On sports car revolution they prove with the mugen acura that by adding a larger diameter brake even though the brake is lighter, you will lose HP

I had no idea b/c every body keeps talking about unsprung weight.

I'm glad I can't afford the brake kit

 

People that go for larger brakes need it to help stopping for the extra power of their mods. I'm sure they don't mind losing a little hp as long as it prevents them from crashing due to insufficient braking.

 

yea... the hp loss probably isnt significant enough. stopping is more important than brake fade and overheated brakes

 

It was about a 12 HP loss: I saw that too. The brake was lighter, but had more mass farther out. the fact that it is lighter would help handling, since every time you'd hit a bump, you'd have less unsprung weight pushing back on the car. But, since the weight of the wheel is farther from the center, it takes more energy to spin.

It's the exact same thing that people argue against 19 and 20" wheels: even if they are lighter, they can suck up more HP. But, yes, if you are having problems with fading, you should upgrade your brakes, but most people get them for looks only, IMO. I have yet to experience ANY fade while driving in the street, and only a little at the one (granted it was relatively short) track day I did.

 

I saw the show, and I have 2 things to point out:

1 - The 12 hp loss was with the stock exhaust that they re-dyno'd with after they noticed that they had lost 5-7 hp with their new exhaust.

2 - As the Z is a rear-drive car, as long as you only put the big brakes on the front wheels (where they do they most stopping work anyway,) then you technically won't lose any horsepower at the wheels on a dyno, as your drive wheels still have the stock size rotors. Obviously, you could still see a slight decrease in performance off the dyno, as the fronts still have to be made to roll.

But in my opinion, it's a moot point, as those few HP lost would seldom (if ever) be noticed on a road course, whereas the benefits of the big brake kit would be noticed at every turn.

I will admit that it was an interesting point they made on the show, but (IMHO) not a valid reason to not get a big brake kit if you take your car to the track.

Gary

 

Gary,

Agree completely. The interesting thing I took from it ws, if lighter but slightly bigger brakes can make that much difference, how much of a difference does going from a 17" wheel to a lighter but wider 18", 19", or 20"? That itself might necessitate the need for bigger brakes, as well (but also causing even more loss). Makes a good argument for 17" track wheels, and give me one more reason to not go any bigger than 18 on the street.

 

So is this the same kind of thing most people have done in physics class: you sit in a chair and you're spun around. As you put your arms and legs out it goes slower, but when you bring them to your body, you speed up?

I forgot the name of the thing, but it's the concept that I'm trying to show.

 

I think it is exactly that: conservation of angular momentum.

For example, if you had this mass, and you double the radios, it makes it 4 times harder to spin the object (4x as much torque required to reach the same speed) .



At least, I think. I'm a EE, not an ME

 

yeah more rotational mass = bad...

hence my 7.25" clutch