Kill No Cone

iTrader: (6)

Ok, so this is what I am thinking of for my exhaust. I will take a RB road race header with its two 2” outlets and run long pipes down to a Flowmaster. The Flowmaster will be a two or three chamber muffler duel inlet muffler with a single 2 ½” outlet. I will run the one, 2 ½” pipe up an over the axle to a a 2 ½” Borla XR-1 racing muffler.

The Flowmaster is a chambered muffler with no packing and will be used as the “Y” collector for this system. It will end up with long pipes that are about a foot shorter than the RB “street port” exhaust. I will actually be running the exhaust into the mufflers two-outlet side, and then using the single 2 ½” inlet as my systems exhaust. (Ok, so all I am doing is turning the muffler around). The Borla muffler is a straight through muffler with stainless steel wool packing, like the RB presilencers.

My plan is to email Flowmaster and check on how much heat their system can handle. I also want to check if it maters what direction you run the exhaust through their muffler.

I know these parts are not made as heavy duty as the RB parts, but I drive the car about 3,000 miles a year to autocross. Also, they will be MUCH lighter than the RB stuff.

This should cost about $350, as opposed to the RB $780.
My costs:
Header $138
Flowmaster $ 72
Borla $130
Pipe and fittings $ 20

Here are my questions:
Will using the Flowmaster as the collector hurt the scavenging process?
How will this flow?
Will this be WAY too loud?

What do you think?

Cone

White84SE

The chambered Flowmasters I've seen have directional baffles. In other words, they're V-shaped with the outside of the "point" of the V facing the incoming exhaust gases, to split the fumes into two paths. I'd tend to think if you'd turn it around the other way, the gases would be collecting in the V, hurting the flow. I dunno.. try it is about all I can think... LOL

--Danny

racermike

First thought is will the flowmaster fit under car ok, (with enough separation for heat). Second is that it will see higher heat than at the rear of the car. I have seen 2 (I think) flowmasters mounted side by side in the ussual spot (each single in and out) with the twin tubes going over the axle.
The heavier the "pipe" the less noise it will make.

hornbm

flowmasters???

correct me if I'm wrong here, but wouldnt the extreme heat from a rotary exaust just kill them?

I dont see anybody else using flowmasters, and theres probably a reason why.

But its up to you, these are just my uneducated opinions, and I'm still a n00b at this, so I could be completly wrong.

fatboy7

As far as scavanging is conscerned, the fact that you are going to mess around with someone else's header to me screams NOT a good Idea. Those headers were made with a tuned length and a collector that augument each other. They're tuning the pressure waves in such a way as to increase power in the top end. Adding your own collector which will seriously alter the returning pressure wave -large increase in volume sends a narrower larger pulse- which may or may not give you power where you want it. I think you could try it, you may be suprised that it works well. Just remember pressure wave tuning is an art, and unless you've made a few headers, you're running around the Louvre with fingerpaint on your hands so to speak.

As far as flowmasters are conserned, I've heard they sound pretty poor on a rotary, but as to its directionality I have no idea. Being that your making it act as a presilencer your Borla might be the dominant character in the sound scene. If you get the stainless version, it should last no problems.

racermike

The headers he's talking about are uncollected, and designed with twin long tube exhaust in mind. Racing Beat system mounts 2 "power pulse"s at different lengths, then collects them at the muffler.

Hyper4mance2k

iTrader: (40)

if you think you're gonna put a flowmaster on backwards and gain flow your drunk!!! flowmasters are as one way as you can get. if you're gonna do that you might as well leave on the stock exhaust manifold and weld it 3/4 of the way closed and see how that flows!! lol not trying to flame just you ccant put a flow master on backwards

Rx7carl

Why not use a borla xr-1 as the presilencer? Its SS wool should last right? Put one in each pipe, put the collector as far back as possible, and if its race only, run the pipes UNDER the axle. Where can I get info on this xr-1? price, size????????

lotsacars

Are you thinking of using Flowmaster's 80 Series muffler?



If you use that one, one of your pipes will end up being straight through. That muffler is designed to have the inlet on the left and then the other two are the outlets. You'd probably get some pretty wierd results having half of your exhaust presilenced and the the other half just blowing straight through.

If you're using something else then disregard this post

Wankelguy

Bear in mind that a quasi long-primary system like you propose is best suited to street-ported motors. If you are running a stock port motor, you may sacrifice a bit of low-end torque in favor of a bit more top end power. Is that what you want for autocross? That is, if using the flowmaster as a collector works at all, which it doesn't sound like it will. -WG

racermike

"""sacrifice a bit of low-end torque in favor of a bit more top end power."""

It can only go so low, but it can REALLY go high!

"When you hear the buzzer, count to 5 and shift!"

82streetracer

iTrader: (1)

flowmaster makes a long skinny dual in dual out muffler for big block trucks. If you put that on a rotaty I bet it would sound sick.


I recently installed one of my old flow 40 series deltas on my friends carrado. with a flowtech header. it sounds really cool. unlike anything else.

82streetracer

iTrader: (1)

also, flowmasters are beefy as ****. you could compare there build to that of racingbeat.

the ones i had must have weighed 35-40lbs easy.

very,very tough.

DriveFast7

iTrader: (1)

Using a 2 into 1 muffler as a collector is not in the best interested of flow. They don't collect as efficiently as a dedicated purpose build collector.

Flowmaster does make a real nice collector. RacerParts sells it. I got it on my racecar and it as a nice big collector area, larger than the racing beat one.

-bp-

rotarygod

iTrader: (1)

I have a friend with a 455 big block running 2 flowmasters in a non collected true dual system. Years ago when the moron welder installed them he put one of them on backwards. For a couple of years the car kept having problems with the header gasket blowing out on that side and eventually that muffler was the first one to disintegrate. The carb was always a bitch to tune as well. After they were properly replaced the car ran faster and responded to tuning much better. No more gasket problems either. They are definitely designed to only flow one way. Summit Racing does not recommend Flowmasters for rotary applications. It says it in their import catalogs. They do sell the collector that DriveFast7 mentioned. I have one on my 2nd gen. The small one is 2-2 1/4" pipes which collect to a single 3". It is too big for n/a header collectors unless you have a peripheral port. I'm using it as the Y-pipe and not a header collector.

This has already been stated but I'll ad my .02. By using a 2 into 1 muffler as a collector you are really losing the scavenging effect of a true collector. Both pulses will enter the muffler and be bounced around sometimes interfering with the other side and sometimes helping the other side. A properly designed collector has a gatlin gun effect. Each pulse stays at a high velocity to further help reinforce the other side and suck it out of the pipes. Without a good collector you may as well use the factory exhaust manifold. It is terrible for flow and wouldn't work any better if it was on the engine or at the back of the car. It will help quiet the car though.

Fennix_sr

my system is a custom made header for my 12A uncollected but collected with a Y tube... followed by a cat for silencing... straight pipe over axel into a SS straight through muffler witha 4.5" tip very loud when you get on it but great when cruising or deceling. this whole set up cost...


Headers,ypipe,cat: 110$
SS muffler : 170$
Shop fabrication of pipe bend over axel flanged onto muffler: 120$ no tax



im very satisfied with this job, i was not going to spend all that money on the full RB exhaust, not that it is bad or anything just im a poor teenager

Kill No Cone

iTrader: (6)

Hey guys,
Thanks for all the great feedback! I have learned a lot from you. I have followed up with the Flowmaster Techline and I have some addition info for those that asked.

 The Tech person stated that Flowmasters are unidirectional, (just like you said). The also stated that the regular Flowmasters are not rated for the heat the rotaries put out, but their racing models would work. His suggestion was to move the Flowmaster as far back as possible, but that this would change the sound.

 Yes tuning the dynamic pulses of an exhaust system is complex and the scavenging aspect of a good collector are not going to be present in a Flowmaster.

 Flowmaster does make a duel in, duel out muffler for a big block, yet this would still not give me the exhaust scavenging effect, but it was a great idea.

 A stainless steel Borla Xr-1 can be purchased from Summit Racing for $130.

 I know there was talk about the sound deadening effect of thinker exhaust pipe. I know that this is true but the weight concerns me. When the weight of the 1/8” steel header, two presilencers, pipe, and powerpulse muffler are added together you get quite a heavy exhaust system.. I want something that is a good deal lighter.

 Yes, my plan is to run a street ported engine and that is why I am looking at the long tube exhaust system. But, RB says it should be 120”, which is a whole lot of pipe!

Hey, thanks again for all of your feedback!