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Index > Engine/Drivetrain > Thread: exhaust
Thread: exhaust

Posts: 458
posted November 13, 2002 10:19 PM


The time has come when I am finally going to put a free flowing exhaust on my REPU that will at least be as loud as my Weber :)
Currently I have whatever the cheapest thing Muffler Masters could give me a year ago. I am going to get a cat welded into that to pass emissions and then start my upgrades.
So far I just have the Racing Beat 2" header/collector. I am thinking of getting the Edelbrock RPM series muffler and that is as far as I have gone so far. It is $95 and I am trying to do this on a bit of a budget. I don't know what diameter to go with, should I go from the 2" collector to 2.5" or larger? I Figure I should also get some sort of pre-silencer or resonator so I can stand to drive it more than 5 minutes, any suggestions there?

'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
really loud!

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1st Gear
Village Idiot
Posts: 23
posted November 13, 2002 11:04 PM

I did my system with a RB road race head section out to a single 3-chamber Flow Master. Then after converted to a true dual w/the RB silencers, sounded sweet and great power! I don't recommend going with anything bigger than 2.5" for a single system or 2" for duals. Increase in exhaust diameter can actually rob power. Your system should be balance and maximized for it's situaltion. A brief on system length and set-up is in the RB catalog and you can peep out MazdaTrix' website (http://www.mazdatrix.com/e1.htm) for a web version.

If you want the complete old-school look I'd go with dual Super Turbos (Dyno-Max) out the back on the same side. If you plan to run a true dual set-up it's gonna cost a bit more. I believe you can get cherry bombs or something put in to quiet it down but DO NOT expect them to last, mufflers either. Rotary exhaust temps get significantly higher than pissed ons and will break down even stainless innards like Flow Masters and such, after they have eaten your cat(s) or pre-silencer(s). The Prima-Flow's from RB or MazdaTrix are by far the best but $$$ too.


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Posts: 319
posted November 14, 2002 07:02 AM

Last time I checked the RB Prima Flow Muffler was $200.

I understand you are on a budget but for only $105 more + shipping you can have the best, and, as far as my expierience goes, only muffler that will live on a Rotary.

Unless the one for $95 is packed with stainless steel it will not live for long.
77' REPU plus a few spare parts
for it.
85' GSL-SE
83' GSL

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Posts: 127
posted November 16, 2002 09:42 PM

If the engine did not come from a dual exhaust rx7, you won't shut it up with any full dual setup. Mazda did some funny port things on the dual exhaust models to take the sharp edge off the exhaust pulse. I thought that a "sawtooth" leading port edge might do it also, but I didn't think to patent and call the factory!!
My '74 was way loud! Full dual, crossover resonator, two mufflers, and tuned exhaust tips.

rx2/3/4/cosmo,repu,94 rx7,

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1st Gear
Posts: 44
posted November 27, 2002 08:01 AM

The loudness or the tinny'ness is coming from the cheap ass pipes that the muff shops use. They suck period. get the RB pipes...nice and thick, and adds a few pounds to the truck but who cares, the thing is heavy already. Everytime i used that cheap stuff, it lasted barely one year and there were holes all over it. The mufflers last a weeks of freeway driving. The primaflows are good but thry don't breath like the turbos like the dynomax or flowmaster. Dyno sounds sweet for a good few months. Flowmasters are just plain obnoxious even with 4 of those RB pre-silencers. Duals do sound cool though but maybe cross it over in the middle to mix up the sound a bit. I know a guy that did dual 22" dynomax and 4 resinators but did not run the spare under the bed. This setup was the best sounding IMHO. Super long primaries and uncrossed. Flames galore.

My current 74 primaries reach the rear axle with two RB silencers, collected into 2.5" pipe and over the axle then into a 26" dynomax stainless and 90 bend to the right side(bends help keep sound down too). Kinda loud but not too bad.
ROTARY POWER!!! V8 is a great juice for consumption.

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Posts: 1672
posted December 04, 2002 07:44 PM

tom, my 74 came with racing beat road race headers (dual outlet, not merged) into dual 1.75" pipes, then four foot long dual glasspacks. the glasspacks are real long and put as rearward as possible. merge together into a 2" or so pipe, up and over axel into a cheap turbo muffler of some sort. it sounds good, u know it's got a rotary engine if u know what i mean. but not loud and not unbearable. but i AM glad i got a rx7 5 speed with a tall 5th gear to go along with the 4.62 diff gears. that 5th gear helps keep revs and thus noise down at freeway speeds! glasspacks are rusty on outside, can't say if they 'burned out' like everyone says they do on rotary, but the truck DOES sound good. nice compromise between hp, noise, price. lots cheaper than the racing beat dual presilencers!!
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-

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