Following on from Michaels Fast car thread..

Some interesting view points and perspectives in that thread.

In particular the talk of BHP/Ton and actual weight of cars. The recent R500 Caterham (426bhp/ton) beating the Veyron (534bhp/ton) around the top gear test track means that (and yes i'm ignoring many factors like weight distribution, suspension setup, tyres etc etc) the overall weight has a significant effect on lap time.

Take a stock supra at say 200 bhp/ton (1520kg car 80kg driver and 320bhp), and a BPU++/Hybrid TT with say 250BHP/ton (same weight and 400bhp)

If you added ballast, like a touring car weight penalty* to the BPU'd one to equalise the BHP/ton it would be 400kg heavier and so slower round the track.......is there anyway to estimate the weight you'd need to add to reduce the BHP/ton of the bpu car but leave it enough of an advantage to make up for the increased all up weight and so they lapped the same?

My gut feeling very rough guess would be the BPU at

1900kg ie 211bhp/ton and 300kg ballast = slower than stocker

1800kg ie 222bhp/ton and 200kg ballast = approx match?

1700kg ie 235bhp/ton and 100kg ballast = definitely faster than the stocker

I know its not an exact science without circuit details etc etc but is there anyway to estimate this power vs weight outcome for the same type of car which limits the variables?

* off to look into this...

Ah, but will it take off?

Ah, but will it take off?

Oh God not again!

Right thats it ..

Get in the back of the van.

Right thats it ..

 

Get in the back of the van.

 

The van? Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! The back of the van?

Right thats it ..

 

Get in the back of the van.

 

The van? Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! The back of the van?

love it here!

Right thats it ..

 

Get in the back of the van.

 

The van? Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! Van! The back of the van?

Be gentle with me. Promise?

.....means that (and yes i'm ignoring many factors like weight distribution, suspension setup, tyres etc etc) the overall weight has a significant effect on lap time.

Whilst I agree with you that overall weight does have an effect on lap times (my gut feeling would be that it's due to increased centrifugal force requiring more grip and therefore limiting cornering speed), I think it's probably a much smaller factor than the suspension, tyres, etc. that you mention.

Whilst I agree with you that overall weight does have an effect on lap times (my gut feeling would be that it's due to increased centrifugal force requiring more grip and therefore limiting cornering speed), I think it's probably a much smaller factor than the suspension, tyres, etc. that you mention.

yes but considering the supra vs supra scenario.....where would you put the importance of weight over power.

1600kg and 200bhp/ton stock car

1800kg ie 222bhp/ton so 200kg ballast = approx match?

So 400bhp but with x2 15/16 stone passengers, up against the stocker, who's quicker?

Bascially is there anyway to at least estimate this?

Well - I guess that going by my previous argument that a heavier car requires more centripetal resistance from road grip and ALL other factors being identical (let's assume that the extra passengers balance the centre of gravity to exactly the same position as the stocker), then I think you're right - the lighter car will be quicker.

As I think the difference will be in corners, the difference in performance (lap times) will be entirely down to the circuit layout. That's where your calculations will have to be applied!

I think.

PS. hope you had a good Christmas, mate!

yep ta mate.....

I know it'll be alot of guess work, i'm just trying to get a feel for it.....

I'm looking at getting a cheap NA and stripping it so I was trying to see how light it would need to be to get to the bhp/ton of my old stock uk of just over 190, realising this was all but impossible it occurred to me that it wasn't necessary as at some point the lower all up weight will make up for the shortfall in BHP/ton.

I feel 170 bhp/ton is possible for a heavily stripped na.

So one would be 20bhp/ton better off but over 300kg heavier.

Something to consider as well is that, IIRC, a lightweight car will suffer more when you add weight (the driver) than a heavier car.

I think I've got that right. I'm sure CW will be able to add more.

Llandow, the dream machine around there would be a modern gearbox kart, no two ways about it. Would probably be quicker than andF3, or even maybe a modern F1. Some circuits favour handling, some outright grunt. Outright lap record at Cadwell, which is no Mickey Mouse track by any means, is held by Nigel Reubens in a 600 cc bike engined, relatively very cheap Jedi single seater.

Not sure what this tells me but i did some digging on BTCC cars and i think the Astras have 300ish bhp and weight about 1050kg's and the max 'success ballast' is only 45kg.

For 1st to fifth it ranged from 45-36-27-18-9kg

Outright lap record at Cadwell, which is no Mickey Mouse track by any means, is held by Nigel Reubens in a 600 cc bike engined, relatively very cheap Jedi single seater.