Ok, I'm still pretty new with this but I want to know.
Why are the two tubes that come from the header merge together, and then split again? To give the catalitic converter a run for it's money while everything else only ends up seeing half the flow?

I really don't know. Due to uncontrolled surcumstances, I want to re-do my exhaust system. I was gonna use racing beats headers.

The Streetable Header/Collector and a presilencer was what I had in mind, but why split the tube to two mufflers? I mean like, what's the point? It's allready being restricted by going through one pipe.

So then I saw the Road Racing Header. Woopee, it's staying as two seperate lines, and it's cheaper than the Streetable Header/Collector. Now it can be run as a true duel exhaust, but that would add more weight. Would it really being that much more wieght? Would the performance be worth it?

Another thing about this equipment... Racing Beat says " *Legal In California only for racing vehicles which may never be used upon a highway." That's just in California, right?...later

 

well, as i see it( i dont think im alone) you NEED a certain amount of back pressure to make the engine run properly. the stock ports on the exhaust side of things(assuming you havent had them street ported) were designed with emissions standards and performance values in mind. not to mention the cats. the only reasons i can think of for the split AFTER the collecter is heat dissapation. that and it just looks sooooo much cooler with two tips coming out of the rear clip!

truthfully if you split to a tru dual set up you could quite possibly lose power, unless you have a motor thats built to the hilt and is designed to run strait dual pipes.

id say if you do any thing custom to your exhaust(assuming your 7 is street driven) you should go with a high flow cat/collecter and a large dia. single free flowing tail pipe. it may not look as cool(in my opinion) but it will certainly get the job done!

of course its harmless to experiment(within reason) with these types of things, and if it works for the better on a street drivin vehicle, PLEASE show me some pics and stuff. hmm kinda itches the curiosity part of the brain!

go boldly my friend....go boldly!

-chris

 

p.s.

not every state has such strict emissions laws as CA does. for example; SC (where i live... yay!) has no emissions laws (yet... waaaaa ). so you might wanna check with local and state regulations. they might not smile upon that kinda stuff.

get at me!

-chris

 

I heard WOM that "true duals" is good for almost 25hp.....do a search and see what turns up....good luck.

 

Your S5 will gain some top end power when you delete the cat, but it will get really loud without a pre-silencer in it's place.
Full duals sound great but you have to budget for two silencers where the cat was.

My 91NA had full duals.
The pictures & a sound file are linked in my sig below.

 

there is only one problem with true dual exhaust is what about the O2 you would have to add 2 of them then haft the voltage from each O2 using a resistor then splice the two together then connect to the harness or other wise your system is only reading one rotor.
hope that helps


rat

 

quote from racing beat: "The 1989-92 6-port engine does not require the use of exhaust backpressure to operate the 6-port actuator valves, but uses air pressure from the air pump. It is for this reason that the backpressure pick-up tube found on the earlier 6-port presilencers is not incorporated into this unit."

Well I guess that sloves that problem, do I have to block the tube off then?

And about the O2 sensor. I read here that it was barely used, so I was gonna omit it from the design. But I can still add it on currently because of my plan. How would this work?

16127-Road Race Header 84-92
RX-7 13B 6-Port 170.00 170.00
16121.1-Tubing 15.00 15.00
16004-Unflanged Collector Assembly 46.00 46.00
16408-Presilencer 89-92 RX-7
Manual - Non-turbo 160.00 160.00
16197-Road/Race Header
Outlet Flange 12.00 12.00
16177-Presilencer Flange 86-92 RX-7 10.00 10.00
16309-Engine-to-Header
84-92 (6-Port) 15.00 15.00
16300-Road Race Header Outlet 8.50 8.50
16318-Down Pipe 86-92
Presilencer 86-92 7.00 7.00
Sub Total $443.50

I plan on putting the Road Race Header on, and merging it with the Unflanged Collector Assembly, then to the pre silencer, then to the splitter to the mufflers out back. This way, I can acctually save $ becuase I wanted to eventually run the true duel exhaust, but don't have enough $ to buy 2 presilencers right now. And I could put the O2 sensor right after the header, where it will merge into one pipe with the Unflanged Collector Assembly.
Question: can I use any O2 sensor, since it will be equally easy to put any type of threads to mount one there? Or is the O2 sensor specific to the rotory?

Any input would be cool...later

 

Exhaust travels in bursts or pulses. Think of the flow as a dotted line. The lines would reprisent high pressure, and the space in between is low pressure. To actually see the pulses, dangle a piece of notebook paper in front of the exhaust pipe. The low pressure areas create a vacume effect on the high pressure areas slowing the exhaust flow. True duals make this worse since the space is increased between pulses is greater yeilding a greater area of low pressure. The best way to run true duals is to have an equalization point via an H-pipe or even better an X-pipe. This will disapate the pulses and blend the high pressure with the low pressure making a semi-even flow. It helps with exhaust port scavengeing and overall exhaust flow.
But noone wanted to know that did they

Oxygen sensors are, as far as i know universal. They might have differant heat ranges, i dunno. I took the new one i had intendet to put in the rx, and used it in an 89 olds calais. Seems like all of the bungs are the same too. There is a differance between 1,3,and 4 wire sensors though. 1 wire-narrow band, 3 wire-heated, 4 wire-wideband. I could be wrong about this one though.

-E

 

i believe the above post regarding the h/x pipe is incorrect. i am not certain, though. there was a thread some time ago about it.

 

too busy at work to read all this.

https://www.rx7club.com/search.php?s...der=descending

 

It makes the mufflers twice as effective since they're only dealing with half the noise enegy each, and if the pipes are sized correctly and it's well-built it can be less restrictive than a single.

Off-the-shelf dual-muffler systems tend to use pipes after the Y that are too small, so the equivalent single system (i.e. from the same company, using the same initial pipe size) will flow slightly better. I doubt you'd see much of a performance difference though. Custom dual-muffler system where that use bigger pipes are a whole different story.

For an NA street car IMO you're nut's going with a single system. Rotaries respond very well to a free flowing exhaust, buy with that come a helluva lot more noise. While you may like excessive exhaust volume, cops and neighbors usually don't, and that's grief nobody needs.