Power, how much does it really matter?

[THR]

How much does power matter to lap times?

if your in a closed formula and you say 5% down on power compared to the front runners how much would u say you would be off the pace over a 1 minute lap?

is there an easy way of calculating how much time you are loosing?

[DAVID PATERSON]

This is a very wide open question, power can be very important on some circuits and less so on others, also, weight is at least as important as power, plus aerodynamics are important too.

Less wing on an identical car can cancel out any power deficit.

All else being equal, and it never is, twice the power and twice the weight equals the same straight line speed.

As an example of the variation from one track to another, my old car had brilliant handling and huge corner speed but it was seriously underpowered. There were several cars in my class who matched my lap times at Lakeside Raceway, a fast flowing circuit, with lots of sweeping corners and no long straights or tight corners, but at Qld Raceway, a circuit that features a lot of very long straights connected by stop corners, the same cars were 4-5 seconds a lap faster!

[RMR]

I race Formula Fords 1600, using 1600cc Kent engines. Last year I was using the engine from when I first brought it a few years before and it hadnt been tuned for a while. I race at Castle Combe a fair bit and last year my times were in the 1:14 mins/sec. I got the engine rebuilt and the company doing it said it was down on power by 15%. This year im racing and im 1 second quicker. Silverstone was the same. Whether its a twisty circuit or made up of straights I think its power matters, the faster you can exit corners onto the straight the faster the lap time.

[Adam43]

The power/weight thing is interesting. It's all Newton's second law of motion. I think any improvement comes mainly in acceleration. Top speed is also effected by aerodynamics/rev limits/length of straight etc...

On this basis (that most gain comes from acceleration) then it will also depend on the type of circuit, as has been mentioned above. If it is a circuit with quick corners and short straights then, I think, the gain will be less than a circuit with slow corners and long straights.

To even get near calculating it you need to know the speeds of each corner and the terminal velocities and lengths of each straights. And even this neglects the way the power is delivered, the fact that acceleration decreased with speed, any changes in gearing and tons of other stuff.

I did however do a back of the envelop calculation (with loads of assumptions) and calculated a 10% decrease in weight and 10% increase in power was worth 1.5s around Snetterton for a car that does a 1:30 lap.

[THR]

yea.. bit of a big question really i guess!

lets narrow it to all 110mph straights, say 5 60mph corners and a lap time of 1:30, on a flat course.. and all the cars weigh the same within 10kg or 2%

[Adam43]

Where's that envelope?