o0Dan0o

http://www.racerpartswholesale.com/ everything a weekend racer (and more) needs.

Mahjik

iTrader: (1)

http://www.racerpartswholesale.com/duct.htm

o0Dan0o

I think we are of the same mind on a lot of these issues, and you do have a point with not needing nearly the stopping power on a 2800 lb RX7 than a 3500 lb f-body. But my point is simply that you can never have to good of brakes. Now, will adding brake ducts possibly cover up some improper braking techniques, certainly but so will putting on race pads. One could change their pads out every track day to race pads, or one could use dual purpose pads, I used Pagid oranges which are technically a track pad but did fine on the street, and add ducts to ensure that the brakes stay at appropriate temps for the pads. Either way we get to the same ends except the latter doesn’t change pads.

Let’s also not forget that race pads are harder to predict and control, and are note for the novice driver (although a novice driver should not be pushing his car hard enough to need ducts either). Simply put, I completely agree with you that the appropriate pads and fluid should be chosen first a foremost, but IMO (with respect to yours) brake ducts are simply cheep insurance. Evaluating ones driving and improving it is very important, but (again, IMO) not at the risk of roasting your brakes and flying off the track.
Dan

primerGrey

iTrader: (13)

Some other questions:

1) Has anyone tried an inline blower motor? I was wondering if such a thing were possible, and lo and behold it is actually sold... for $32 bucks.

See http://www.pegasusautoracing.com/pro...asp?RecId=2771

2) Is there any prayer that the combination of a cooling system (ducts, blowers - whatever works best) and the higher temp brake compounds available today (e.g. CarboTech XP10 or XP11), could allow an expert driver to survive with the stock brakes and rotors, on a track that is "hard on brakes"? I suspect many will immediately say no - while I would like to hear why you think so, I would especially like to hear from anyone who has made the attempt.

My experience (by no means extensive) - I have so far gotten by without ducting on the stock rotors and calipers with XP10 pads at Thunderhill with absolutely no fade, but I am running through the pads in a day, vulcanizing the front piston dust boots (getting holes in them in a few spots), and the guy who turns my rotors says he almost couldn't cut the last set I gave him (although I am not sure why that would be - maybe heat cycling the rotors hardens them?). And I know Thunderhill is not a track that is considered really tough on brakes. I brake as late and hard as I can - I'm not early on the brake, and I don't trail brake in the turn.

Why bother trying? I like the stock look, BBKs are expensive, and smaller rotors and rims do mean less rotational inertia, although I haven't calculated whether it would be enough to really matter.

o0Dan0o

1. Even if the air going through the duct is only going 1mph (honestly, I don't know how fast it might go), the duct is still flowing ~622 CFM. I simply don’t think that fan is going to do the job of a proper duct.
2. I certainly think one could get by with the stock calipers and rotors if you use good pads and a good duct setup, but that would probably only be for a mildly modified car. I think you could quickly outgrow them with sticky tires and HP… The added capabilities can easily overcome the increased moment of inertia.
Dan

Mahjik

iTrader: (1)

primerGrey,

The simple truth is, you'll have to find out on your own. Each car/driver is going to be a little different. A lot of FD owners (including me) have had great success using the stock brakes and N-Tech track pads:

N-Tech Brake Pads

However, others have needed to go with a BBK. I have run my car with r-compound and the N-Tech Lapping Day pads without a problem. I would say back then I was running about 310rwhp at the track (mostly Heartland Park). I would say that there are probably some tracks that going 9 or 10/10th the stock brakes with tracks pads still may not cut it. Adding some ducting in those cases would probably keep the stock calipers/rotors in check.

primerGrey

iTrader: (13)

Thanks for the feedback DanO. Your numbers made me do the math, and I am getting something different. Let me know if I screwed something up:

Blower is 140 CFM
3" DIA tube has an area of pi*(1.5/12)^2 = .0491 square feet

140 CFM/.0491 ft^2 = 2851 linear ft/min

2851 ft/min = (2851 * 60 min/hour) * (1/5280) mile/ft = 32.4 MPH

So assuming no friction in the ducting (or the blower located at the inlet so that both cases see the same pipe friction), break-even would be 32 MPH. Above that, seems like the blower is in the way and below that, the blower is helping. Now, the NTech backing plate actually has a much smaller exit area then the 3" tube, so maybe the number is higher. If it is exit is half the area of the tube (I actually remember it being less then half, but it is in the car now and hard to check), break-even would be at 64 MPH, which is starting to sound pretty darn good.

o0Dan0o

Yeah, well if the tube dia was 3 feet!! Sorry, I always forget something...

I get ~4.4 CFM per 1 mph airflow rate, which corresponds to what you have. Now, this is assuming that the flow rate through the ducting is equal to that of the cars, which I highly doubt. It’s hard to say what reduction there would be, but there would be some. Of course this is also assuming the blower motor puts out 140 CFM through a restrictive ducting setup, but again your guess is as good as mine as to how much lower it will be. I wouldn’t bother with it, but it is cheep enough to give it a try.
Dan

EDIT:
You got me thinking about this. The way brake rotors are designed, they are centrifugal air pumps, so when the rotors spins air is forced from the center of the rotor through the veins and out. The efficiency of the rotor at doing this greatly depends on vein design, and the rate at which air flows through the rotor is dependent on rotor speed and efficiency. I believe the rate should also increase with the diameter of the rotor, minus any increased restriction. Anyway, air coming in through a brake duct is not at a much higher pressure than ambient (which is why “ram air” systems are basically just cold air systems), so the duct isn’t forcing air through the rotor, rather it’s just supplying it with cooler air. Now, the thing is even though the blower motor will likely provide more pressure than the brake duct alone will at any speed, I doubt that most backing plates fit close enough to use that pressure to force air through the rotor. Even if it did, I don’t know how much pressure that blower can produce, but I doubt it’s enough to significantly increase airflow through the rotor. Simply, when at low speeds the rotor is spinning slowly and isn’t flowing much air through itself, so the lower velocity of air through the brake duct is not an issue since the blower wouldn’t be forcing air through the rotor. On the other hand, I believe NASCAR does use something like this, so I could be way off base here…

Section8

iTrader: (6)

Thanks for all the input guys, some great setups in here.

DamonB

If running stockish horsepower and street tires the stock brakes with a decent pad will be ok at most tracks as long as your sessions are short and you don't try to punish them. Once on R compound tires I have to run a true track pad or I'll overheat the brakes within a couple laps.

Ducts are great if you need them, but it's just as bad to run a race pad too cold as it is too hot. Too cold and they will wear rotors much more quickly. Ideally you can zap the rotors with a laser temp gun to get an idea of what your brake temps are. If you find that the more laps you turn the less effective the brakes are (even though the pedal is high and hard) you're overheating the pads.

Brakes run cooler with longer, less aggressive braking distances than they do with short aggressive ones.

...those blower motors others are talking about aren't really intended to be used at speed and it's pointless anyway. You still need a hose and duct to stick the motor in and if you already have that you don't need a blower! Those motors are typically used after the car has stopped. They're plumbed into the brake duct openings to cool the rotors while the car sits.

CrispyRX7

iTrader: (139)

Hawk Blue pads on stock sized brakes (and GOOD fluid) will work for a novice driver on reasonable tires *but* may lead to premature demise of brake rotors and potential for early brake piston seal failure. Back in the day I was rebuilding my front calipers once a year at the end of the "season" to be sure. I applied temp indicating paint on the rotor hub and pad backing plate and the pads were right in their optimum range...or at least peak temps were. Thsi was on Street tires. In that situation this combo did fine...***with proper routine inspection and maintenance.

Fast forward to current day. I run an AP front BBK with '99 RZ rears on 2 piece rotors, Perf. Friction 01 front and 99 rear compounds, ATE superblue or Motul 600 fluid, on 275 width Hoosier tires. Temp strips on the *exterior* of the calipers show I'm nearing the max temp range of the fluid. The brakes hold up ok but I've overheated and cracked a recent set of front rotors (slotted) after less than a dozen track weekends. In short the rotors are cooking under peak braking. Oh and the VERY first corner of a hot lap at SPR (145 down to about 40) is enough to fade the Ferodo street pads in my AP calipers. ONE corner!

Given all that, the only real way to tell what's happening with your brakes is to measure temps. Temp indicating paint or temp strips are cheap and easy to apply. They will tell you EXACTLY what you need to know. My suggestion: get your data first and only then decide what is best for your application. Personally I KNOW I need better ducting as do some of you other hotshoes. Some people on the other hand may be just fine with a decent set of track pads.

FWIW, IMHO, ETC ETC,
Crispy

patfat

^^ Crispy, I'm having Mitch make some money ducts like John Magnuson for the 99 spec lip then to my N-tech backing plates. I also have a BBK and need some ducting. I know you have the CCW backing plates. If you're interested in these ducts let me know. Maybe we can get Mitch make a few and cut the cost a bit. I have an apointment with him the first week in June right before the Mazda event.

jayk

I'd like to see what you end up doing at VIR. I'll be there, most likely without any brake ducting...

CrispyRX7

iTrader: (139)

Well I've had a set of the N-Tech backing plates (and hose) in my garage for many months now with no time to install them.
A friend of mine made some adapter ducts to fit to the back of the 99' lip. He used a rapid prototyping machine to make them from a CAD drawing. They fit relatively well but have yet to be installed.

IMO any source of fresh cold air to the brakes is better than none. Johns ducts I'm sure are the ultimate performer but frankly I drive a modified street car, not a race car (I have one of those also) and I think they "look" aweful from an aesthetic perspective (Sorry John). As such I won't be doing anything like that to my car. My issue is not specifically with brake fade issues, I just want to get a little bit more life out of my rotors. My plate is full so I doubt I'll have my ducting on the car by June but we'll see.

As for what Mitch comes up with for you I'm interested to see the results. Although, unfortunately, at his current labor rates he's pricing himself out of my market

Crispy

John Magnuson

No offense taken! I agree that the stock lips do look better. However once the car is sitting on the ground the ducts are not that noticable really. And my car is still a modified street car also although it keeps slipping down the path toward track car and away from street vehicle. Funny how that happens.

primerGrey

iTrader: (13)

That paint is a great suggestion! I was thinking about getting a brake pyrometer, but they are expensive and it seems a one-person crew like me could only use them after running a warm-down lap, or the pads would bake onto the rotors while I was out taking the measurement.

I didn't know the paint existed, but found some here by googling.

http://www.raceshopper.com/temperature_paint.shtml

If anyone knows of a better source, please post it.

primerGrey

iTrader: (13)

McMaster-Carr has a wide range of paint and stickers - go to www.mcmaster.com and search for temperature indicating products. They appear to be the same brand as the racerwholesale package but with a more complete range.

Julian

iTrader: (14)

Try Pegasus Racing

http://www.pegasusautoracing.com/pro...asp?RecId=4974