MrWigggles

There is something else wrong with their test. If the different rotors made 12HP difference, then you should NEVER do a dyno without measuring the size and mass of the wheels, drive shaft, flywheel, etc.

For instance changes in the flywheel for instance when in a lower gear would make 10 times more difference than changes in wheel mass.

I mean forget the "15-20% losses" figure that most people assume for dynos. If different rotors were 12HP, then different wheels would change things 30HP. Different flywheel would be 30HP, drive shaft 20HP, you name it. Hey, Forget turbo chargers, just lighten the compoents and you'll get "100HP" easy.

That is until you take it to the track and wonder why your dyno results aren't matching your track results.

Big Bembo kits wouldn't sell for **** if they cost 12HP for anyone who put them on. What good is a 5% better deceleration rate if it costs you 5% acceleration (i.e. much slower 0-100-0 times)?

It doesn't add up. Somebody hit the A/C button by accident or maybe their new brakes were installed improperly and are slightly engaged without them knowing it.

-Mr. Wigggles

Lawerence

lol i wouldnt put it past those guys.

wakeech

well it wouldn't really matter if they weren't changing between every pull you were making, but *shrug* ya as i was saying could very well be any number of things related to that. if it wasn't the brakes, than it was something else, although i dont' doubt for a second that the brakes account for some of the "loss".

btw, a lower gear won't make any differene, as although it's a lot more force, the drum's maximum speed is way lower, and it would all multiply and devide out to the same amount of power.

MrWigggles

No wakeech that is not true,

At lower RPM's more energy is being stored in the flywheel et al faster. That is to say less work is being done to acclerate the car while more work is being stored in the acceleration the internal engine components. The drum would have to force the car accelerate very slowly in order remove all interial components out of the equation.

This is why top acceleration in a low gears is lower than the gear ratio would imply. For instance if you reach peak accleration of .3 g's with a 1:1 fourth gear, a 2:1 2nd gear is only going to give you .55 g's not .6.

In fact there becomes a break even point at about 20:1 (VERY SHORT) for most vehicles where max acceleration is achieved. Going to 30:1 would actually make the car slower in such an extreme case.

Don't make me do the math.

-Mr. Wigggles

Ps. You do get some of the inertial "losses" back when you shift gears. Some will be transferred to the wheels while some will be lost in the clutch as heat.

wakeech

oh please do, i completely fail to understand what you're saying.

VividRacing.com

I saw the same show. This is true that you do loose a few ponies when upgrading the rotors to larger than stock size due to the extra material and inertia created with them. Mabey that car lost 12 hp but didn't they also but a larger caliper on as well?

This is a true statement. It's the same as driving with a passenger in the car. H/P is lost due to extra weight in car. Not that much of an issue though beacuse usually when all that work is done to the brakes and suspension the car is acctually faster around the track even though it may loose a bit of power.

I'll take the little loss in power and make it up in overall handling and braking. Besides, with the upgraded brakes and suspension you can carry more speed through a turn and have better balance. That suits me fine.

Charles R. Hill

iTrader: (7)

Isn't it sorta humorous how these conversations become reduced to not much more than something akin to "Slingblade" arguing with "Rainman"? Just enjoying the reading...

Charles

MrWigggles

wakeech,

At 9000 RPM the flywheel (among other things) has X number of Joules of kinetic energy. It don't matter what gear you are in because this is before the transmission.

In low gears you get to 9000 RPM much quicker, this means the car is storing that X Joules of interia energy at a faster rate into the flywheel. Same energy in less time means more power is going into the flywheel at lower gears. This power has to come from somewhere and it is from the overall power the engine is putting out. This means that less of the power is going to the wheels.

Have Bugar peer review it if you don't believe me. He is more than qualified to check my calculations and is someone we mutually respect.

-Mr. Wigggles

Ps. Don't make me do the math.

MrWigggles

So, "This is way over my head", is supposed to be an insult?

-Mr. Wigggles