Originally Posted by
muahdib4
So, are you folks not running the spec motors? Is there going to be such a huge difference in each one that you have to do this? The only difference I can see that would make cars slower or faster are gearing, timing and how free things spin in the chassis right? If you are slower, change those things to be faster. Am I missing something here?
Yes, we are all running Ballistic 25.5 motors (one person has the SS). There are differences in every motor and at any other track you can adjust timing and gearing to make up for these differences. Before we did the RPM limit there were some very frustrated racers. Imagine you setup your car perfectly, run a clean line and not touch a single wall but you are still a full second behind the pace.
This actually happened...a lot more than you would think. We did some testing and running clean laps, in the same car we switched motors and the times dropped a full second. Yes, there are surprising differences in motors.
Due to the size of our track and the fact we want a slower class we originally decided to cap the FDR to 6.9. We wanted the class to be noticably slower than a 17.5 class. The trouble is with a 45 degree timing limit and a gearing limit is if you have a slower motor there is nothing you can do. Everyone is gearing their car to the max gearing allowed and cranking their timing to the limit. There is no room for adjustment if you find yourself the slow car.
At other tracks with no gearing limitations you can adjust accordingly to keep pace. Not so at our track. The only thing you could do is buy another motor and hope to get a faster one. This goes against the spirit of the VTA class by forcing racers to buy more gear to keep up. We needed to change something but also keep a limit in place.
I looked at serveral dyno designs and eventually we decided to keep it simple and just tach the wheels. Racers could buy their own tach at a cheap price to tune their cars as needed. The handheld tach works great.
With the new RPM limit racers need not go out an gamble that they are getting a fast motor, they can use the gearing and timing to adjust the cars to meet the rpm requirement. I know we are no where near the limit of these motors and not following the VTA rules exactly but we are having a ton of fun every Friday on out little track.