Introduction
The SAC and SEB have a bit of a thankless job at times. People want new cars classed as they are released, but often there is little actual autocross data to go on. Subsequently, people may write to have cars moved, but rarely are a group of cars with multiple drivers gathered together on equal tires for testing.
Although the M3’s (both the E46 and E92) have been in F-Street for a few years (going back to the final years of Hoosiers in F-Stock), they really weren’t seeing a lot of national use initially, especially the E92. However, that changed in 2015, with multiple cars running nationally on both sides of the country. In a class of American cars, that before 2015 had never been won by a foreign car of any type, the BMW’s are viewed as outsiders. It became clear that not everyone agreed the cars fit with the class. As an F-Street competitor for the last two years, I was interested in evaluating the parity of the class.
With the intention of gathering objective data, I contacted some members of the SEB and SAC to arrange for a test session at Lincoln. The SEB and SAC were also interested in the data, so they made arrangements. I also reached out to some of the F-Street competitors for vehicles, and big thanks to Doug Wille and Jackie Mutschler, David and Lorien Feighner, and Casey Weiss for their help!
Note: In the interest of full disclosure, I do drive an E92 M3. However, I did not participate in the testing directly (I recorded the data, but didn’t drive in the test), and I have tried to present the data here in an objective way.
Test Procedure
In order to generate test data on the same course under the same conditions, a group of cars was collected from the F-Street field (all prepared and nationally competitive). The following cars were selected:
- 2011 BMW E92 M3 ZCP (2015 FS/FSL national championship car)
- 2007 Ford Mustang Shelby GT
- 2014 Chevrolet Camaro SS 1LE
- 2015 Ford Mustang GT Performance Pack
With the cars selected, the SEB and SAC got together and arranged for test time on the Nationals Test and Tune course in Lincoln. Big thanks to the Nebraska Region for leaving the timing equipment running for our testing!
In addition to the cars, a group of available drivers was selected. A primary driver went through all cars and then back to the first car as a control. The secondary drivers then drove select cars.
- Primary Driver: Sam Strano
- Secondary Drivers: Shelly Monfort, Andrew Pallotta, Doug Wille
For testing, Sam drove each car until he felt that he put together a few solid representative runs. Then he moved to the next car.Times were recorded, along with data via SoloStorm. Unfortunately, due to the available mounting hardware no data could be collected in the 2015 Mustang (note to self: buy suction cup mounts!). That said, the fast runs were recorded in the other 3 cars.
Testing
Sam began the test in the M3. After 3 runs he moved to the Shelby, then the 1LE, then returned to the Shelby for 3 additional runs with some setup changes, followed by the 2015 GT.Sam then finally returned to the M3 for a control re-run. The times are listed below:
| M3 (control) | Shelby GT* | 1LE | Shelby GT (with setup changes) |
2015 Mustang GT | M3 (control re-runs) |
|
|---|---|---|---|---|---|---|
| Run 1 | 37.922 | 38.655 | 37.994 | 38.616 | 38.838 (all 2nd Gear) | 38.189 |
| Run 2 | 38.284 | 38.878 (bad slalom exit) |
38.402 (slalom mistake) |
38.785 | 38.278 (all 3rd gear) | 38.240 |
| Run 3 | 38.044 | --- | 38.049 | 38.432 | 38.232 (all 3rd gear) | --- |
| Fastest Run | 37.922 | 38.655 | 37.994 | 38.432 | 38.232 | 38.189 |
* Unfortunately, Sam did not feel that the Shelby GT rear differential was locking up properly, potentially resulting in slower times.
Based on Sam's results, the secondary drivers primarily focused on the two fastest cars – the M3 and the 1LE. Their fastest times are included in the summary data table below. In addition, the drivers submitted subjective comments regarding the differences between the various cars.
E92 M3
Sam – Good turn-in with great brakes (best of the group), but the differential is a bit tricky to get used to. Engagement can be a bit abrupt.
Shelly – The M3 tucks in well off throttle at corner entry, and seems to be slightly more neutral. I prefer the feel and steering in this car.
Doug – Corner entry seems to be a bit easier in the M3, with better sightlines than the 1LE. The M3 seems more balanced, and may be an easier car to jump into and drive fast - really no tricks to driving it at 95 % of its capability. I was able to pretty much match my Camaro times in 2 runs. It is a very honest car. Push really hard and the differential is quirky, yielding some brief sideways surprises. Understeer is present in the final sweeper. The brakes are simply a joy to use – phenomenal really.
1LE Camaro
Shelly – The ABS is a bit tricky – you can end up in ice mode without a lot of input. The 1LE seems to transition well, with minimal roll.
Doug – The 1LE seems to pull stronger up top than the M3. In addition, it feels like the 1LE generates more lateral g’s in sweepers. It never feels as big as it is, except when you drive it after the M3. Like the M3 it is a very honest car. The brakes feel numb and disappointing after driving the M3.
Shelby GT
Sam – Unfortunately the differential in this car feels a bit weak. I was fighting it in several sections of the course, which likely slowed the car down.
2015 Mustang GT
Sam – On run 1 I left the car in 2nd gear. I was on the limiter in several places. After some discussion we tried a run all in 3rd. I was impressed with how well 3rd gear worked – the car still pulled strong and slalomed better in 3rd than in 2nd. I suspect on many courses the car may work better with 18’s, geared down to make 3rd more useable.
Shelly – This car feels like a hybrid between the 1LE and the M3. There is a bit more roll here than in the 1LE, but it has a better entry. The car does feel sluggish out of corners when in 3rd gear.
Vehicle Specifications and Objective Data
Generally the objective data lines up well with the subjective comments. The 1LE appears to have an advantage in sweepers, while the M3 has an advantage in slaloms. This makes m sense given the physical dimensions and specs of both cars. Interestingly, while the M3 is strong off the start in terms of time, it is actually the slowest at the end of sector 1, which may suggest a strong launch but potentially either less confidence in the initial turn or just slower acceleration. This data was consistent across Sam's M3 runs.
Overall Thoughts from Sam
As I recall the speeds for all 3 cars w/data was similar on acceleration which surprised me. I think that means parity on most courses for power concerns. But the clear difference between slalom and sweeper abilities shows the need for fair, balanced courses as much as possible. This is not the case only with FS but many street classes where you have vastly different cars but are looking for parity. For example, the 2015 Nationals West course becomes a huge advantage for the M3, while 2015 Nationals East becomes one for the 1LE, assuming equal conditions.
The M3 is the easiest to drive fast. The car responds to throttle changes readily, is geared perfectly, is narrow, and has stupid proof brakes/ABS. The Camaro drives much smaller than it is but still has a 112" wheelbase, a lot of width, and the torque is used up pulling a really tall 2nd gear. The Camaro is the best steady state sweeper car likely due to camber, wheel size, and little camber loss due to the flat chassis. The Mustang S550 is hard to analyze without hard data. I suspect it slalomed closer to the M3 than the Camaro, in between the two due to the 5" shorter wheelbase and lighter weight. The gearing hurts it, very short in 2nd but the 5.0 has a lot of grunt and can make use of 3rd really well (top of 3rd is about 5-10 more than top of 2nd in the Camaro depending on tire diameter used).
Closing Thoughts
This test is only one set of data points. However, it represents some of the cleanest data available - the same drivers on the same course on fully prepared cars running the same tires. Based on the results, the M3 and the 1LE appear to be very close on this course. As with many classes it is likely that course dependency would play a factor, as a slalom-heavy course would likely favor the narrower M3, and a sweeper heavy course would likely favor the 1LE.In addition, the 2015 Mustang did not seem to be far off, and as mentioned previously 18in tires would provide for a more-useable 3rd gear on courses where it is necessary. The Shelby GT was the slowest of the group, but some of that time gap could be closed with some work on the differential.
In the end, this is only one piece of the full data set, based on one course on one day. Parity isn't necessary determined by autocross speed alone, but a variety of factors, including availability, price to purchase / run, course dependency, etc. It is ultimately up to the SEB, the SAC, and the membership as a whole to determine what fits in specific classes. Hopefully this data can be of some benefit in the decision making process.
Appendix – Thrust to Weight Chart
This chart shows the theoretical thrust to weight of each car at a given speed, a calculation using vehicle weight, gearing, tire diameter, and actual engine torque at the wheel. Effectively, this should represent theoretical acceleration G. It does not account for tire traction or various drag loses affecting the vehicles.
This can be useful for determining what gearing, weight, and horsepower actually mean, as looking at peak numbers doesn’t always tell the whole story.
