This is controversial!

I don't race, so maybe I'll mount fog lights in the intakes instead. There are some mounting holes in the surrounding plastic behind.

 

[QUOTE]Originally posted by E30M3:
[B
<Dunno if I agree with that. If the rotor shield is there to dissipate heat, then cooling the shield should be as good as cooling the rotors.>>

You don't cool the discs by cooling the splash shields.

 

Mingster-









We are working out a revised production process with the brake ducts (should be available very soon). The front spoiler will be quite a bit longer before production (although I do have three in stock right now).

Ben
Bulletproof Automotive Inc.

 

I said: You don't cool the discs by cooling the splash shields. You need to cool the rotors.

And Luis said: That will be true if the shields are not heated as a result of braking, otherwise I stand by what I said, it's pure thermodynamics.

That's not really how the physics of the situation work. Why not cool off the motor by cooling off the car's hood and skip the radiator? There are no race cars anywhere cooling off splash shields to cool the nearby disc brakes.

This is because it's ineffective since it's so indirect.. Not enough heat energy and too much time lag. The heat reaching the splash shield comes in primarily via radiant means and via conduction of heat coming in from the spindle mounts and from nearby air. There is no contact with the disc. The car's kinetic energy is converted to heat at the interface of the pad and disc surfaces. A large quantity of air with a large great a delta Temp is needed. Racers have found that you need to do the cooling where the heat is generated.

BTW if you reduce speed from 60 MPH to 0 and compare this with slowing from 120 MPH to 60 you see the same 60 MPH speed differential. But the higher speed instance needs to disipate 4 times the energy of the slower example.

The splash shield holds heat into the rear of the disc due to the reduction in air flow. Rather than cool the shield, ditch the shield. Or if you want to keep it, you can still cool the disc properly as previously described.

Stan

 

E30M3-

I agree with most of your points except one- never ditch the dust shield, because it protects the rotor from the elements in the back. Without this the rotor is very exposed- not necessarily a good thing for a street car.

My ducts are as Greg Stevens described. The dust shield is cut and a hose adapter welded on to affic the hose. The adapter is welded onto the backside of the shield, as near to the center of the rotor as physically possible. A close relative (some would say- from where it was "plagarised") can been seen on Porsche race cars from the late '80s, from which almost all the brake ducts around on street cars have been copied from thereafter in one form or another...

The brake ducts were a necessity because I faded the stock pads in 10 minutes at a local track. I don't know if it's worth the hassle blocking the ducts for normal street driving- although I do understand your collective concerns. Another concern that was raised by a friend of mine is that the relative uneven cooling effects *may* prematurely crack the rotor. I think I'll test the theory out- but King hasn't had any problems with that type of brake duct on any of their Motorola Cup cars or Speedvision Cup cars they prepare for others.

-Nick

[This message has been edited by GTRPower (edited November 25, 2000).]

 

<<I agree with most of your points except one- never ditch the dust shield, because it protects the rotor from the elements in the back. Without this the rotor is very exposed- not necessarily a good thing for a street car.>>

Thanks.

FWIW I have run without splash shields on several different dual purpose cars for nearly 10 years and find no problems whatsoever. BUT I dont drive in muddy, heavy rain conditions much if at all. If you want to keep them, keep them. If not, you are not gonna destroy your car. Some folks are able to easily bend their shields back away from the disc for track events. And then move them back for the rest of the time. The shields likely increase the life of the rear of the disc a bit under adverse conditions. Sometimes they also provide mounting points for other components such as ABS wires. And they can also shield ABS sensors and rings, wheel bearing seals, etc etc. For sure they hurt cooling under heavy braking conditions and so hurt life in that instance. So if you understand your true needs it should be easy to figure out what will work for you. I have eeen cases of about 8 times longer pad life, 3-11 times better disc life (premature warpage), nearly lifetime wheel bearings, etc when adequate cooling is achieved for the brakes under track useage conditions. My point is that any mods to a car need to take into account the intended use.

Stan

 

[QUOTE]Originally posted by E30M3:
[B] Why not cool off the motor by cooling off the car's hood and skip the radiator?

 

Don't know what is the relevance of this assertion. But at the risk of stretching the limits of my memory I believe the number is actually 3.

Proof:
Energy spent in slowing a vehicle in motion is directly proportional to the mass, the deceleration and the distance.

Assuming it takes the same time to bleed off those 60mph, then the deceleration will be the same. However, from 120 to 60 you'd cover 3 times the ground you'd cover from 60 to 0, hence 3 times the energy and not 4.

QED?

 

Kinetic energy is proportional to velocity squared. So the ratio of energy released is (120*120-60*60)/(60*60-0*0)=3
Thus, Luis wins the physics quiz

 

Kinetic energy is proportional to velocity squared. So stopping from one speed versus twice that speed reflects four times the energy. For just a snub (which is a reduction in speed via braking without stopping) we need to subtract out the first speed. So 4-1 = 3 times as stated correctly above. My statement should have shown something like the 2nd sentence above. I'm glad to see that I've got some of you guys thinking a bit!!

Someone asked why I brought up this kinetic energy thing. Because it helps shows why you need or don't need additional brake ducting depending upon your use of the car. Most folks think that dropping 60 MPM uses up the same amount of energy in all cases but it doesn't. It depends upon things like the starting and ending speeds.

This means that brakes and cooing approaches are adequate under certain conditions may not be under others. Another interesting point is that fade and pad wear happen at the same time and that there are various types of fade with diferent causes and effects and related solutions. If you are wearing out your pads quickly under track conditions then you are experiencing fade whether you realize it or not. It's enlightening to review the friction verus temp versus wear charts for different par compounds.

Stan