course becomes higher speed. The stopping power of the C5 was the best of the three, likely due to having the longest wheelbase.
The STi was the hardest to drop in and drive fast in just three runs, but it feels like it has the most potential. The acceleration is enormous and it obviously puts power down well. While the STi is the narrowest car, it had the lowest slalom speed at 47.8 MPH due to getting out of phase in transient maneuvers. This performance is likely a compromise to improve the sweeper performance, which was on par with the other cars despite occasional pitch/roll hop mid-corner, mainly in lower speed corners. The STi does very well in slow, small radius corners. It will likely be the hardest to drive at the limit on a Nationals course because of the frequent shifting. While the short gearing makes shifting a requirement on most Nationals courses, the STi accelerates faster in second gear than the other cars accelerate in first. Third gear in the STi tops out at the same speed as second gear in the C5.
Overall, we feel the C5 is the road course car; the STi is the slow course, long digs car; and the 350Z is the jack of all trades, but master of none.