RB Exhaust comments?
 

Hi All.

I have a 1985 S, all stock. The muffler is pretty rusted, and one of the chrome tips is pretty loose as a result. I was thinking of trying to rig some mechanism to hold the tip in place, but finally realized that replacing the muffler is the best way to go.

So...I've read time and time again that Racing Beat makes great stuff. If I were to replace the stock exhaust pipe, cats, and muffler with the Racing Beat setup, what sort of exhaust sound could I expect? I don't mind it being a little louder than stock, but I'd like to avoid obnoxious.

Any thoughts? My intake is all stock...nikki carb, etc.

As always, thanks!

You will be delighted! I would've done that had my wallet allowed.

In my view, far superior than any other setup. I tried several different setups, they were either too loud, or they killed power. The RB setup is in my opinion the best of both worlds.

I have large streetports on the "streetport" setup (dual pipes back to the muffler) and it is not too loud at all, nice tone as well.

^What they said, it's the way to go if you want a nice tone without being too loud and make good power. They are also ridiculously overbuilt and will last a very long time...

Go for their Street Strip true dual set up. I've been running mine for over 10 years.

I picked up a RB SP dual setup form the header all the way back used for $400.00. They are so
thick they last forever so getting a used one is not too risky and a lot cheaper than the new
price. Blasted and painted with some BBQ black and it all looked brand new and mostly still does.

Much better than my old RE single pipe exhaust.

Get an RB exhaust. They are perfect. Best tone and long lasting. Ive never had a problem with mine.

exhaust sounds great!

Look it up on youtube

RB's full long primary "streetport" exhaust really is the best made, best sounding exhaust out there for an NA that is driven on the street. It costs a lot but lasts forever. I have one on mine and won't take it off unless I throw a turbo in there.

You can immitate this exhaust if you build your own presilencers, but the powerpulse muffler in the back is pretty much a must have part as no aftermarket mufflers can come close in flow and sound reduction in a single canister straight through muffler. The powerpulse employs several key quieting features which other aftermarket mufflers don't have. I could type more but you get the idea.

^
Please type more, I'd like to pick your brain.........

ONE WORD : LAWNMOWER!!! not too loud though

Ok I'll see if I can type this all out. Firstly, you have two options ahead of the muffler, that is, in the center section. You can either have a set of preseilncers, one per pipe, or not. But the presilencers do help with the supersonic exhaust pulse by way of a 4" expansion chamber in front of a 16" core packed with industrial strength pot scrubbers. The expansion chamber and the pot scrubber material help to "shape" the pulse to something a little less like an angry weed whacker. That was key quieting feature #1

#2 is where the two parallel pipes join together at the collector. When you join two primary pipes together, it has a similar effect as when you hook two woofers out of phase with each other. What does out of phase mean? Well, let's just say it kills the bass. This works similar on a rotary. The problem however is if you collect really far away from the engine, the effect is less pronounced. In other words it stays LOUDER the further away from the engine it collects. That is one of the reasons why an exhaust manifold tends to be the quietest, and weakest flowing, followed by the short collected header, then followed by the long primary in that order. There are other reasons, but these are the main ones.

Another reason a long primary is loud is like a columnated beam affect like a laser. If you listen to a rotary without anything on the exhaust ports ie open to the air, it's not that loud actually. But add on a header and long primary but ommit the muffler, and you'll jump out of your skin when you rev it. :) The key here is that the pulses haven't joined. They are totally separate. Like shooting a laser beam of noise at your neighbors. ;)

But I was talking about key quieting features. Getting back on track, #2 was the collector in the 81-82 powerpulse muffler. it collects up above the rearend. It goes from the center section which has RB's thickwall 11 gauge mild tubing in 2" OD with 1/8" wall which is an ID of 1.75", into the *1.6" ID 14 gauge mild aluminized tubes which collect above the diff into a single 304 stainless 2.375" tube which curves down into the muffler. Takes a breath.

*By the way the 1.6" ID muffler tubes look way smaller than the center section tubes, but they aren't in the ID. It's one tenth of an inch step down which is perfect this far back from the engine where gasses cool and contract! Measure and you'll see. Plus it's backwards compatible with a stock 81-82 system which was their other goal.

Quieting feature #3 is the core in the powerpulse muffler. It goes in about half way, then Ys apart. This splitting quiets things. Ask anyone with a single exit exhaust on an FC. They're always louder than the stock FC Y pipe.

Quieting feature #4 are the smaller perforated tubes that Y from the single inlet tube. They are 1.5". Smaller equals quieter.

Quieting feature #6 are the exits of the 1.5" tubes. before they enter the tips. They expand out to a 2.5" mini expansion chamber which slows velocity and reduces noise, similar to a stock exhaust port in our engines!

Quieting feature #7 are the trumpets inside the shiny tail pipes. They have a venturi effect or a velocity stack effect, except there's a bellmouth at both ends. This stretches and speeds up the pulse and then expands quickly but smoothly to the outside world so it in effect shapes the sound once again into something the RB engineers were proud of. I like it too.

Now I'm tired of typing. I hope this was educational. Tuition only cost me one RB powerpulse muffler which I succesfully redid with a set of resonated slant cut tips to try to regain some of the key quieting features lost from an earlier experiment. The result sounds pretty good actually.

I thought of more to type. :)

The current engine in my car has FC NA sleeves modded into something more like T2 sleeves - the diffusers were removed. These are arguably the loudest stock exhaust ports, and yet the full RB exhaust handles them quite well.

Another thing to talk about is the subject of exhaust tuning. I know rotarygod would play with this subject in the past, but he's not here right now. Anyway you know how a guitar string will go up one octave when you touch it in the middle and pluck? Yep, that's called a half wave effect (my term). The exhaust can do this too. :)

Ok, RB says the best exhaust primary length is 102". That's long! Too long for an FB. But if that's ideal, why can't we fake it by going to exactly half that length? So a 51" long primary measured from the intermdiate plate (it averages both due to slightly different exhaust port locations) to the crotch of the collector. Sounds easy right? And it is easy.

In fact, let's say the perfect length is 100" for argument's sake. Then half would be 50" and a quarter would be 25". Well it happens that the RB short collected headers are about 24" so there you go.

But what about 3/4? You know, 75 inches? Would that work? No, I don't think so. The harmonics probably would be outside the range of a typical power band. Rather I'm sure one would be, but the the other two would probably not be ideal. Like maybe at 9500 rpm or something. Too high for most of us.

You have to treat it like a string. You can do 100% or 50% or 25% but 75% won't work. Well, it works but not in the way that will work for us.

But then something occoured to me. In radio, you can have a full wave antenna, or a half wave or a quater wave and they all work quite well, but there is an oddball length called a 5/8th wave. They apparently work well too and can sometimes be the perfect solution for some installations. So then what about a 5/8th wave exhaust? That would be 63.75" (if full is 102").

It just so happens I accidentally have already made and tested a 5/8th wave long primary exhaust and was blown away by the performance both in NA mode and with a Camden SC! It's in the REPU and was honestly the first time I'd ever felt that kind of torque out of a rotary in such a heavy vehicle. The engine was a fresh rebuilt S4 NA with a crappy modded Nikki manifold to fit the 6 ports. No aux actuators or sleeves so all 6 open all the time, and it still had the most torque I'd ever experienced in this truck! The next engine was a 74 ported R5 with a Camden and this time it felt like it had a V8 in it. Of course I'm power hungry now and will go turbo next, but I digress.

I did a quick measurement just dropping a tape measure on the ground next to it and got about 60 inches but didn't account for the 2ish" of curve from the exhaust ports. So I'm calling it about 62" which is close enough to qualify as a 5/8th wave exhaust!

Not sure what the harmonics are like - in other words where the peaks will be, but it feels like there is one at low RPM. This would be that torque I was alluding to earlier. ;)

But don't take my word for it. Build or buy your own long primary and enjoy another dimension in rotary awesomeness that the piston guys can only kinda get close to with an X pipe or whatever they have to use for scavenging. Oh and sorry if anything I typed was hard to follow. It's close to 2AM over here.

lol @ jeff

all good points though. your wisdom never ceases to amaze me sir. and for the record i agree with everyone else about the sound of an rb setup. in one word : godly.

if you get the chance to hear it in person it is way better than the sound on youtube...i had a joygasm the first time i heard one :p

That is a lot easier said than done. You don't see many of them in the classifieds. Of course I'm limited even more needing the ones for the SE.

I have a RB collected header and presilencer on the gsl. The butt-dyno says I lost some torque and maybe gained a little in the higher rpm's (which I am not often using) along with a good bit of noise. Gets a little "raspy" above 3500. I'm hoping it will "mello-out" a little with a power pulse muffler over the stocker when I get around to it....I've read some posts on here that a stock muffler with RB header was a bad combo, I'm curious how much it will change with the powerpulse....ehhh, car is running good and sounds kinda good so we'll see. Couple hundred bucks for a muffler just seems like too much.......

I was running the same combination (all I could afford, used bargain). The sound was too metallic for my taste. I bought over a month these:

Attachment 499705



Attachment 499706

The magnaflow essentially became the mid pipe. I hope it's far enough down stream to last. The borla replaced my stock muffler. The stock tips fit perfectly on the borla, though the outlets are a little farther apart than stock. I'm pleased with the sound. The flow is definitely better.
The magnaflow was 60 some dollars on Amazon, the borla 99 on Amazon.
I think I paid 120 to have it all welded together.
So about the same, but not all at once.

Edit
Wrong pic. My magnaflow is 2" pipe. The borla is 2.5".

uhm.....
Okay, I suppose the following are more of novice / shade-tree mechanic questions. I'll reiterate that I'm learning as I go, although I fancy myself as being able to actually learn:

I have no modifications at all to the 12a that is in the car.

Question 1)
Do I want "Exhaust System: 84/85 12a Manual Transmission" part number 16417
or
Do I want "Street Port Exhaust System: 84/85 Manual Transmission" part number 16423

I am assuming I want the first one, correct? I really have no plans to port the engine...at least not at this juncture.

Question 2)
If down the road (and I mean waaay down the road) I were to swap the 12a for a 13b, would I be able to keep the hypothetical Racing Beat Exhaust system? Would I only need to replace the headers? Or is the entire system specific to one engine or the other? It would seem I could just replace the headers, but I dunno.....

thanks again!

Not really, the second one is misnamed, it should be called the long primary
exhaust system. Its a better solution all around compared to an early collected
system like the first one. Also, it works just as well with stock ported engines.

Yep, just replace the headers and away you go with either one.