Power to weight advice

[TobyLaRohne]

Hi guys, we have power to weight ratios coming in next season and I was wondering if some of you guys with more experience could give me a running start on what angle I should try with regarding to getting the best setup from my car...

I race at only 1 circuit, Losail. Which is a pretty fast circuit with lots of high speed corners (average corner speed over 70mph) and it has a few pretty long straights.

At the moment the rules are not released but we're expecting a Power to Weight ratio of 6.0kg per bhp to be set.

For me that means either

1) Adding 106kg to the car and leaving the power as it is

2) Losing 18 bhp and no weight addition

3) Losing 10bhp and adding 50kg

I'll add that the car is very well setup and currently runs about 200bhp at the wheels and is 1100kg with driver and 40kg of ballast where the passenger seat is.

What would your natural inclination be to go with?

[andycaca]

I would be inclined to leave the weight as it is and lose 18bhp. we all know weight is the enemy of any racecar.

<- sprint racer with a few years experience

[Cyder]

Without knowing what you race, and without being an expert in any way shape or form on engines would it be possible to do something with the tuning to reduce the peak power but change the torque/power curve to compensate a bit?

As said I know nothing about engines, so could be talking utter pish!

[McSam]

For a fast circuit, you generally want as much power as you can get. This is because the quicker you go, the more important power vs aerodynamic drag becomes. Weight is of course bad in every respect for a race car (or indeed any car), but at high speed (>100mph) it has a much less significant effect on your acceleration performance. Having enough power to overcome aero drag what matters most.

For circuits where you have no chance of getting up to a decent speed, the lightest car will work best. But for a circuit like you're describing, hang the weight and keep as much power as possible, because it's going to work for you at high speed. Plus it's a damn sight easier to pass someone through overspeed on a straight than it is through a 2mph corner speed advantage!

Obviously it depends on the car and the tyre, 106kg is a hell of a lot and it might knacker your nicely sorted setup. Try it out and see how it feels, if it still handles and stops OK and doesn't nuke its tyres, I think that might be the quickest solution.


I'm speaking in general terms and your experience may vary but it'd be interesting to know how it turns out.

[Jacobyte]

Reduce BHP by moving the torque further down the rev range with a different cam profile (if regs allow).

[TobyLaRohne]

Regs will allow ecu tuning if the power to weight is introduced, the engine is a k20a.

Thanks for the responses guys. I'm kind of reluctant to add alot of weight to the car because of concerns if I have a big shunt I dont want it breaking loose in a high-g accident and killing me...(remote possibility I know)...perhaps I'm being paranoid.

[McSam]

Hmm, I hadn't considered the prospect of physically adding 106kg to a fairly lightweight car. I'm sure seat rail eyes would stand up to it, though, it's not the heaviest thing you'd ever have in the passenger seat!

[RC Developments]

In my experience with this in Lotus Cup it depends if you can drive fast enough in the corners to take advantage of the lower weight. If not you may be better off with more power. maybe consider switching to fly by wire throttle and reducing throttle angle at high rpm to reduce max power..

[350Matt]

thing is engine tuning to shift the power peak down and gain torque is going to be a lot more expensive than bolting lead ballast to the floor of the car

one advantage of doing this is you will shift the CoG down by quite a lot so teh car will roll less and corner faster anyway