Mazda rx3sp exhaust build
 

I am about to start my full stainless steel exhaust ,here is where I'm at : Bought a racing beat SS cast header flange , pre silencer and prima flow extreme muffler . All the other SS I bought from ace race stainless , best prices I have ever found . I bought my mandrels (3") , pipe , schedule 10 weld els ( for the header ) , o2 bung and male/female v band clamps from ace stainless . First two pics are of all my material , last shot is of the prima flow fab to fit in the stock location . We are using solid works to create the header , more to come

I might as well show some pics of the car while I'm at it.

Love the car! That interior is on point.

Did you just grind the paint and polish the PR Muffler????

The muffler came all semi polished stainless steel , that was definitely a plus to me .

I thought they came pianted black like all the Primiflo's??? pretty cool man

I fit the rear muffler using all factory mounting original to the body , no hacking . Hopefully I will get some time to go over the axel tomorrow.

looking good
 

:nod:your car looks in outstanding conditions! Enjoy it man!

Question: Does that extreme muffler come unpainted or did you have to request it like that?

it came unpainted

Thank you!

It's been a while but here is my progress : schedule 10 stainless steel ( about 1/8" wall) 90 and 45 degree weld ells and a rb ss header flange . The length is matched , what a pain .

Nice work !!

very nice work. what porting on the engine? i really look forward to hearing it when you put it all together.

also, what's the inlet on that muffler. Primaflow Extreme, eh? i didn't realize that there was a custom Primaflow muffler available from RB until now. that's good news.

It's a powerpulse with straight cut tips that have a trumpet insert inside. It looks like all the others over the last ten years or so. Maybe the inserts are bigger on this model?

The inlet is 2.75" so it is compatible with 2.5" or 3" systems.

I'd like to try one with a turbo. Being at the end of the system, a little bit of restriction, if it is slightly restrictive, shouldn't hurt anything. The exhaust gasses have cooled and contracted by the time they get back there so I'm not too worried about it.

Thanks , the header is going on a 13 b full bridge

Looking good. What did you choose for header length? How much distance do you plan on leaving between the collector and the presilencer? Here's RB's exhaust tech tips for reference.
Attachment 622480

Racing beats specs are not the end all imo. Dave Lemon of mazdatrix says point conversion makes no difference for a rotary exhaust collector and the book "street rotary " says there should be 3" between the exhaust flange and the first 90 degree bend . All I was interested in was keeping the first 90 as far from the flange as I could (1.75" on mine ) and as close to equal length as possible (my system is equal length ) . I like Racing Beat and they're products but they are not my go to spec . RB air cleaners take away 2 top 5 HP on a holly and people still buy them ,and RB still sells them .

Would that be the RB foam or the K&N paper element? I've got an old K&N for the RB spun aluminum "UFO" that seamed to work ok. Just curious about your thoughts.

As for exhaust spec, I prefer doing a long primary on any NA I do, if possible. I was even able to fit one under the MG Midget which has a streetported 13B and will use an unrestrictive scotchbrite filter (seriously, I had to sew up under the metal mesh of a low profile filter assembly that originally used restrictive foam) and a hogged out Nikki. I don't recall the length of the long primary but I think I decided on 5/8 of RB's full long primary spec. Figured it would work. Will test fire it to test for noise later this year.

What are your thoughts on long primary vs short collected?

I had a foam filter and when I used a k&n I picked up 5hp on a 13b street port (on a mustang dyno) I don't think long or short primary length makes a difference . My friends fc race car makes 195 hp on a 6 port 13b with no port work and his exhaust looks like crap , I think a lot of it has to do with the tune. IMO . The 12a header I made on my old glc 12a stock port with a holly and 2 1/2 " mandrel exhaust made over 130 hp and my point of convergence was only 18".
Here are some pics of the header mounted , next up : heat shields

That's interesting. I used an FC RB header in my GLC. It only needed a little rework of the pipes as they come out of the engine flange and curve up around and the past the idler arm and steering centerlink, then back into the FC RB collector. It's 2.5" all the way until the rear muffler where I threw on a 2 1/8 or so Borla. All the others in front of it are 2.5" Magnaflows. Sounds good.

Equal length and minimum 3" straight length off the motor sound like good guiding design features.
I've also heard that flow disturbances should be kept away from the collector. For example keeping presilencers a few feet from the collector helps maintain the tune of a header.
Regarding long primary vs short primary exhaust, I've heard that short primary will have a narrower powerband but would create stronger pressure pulses. The stronger pulses could be better at overcoming downstream restrictions like mufflers.
On header length I think there should be nodes at every multiple of an effective short header length. You would need to factor in about an inch to account for the length the exhaust sleeve adds to the gas path. So if RB suggests 15-18in there should be another similar, but slightly weaker, node at 31-37in. If this is correct then it somewhat supports the idea that collection length doesn't factor in much. I look forward to reading about the success of your results.

Jeff only problem I have with magna flow as a pre resonator is they burn out . I usually buy 1 lb. of coarse stainless steel wool from Mc Master Car , cut the magna flow open , pull old packing , re pack and weld it up . Problem solved and the pre resonator works great .

That's a good idea. I think you said something like that before regarding my Magnaflow being used as a presilencer. I predict it will last only about 6 months. It's a 5x8 but it hangs down pretty low. I might redo it as a 4x8 with coarse ss wool and maybe wrap the perforated tube directly with pot scrubbers. Then wrap those with the wool. Thoughts?

the header is now welded out