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magnumP5's RX-7 Build Thread
- Thread starter magnumP5
- Start date
Take it easy Jon. We need some time to clean up. lol! Like you I am not a fan of how close the exhaust and intake manis get to each other. I wonder if an exhaust shop could modify the exhaust to get some clearance. As far as the mufflers go I have no idea. It suprises me there aren't many (any) rotary guys following along with the rest of us, they would surely have some insight.
I guess only Racing Beat offers "rotary-specific" but any muffler with thicker, SS walls and SS and/or ceramic packing fits the bill. Thinner, mild steel walls are quickly oxidized away and fiberglass packing can't hold up to the heat.what is a rotary specific muffler lol
and that intake/ exhaust tube set up is straight sex.
Yeah it's a little annoying they didn't tweak the design considering it's the same shop that made my intake manifold.That manifold is pretty bad ass. I can definitely see why you'd want that particular one. That's scary close to the intake mani! I dig it tho.
Do you think a single pre-silencer and muffler combination would be sufficient? I think I could run two mufflers in series but I'd be worried that wouldn't address the higher frequency noises. Running a single pre-silencer into dual mufflers would probably be the best but I want stick with a single for the lightest possible weight. I don't mind loud; I just don't want to be black flagged on track.I'd go racing beat, especially since it saves money.
i think its kind of stupid how much that header pipe curves up.... the clearance issue wouldnt exist if it wasnt so radically turned upwards
What Phen said. The purpose was to make the runners equal-length. That being said they probably could've pushed the trailing running outward a little farther toward the side of the car to avoid the steep upward curve.Gotta make an equal length somehow.
With the gaskets in the clearance will probably be a little larger because the exhaust manifold gasket is thicker. Milling down the flange on the intake manifold will also give me some clearance but I wouldn't want to make the flange less than 3/8" thick.
I think you will be fine with the pre-silenceer and muffler combination. Racing Beat has put a ton of research to get a good sound at an acceptable level. Only thing to do is try the single and see if it is acceptable to the track. I don't see why not, as long as you aren't straight header dumping.
The only thing about Racing Beat is I've read several posts now of racers having to replace their presilencers or mufflers after a couple weekends due to the packing burning out. This had me looking into repackable mufflers and I recalled an article in Grassroots Motorsports a while back about Burns Stainless mufflers. Apparently they had good success with sound reduction and power on an autox-prepped CRX. I've been talking to them about a rotary application and they're under the impression I could get away with two of their mufflers in series and that even one large one would be sufficient. The general impression of Burns' mufflers on the net is that they're LOUD but I couldn't find any examples of them on a rotary let alone in a two-muffler system. Anyone have any experience with them? This has also got me thinking about a system where I could easily swap out the upstream muffler for a straight pipe on race days if the single downstream is sufficient to meet track sound limits.I think you will be fine with the pre-silenceer and muffler combination. Racing Beat has put a ton of research to get a good sound at an acceptable level. Only thing to do is try the single and see if it is acceptable to the track. I don't see why not, as long as you aren't straight header dumping.
The forum isn't letting me enter a "return" in edit post mode so it's double post time. Got the MC bled last night and the BPV bracket painted so hopefully those'll get permanently installed this weekend, which wraps up the brakes. This is my first experience with ATE Super Blue and I have to say it just doesn't look right, haha.
Jon I've been using a complete racing beat exhaust on my rx 7 for over 5 years and itsholding. up just fine. I'm going to use a Burns Stainless muffler on the the rx7 that I am building. I am also going to use 3" stainless steel pipe as well. Go checkout prodracing .com an search for rotary or rx 7 exhaust and they will give you some options as well. Mazdaspeed does sell a stainless muffler with lava rock as a baffling material it works very well but stays hot for a very long time and is pretty heavy.
Jon I've been using a complete racing beat exhaust on my rx 7 for over 5 years and itsholding. up just fine. I'm going to use a Burns Stainless muffler on the the rx7 that I am building. I am also going to use 3" stainless steel pipe as well. Go checkout prodracing .com an search for rotary or rx 7 exhaust and they will give you some options as well. Mazdaspeed does sell a stainless muffler with lava rock as a baffling material it works very well but stays hot for a very long time and is pretty heavy.
I forget what all's done to engine going into your race car but the blue car is still a stock 12A, right? Maybe that's why the Racing Beat stuff has held up? I've read about the Mazdaspeed muffler. It uses that "lava rock" stuff I believe. Probably heavy as crap. So you're going with a 3" exhaust on your modified 12A? Makes me wonder if I should step up tp 3" as well. The guys at Defined were pretty adamate about sticking with 2.5" though. Waiting on a response from Burns today but if you think a single 3" unit will be sufficient on your race car I'd think a smaller upstream muffler followed by a larger downstream would be fine for me.
On Saturday I got the MC on the car and proceeded to bleed the lines. Did all four corners and the pedal still went to the floor. Damn. Bled all four corners again with no luck so out came the MC to be bench bled again. I didn't get any large bubbles but there was definitely some air in there. I'm guessing I went to quickly the previous time and aerated the fluid. Took it much more slowly this time and checked out the piston motion before reinstalling. ~1/16" movement at most. Got everything installed on Sunday but didn't get a chance to bleed the lines.
Brakes bled again. Still a squishy brake pedal. So far I've bench bled the MC twice and bled the lines three times (twice after first MC bleed and once after second). MC was bled properly - I could move the piston <1/16" when I was done. At this point I only have a few more ideas:
1) Get the car off jack stands so the corner being bled is the highest point. Currently the front of the car is up in the air and I've been raising the rear just enough to get the tires off the ground. Maybe this is causing air bubbles to get stuck at some high point.
2) Bleed the lines more slowly. I've been cracking the lines open quite a but allowing the fluid to move quickly. Maybe I'm aerating the fluid.
3) Brake fluid has "gone bad." I've had this brake fluid for a while (>2 years) but I didn't open it until a week ago or so. I know you're not supposed to keep opened brake fluid for more than a year so I don't think this is my issue.
4) Bad MC. There's always horror stories about new aftermarket MC's being "bad." I don't think this is the case because it holds pressure when bench bled and even installed on the car with the ports plugged. The pedal isn't squishy until I reinstall the lines.
5) Something wrong with my bleeding technique. I'm using a Motive pressure bleeder. It applies pressure to the MC resevoir to force out air/fluid. I've pushed anything from 5 to 25 psi with the same results. I've also tried forcing fluid (filling the Motive bleeder) and air (leaving it empty) with the same results. I don't think I have any leaks in any of the lines because I'd see fluid leaking when pressurized.
Any other ideas?
1) Get the car off jack stands so the corner being bled is the highest point. Currently the front of the car is up in the air and I've been raising the rear just enough to get the tires off the ground. Maybe this is causing air bubbles to get stuck at some high point.
2) Bleed the lines more slowly. I've been cracking the lines open quite a but allowing the fluid to move quickly. Maybe I'm aerating the fluid.
3) Brake fluid has "gone bad." I've had this brake fluid for a while (>2 years) but I didn't open it until a week ago or so. I know you're not supposed to keep opened brake fluid for more than a year so I don't think this is my issue.
4) Bad MC. There's always horror stories about new aftermarket MC's being "bad." I don't think this is the case because it holds pressure when bench bled and even installed on the car with the ports plugged. The pedal isn't squishy until I reinstall the lines.
5) Something wrong with my bleeding technique. I'm using a Motive pressure bleeder. It applies pressure to the MC resevoir to force out air/fluid. I've pushed anything from 5 to 25 psi with the same results. I've also tried forcing fluid (filling the Motive bleeder) and air (leaving it empty) with the same results. I don't think I have any leaks in any of the lines because I'd see fluid leaking when pressurized.
Any other ideas?
Did you check around the SS lines to hard lines for any leaks? I'm sure you have but it wasn't mentioned. I somehow slightly bent one of the flares when doing mine and caused a squishy pedal.
I didn't even touch those connections for this install. They've been problem-free since I installed them in 2010 but I'll take another look. I've been closely monitoring the connections I touched and so far I haven't found any leaks even with 25 psi of pressure in the reservoir.
Is your clutch line also connected to the MC? Is that hooked up and sealed?
Sorry Evan, I didn't see this. The clutch is its own system with a separate MC and line so no issues there.
I'm still fighting this. I've tried everything I can think of short of removing and rebleeding the MC AGAIN or just flat out replacing it. Last night I was getting pretty good streams of tiny bubbles from the right rear caliper, which I thought was progress, but no change in pedal feel. I've run so much fluid through the lines I've probably flushed them 5 times by now. There's no way there could still be air in there. Does anyone know how to tell if a MC piston is stuck? If no one has any ideas I'm going to disconnet the lines again, plug them and confirm I have a stiff pedal. If not, rebleed MC. If stiff...?
Did a little test last night to figure out what's been going on. Starting with the front left I blocked and ending with the rear brakes I blocked off the ports on the MC to see if the pedal feel changed. Basically, I was trying to see if any one line was giving me issues or it was something in the MC itself. The pedal feel was the same with all the ports blocked so go figure the MC somehow got air in it. I removed it, and fortunately there were no leaks between it and the booster, so at least the rear seal is okay. I bled the crap out of it and get the piston movement back to what it was before. I'm going to check/bleed it again before putting it on the car to make sure it isn't drawing in air from somewhere. I also adjusted the brake pedal some more. Should be a nice high, hard pedal if/when I ever get the whole thing sorted out.
20 days later and I'm calling it quits on the brakes. Another new MC and another complete system flush and I'm pretty sure it's as good as it's going to get. It's definitely better than before and at this point I'm spending too much time on the brakes. I'll deal with them again once the car is running and I know how they feel with the booster doing its thing. The only other things I'm considering for the brakes is brace for the firewall/MC in the engine bay and a brace for the pedal assembly. I'm getting some flex in both I'd like to eliminate.
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