School me on Brake cooling

i drive a land yacht.  it has well over double the power it was ever designed for originally.  I have done what i can with off the shelf stuff to get it to stop better (drilled/slotted rotors, better pads).  it stops great, but i do want to get into maybe doing a bit of auto X with it.  It big, underpowered for its size, but i just think it will be fun.

One issue i have read is the stock braking system can be taxed pretty quickly when pushed hard.    So,  taking advantage of some vent holes GM put in the front bumper i made some brake intake ducts.  

Now,  what is the best method of attach when doing the wheel side?  cool the caliper, just weld a bracket to the dust shield and let the air hit the backside of the rotor,   try to come up with something to push the air through the center vanes of the rotor?   I want to give it my best go,  but not sure what will be most effective.

BTW, pics of what i have done so far.   Factory,  the 77-78 cars have bumper vents.  i modeled, and 3d printed some intake ducts that mount in the stock vent holes in the bumper.  

Notice two vents in the bumper

Nice 3D modeling!

First thing I'd do is test brake temps at an Auto-X and see if you actually will gain any benefit.

The brakes don't care how much power you have available. Weight, speed, duration of braking, tire grip, and pads/shoes optimal for the temps and other things have an effect but not power.

Drilled/slotted rotors were designed for pads used years ago and typically are less desirable now. BUT, they look cool.

Those ducts look awesome! You are making me miss my caprice wagon.

For whatever it's worth, I autocrossed mine on the same brakes, much stickier tires, too much power, and a manual trans, and I never had issues with brake heat. I think I was using Hawk HPS pads? It has been a while.

Try to direct cooling air to the inner vanes of the rotor, that is generally where the air will do the most for you. If the rotor is cooler, the pads are cooler, and if the pads are cooler, the caliper will be too. I've only made few duct brackets, but typically I weld a tube to the dust shield and then weld in a little piece of plate to block the part of the diameter that would be directed at rotor face so all the air is directed into the back of the hub to go through the vanes.

Is there enough air velocity at autocross speeds to really cool things off much?

This video is when it still had the TBI 350, but I did autocross it later with ~350 crank hp and didn't have brake issues then either.

Video with the new engine but just a baseline conservative tune. I'll stop jacking your thread now.

In reply to gearheadE30 :

Hijack of thread is welcome.

as of now, I am bench racing.  Never even attempted autocross, but do intend to try.  The brake ducts can't hurt (i think??) so why not.  I enjoy the build just as much as the end result so always tinkering.

Glad to know the wagon did ok without brake fade in autocross though.  any tips or tricks on setup?   

i will try to focus the duct on the inside of the vanes then,  should be simple enough.  

In reply to Underpowered :

Keep in mind that the warmed up air needs a path to exit too.

In reply to gearheadE30 :

Just curious, I'm former a CalClub member, What location are those vids from?

New reader with Username "Underpowered" has a land yacht with "well over double" factory horsepower. Something tells me you'll fit in well here 

This doesn't have anything to do with what you've got right now but would it be easier to plumb the tubing if you used a bumper off a later caprice with the turn signals at the ends of the bumper?

Yeah, I'm really good at spending other people's money.

If it's really dire, in-line electric fans would greatly supplement the air flow at low speed, and also allow you to cool them sitting still.

In general, autocross runs aren't long enough to worry about cooling as much as total heat capacity/thermal inertia. Just talking theory here, but if you're fading in a ~60 second run, I'd rather add mass to the brake system (wider and/or taller rotors) than add airflow. The same heat energy will add more degrees to a smaller mass. 

I love the duct design, that's very much the preferred way to go for road course lapping. Most pro racers (as far as I can tell) use aircraft SCAT/SCEET tubing attached to rotor backing plates with a duct similar to your intake. If you can aim the air specifically into the internal vanes, that's your best bet. Just directing air towards the rotor makes a big difference though, since airflow tends to stagnate inside the wheel barrel.

You want to pump the cold air into the center of the rotor. It is designed to pull air from the center and expel it around the edge. 

Horsepower very much has an effect on brake temps, as the amount of kinetic energy (and thus heat) goes up with the square of speed and that's a direct result of horsepower. Weight is only a linear relationship. But in autocrossing, you're not usually running long enough to have brake problems. 

Interestingly, raising your straight line speed and your cornering speed by 10 mph will put more of a load on your brakes - even if the delta between straight line and cornering speeds is the same. In other words, slowing from 50 to 30 is less work than slowing from 60 to 40. It's that pesky exponent again.

That's a good looking air inlet, nicely done.

Will it help any to have "water injection" from a windshield washer bottle spray into the vents ?

If you're just autoxing you'll never get them hot enough to matter. If you do, you're probably on the brakes way too much. 

Just throw some decent pads like HPS 5.0 or maybe HP+ if you're really concerned, remove the backing plates entirely.

If you don't mind spending a bit more, G Loc R6 or R8 compounds are awesome.

Track driving is another deal entirely in which case yes you will want to work on cooling or increasing thermal mass or both.

iansane (Forum Supporter) said:

This doesn't have anything to do with what you've got right now but would it be easier to plumb the tubing if you used a bumper off a later caprice with the turn signals at the ends of the bumper?

Yeah, I'm really good at spending other people's money.

well, as it stands i do have a 1989 caprice parts car with that bumper on it.  but i think plumbing the tubing will be just fine with my current setup.  If not,  that can be plan B

Thanks for the tips guys.   

as mentioned above,  never actually tracked the car as of yet.  Went to LS Fest,  Auto X looked like a ball so i came home and started working on this setup.  But at LS fest, If i can get into AutoX (limited classes every year)  they do rotated between on site course and one set up at the NCM track which may bring higher speeds and such.

Gotta get this done, then find a local event to go to first so i don't make a fool of myself in front of a very large crowd next year.  

Adding thermal mass is certainly the preffered method,  as in my reading the B-body had small, thin rotors in comparison with other vehicles.  Options are slim for upgrades without breaking the bank.  They use a hub style rotor,  so it will require some heavy modifcations for a junkyard upgrade as well.  Also, it uses a larger 5x5 bolt pattern typically shared with older GM 2wd trucks and in todays world, Jeeps.  Neither of which really have a good high performance braking setup i can borrow.    The whole car was built with off the shelf parts in mind, so i would kind of like to keep it that way just simply for ease of finding replacements no matter where i am at.

Trucks do tend to have pretty burly brake setups, I would not discount them. Braking systems are fundamentally pretty simple, and the easiest/best way to get thermal mass is a big honkin' rotor. Which are often found on trucks.

Keith Tanner said:

Trucks do tend to have pretty burly brake setups, I would not discount them. Braking systems are fundamentally pretty simple, and the easiest/best way to get thermal mass is a big honkin' rotor. Which are often found on trucks.

sadly, not on trucks that share my bolt pattern.   I've already looked into them as an easy swap.     They have a marginally thicker rotor, but same diameter.  While it does provide a very slight increase in mass, i don't think the juice is worth the squeeze for such a small gain.

thus far, the best option i have found is newer jeep grand cherokee./dodge durange stuff.  they come with some burly brakes on them in as both are available with an SRT8 option.   This is gonna be how i go when it comes time most likely, but it is a much larger project to adapt the newer, larger brake setup and will require an entirely new wheel/tire combo that what i presently run.     all in due time, but for now,  ducts are the simpler, easier option with bigger brakes coming at some point in the future. 

I'll be all in for ducts for under $100.  Bigger brakes will be $1500 in wheels and tires alone,  plus actual brake cost of at least another $500.  Then onto the fab of mounting calipers and figuring out how to do the rotors on my hubs.     

Keith Tanner said:

 Braking systems are fundamentally pretty simple

no way dude, they're totally complicated and the math behind them is practically Einsteinian so the industry has to keep paying me and my colleagues the long green for at least another 7 years ;-)

Keith Tanner said:

Horsepower very much has an effect on brake temps, as the amount of kinetic energy (and thus heat) goes up with the square of speed and that's a direct result of horsepower.

Yes.  Horsepower accelerates you, brakes decelerate you.  Its the same effect, in reverse.  You can measure the horsepower of your brakes if you want.  Its likely very high for a single stop, but when it comes to repeated stops, it will plateau.  You run into braking problems on track if your brakes cannot sustain an average horsepower output greater than your engine (minus RR and WR losses).

Weight has a big effect on a single stop, but on repeated stops your car is just a kinetic energy storage device.  Being heavier makes it more efficient at storing that energy because the losses are more due to RR (linear) than WR (exponential).

In reply to Underpowered :

Not a ton of tricks on setup, but maybe some of this will be useful.

I never ran a rear bar on mine because it made 1 wheel peel problems terrible, but P71/crown vic bars can be adapted pretty easily if you want to try it.

Get a 9C1 steering box, it is much faster ratio and is valved differently so you actually have steering feel. Transforms the maneuverability of the car and can be found in junkyards pretty cheap. Read up on the steering box adjustments too, there are 2 adjustments that need to be pretty dialed in to get rid of steering box play. Makes a huge difference, and even remanufactured steering boxes tend to be set up incorrectly. Replacing the rag joint with a U joint (Flaming River or a Jeep, I think a ZJ grand cherokee? column fits) also helps a lot, but only if yours is trashed like mine was. This was the single most "modernizing" feeling thing I remember doing.

Poly front sway bar link bushings help - the pogo joints deflect a lot and you lose a lot of roll stiffness. Replacing the front upper shock bushings with poly also helps a lot - the shocks react much more quickly and positively. It's amazing how much the normal rubber ones move before the shock actually starts to work. Energy suspension makes all this stuff and it is pretty cheap.

The stock suspension was fun in a terrifying way at an autocross, but it's unbelievably soft.

Stiffer springs are as close as the Moog parts interchange. I think I ran Moog 80098 front springs and CC603 rear springs, and I can't remember if I had to trim the fronts to dial in the ride height. Stiffer springs will mean you need to get good shocks, though. I ran Hotchkis single adjustable Fox shocks for an impala SS on mine all the way around. The rears were great, the fronts still needed more low speed damping. Something from a Chevy Express 2500 was the next thing I think I was going to try but it was never quite bad enough for me to get to it.

If you are near southern Indiana (Columbus) I have a set of what I think are Moog 5662 springs you can have if you want them.

Get some ZQ8 S10 front bump stops for the front. The factory hard rubber triangles are springy enough that they kind of boing the suspension back up through rebound after they contact, where the foam ZQ8 (or rear GMT800 SUV rear stops if you end up really low) seem to be more progressive and self-damping so the suspension stays more settled after a big compression.

In reply to L5wolvesf :

There must be two CSCCs - this was Columbus Sports Car Club in southern Indiana.

In reply to gearheadE30 :

Good tips.

thus far i have a Crown vic 21MM rear bar (goin on this weekend),   front 36mm 4th gen camaro bar (also making its first appearance this weekend)

earlier this spring I upgraded to some shorter/stiffer springs.  Not much lower, only 1-1.5" all around but each spring is 50-100lbs heavier spring rate than stock per Moog's spring chart.  Cross reference for some off the shelf lowering stuff.  Shocks are just off the shelf, non-adjustable KYB's for the moment.  

springs are AC Delco 45H0181 front and AC Delco 45H3020 rear.   

All new suspension bushings all around, boxed rear LCA's as well.    All rubber stuff, as the car see's tons of road miles and the auto-x will be more of a couple times a year thing most likely.

bump stops are new to the list that I will have to look into.

After sway bars are installed this weekend, and looking into the wheel side to make a mount there, i will have the brake setup done for the time being.   Going to the dragon in a couple weeks to see how the new mods handle.

I think that step 1 is avoiding the temperatures in the first place.  Note the distinction.  You'll still be making the same heat energy, but increasing thermal density has many great effects.

Raid the GM parts bin.  It's possible you already have bigger brakes because wagon, but the junkyard has you totally covered.  Later 9C1/Impala/Caprice stuff is nearly a bolt-on.  Get later, larger discs and associated calipers up front.  Out back, you'll have to get a little more creative.  Assuming you have an 8.5" (because wagon), it's mostly a bolt-on, but wagon/sedan have slightly different hardware back there starting in 93-94.  Just do some quick measurements before you put your money down.

If you have a factory aluminum "tetris block" proportioning valve, it can be easily modified for disc/disc in about 3 minutes while still installed.

Starting with brakes that have more space for heat means less threshold temperatures.  The brakes on the 9C1/Impala SS in the 90s were way more than adequate on the street, and careful pad selection made autocross a non-issue.  

Also, if you find a 9C1 or Impala SS, grab the springs.  9C1 should drop you about 1" and they're 10% stiffer.  Impala SS should drop you 2" and are about 15% stiffer.

In reply to Curtis73 (Forum Supporter) :

the wagon does have larger brakes factory as it stands,  using the larger 12" factory rotor.  I believe it is the same size as the later SS cars were.  By going with a later rotor is the only way i was able to get a Drilled/slotted rotor as it is not actually listed for my car but thanks to GM and their wonderful parts interchangeability the rotors are actually for a 90's bubble top caprice,  just had to change to metric lug nuts.  Coincidentally the complete rear axle assembly is out of a 96 wagon, as mine originally had the oddball 8.75 10 bolt rear and i could no longer source parts for it, as going to the T56 required me to regear the rear axle.  

as mentioned above,  there is nothing that is an easy swap for bigger brakes.  the wagons use a larger, 5x5 , bolt pattern as compared to the majority of other GM passenger cars using the 5x4.75 or later 5x120 pattern.  its as upgraded as it gets for GM factory stuff really.   Even with the D52 calipers (thanks again to GM and interchangability) 

thatsnowinnebago (Forum Supporter) said:

New reader with Username "Underpowered" has a land yacht with "well over double" factory horsepower. Something tells me you'll fit in well here 

There is a build thread on here somewhere for the car.   But mild built LS 6.0/T-56/4.10 rear end.