Does anyone have and has heard a Racing Beat muffler behind a 20B?

I currently have a 2.5" mild steel pipe system with a well known rotary shop in oz 3: s/steel muffler. Although it seems to flow well (made over 400 rwhp on only 6 lbs) I don't like the sound it produces in low revs.

It has a sort of high pitched raspiness, not the nice low deep 20B mellow I want.

It has been suggest to try a a RB muffler, any ideas? Also pipe.. will go to 3 or 4", mild steel still ok?

Finally.. I have been reading about Borla mufflers, they aren't available in Australia, what are your thoughts on these?

 

I too would like to hear what a dual tip Racing Beat muffler sounds like on a 20B. Am contemplating this change for my car.

Borla mufflers are very good and of high quality. I have a few friends that have used them for a mid-pipe muffler, to help further reduce noise. I have this setup, but with the Magnaflow mid-pipe from the rx7store.net:

http://www.rx7store.net/product_p/resmidpipefd3s.htm

Really helps to control the droning you get at speed on highways.

 

Setup:
4inch dp
3inch mp
Racing beat Dual tip muffler

Plan on going full 4inch, however I love the RB dual tip and the setup sounds great.

 

I think this is an RB single tip on a 20b FD.
http://videos.streetfire.net/video/1...7969646cd4.htm

 

Sounds nice.

Are most people using stainless or mild steel for the pipes?

 

Also.. are you guys running cats, if so what type? metal or ceramic

 

No cats. Straight downpipe, rx7store.net resonated mid pipe, and Greddy exhaust.

 

no cats, resonated mid-pipe also

 

ive got 20b SP on my FC with TII mufflers and a magnaflow for midpipe and sounds really good, quiet and low sounding

 

Should I get an RB muffler? I was going to get two Borlas. I want the exhaust to sound good and flow up to 300HP. If anyone knows whether the RB powerpulse main muffler for a 1st gen will do that, I'll get one.

 

^I would think two Borlas would do the job. They are high flow so that wouldn't be a problem. Don't know how loud the setup would be but Borla's in mid pipes are pretty quiet.

 

I know Steve84GSTII has an RB muffler, and he makes around 300HP with an S5 turbo. It's quiet enough and works well for him.

I would very much like a quiet midpipe. I currently have a loud midpipe in the REPU with a Rotary Engineering glasspack. I think I can quiet it a bit with a stock ported 13B. The current engine has very large exhaust ports and really gets loud at mid to full throttle. I'm hoping the new engine will have better low end (smaller ports) and stay quieter.

If you say a Borla works well in the mid position, that's great. It means I won't need to get an RB presilencer. As for the rear, either RB or Borla is ok by me. I'd like to know which would flow the best and sound the best. I got into 20Bs mainly for the awesome exhaust note, so it's got to sound good. Quiet in the car with enough volume outside so you know it's a 20B.

 

After doing a bit of research the Holley Hooker mufflers were pointed out to me. I am going to go 2 x Aero Chamber Hooker mufflers, centre in centre out, either 3 or 3.5"

http://www.rocketindustries.com.au/d...partno=HK21506 (picture shows offset type, I will be getting centre in, centre out)

Should I go the bigger pipe size? Anyone had personal experience here?

 

i had the racing beat turbo back on my fc 20b, it sounded nice, but it was really quiet. i did run it with a cat for a while, and the cat was a little louder.

 

Way off topic question but was the 295 HP run on a stock ported engine with 9.0 rotors?

 

No it wasn't. The engine was extend port, or strret ported I think you guys call it.

It was also running the triple throttle bodies at that stage, this alone made a gain of over 50 rwhp

And yes it was with 9.0 rotors as I always had plans to run turbo later on.

 

Yeah thats what I've been hearing, the RB systems are too quiet, I still want a bit of noise.

A well known street 20B over here is running these Hooker mufflers and they sound very nice. He is running 2 x 3" but I am thinking of 2 x 3.5", hence the question

 

I'm still thinking RB muffler in the back. I'll get the '81-'82 version because it will bolt right into my car for now with the 2 rotor (it's an '81), and then when I'm ready I can hack off the 2.375" pipe and weld on a length of 2.5" thickwall mild steel up over the axel. See here: http://www.racingbeat.com/resultset....rtnumber=16433

 

Thanks for the post but I have to say backpressure is the devil. You never want backpressure on a rotary, unless it is useful for opening aux ports on a 6 port setup, and only then try to keep it minimal. Backpressure is a misconception harkening back to 2 strokes, which some folks still confuse with rotaries due to needing oil premix/injection and an ignition event per every cycle. They are similar, but not by very much in that respect. Like how the sun and moon are similar in that they move across the sky and provide light. Close, but not really the cigar.

What I want in an NA exhaust is velocity. As high as possible without being restrictive, but also quiet enough to drive comfortably and not attract the wrong kinds of attention. So yes I agree with 2.5 or 3 inch. Well, not so much 3" since it's harder to muffle.

When I used my horse sense and compared notes with a math whiz, we both concluded that 2.5" would be best because it's close enough to the size we worked out (within 1/4 inch anyway) and easier to find in thickwall. Plus RB happens to make a nice presilencer in that size.

One more happy thing I'd like to point out is Steve84TIIgs (I probably got his username right) has a 300HP S5 T2 in his FB that is piped through one of these RB powerpulse mufflers. He chose the '81-'82 model presicely for the larger inlet pipe. Then cut it off and added a 3 bolt 3" header flange and ran the entire exhaust system in 3" including a high flow cat. His car actually passes California emissions and is apparently quiet enough as well. Not hard to imagine with a turbo taming the exhaust note, cat and RB muffler.

I'll have a header, so already we're lots louder, then a presilencer so some quieting, and lastly the RB muffler. It should be only a little louder than a typical RB dual pipe 'streetport' system. I think that system sounds very nice. I can't wait to hear the 20B version.

 

I don't want to debate it either. I defer to rotarygod and his opinions about backpressure vs velocity.

 

ive been sciencing out exhaust stuff for mine too.

basically piping is measured by OUTER diameter, but we're computing in INNER diameter.

thus to get 2" ID you need 2.25" pipe...

oh and mazda in the 'rotary engine' book has a graph of backpressure vs power for a PP vs stock port. book page 46, fig 4.27.

 

Since this thread was resurrected, i'll add my clip for a 20B with RB exhaust on an FC in case it comes up in searches later on. Then I'll let you guys get back to the debate on backpressure vs. no backpressure.

http://s147.photobucket.com/albums/r...t=MVI_1480.flv

 

Yeah, Mike. The ID with thickwall pipe was what we were using. I was very pleased when the numbers added up to allow the use of RB's thickwall 2.5" OD mild steel pipe. This opened up the possiblity to use the RB muffler as well because the difference between 2.375" and 2.5" is very minor. Also since it's NA the 'restrictive' RB muffler will be less of a detriment than it is on Steve's car with his turbo.

If I was peripheral or bridge porting, I would reconsider my exhaust choices, but fortunately streetports can handle a little bit of muffling and still work well on the street, pass noise laws etc. so I should be fine.

 

Good luck on your project, Gordon.

I still haven't heard back from Steve or Rotary20B on their use/opinions of the RB '81-'82 Primaflow/PowerPulse muffler in 300HP territory. I'd really like to use this muffler because it will bolt right up and work fine with the 2 rotor. Then a little inlet pipe mod 2.5" to 2.375" and it's good to go.

Gordon, you were saying 2-2.5 is where I'd get my best overal results. Well, in case I haven't relayed my story yet, I will do it now. I test ran the 20B in the GLC. It barely fit and made servicing the manifold and injectors difficult. It also got hot quickly because the cooling system was small (but perfectly adequate for the 2 rotor). Anyway it had the most tip-in I'd ever felt from a rotary. It was disturbing, as if I had been rear-ended when I'd flex my ankle, hehe. I checked my mirrors to make sure there wasn't a car behind me. The exhaust system was straight-through 2". The engine ran out of breath by about 5.5k. It was not tuned (MegaSquirt), I had no O2 sensor at the time so it was just a guessing, and it would smoke a lot because it needs a rebuild. Plus some of the apex seals are getting sloppy and have low compression so I pulled it for a rebuild before seal breakage could occour.

I found out later the stock 20B ports were optimized to move a big luxury car, even off boost, and start to run out of breath around 5.5 or 6k anyway. I want to perform a basic street port to open the normally late opening primarys at least as early as '84-'92 spec, and close a few degrees later than 20B spec. Maybe more. The secondaries will receive some attention and the exhaust ports will probably get some T2 sleeves swapped in. I feel this willl allow the engine to breath up to 7k or higher but I still have some research to do on '84 and later injected engines with differing port sizes as all my research thus far has been on older 4 port engines where primaries and secondaries are the same size.

Do you think a full 2.5" system will perform adequately for me? Even with the RB muffler and a single 2.5" presilencer in the cat location? I don't need a loud exhaust, but it needs to flow enough to make 300HP at 7k or there abouts.

 

Mine is 4" from the turbo back(no cat).. even though I dont really apply here I could submit a clip of an HKS Ti exhaust.. to tell you the truth tough, it's ******* loud and obnoxious. You can't make out the HKS tone over a straight / open exhaust.

Anyhow, should Gordon ever send me the files I need.. I'd be happy to provide the clip.