Power / weight ratio racing

[ger80]

Dutch supercarchallenge used power / weight ratio to divided the different cars into classes. I like it because you dont need to run the engine on the limit without losing the possibility to win races.
But with engine mapping its very easy to cheat.
Maybe someone knows how other series solve this problem

[Tim Falce]

How would it be easy to cheat by doing some re-mapping? In our series here, if you alter your power to weight ratio you change classes

[graham bahr]

i think the kumho bmws are classed according to power to weight, and all have to be run on a certain rolling road to varify the power. cheating would be very easy with modern ecu's and not obvious unless it was a boring one make series.

a schrick motor meter can be used to moniter power, well sort of, all it does is meassure the engines acceration rate off load when the trottles floored, in theory if you increase power the engine will rev faster, however if you increased the engines power and made the flywheel heavier by the right amout as far as the power meter is concerned the engines power is still the same, and that still wouldn't stop someone having a clever switch on an ecu to switch between a "testing" and a "race" map

[ger80]

Well, you go with one mapping with less power on the dyno and after that you remap the engine.

[Tim Falce]

Originally Posted by graham bahr

techy stuff

Oh, that kind of cheating, but that's not gentlemanly is it.

[ger80]

Maybe datarecording unit from the series with RPM and torque sensor is a solution. found something @ http://www.piresearch.com , but think that will be very expensive for a club racing series or not?

[Al Weyman]

I think a car with say 250bhp and weighing say 700kgs would easy beat a car with 500bhp weighing in at 1400kgs although they would be classified the same. What about breaking and handling they have far more influence on a fast lap than shear power amd the lighter car would definitely out brake and out handle the heavier one all other things being equal. I think it is a poor way of classification and would only be relevant in drag racing. I read somewhere Chevrolet used to dominate SCCA (I believe) racing in america with a V6 Camaro until Ford entered the lighter Mercur Turbo with 500 odd horse power and wiped the board. It is the same with the turbo powered and lighter cars today against that big old Monaro, it can't hold a candle to them

[graham bahr]

al's got a good point, whilst light cars with a good power to weight ratio will match the acceration of a heavier car with the same ratio, it doesn't stop there, the light car with its lower power cannot match the heavy one in terms of top end speed, a high top speed relies on pure power rather than power to weight

[PoloG4tracer]

The VW Racing Cup uses power to weight as an equaliser, 200bhp/ton. But we found last year when my friend raced his Polo G40 in the championship that although he had the same power/weight and was lighter than the rest of the field generally, it didn't help him much (ok, first year of racing so lack of experience will have counted) because the other guys had him on the torque that their turbo'd cars, TDi's etc put out.

[Al Weyman]

Good point Graham, top end speed and frontal area all things being equal there would for example not be much difference in the CD of my black Mk3 Camaro than your BMW infact I would say the Camaro was slipperier so in that case it would hit the higher speeds than you lighter car but there are not many tracks where you can do speeds like 170mph plus and even then you have to stop the thing so I would say the smaller lighter vehicle would win hands down on the majority of UK circuits which would not be a problem apart form the fact that with this form of classification (power/weight) we may well end up in the same class and the highest capacity class does not always win overall in fact in the ModProds several years ago rarely did.

Also a good point GTPolo, torque is very important for a good lap time, I once built a 400cu engine that had over 400 ft ibs of torque at 2000 rpm (dynoed not make believe ) it was crazy shame it did not live long.

[graham bahr]

Originally Posted by Al Weyman

Also a good point GTPolo, torque is very important for a good lap time, I once built a 400cu engine that had over 400 ft ibs of torque at 2000 rpm (dynoed not make believe ) it was crazy shame it did not live long.

i can it believe big engine = big torque, and having seen a fairly std TWR v12 jag mapped to suit an aftermarket ecu on the rollers make monster torque, cant remember what peak torque was but it made 300lbft @ 1,000rpm!!

[graham bahr]

i would suspect any circuit that produces top end speeds of over 130mph would start to heavily favour the big power heavy cars

[Al Weyman]

OK then if I come out for a few rounds next year you won't see me at Lydden, Brands Indy (just maybe as it is Brands after all) and definitely not Micky Mouse kart track Stowe, where else will you be where I can stretch me legs? Incidently the black camaro will be in the shop next week in preparation for next season, the yellow peril is ready to rumble. (Still relevant to the thread as we are talking heavy powerful cars here!)

[jonners]

gearing also has an effect and the Kumho regs don't take this into account

bhp is not a real world value - power to weight formulae should measure torque/weight

also, you racer types are probably quite good at sandbagging...

[Al Weyman]

I think in a one make challenge like BMW's Kuhmo it may work (well it does obviously because the championship is successful) but for something like ModProds, CTCRC or TRC which is for a vast array of different machinery it is a none starter. I think the CTCRC are kinda on the right lines with there minimum weight per cc classification and works well for the pre 73's for example where I run the old yellow tub but unfortunately I think the new 93 series that I may have ran my 88 IROC 3rd Gen Camaro in it does not work out at all well for me at least because more modern cars are lighter and that car from the factory fully trimmed comes in a fair bit lighter than their imposted weight limit for 5800cc so there is no advantage and I may as well run the older heavier car cause there is absolutely no way I am gonna go out there and bolt on 150 kgs of lead in the thing .

[Tim Wilkinson]

Al, as modern cars are lighter maybe the pre-93 regs will give lower minimum weights than the regs for the other series that you're basing your assumptions on. As I understand it the pre-93 regs were to be of a similar ilk to those of the other CTCRC series, but that does not mean that they will be identical.

Have you taken up your weight issue directly with Stacey or another member of the CTCRC committee? Maybe this is something that was discussed at the recent meeting?

Quite a few series run with minimum weight limits, rather than a power / weight ratio. That can work well when developed over a few seasons and only a limited number of cars can compete (eg Stock Hatch), but for something like TRC where the grid variety is much greater it seems a little too tricky to use effectively.

[Al Weyman]

As I read it they were to be the same as the current pre 90 regs which means I would have to ballast the car to weigh in at 1450kgs from memory, it is 1300kgs at the moment and has not been over lightened and is all original steel and glass, with the multu point roll cage etc it probably only weighs slightly lower than stock which is why I built it as they came out the factory many many kgs lighter than any previous models in fact the later 4th gen cars are even lighter using many plastic body components.

I agree however that my heavier Mk2 car is fine within the regs and will continue to race it with the CTCRC in fact it is now already to rumble. It is about spot on the limit as it is so I have no problem there and it also means that Minis and Cortinas can give you a run for the money which is good surely. Who wants to go out and totally dominate the proceedings and not get a race, well I know some people who do but not me :-). I think I may take the later car out with the TRC boys as it slots nicely into their new class B regs and they do not have a minimum weight limit but as I say I will still continue with the old car in pre-73 as I enjoyed the racing for the brief period I was envolved.

[greenamex2]

Originally Posted by teej

modern cars are lighter

Minor point/nit picking if you like but almost all modern cars are HEAVIER than there older equivelents, particularly out of the factory.

OK a lot of the stuff is 'rubbish' like aircon, sound proofing etc that most series let you chuck out but a awful lot is extra metal for safety, additional passenger space etc that most series DON'T let you chuck out.

[Tim Wilkinson]

Sorry, I should have put "as Al says" as I was just replying parrot-fashion.

I have to admit to not paying much attention as my Astra is well over any 2l weight limit, even tho it weighs less than a Saxo.

Al - maybe a case for a "min weight of xxxkg or production weight, whichever is lower"?

[Al Weyman]

Teej, off topic but noted you have an Astra, I have a pair of Astra caliper mounts that came with some Bremsport calipers I bought off ebay, must be a common caliper spacing size because they bolted straight on to some mountings for a BMW 7 series caliper I made a long time ago. Yours if you want them, they are extremelly lightweight, don't want nothing for them or if anyone else wants them.

Yanks may be an exception to that rule Dennis as the yanks had a big problem metting CAFE fuel economy rulings so did a lot of lightening, I believe the later offerings came with all alloy engines as does the Monaro (I believe)which is an American designed car. I think the 2nd gen camaro went on the scales at something like 3800ibs or something rediculous, the 3rd gen came right down even having a plastic bonnet (hence my legal fibreglass bonnet!).

[greenamex2]

Al, I think the sceptics were getting desperate to get the cars through the average MPG/emissions rules!

My car weighs about the same as the next gen Corolla, but after that they larded up by about 200KG!

[graham bahr]

any one read the lastest issue of MSA motorsports now?

its got the longest judicial report i've ever seem in it, relating to a VW cup car and its power to weight ratio!

[graham bahr]

although no body quotes it a torque to weight ratio is just as important,

my beemer and AW64's escort have very similar power to weight ratio's, but the beemer just blows the escort into the weeds in a straight line why? look at the torque to weight ratio i've got a huge advantage.

[Al Weyman]

Was'nt arguing about Junior Cadet Karts then Graham, they often make good reading especially the one where the father of the kid through the (he claimed) underpowered kart engine through the caravan window of the engine supplier! Great stuff

Yes I know what you mean with the Corrolla Dennis but the 3rd Gen camaro had a shorter wheel base and was based oin the Vega/Monza floor pan and was substantially lighter and smaller than its goliath parents. It also dod not have a great big subframe up front as the earlier cars had, and a double skinned roof and massive steel bumpers.

[greenamex2]

Can't remember the last time a manufacurer made the model of a car SMALLER. Must be downsizing.

I like the kart reports where two Dad's have been taken lumps out of each other for some really petty reason. Go back to football for gods sake!

Having said that my Dad was going to thump the last bloke who hit my car. I suppose I am ONLY 36!