A Launch Control primer with SRT engineer Marty Jagoda.
Launch control is now a standard feature on the 2013 300 SRT, Challenger SRT and Charger SRT. The system, designed to mitigate wheel slip in a launch situation, also improves straight-line acceleration of these three 470 HP SRT vehicles. Marty Jagoda, one of the masterminds behind the system, recently sat down to discuss the inner workings of launch control and its operation.
Q: While behind the wheel, how does the driver engage launch control?
A: "With a couple pushes of a button on the center cluster. The first push from the ESC button puts the driver in partial. A second push puts them in launch control mode and it will say launch control is active on the cluster. There are also a few other things it will remind the driver of, such as if the steering wheel is not straight, or if the car is on too much of an angle, either lateral or longitudinal angle surface. More than five degrees of lateral or longitudinal incline, and the system will deactivate. It's probably not ideal to do a launch control in that instance, so the system will not let drivers perform a launch"
Q: What engine rpm range does the system operate in?
A: "With the manual transmission, the system allows the driver to select anywhere from 2,500 to 4,500 rpm in 250 rpm increments and it will remember the last rpm that was used. We started out at 3,750 rpm based on a lot of the development that was performed. We found that to be the best rpm starting spot in a variety of situations. The automatic transmission version is a little different since you are missing one pedal in the car. The engine will rev to 1,825 rpm and it will hold the rpm there until the driver quickly takes their foot off the left pedal."
Q: What were some of the challenges when developing the system for the manual transmission?
A: "With a manual transmission there is the variable of the clutch. The driver is not just two-footing it with the brake and the accelerator. Not only did we have to modulate the acceleration of the vehicle, but we needed to modulate how fast the torque being generated by the engine was applied to the rest of the driveline. Spike-loads with high horsepower, high revving engines can often lead to instantaneous wheel slip. That's the added variable on the manual transmission vehicle. At the same time you want to achieve the maximum acceleration with your best launch possible, but you don't want to degrade the clutch either. I'm sure we've all seen people out there that think they are doing the world's greatest burnout and it's really just smoke coming from the front of the car. We wanted to eliminate that variable as well."
Q: Is there a noticeable difference between how launch control functions on the automatic transmission versus the manual?
A: "The automatic transmission version is a little different, since you are missing one pedal in the car. The way you enter the mode is still the same. You'll get the same messaging, straighten your wheel and make sure the car is on flat ground. It will also tell you to apply the throttle and put your foot on the brake. It's looking for 30-bar brake pressure at the booster, that's how it knows you are in a launch control event. By the way, 30 bars is not a lot of pressure. We wanted to keep it as low as possible just for robustness of this feature. You put your right foot on the accelerator and put it to the floor and it will rev to 1,825 rpm and hold your rpm right there. You'll be two feet in on it, get your foot off the left pedal as fast as you can and the car goes."
Q: What are the optimal conditions for executing the perfect launch?
A: "The system was developed around a good grip surface. It doesn't have to be a race track with prepping, but it needs to be a good surface and our Goodyear F1 three-season tire will enhance grip. In other words, not a slippery surface. However, with that said, if you are on a surface with a little less grip or running four-season RSA tires, the system still is going to work for you. You may just get into a very small amount of wheel slip right at the beginning before the system locks you down to control that peak amount of acceleration."
Q: What speed does launch control operate to?
A: "It limits slip up to 62 miles per hour or 100kph. The reason for that is kind of two-mode. One, obviously, 0-60 is a world-renowned metric for performance. After that, in theory, you should have a good amount of grip that you won't need Launch Control intervening anymore. However, the other thing was the manual-transmission Challenger does not make it to 60 miles per hour in first gear, so we wanted to account for the gear change. If you are on a less-than-ideal surface, or you are a really good driver, you can bark or chirp the tires. As cool as that sounds to your friends, that's giving up time. We hold it through 62mph / 100 kph to get the maximum performance and also to account for the gearshift."
Q: Is there a limit to how many times the launch control system can be used?
A: "It's good for the life of the car. We actually ran with both vehicles in a pseudo-drag cycle durability test for a useful life and passed. We already know that with the manual and the rpm we are launching with, that spike loads will be worst on the rear-end. So, we fully instrumented up manual transmission cars. The half-shafts, axles, prop shafts, the whole bit. We went to the drag strip and took all the data and what the data showed us was that we don't yield. We don't fatigue any of the parts. We put the system on with no caveats. This isn't a secret mode. There is nothing secret about it. We're encouraging customers to use it. Just go run it."
Q: In a nutshell, how would you sum up the launch control system?
A: "It takes a lot of thinking out for the driver. We believe it will enable our customers in both manual and automatic form to become better drivers. Go have fun with the car. Use this mode to not only maximize the performance of your car, but also teach you. Once you've learned the car enough, you can turn the mode off or run it in partial mode and get a little bit better time. You can learn in segments how to launch these cars."