nima_taba

Yeah I will be driving it places....but with a pre-silencer, teh single won't be unbearably loud will it?

PaulC

I liked the singe N1 and bonez cat combo I had on my 87 sport. It also seemed to have more power over the dual 2.5" custom that was on there.

flubyux2

Single canister ricey? not quite so

Driverside exit looks goofy? just as goofy as pass side.

single exhaust too small? an 2.5" exhaust is almost too big for an NA single. at least tahts what Mazdatrix says.

my excuses for single can on the driverside are:

its Jspec routing. in japan, they are right hand drive right? and the single exhausts are supposed to come out on the passengerside of the car. look at all the cat backs. every single one exits on the passenger side. in japan, the exit on the LEFT side of the car. btw, i took off my Mazda badges and put "Savanna" badges on it too. but no GTC or GTX badges since its not turbo.

this single exhaust is WAAAY lighter than the original set up, or any other dual. the mufffler is an Arospeed bomb. and u know how cheap/shitty they are right? well its cuz they dont put stainless steel packing in their mufflers like Apex. its like 8 lbs. the N1 is like 20 lbs or something crazy. not to mention, to run duals, you have to split the pipe (creates turbulence), and then have Double the pipe and mufflers. and all that weight adds up. i come from a muscle car background, where you are a POSER if you have duals that came from a Y pipe. its TRUE DUALS all the way, or just keep it single and stop trying to pretend.

and mine is NOT hanging down excessively, sticking out 4" past the bumper, or offset and pointing out "crooked". its tucked up under there, and looks very understated. belive it or not its a 4.5" tip, and an 8" can. my only problem is, it gets the bumper sooty and carbon-y over the months. just takes gelcoat cleaner, meant for boats. ive never banged that muffler on anything.

the sound is ANYTHING but understated. its as loud as a crotch rocket w/ a pipe. you can hear it from MILES away at night time (air is cooler, denser, so it carries sound farther).

the Benefits? since its single pipe, all the exhaust has to travel faster to get out the same orifice. this means BIGGER FLAMES! ive got one on video thats about 2 feet long. almost as big as the flame from that white T2 on the road course being used as an Avatar.

weight savings. right now, my car is down to ~2500 w/o the driver, couldnt have done it w/ the stock exhaust, or any cat back system. this is completely custom.

Aesthectics: very subdued and understated. wont get you pulled over (Except for noise violation), wont get you revved on by every neon, escort and Fokis. sticks to the "Less is more" attitude.

DUAL EXHAUST:

the engineers at Mazda are right for putting duals on the cars. do you know why? ill TELL you why

as the exhaust cools, it contracts, so it takes up less space. BUT, that doesnt mean you can actually use smaller pipe as you go farther away from the engine. the truth is, since it gets more compact, its more DENSE, so its heavier and harder to push. so you need a BIGGER pipe w/ more cross sectional area. cuz as the exhaust rubs up against the pipe walls, it creates friction and resistance to flow. to the farther away you place the walls, the LESS friction/resistance there is. meaning, you can get the heavy, colder, denser exhaust out of there much faster and easier. and 2 smaller pipes flow more than one Big one. this is the SAME principle behind mutli-valved engines. 2 small intake valves flow more than 1 big intake valve.

single 2.5"= 4.90 in/2
dual 2.25"= 7.95 in/2

theortically, duals can flow more than the typical single. but, throw in Crush bending, poor joints, or too Many unneccesary bends, and either one can suck worse than the other. so make sure you go to a GOOD muffler man.

besides, you wont have an empty cut-out on your rear bumper...

chris

omochi

single doesnt look sutpid


i have dual but woudlnt mind single..

NZConvertible

Technically correct, but the weight difference between single and dual is probably ~25lb, or 1% of the weight of your car. Lighter yes, but noticeable...? No, that’s wrong. The density does decrease, but it’s the volume that drops. The mass can't increase; that’s physically impossible. It’s takes just as much work to push, it just takes up a bit less space. Exactly, this is why dual 2.25” will flow at least as much as a single 2.5” (NA) and dual 2.5” will flow at least as much as a single 3” (Turbo), even allowing for the Y.

2ndGen.rocket

HAHAHA, well said. I live in upstate NY, this is ponycar heaven up here so I know exactly what you mean. if you aint got true duals, there's no point in pretending you do.

rico05

N1 single is the ONLY way to go!!










Ok....so I am a bit based!! That's what I use.

Matlock

Everyone seems to think that the singles add a lot more power. I really don't think anyones single is going to yield 50hp here, maybe 5, maybe 10 at most. Go with what you like, I personally like my dual RB's but some would prefer single. The only real advantage to a single would be cost.

kabooski

Sorry bud Let's compare REAL WORLD results
shall we

Me: Single Ultra FLow - 13.5@105 MPH
Only "external" Mod
Mild Ported engine

The advantage of RB Duel is NOISE managemnt with added performance over stock

The choice is yours, Loud single exhaust under WOT
Best HP increase

RB duel with marginal increase in HP but near stock sounding decibles

Kurgan

I ditched my RB dual exhaust beacause it didn't flow enough. It was like a plug in the exhaust.

I'm going with a single exit, Borla XR1 with 3.5" pipe all of the way off the exhaust housing on the turbo.

As far as looks, I used to favor the dual, but now I'm really starting to like the look of a single...

In my case, form follows function... which is how I think fast cars should be built.

Matlock

kabooski I fail to see the real world results, how much horsepower did you gain on the dyno, what did you run with dual, in paticular RB's! Real world results are not just your time, I need to see what you ran before. I totally believe there is an increase, but not much. Did you run a 14.9 before with RB duals or what? And I do believe that we are talking N/A atleast thats what the starter of the thread has.

kabooski

no problem Forum member Little Donny has a complete RB Duel exhuast
with 680 secondarys and a Apexi s-afc
mazda reman motor

we both ran at a Import Battle event last year
ask him what he ran and what I ran
both on plain street tires

PM him

Matlock

I pm'd him, I am curious why you can't enlighten me as to what he ran. I just would like to know how much hp gain you really get single vs dual on an N/A. I don't think it's a whole lot. If I could gain another 5 going to single I wouldn't just because of noise. If I could gain 25 I would go single because that's a substantial gain.

Turbo Timmy

My personal best is a 14.1@99. Since I got the SAFC and a walbro my times have been high 14's since I'm having a hard time tuning it.

kabooski

<----soon 12's on STOCK turbo
1 more month till my car gets done

Matlock

But whats the point? Those are excellent times guys. However this guy has an N/A and will probably never see 13's unless he plan's on N20. My other question for a fair comparison between single and dual is, do you guys have identical reaction times? And do you guys have identical mods excempt for exhaust?

Impressive times, I wish my N/A would run 12's but can't complain about my car.

Turbo Timmy

True plus he's ported and I'm not For an NA get the bonez pipe and a Apexi N1... you'll rip the stereo out of your car it sounds so nice!

autocrash

uhmm... wtf.... I plan on having my car a LONG time....

flubyux2

the density increases which is the problem. since the molecules cooled, it means that they are less excited, and can stay closer together, and get packed closer together, more densley packed if you will... the exhaust cools, and it gets DENSER, thus heavier to move. thats why a lead brick is heavier than a clay brick, its more DENSE! its harder to push.

think of hot exhauts and cold exhaust like Syrup. stick your Log Cabin maple syrup (or honey, whatever) bottle in the microwave for 30 seconds, its easy to squeeze out thru the small orifice. now stick it in the fridge for an hour. then try to squeeze the same amount of syrup out...it flows LESS readily cuz its DENSER, and COLDER, and HEAVIER (per cc) this is a weight issue, not mass. it would take much longer to squeeze out that cold syrup thru the one orifice, now try to squeeze that same amount out thru TWO orifices, or 3 or 4, or more. you can flow that same amount FASTER w/ greater ease as the cross sectional flow area increases. whats so hard to understand about that?

are things opposite down under? should we call it Opposite land?

j/j. but seriously, think about that.

Duals are really only more beneficial from a HP stand point if they are TRUE duals. including un-collected primaries, and twin pipes all the way back. its supposedly loud.

Y-pipe duals have benefits, but are probabaly offset by the weight penalty over a single.

Collected header into single exhaust is probably the best way to go for an NA. weight savings, and unmolested exhaust flow. plus cheaper than having a custom or pre-fabbed true dual system.

btw, when modding an NA, the easiest way to go faster, is making the car lighter. my car is pretty quick considering the mods.

~2500 lbs w/o driver, typical weight loss program
stock ports, unported mannifold, stock 6PI opens @4000. the significant upgrades are K&N filter, gutted precat, race pipe, single 60mm exhaust, TB mod.

i ran a 15.2@93mph, spinning off the line, thru 1st gear, chirping 2nd, at Norwalk raceway. so its a quality track, complete w/ traction compound. if i can get it to hook, i think its possible to break into the 14s. this is ALL before adding a Header, Pineapple sleeves, and intake porting. maybe a cold air box too. btw, Stock ports, not streeet port or bridgeport. stock clutch and driveline.

like i said, cheapest way to go fast is get LIGHT! every little weight loss mod will add up. ever hear the phrase "its gonna Nickel and Dime me to death!" 5 lbs here, 10 lbs there...before you know it, youve dropped 200 lbs, like me.


chris

BLUE TII

iTrader: (9)

quote: Sorry to generalise, but there's that American off-the-shelf attitude again. You can have any exhaust you want by buying the muffler(s) of your choice and having the rest custom-made. Pick any pipe size and configuration you want

Off the shelf stuff is usually cheaper for the same item here in the California, since it has the advantage of mass production in a large marketplace. I'm sure I could have a cheaper exhaust made, but it wouldn't be the same quality. Maybe in NZ everyone thinks Japanese performance parts are gold, but here in California everyone thinks their labor time and equipment overhead is gold. Its called "custom work" and it usually costs more for equal or lower quality than off the shelf goods.


quote: Why SS? There're only two advantages; longevity and looks. A system made from aluminised mild steel painted with a quality high-temp paint should last many years before it rusts out, and who here would keep an exhaust that long, let alone a whole car! As for looks, it's under the car! Apart from the fact it'll be covered in road grime in under a week, it's barely seen.
Sorry for the rant...

SS has much better strength and resistance to heat- in addition to the advantages of longevity and looks. Thus, they can make the piping out of much thinner metal w/ a SS system for less weight. For instance my Spec 90 looks to be ~18-16 guage SS- how long would that last w/ mild steel, especially in a downpipe exposed to the heat of a turbo running antilag? Yes, I plan to keep my car for a very long time- I like it! My crome look ceramic coated RB system's piping stayed nice and shiny on my car for over a year, SS should be the same. I don't rally my car! I don't mind the rants, for sure- but remember everyone's circumstances and quality/performance criteria are different. To generalize, your NZ custom is cheaper/better attitude just doesn't apply everywhere. We are blessed w/ good availability and decent prices for off the shelf goods and cursed w/ terrible prices and workmanship on custom items.

ReZ311

iTrader: (4)

Here is my single:

VIDEO: http://www.calinetworks.net/rez/movies/rezRX7T2.mpg

*right click, save as.*

The first 20 seconds is the HKS superdragger muffler. turbo on back is 3 inches. the second part is the APEXi N1 3 inch all the way back.

Too bad a drunk driver had to hit me 2 months ago. =( Now I gotta swap all my stuff.

PIC:

NZConvertible

I think you need to go read a physics textbook…
Density is mass/volume. When something cools, it contracts (reduces it’s volume), it does not get lighter! For an object to get lighter, you must remove mass. Since we’re talking about a flow situation, the mass flow must remain constant. The mass flow in must equal the mass flow out (unless you have a leak…). Exhaust flow is nothing like golden syrup. You can’t compare a gas to a viscous fluid, they behave quite differently. For starters, you’re confusing density with viscosity. These are two completely different things, and viscosity is completely irrelevant when discussing gases. Your microwaved maple syryp will have expanded very slightly because it is warmer (but it has not gotten heavier), but it’s the large increase in viscosity that makes it flow easier. Wrong again, mass is much more important than weight. Weight and mass are often thought of as the same thing, but they are completely different. Mass basically relates to the number of molecules of a substance present. It is not changed by temperature or pressure. Weight is the force that results from a mass being accelerated. For example, the mass of your body is accelerated downwards by gravity resulting in a weight force on the earth.
Back to our exhaust, neither weight nor mass are changed when temp changes, so neither are actually relevant to this discussion. Um, I’m the one arguing for dual exhausts...

Please don’t try to explain physics to me. I’ve been doing it a long time.

nima_taba

First of all, the density isn't changing. If you cooled a balloon full of exhuast, then density would change as teh balloon shinks. A gas will always fill its container. Therefore, since mass isn't changing, and the volume of the exhuast isn't changing (theoretically speaking about a straight single pipe), density isn't changing. And the drop in temperature might be 200-300C....again, not a significant enough temperature drop to cause the viscosity of a gas to change significantly. A gas will flow extremely well until you approach its condensation point.

Nima

Thaniel

I totally agree. Why wouldn't anyone keep thier Rx-7 a long time? If it's a good car I say keep it. After 8 years I am still saying that.

NZConvertible

Yes it is changing. Any time a gas cools it contracts, and if yolume drops, density rises. In an exhaust pipe this means that as the exhaust cools and contracts it must lose velocity. So even though the mass flow cannot change, the velocity is higher at the engine end than at the tailpipe.