Droops83

Hi Patrick,

Sorry for the delay, I did not get a chance to get under my car again till this past weekend. I also must apologize for the horrible iPhone pics but that is all I had on me at the time.

As you can see from the pics my setup is nothing fancy, just a "Cool Brake" kit that my shop installed for the previous/original owner circa 20 years ago. The pictures show the left side, then the right side, and the last pic shows the plastic scoop stuffed next to an additional factory oil cooler on the left side still exposed to plenty of air.

The hoses are long and flexible---most brake cooling hose I see today is pretty stiff. That of course makes it stronger but it also makes it more difficult to route and they usually rub on the wheels of you apply too much steering angle during parking lot/paddock maneuvers (OK on a race car, not so OK on my dual-purpose car). They are also amazingly free of tears after all these years, and I have never had fade problems on the track using Pagid oranges (keep in mind I am stock '86 220 hp so my terminal speeds are not as high as yours, but I also have the smaller '86 brakes).

I have confirmed that the hoses dont get crushed when the wheels are on the ground, when turning, etc, even though it looks like they would!

If you can find some hose like that, you have many routing options, I simply use zipties to secure them!

Good luck, I hope I can turn my car into a monster someday like yours!

944CS

Patrick,

In your quest to beat the GT3's, you must one up them in every department you can! In the US ebay you can find Carbon rotors and said calipers for said rotors for relatively cheap...old stock from the stock cars when they were allowed to run them..

http://cgi.ebay.com/ebaymotors/New-c...Q5fCarQ5fParts

it's the pads that will get expensive

ninjabones

240 CFM 3" in-line marine blower costs $19. I just installed two of these as defoggers after removing all the hvac in the car.

I wonder if 240 CFM is enough air flow to have any meaningful effect on brake cooling, and comparatively what flow rate most guys are getting with their home-rigged ducts running from the front bumper (with all the kinks and length of tube compromising airflow). Plus, having active air flow would be nice to cool down the brakes/rotors after coming off track.

DanR

^ wow glen - you have really gone the full 9 yards this winter!

JoeMag

ok. gotta do the geek calculation on the 240 cfm to see how that equates...

lets do 100 feet/sec (~70 mph), or 6,000 ft/minute

3" diameter hose, area 0.05 sq feet (3.14/4X(3/12)^2)

so going at 70 mph, with air flowing into a 3" hose, you get 300 CFM (6000 ft/min X 0.05 sq feet). So 240 cfm is roughly equiv to 56 mph.

Larry Herman

You are assuming that there is no static losses, which is not the case. It would take quite a bit more calculations to derive the static pressure that you can provide based upon your speed and the size of the inlet. The static pressure of the fan outlet is a known quantity. Was never a physics major so I would not know how to figure which would be better.

333pg333

The losses through the ribbed duct will have an effect, let alone all the bends and crimps. Guess you could run a pressure sensor at the outlet?
Still, one would have to assume that it's providing some air flow to the brakes. Perhaps an inline fan might not be such a bad idea though.

mark kibort

We sold eRAM electric superchargers to a NASCAR team for a couple of years. 1000cfm blowers basicallly. I might take a few of my old erams, detune them, (maybe run (2) 12 motors in series to half their power consumption from 60amps to 30amps) and then bolt them on some brake cooling housings. Or maybe just strap them to the a-arms and use the wheel well air to illiminate the need for ducts. Problem is, there is usually pretty decent cooling on the inside of the rotors, but on the outside , there is no air flow, thats why they crack usually only on the outside. I think the wheel should be more involved in the cooling process.

JoeMag

yea, you're right on the 'simplicity' of the calc... however, if you're blowing a fan into a ribbed hose or getting the pressure from the front of the car i would guess losses might be the same, or maybe it was a worthless calc.

ninjabones

Just trying to keep within striking distance of the green gobblin Here's another taste for inquiring minds.

in the theme of this thread:

333pg333

I was thinking the same thing Mark. I'm sure those old 'sewer lids' from the 959 and other racecars had directional venting.
Not sure if it was exit or entry though. Wonder if they couldn't incoporate both?

Mahler9th

Since I started track driving Porsches in 1987 I have seen no major breakthroughs when it comes to ducting. Various cars, various levels of prep. For years I ran a heavy 951 with big tires and lots of bhp toward the end. Addressing braking heat was pretty straightforward. The Puhn brake handbook covers everything, and the old Holbert and AJ USA kits with or without application-specific mods have stood the test of time. With all of the track cars and those on which I have worked, the song remains the same.

Perhaps somewhat forgotten old school deal for Porsches with stock hydraulic systems was to change to more aggressive factory proportioning valves... hopefully folks still know about that. In the end in my 951, I ran a 965 valve which was five steps more aggressive in the PAG product line-up than what shipped with the car. Effective and cheap.

Many, many times since I started corresponding about Porsches on the internet in about 1993 I have advocated getting local perspectives and perspectives from folks with pro racing experience. I have also advocated using the lightest, simplest and least expensive approaches.

I have never, ever witnessed a Porsche racing situation where one car had a significant advantage in braking over another car in a similar or the same class of prep (as long as the systems were functioning properly). I have seen folks throw on the biggest brakes they can fit/afford.. and when they are my competitors that's fine with me. They have more weight to deal with. But they will not out brake me.

Mahler9th

To me, if you need to go there, water cooling/misting makes more sense than electric fans.

333pg333

Were those Holbert and AJ kits essentially tube ducting as shown above?
What I will try firstly is to balance the pedal box / dual m/c correctly and also try to fit tube ducting with 285 tyres up front. If we need to go up to bigger brakes that is always an option. While I understand the issue of adding unsprung weight and more inertia with larger rotors, there must be a reason that a 2700lb Cup Car with 450bhp runs them. My car will be a bit lighter and have more power so I don't believe it's such a wild and crazy idea to look to a larger Monoblock caliper over the Big Reds which will also have a better ability to rid heat and greater stopping power. I take your point however.

Mahler9th

What are you building? Is it a 951?

I have a 1950 pound 911 that runs slicks and has about 350 bhp from an NA 3.8 liter lump. My buddy ran basically the same car but with a 3.8 liter tt lump. So maybe 700 bhp? His braking system was similar, and very lightweight. And inexpensive. And straightforward. 930 calipers.

I think you can study the ajusa kit on the smartracing products web site or maybe aj usa. I think Paragon Products selll some kits too. Many/all of these commercially-available kits can benefit from modifications.

I think the reason that the factory cars have such big heavy braking systems is that they are heavy cars. And they have to design for endurance racing. If I started out with a Porsche platform and wound up with a car with the same specs as a Cup or RSR, that needed to operate in the same environment, I'd wind up with the same heavy system.

The range of variables is well-contained and pretty well known, as is the range of approaches. Now if you are building a 1200 pound 951 with 1000 bhp and ground effects... then you may be outside of those ranges.