mazdaspeed7

Quietest depends more on mufflers than anything else. And I dont know if there would even be a measureable difference between a collected dual and a collected single using the same mufflers. At most, maybe a hp or two.

1987RX7guy

iTrader: (3)

DUALS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

well the fact that the duals use four mufflers (counting the two pre-silencers) they are still kinda loud for that but I love the sound of it. Specialy after hearing it from the outside of the car.

BDoty311

Thanks Mazdaspeed. Good to see you around again, where have you been? nopistons??

controler

You say the cork sport exhaust is really loud? how does it compare to the Apex-i N1? Pricing is a lot better on the Cork Sport, that is why I am interested.

mazdaspeed7

From what Ive heard, the N1 sounds better than the corksport. And the corksport is very loud. I havent heard the N1 in person though, so I cant compare them.

DriftDragon28

After reading this thread i think ive changed my mind on this topic.

I used to think and belive that only collected duals belonged on a 2nd gen. I think most of this came from the fact that it made the car look complete. But now im starting to realize that if the exhaust is collected then it may make more sense to come out single.


However when it comes to drag racing cars where weight is crucial they still run duals with a crossover H or X pipe. Part of me wants to run a single for the weight savings and the "Form follows function" credo but I think im still gonna run collected duals. ITs a much cleaner look and the weight savings isnt really all that much. After all I do have an aluminum hood and no more AC.

Rxmfn7

iTrader: (4)

On your referance to drag racing, are you talking about FCs that run X or H pipes?? Ive never seen that done. On a V-8, yes the X or H pipe is very important, as the flow of the exhaust is way different that that of a rotary.

Jimmy325i

Not really all that different at all. H pipes are used to provide scavenging to the opposite cylinder bank the same as the collector is used to do the same thing with a rotary header. Type of racing has nothing to do with it.

I bet if you properly located an H pipe on those true duals you'd see another couple HP and probably a wider powerband.

RX-7Impreza

you guys who fight about the single looking "unbalanced" or looking wrong on a car with cutouts for duals. i have a single exit that looks completely balanced from the rear. in fact, you cant even tell which side the exhaust comes out from the back and i think my exhaust is lighter and flows more than any exhaust with a muffler.

i personally absolutely hate the sound of duals, true or fake, i think they both sound like crap. collected just has a much smoother note to it no matter how you look at it, plus it requires less "muffling" in order to get a tolerable note.

Ive never seen that done. On a V-8, yes the X or H pipe is very important, as the flow of the exhaust is way different that that of a rotary.

actually they are exactly the same, minus a little volume diff. the X and H pipe work on the principle that there are alternating pulses of exhaust. the collector is placed at a measured point from its origin.

in boinger terms, when one valve opens at X rpm the pulse from another cylinder will pass the collector, creating a low pressure in the opposite tube, thus "pulling" the exhaust out of the opening chamber. this gets more of the burned fuel out of the chamber to allow for better combustion next fire. this is scavenging if i am not mistaken

depending on the distance from the "valve", the rpm at which the optimum scavenging is achieved will fluctuate. thus a tuned x-pipe for a V8will have most of its effect at a low rpm since that is where the power is for those motors.

tuned collector for a rotary will have optimum efect at a higher rpm. generally you want to tune it slightly lower than your peak power or torque.

all of this works the same for a rotary with different terminology. (i.e. valves = apex seal passing exhaust port)

y pipes and x pipes work on the same principle. x pipes work a bit better at this but this can cause problems. if the scavenging is too strong and badly tuned on a rotary, the result can be that during overlap fuel and fresh air can be pulled all the way through , straight into the exhaust. not such a big deal if you are just pulling air, but the injectors only fire once per face. gotta burn all the fuel in the chamber, no the exhaust tip.

so the renesis, with no overlap, would benefit greatly from a well tuned x pipe.

oh, this is also part of the reason that pacesetter headers suck donkey *****, the tubes are different lengths, i know of people who have dynoed lower numbers on the pacecrappers than a stock exhaust, probably due to the fact that they were collecting them and two pulses were reaching the collector at the same time. plus they have crappy welds.

i think i babbled on long enough, adam tell me if i missed anything

Justin

mazdaspeed7

Youre a little off on the problems with x pipes on a rotary. Rob Golden had some experience with x pipes, and his problem was the powerband was too narrow. The pulses interfere at rpm's other than what its tuned for. This is problematic on the x pipe, b/c it makes very effective use of the pulses. It lost a lot of power out of th epowerband, and gained a lot within the powerband. But the powerband was too narrow to be worthwhile.

Y pipes dont scavenge as effectively, and therefore lose less power out of their powerband. Also, the nature of the transition from 2 pipes to one helps the flow of exhaust gasses. Again, less losses out of the powerband.

In defense of x pipes, I think Robs tests were far from definitive, and I would imagine he didnt spend a great deal of time testing and tuning it.

X pipes work great on V8's for 2 reasons. One, ots crossing over exhaust from 4 different cylinders on each side. There are considerably more pulses, and theyre not very strong, and run together soemwhat. Second, they have inherently narrow powerbands. The simple fact that rotaries can easily run 8K rpm with bolt ons requires a completely different tunign strategy than an engine that will never see past 6K rpm, an usually makes peak power closer to 5k.

Net Seven

iTrader: (5)

So what would be the best exhuast system for an NA? I want to keep dual exhuast because i like how it looks... so I want to get the y-pipe kind since its cheaper. Lets start with RB road/race header, then what?? then the y-pipe with mufflers at the ends.

1987RX7guy

iTrader: (3)

I think that the DUALS would be better for the N/a since you want to keep the two outlet design

SerpentineGX

Get titanium cans. Light weight but very expensive.

RX-7Impreza

actually that isnt true, the convergence of a y pipe increases hp and torque, breaking them apart after that is purely for aesthetic value and would have a minor negative effect due to weight.

in response to the tuning of y and x pipes. the increases in the powerband are actually audible since when the pulses are perfectly timed you will get a steady beat. you could actually measure the note it creates by calculating the frequency of the pulses, but when the exhaust starts to "sing" that will be where you are getting the most gain. funny thing i noticed on my exhaust is i have 2 areas where it harmonizes. just based off of acoustic principles, approximately 1 octave apart

thinking about this, i assume when Rob did his test he shot for gains in the middle of the powerband, but theoretically there should be multiple points in the powerband where the scavenging effect is optimal, unusable for low rpm v8s, but a rotary with its two distinct, high volume pulses could possibly use the multiple "harmonizations" to a great effect. i have to do some math to figure it out, but, with a high rpm built motor (10,000rpm) it could be possible to cause the powerband to become very flat, this of course would lower the peak power, but the longer band would be much more useful, especially in AutoX


Netseven,
if you want to go with a dual exit, go from headers-ypipe(2-1), go however far back you want then split into whatever heavy assed mufflers you want to use. this is far from my recommendation but it would be the best for power if you have to look "balanced". waste of space and money if you ask me, for less overall gain. take a look at supertrapp mufflers though.

Adam what do you think of my theory?

Justin

mazdaspeed7

Sounds pretty good. I guess now might be a good time to tell you that your exhaust (and all other short primary exhausts) are tuned at the 2nd octave. An exhaust tuned on the first octave would require each of the pipes to be betwen 6 and 7 feet before the collector. That would put the collector right about where the differential is. Its possible with a single muffler, but duals is impractical. Thats one of the reasons you rarely see long primary exhaust on an FC. I did see pics of soemone who did that a little while ago, btu I dont remember who it was.

The short primary also can have 2 rpm points where its tuned at. The wide powerband of a rotary makes that possible. Thats what Justin noticed. And he is right abotu the exhaust "singing". It will sound different at the rpm its tuned for.

Mephis

ITS ALL RICE go for the single who cars if ya try and hop up yer car yer a ricer, o well put a huge tip on there be different!

RarestRX

Yo,


Mazdaspeed, did you have the Mazdatrix True Dual system with the dual Racing Beat presilencers, or did you go custom?

Kevin
1989 GTUs "Now he tells me...."

V8kilr

duals all the way

1987RX7guy

iTrader: (3)

TIMMA!!!!

DUALS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

RotaryWeaponSE7EN

iTrader: (6)

Oh man I have no idea whats going on.

Single!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!

Rx-7Blazin

mephis your so true no matter what you do if you own an import in other peoples eyes if you do any modifications expecially exhaust your considered a ricer. still what i think the definition of a ricer is any overy exjurated car that was once a family/economy car urned into a race car, rx-7's supras, 300zx's, 240-280z's all those are forgine sports cars built for speed and built so people could modify them so i do not consider any forign sports car rice unless of corse there car has been way over exhajurated with wings stickers ducts bodykits ect
just my 2 cents

NZConvertible

Must... resist... posting...!

RarestRX

Yo,


Jason, please post! I just bought a used Mazdatrix True Dual set up, and this damn post is giving me buyer's remorse!

Tell me I did the right thing!

*grin*

Kevin
1989 GTUs "Damn Mazdaspeed7!"

deltr0n`

all the race cars use single...

rotary>piston

yeah but real race cars also strip every possible pound off the car. This is a street car, where form is important too, not just function.
Yes, I think any car that was designed as a sports car cannot be "rice". The only time I ever mutter "damn ricer" to myself is when seeing a protege with euro-lights, a civic with a fart cannon, etc.
Think about it. The F&F supra was a rice car in every respect, but almost everyone still thinks it's sweet.

Anyway, I say go collected header+presilencer+dual cat-back of your choice. You get the weight savings and peak power of collected, plus the much better look of duals.
I could understand putting on a single if there wasn't a section cut out on both sides of the bumper. If you fill in that little 1/3 circle, then it would look alright.