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The difference between stainless and mild steel headers:
The original .125" DOM mild steel from Racing Beat lasted 4 years behind a stock port 12A - about 30+ SCCA Regional races with a long primary exhaust
I replaced it with an ISC stainless header that I bought used from another racer. it has about 90 SCCA Regional/National races on it including a short enduro. As a part of the STU build I had it modified to fit a 13B. This header is still on my car.
More mild steel header hate....I witnessed a wrapped Racing Beat header die in ONE racing season. Don't ever wrap a mild steel header.
For the rest of the exhaust I mostly used mild steel for a long time but it required numerous repairs due to cracks. Starting last year I switched to a short primary merged exhaust with a used NASCAR merge collector I bought off of eBay. This connected via V-Band clamps to 304 Stainless 3" tubing also bought off of eBay. I purchased a 4ft straight section and a combination J and U Bend piece to get it over the axle. I welded it all together using 409 Stainless unions with my Lincoln 180 MIG welder. I had no issues doing this. In fact is is easier to weld than mild steel by a long shot.
Stainless for the win. Also use Stainless fasteners on the every connection.
Steve Eckridge has the tooling for the old ISC stainless header, he doesn’t advertise or try to sell many. I live in the same town, so I just got the flange and tubes from him, a nice merge collector and fitted it to my car.
After years of fighting mild steel exhaust and having to rebuild it after every race I bit the bullet and built a bullet proof system. All stainless, all v-band connections, lots of hangers, and Racing Beat rotary specific mufflers. Car is super quiet now and I don’t have to worry about it falling apart every race.
After suffering multiple failures of our remaining mild steel exhaust pieces at ThunderHill last November, we rebuilt the system from the header back in stainless. I bought a mix of pieces and kit through amazon of 2.5" 16ga 304 stainless. We went full dual all the way back where previously
we went from two to one right before the rear axle. Snaking two pipes over the rear end and past the fuel cell. V-band connections FTW. We also cut a section out of the passenger side floor to tuck the first pair of silencers up. Now, all of the exhaust hangs no lower than the "frame rail".
Wow that is a crazy amount of tubing and mufflers. Is that to deal with noise restrictions where you race?
My system is embarrassing simple by comparison.
Well, it reads below 97db. When we autocross it for testing that's the noise limit. Tracks around here are 103db I think. Mostly we did it that way because we've been told dual all the way back is ideal... One of our guys has an FP (autocross)Rx-3 SP he's had since new and has always run two pipes and mufflers...
With a stock port 12A (135WHP) and street port 12A (150WHP), I am still using the Racing Beat 2 into 1 short header. I agree that they don't last long under racing conditions. Somewhere around 4 years. The most recent header (on its 3rd year now) is ceramic coated on the outside through some work associates. When the last one failed, I cut it apart, it was clear the failure was happening from the od to the id and appeared to be basically oxidation. As such, I am hoping the coating will lengthen the life. Next time around I will go stainless. The rest of the system is a Racing Beat presilencer that I bought used 10 years ago and it is still in great shape. Downstream of that is a 14" long, 4" round Magnaflow. My guess is that it is dead and probably is not needed anymore anyway. The final muffler is a stainless steel 2.5" in and out "Max Flow" muffler from Mandrel Bending Solutions. It costs $35. The car meets 93dB which is really nice for endurance racing. All the tubing is carbon steel muffler pipe and has been in service 5-10 years. The only reason some is only 5 years old is that I had to add mufflers over time to meet increasingly strict sound. The header with just the presilencer was deafening in the car. Adding the Magnaflow made it tolerable, although a little tiring after an hour and also did not meet Lucky Dog sound limits. The final muffler makes it dream to drive for long stints and can be used at any track.
Maybe a 13B (or more aggressive porting) has different requirements, I don't have any experience.
With a stock port 12A (135WHP) and street port 12A (150WHP), I am still using the Racing Beat 2 into 1 short header. I agree that they don't last long under racing conditions. Somewhere around 4 years. The most recent header (on its 3rd year now) is ceramic coated on the outside through some work associates. When the last one failed, I cut it apart, it was clear the failure was happening from the od to the id and appeared to be basically oxidation. As such, I am hoping the coating will lengthen the life. Next time around I will go stainless. The rest of the system is a Racing Beat presilencer that I bought used 10 years ago and it is still in great shape. Downstream of that is a 14" long, 4" round Magnaflow. My guess is that it is dead and probably is not needed anymore anyway. The final muffler is a stainless steel 2.5" in and out "Max Flow" muffler from Mandrel Bending Solutions. It costs $35. The car meets 93dB which is really nice for endurance racing. All the tubing is carbon steel muffler pipe and has been in service 5-10 years. The only reason some is only 5 years old is that I had to add mufflers over time to meet increasingly strict sound. The header with just the presilencer was deafening in the car. Adding the Magnaflow made it tolerable, although a little tiring after an hour and also did not meet Lucky Dog sound limits. The final muffler makes it dream to drive for long stints and can be used at any track.
Maybe a 13B (or more aggressive porting) has different requirements, I don't have any experience.
We have a street ported 6 port 13B that makes somewhere around 200hp. Our last RB header we had ceramic coated with the highest heat coating they had (turbo coating) and it burned off after a couple hours. That's when we decided to fab our own heavy duty stainless header.
Are you still running the FC rear brake calipers? We are trying to upgrade/update our rear brake as the GSL-SE calipers...and all RX7 rear calipers appear to have disappeared...looking for ideas to make something serviceable.
Interesting. Do you know what your egt temps are? Mine are typically around 1500-1550 degF (peak 1600degF). That is measured 6-9" from the header flange on the rear rotor. The ceramic coating I had installed was done by an industrial thermal spray coating company that applies their coatings (they do alot more metal coating than ceramic though) to large coal fired power plants. It was also cured at temperature before going on the car. After 2+ years of racing the coating still looks like new. I assume that won't last, but so far so good.
I think at the first bend on the header we were seeing over 1500 degrees. We don't have egt sensors but aiming a temp gun at it the temp was higher than the gun could read. AFR readings are around 12
Are you still running the FC rear brake calipers? We are trying to upgrade/update our rear brake as the GSL-SE calipers...and all RX7 rear calipers appear to have disappeared...looking for ideas to make something serviceable.
Yes I have a pair of Turbo II rear brakes that I modified for the build. So far so good. I have stocked up on 4-Piston Turbo II front calipers. I even figured out how to turn a left front into a right front and the reverse. If it really becomes a problem for me I will do some sort of a racing caliper from Willwood or Coleman Machine.
If the rules allow, I would recommend using aftermarket racing calipers or find suitable OE replacements from common American made cars. If you have a dual master set up you can get the hydraulic balance right using your choice of calipers. On my Autox Mustang I used front Corvette C4 calipers on the front and back and made them work by running different bore MCs
My EGTs are 1500-1550 6 inches from the port. Years ago stainless was very cost prohibitive but I was able to put my exhaust together for not much more than mild steel. Plus it was easier to weld.
There are allot of things that affect the life of an exhaust system. Heat is one thing but so is how the exhaust is hung on the car. If the car's engine moves allot the exhaust needs to be able to move allot too. Also how an exhaust is hung should allow for thermal expansion because a system will get longer when it gets hot.
When I was running a stock port 12A (Improved Touring) I could make sound limits with no muffler at all. It was stupid sounding and a grid worker punched me in the arm after one race cause she said my car made her ears tickle. Later I determined that putting a ricer fart cannon (2.5" in and 4" out) on the back was really quiet. Currently I am running a 5" round 3" in/out Magnaflow on the back of the car. So far the packing is holding up so it is pretty quiet at speed.
On my IT car I ran duals to rear axle and merged them into a 2.5" before the axle. I stuck with the same thing when I built my street port 13B but increased the size of the pipe over the axle to a 3" pipe. I have recently switched to a short primary merged into a 3" pipe. No one I have raced with with or against ever ran duals all the way back. So I have no experience with that good or bad. Some of friends experimented with an expansion chamber after the header merge on their EP cars but it didn't seem to do anything.
Yes I have a pair of Turbo II rear brakes that I modified for the build. So far so good. I have stocked up on 4-Piston Turbo II front calipers. I even figured out how to turn a left front into a right front and the reverse. If it really becomes a problem for me I will do some sort of a racing caliper from Willwood or Coleman Machine.
If the rules allow, I would recommend using aftermarket racing calipers or find suitable OE replacements from common American made cars. If you have a dual master set up you can get the hydraulic balance right using your choice of calipers. On my Autox Mustang I used front Corvette C4 calipers on the front and back and made them work by running different bore MCs
I think Willwood will be our ultimate solution. Pay a lot now or a whole lot later right? We do run a dual master set up so that can make things easier. We have been looking at OEM calipers we could use but are having a hard time finding one that fits the rotor with and also clears the rotor hat. GSL-SE rotors are very small diameter compared to hat diameter. Time for some more trial and error...
Last edited by Conekiller13; Apr 9, 2021 at 10:22 AM.
Here is what my Wilwood setup will look like, I have a friend I used to work with who is one of the main tech reps at Wilwood and he hooked me up with piston and mc diameters. Superlite radial front with 11.75-inch rotors, I may 3D print a mockup bracket to see if I have room for 12.19 rotors. Dynapro radial rear with 11-inch rotors. Both calipers use the same radial adapters, and my brackets are simply 3/8 laser cut steel. I am willing to share my design info, but I doubt that it would help too many people, it is so customized to the particularities of my car. I am running a drum brake rear end housing, and wheel adapters to fit 4X100 Miata wheels.
Make sure when you buy Wilwood calipers to get the Thermlock piston upgrade, it makes a huge difference for road racing.
Here is what my Wilwood setup will look like, I have a friend I used to work with who is one of the main tech reps at Wilwood and he hooked me up with piston and mc diameters. Superlite radial front with 11.75-inch rotors, I may 3D print a mockup bracket to see if I have room for 12.19 rotors. Dynapro radial rear with 11-inch rotors. Both calipers use the same radial adapters, and my brackets are simply 3/8 laser cut steel. I am willing to share my design info, but I doubt that it would help too many people, it is so customized to the particularities of my car. I am running a drum brake rear end housing, and wheel adapters to fit 4X100 Miata wheels.
Make sure when you buy Wilwood calipers to get the Thermlock piston upgrade, it makes a huge difference for road racing.
Wow...those are impressive renderings... If you would share parts numbers for hats, rotors and brackets that would help get us in the ballpark. We can then fab the axle/spindle mounts from there. On the front are you using a cut down FB hub?
Great info here and very timely for me. Spent the winter rebuilding my brother's ex-Pro7 car for my younger son. Will hopefully dabble in Lucky Dog at some point and the current exhaust arrangement is way too load for the lower dB's req'd.
Nice exhaust system. I would go that way if I could weld stainless well enough.
Another question. I see that you have a fuel cell. How big is it? I assume big enough to get just under 2 hours? I am thinking 20-22 gallons? How did you isolate the fill from the interior. I don't really want to have to lift the hatch and potentially spill some fuel in the driver compartment. I am sure you have it figured out. Anything you can share would be great.
So regarding stainless welding...I cheat. To connect each piece of the system together I use 3" ID unions. The unions are also stainless and they slip over the ends of the 3" OD sections. I like the unions because they allow the various pieces to be manipulated into place before tacking them into place. The other thing that the unions provide is more metal thickness when welding. So very little chance of burn through with a strong connection. They also make it easy to remove a section for repair.
I welded everything up with my Lincoln 180 mig welder using .025 wire. Then I paint the welds with high temp paint to prevent rust. I'll take some pics over the weekend as I have to cut out a damaged section due to a driveshaft failure.
Very cool renderings! This is basically what Charlie Clark at KC Raceware has been working on for his EProduction brake kits. He is using Coleman Machine 11.75" rotors and a Willwood caliper. I don't know which caliper he is using but it is common.
Exhausting
