powerband selection

[abhdrt]

i am involved in designing my first fsae car,i have few questions to ask...
1. i am starting with engine powerband selection to set my performance goal..am i going the right way?
2. i am using hondacbr600cc...as peak torque rpm changes with manifolds dimensions does the value of peak torque also change...and after all i am not going to use the peak torque due to tire and suspension constrains...can anyone please explain what is benifit of getting peak torque at lower rpm than stok?

[abhdrt]

i am involved in designing my first fsae car,i have few questions to ask...
1. i am starting with engine powerband selection to set my performance goal..am i going the right way?
2. i am using hondacbr600cc...as peak torque rpm changes with manifolds dimensions does the value of peak torque also change...and after all i am not going to use the peak torque due to tire and suspension constrains...can anyone please explain what is benifit of getting peak torque at lower rpm than stok?

[VFR750R]

your first question is right on track. Required (or desired) powerband would be a great starting point. Ideally before choosing an engine, to open up any and all design avenues. Since you have a CBR600, you've settled into a specific torque capability, and also gear ratios (which should also be figured in).

On your second question, peak torque does not change significantly with tuneup location; most things that would change it seem to cancel out (within reason). But, changing powerband width can and usually does have an impact on peak torque. Narrower powerbands typically make more peak torque and sometimes more peak power if that torque peak is also at a high RPM (but it doesn't have to be).

The second half of your question is some teams factor in that their drivers aren't in the right gear all the time. In those situations the taller gear allows you to apply all of the engines torque, and thus having the torque peak arrive sooner helps compensate for the poor leverage through gearing.

Additionally, the restrictor generally limits the ability to make torque at high rpm (limits power), so some teams figure they can widen the powerband by moving peak torque to a lower RPM without sacrificing much power to do so since they would be limited by the restrictor anyway.

[Warpspeed]

While in "theory" peak horsepower, and power under the curve is what is supposed to provide us with the highest on road performance.

This often seduces the unwary into believing that an absolutely minimal power band, and the largest number of closely spaced gears is the optimal engineering solution.

It may well be, if you have a world champion driver capable of driving it consistently to its theoretical maximum every single time.

But something with a wider spread of torque and fewer gears will be far easier to drive, be much more consistent, more forgiving, and probably even faster around a closed track with an average to good driver.

Don't get too carried away with over designing the power train, it needs to be drivable by a less than perfect mortal doing his/her best under stress.