DIY Brake Ducts for a Series II - Page 2 - RX8Club.com



Series II DIY DIY projects specific for Series II RX-8s

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Old 06-27-2017, 11:12 AM   #26
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When I bought my Miata last summer, I said to myself, "Self, if you have 2 sports cars, 1 will always be ready to go to the track. This idea is brilliant!"

The reality is, that 2 sports cars are always on jack stands, instead of just 1. RX-8 still has no hubs. Broke an end link on the Miata and heat cycled the tires out of service last Saturday. No cars ready to go to the track.
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Old 06-27-2017, 12:01 PM   #27
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I still have the ducts that are made to go in the S1 bumper if anyone is interested, I was going to use them for something else but never installed them.
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Old 06-28-2017, 09:33 AM   #28
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Minor update to this thread.

1. Hubs finally came in, car is back on the ground on its stock wheels.

2. No signs of rubbing during the drive to work this morning. I'll visually inspect it tonight.

3. The sound of wiffel ***** tells me the rotors are receiving air pressure.

4. I believe my track wheels (255s on 17x9s) will rub at full lock. I have that "problem" with my Miata, too.
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Old 06-28-2017, 11:42 PM   #29
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Minor-er update.

Pulled the front wheels tonight. No signs of rubbing with the stock wheels, and I tried to make it happen.

I'm still pretty sure my track setup will rub under full lock, but #supernicegrandtouingfivepercenterracecar.
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Old 07-09-2017, 06:30 PM   #30
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I have some data. Unfortunately, I do not have good comparison data against the Miata photo above, because I ran a different track configuration this morning, and the session times were different.

Let's talk about that track configuration. I ran the 1.3 mile track on the left side of this photo. You'll notice it has no long straights. It also has mostly low speed corners. Those two things together make it absolutely brutal on brakes. I normally dry boil fresh 600 fluid after about 15 minutes on this track. The Miata temperatures were shot after a session on the 1.7 mile track on the right side, with its long straights and sweeping, high speed turns. Totally different animal. This morning's sessions were 30 minutes long, and the Miata sessions were 20 minutes long.




Here's a video of me driving that track last year.



I shot brake pads temps after sessions 2 and 3. I was able to run a full cool-down lap at the end of session 2. I managed only half a cool-down lap at the end of session 3.

These photos are of the right side brake pads, which get the hottest on a CCW track.

Session 2:




Session 3:




So, low 500s. I was hoping for a little better cooling performance, but this certainly is not terrible. Previously, my pyrometer would not even measure this, as it maxes out at 800F, and my pad temps were higher than that on every track configuration. This is definite improvement. I am not displeased.

The other consideration has to do with robbing air from the radiator to cool the brakes. That seems to be OK. I don't have any new data for very high ambient temps to compare to my old data (see radiator thread linked above), as the ambient temps for session 2 and 3 this morning were 86F and 90F, respectively. No idea what a 95F or 100F session would look like, and I no longer care to find out.

These charts don't look too far out of line. I may have lost a few degrees of cooling capacity, but the difference is not dramatic.

Session 2:




Session 3:





Wait. What happened there in session 3? The answer is, I ran up on a Miata that would not let me pass. So, I backed off to give him half a lap of space. Then I caught him again. Then the session ended. Some people.

.

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Old 07-10-2017, 07:02 PM   #31
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800F+ down to 490-510 is pretty amazing. The coolant temps are fine compared to a lot of your older charts. It might not be the fairest of comparisons, but it would seem like the smaller slower track would exacerbate these problems if anything.

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Old 07-11-2017, 08:11 AM   #32
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Agreed on all points. I tried to stress that the track drives up brake and coolant temps due to its layout.

I take turns 1 and 2 in 4th gear. The rest of the track consists of bouncing off the rev limiter in 2nd and 3rd, so RPMs are unusually high nearly all the way around. Otherwise, there is lots of hard braking with little opportunity to cool the brakes back down. This track is basically a torture test. Not displeased at all.
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Old 07-28-2017, 04:18 PM   #33
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By no means was I trying to be confrontational in the other thread about pads. Hope you didnt take it that why. Figured Id bring the discussion here though. Did you check temps with different pads before or after you installed the ducts? Curious if Hawk pads were running at different temps than your carbotechs.
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Old 07-28-2017, 04:42 PM   #34
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No worries. You were right. I was causing the discussion to meander.

I don't have hard temp data on different pads. I did shoot Hawk pad temps now and then, and I remember them being similar to Carbotech temps. I know I was eating those too. Hawk's pretty powder coating didn't last through 1 track session.

The main reasons I quit using Hawk pads were rotor wear, pad wear, ungodly loud noise, and poor modulation. Carbotech pads cost more, but brake parts last at least twice as long, noise level is lower, and pedal feel is very linear.

EDIT: For data points, the Hawk pads I used on track were HP Plus, Street/Race, DTC-30, and DTC-60.

.

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Old 07-28-2017, 04:49 PM   #35
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Quote:
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No worries. You were right. I was causing the discussion to meander.

I don't have hard temp data on different pads. I did shoot Hawk pad temps now and then, and I remember them being similar to Carbotech temps. I know I was eating those too. Hawk's pretty powder coating didn't last through 1 track session.

The main reasons I quit using Hawk pads were rotor wear, pad wear, ungodly loud noise, and poor modulation. Carbotech pads cost more, but brake parts last at least twice as long, noise level is lower, and pedal feel is very linear.
Interesting. And you mentioned youre just using any low cost off the shelf rotor? In the interest of weight and heat dispersion is there a reason why you don't have a two piece rotor where you could just replace the ring?

FWIW I ask because the stock brakes on my newly bought rx8 are all but trash.
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Old 07-28-2017, 04:55 PM   #36
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At the time, I was buying OE rotors from Mazdaspeed Motorsports Development. My RX-8 is currently wearing StopTech Sport slotted rotors, because they were on clearance somewhere online.

I use any old cheap rotors on my Miata, on which I installed brake ducts immediately. I will probably do that on the RX-8 going forward, now that it is ducted.

I don't use 2 piece rotors on the RX-8 mainly because of cost. IIRC, Racing Brake may be the only option, short of a BBK, and there are "issues" with RB and pad selection. I haven't gone to a BBK, because I don't need more stopping power. I only need more heat dissipation capacity, which a BBK would give me, but ducting is more effective and much less expensive.

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Old 07-28-2017, 05:44 PM   #37
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At the time, I was buying OE rotors from Mazdaspeed Motorsports Development. My RX-8 is currently wearing StopTech Sport slotted rotors, because they were on clearance somewhere online.

I use any old cheap rotors on my Miata, on which I installed brake ducts immediately. I will probably do that on the RX-8 going forward, now that it is ducted.

I don't use 2 piece rotors on the RX-8 mainly because of cost. IIRC, Racing Brake may be the only option, short of a BBK, and there are "issues" with RB and pad selection. I haven't gone to a BBK, because I don't need more stopping power. I only need more heat dissipation capacity, which a BBK would give me, but ducting is more effective and much less expensive.
Thanks for the help and insight.
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Old 07-28-2017, 07:40 PM   #38
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Hey Steve, what do you use to record the track footage? Harrys lap timer and a smartphone?
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Old 07-28-2017, 07:59 PM   #39
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Hey Steve, what do you use to record the track footage? Harrys lap timer and a smartphone?
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Old 07-28-2017, 10:21 PM   #40
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Yes. Exactly that. I also have a GoPro that I use sometimes. I wish data overlays were easier with the GoPro. That leads me to use Harry's on my phone, which is out of sync and just not very good on Android.
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Old 07-28-2017, 10:25 PM   #41
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Yes. Exactly that. I also have a GoPro that I use sometimes. I wish data overlays were easier with the GoPro. That leads me to use Harry's on my phone, which is out of sync and just not very good on Android.
Sorry to hijack thread, but what mount for you use for your phone? ?RAM?
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Old 07-28-2017, 10:28 PM   #42
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I'm using an Encased mount for a Galaxy S5. It doesn't suck too badly after liberal application of glue. A Ram mount would probably be better, but much heavier.
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Old 08-02-2017, 08:56 AM   #43
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In the spirit of confusing this thread a little more, here is a photo of my left front brake rotor and pad on my Miata. This is Centric's cheapest blank and a Carbotech XP10 pad. These brakes were ducted from the beginning and now have 13 track days over 6 months on them. A few of those track days were at least partially wet, and two featured my son driving as a novice, so let's call it 8 or 9 real track days.

The rotors show very little wear, and the pads have roughly 70% life left in them.

Cheap rotors + gentle pads + ducting = winning combination.

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Old 09-21-2017, 09:27 PM   #44
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Stay tuned for more data. I am going to a 4 day instructor training at Hallett Raceway mid October with BMW Club, and their convertible rules are so insane, that my Miata will nowhere near pass inspection. That means taking the 8, which also means more brake torture and measurements. Expect more photos of my sexy thumbs.

.

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Old 10-17-2017, 09:07 PM   #45
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OK, so no time for actual data. Just anecdotes.

I put on a new set of brakes, including whatever Raybestos rotors were on clearance and Carbotech XP10/XP8 pads, bled the calipers with fresh RL-600, and took the car to Hallett for 4 days of pure torture. At least 7 high-level instructors / racers drove the car, and it was on the track almost constantly. All reports are that the brakes never gave any indication of fade. I was the 1st and last to drive a track session, and the brakes were just as strong at the end as they were at the beginning.

Before adding the ducts, we would have experienced fade near the end of every session, and I would have had to bleed every night. I'm calling this effort fully successful and absolutely worth doing.
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Old 11-08-2017, 11:32 AM   #46
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This is awesome, great write up!

Interesting that you didn't need to bring the hose trough the liner to scoop air directly from the front (where you can see it visibly in bumper mouth)

Really need to do this as well. I would like to figure out the way to attach the hose to the OEM brake dust shield so I don't have to pull the hubs. Do you think it can be done that way?


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Old 11-08-2017, 03:02 PM   #47
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You need only the positive pressure in the bumper mouth to "force" air into the ducts toward the negative pressure area in the wheel well. The heat exchangers (AC condenser and radiator) are capable of only so much flow rate. What cannot flow through the exchangers buffets back out the front. What I am doing is stealing some of that excess for the brakes. The pressure differential directs flow to the brakes. A ram air situation is not needed.

That is roughly how Ian did it. He hammered the scoop flat and riveted a 2" flange to it. In my guesstimation, I did not think there was enough rigid material to hold a 2.5" duct, and I thought (and still think) 2.5" is the minimum that should be used for an RX-8. I honestly wish there was room for 3" hose with 255 tires.

Having said that, you have to remove the hub to remove the dust shield. It is sandwiched between the hub and spindle. I suppose you could manage to flatten the scoops and attach a flange without removing the hub, but I thought the $120 was worth it to have purpose-made parts, and I kinda thought my hubs were toast anyway, after a whole lotta track hours.

.

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