Scott Bloomquist knows a thing or two about good throttle control and how having it allows
CT - In terms of how you recommend gearing these cars, have you found that what you might call "driver preference" comes into play, too?
Wells - Yes, and sometimes this can complicate the matter. For example, you may have a driver that has really good throttle control with his foot and will want an engine that's really powerful. He'll hunt for the tacky spots on the track. Then you'll get another driver who wants to gear the car higher to where the engine is really "soft" most of the time, so he doesn't spin the tires because he doesn't have the good "foot feel" like the first driver I described. So the bottom line is that no two drivers will want the exact same thing regarding where the engine makes power or how the car is set up or geared.
CT - So is it fair to say that with the number and range of variables that come into play, it's difficult to lay down any hard and fast rules about gearing for all circumstances?
Wells - I think a more accurate way to look at this is to say there are some "guidelines" to be considered, not strict rules.
CT - Let's talk about guidelines.
Wells - Well, first you need to consider that some of the variables over which you have no control, like track conditions, weather, on-track traffic, and other uncontrollable factors, not only change from week to week but even during the course of a race. So what I'll call the "gearing target" is constantly moving. So black and white steps just aren't practical. However, there are places on the track where you'd like more power or torque than others. This is especially true during corner exiting. In our experience, you'd like the engine to be geared where it's slightly below peak torque rpm when you begin to exit the corner so it'll accelerate toward peak power in the straight. Based on track conditions anticipated, this will provide you a starting point from which ratio changes or driving technique can be adjusted accordingly to fit the needs of the track. We've also found that this approach will help compensate for traction problems during corner exit. Of course, much of this is a compromise that's driven by the fact that there are variables like the ones we mentioned, over which you have much less control than when selecting gear combinations.
CT - Let's go back and talk a bit more about where you think engine rpm should be when corner exit begins, if you're running a longer stroke combination. Stroke and rod length, all else being equal, can affect the rpm span between peak torque and peak power.
Wells - That's right. In these cases, where the rpm between peak torque and peak power becomes more narrow, you'd probably want to gear the car to a slightly lower rpm below peak torque so you won't run out of rpm between there and peak power during acceleration onto the straight. Normally, these guys will run a higher gear ratio than those with the shorter-stroke engines, primarily to compensate for how the longer stroke affects low-end torque.
CT - OK, where else on the track do you consider gear selection critical?
Wells - Some of the drivers I work with like to use lower gears to help engine braking during corner entry, rather than rely more heavily on the brake pedal. Of course, like in so many situations, compromise enters the picture. For example, gearing lower for braking into a corner means the car will try to accelerate more quickly out of the turn, but the tendency to break the tires loose is increased. Depending on traction conditions, this can become another problem.