Not actualy true, Two muffs = greater flow.

 

^yes but less bends also = greater flow

 

And your the guy that thinks all RX8's dyno exactly the same right? 2 pieces cut from the same cloth ring a bell? hahaha

 

same here

thanks for putting the vids together!

 

I could be wrong but, I believe the exact quote was with a 5% variance so that would not be exact would it?

 

Well, DDub, didnt you have the Legamax first and now do you have the single exhaust....the Legamax pipes are smaller in diameter as well right? Have you dynod them both? Anyone dynod both on the same car?

DD, at it again ay? Stick with HKS and all your XS worries will go away....

 

That is true if the exhaust is under 0 pressure, if the exhaust is underload then it does not matter how many bends you have. The issue would then be whatever the greatest restriction is. If you are catless pipe that would be the muffler.

In doing some fuzzy math with information on this site the HKS single would be at approximately .27 - .32 under WOT (estimate because I could not get an exact CF or muffler restriction).

The only way to be absolutely certain it is to cut a small hole in the exhaust and place a pressure gauge in the hole.

If you have the exact same pipe and two mufflers it would flow more freely because you would be providing twice the through put. The gas does not care which way it started it just cares where it can get out.

 

If they made a 3inch worth anything then I would switch.

My only worry with the XS is it hangs too low.

 

Not necessarily true. I dyno'd 19 RX-8's in one day and the HP figures ranged from 198.490 to 169.070

 

the peak power was about the same (Hi-Power vs Legamax), but the single side graph had slightly less upper mid range, but slightly more top end.

 

Those 19 were all stock or had the exact same modifications?

 

no major modifications. mainly exhaust and only some had intake. The one at 169 had intake AND exhaust. Even with the 2-5 hp that an intake / exhaust COULD give you, that's still a fairly wide margin

 

One guy had intake exhaust flywheel, mid pipe, rb flash, and dynoed one of the lowest..hehe i have intake exhaust only and made 190 whp on a couple of runs.

 

But the cars did differ, the argument was this.

I stated that a car with the exact same parts would have a small variance of 5% (I believe). Even with the top bound and lower bound you have stated and tossed against an av bell curve with a shift of .25 you are looking at around 6% variance.

That is even with a tainted sample because of the un-matched modifications.

I'm almost willing to bet if you provided me the numbers it would fall into the stated variance.

 

Actually less bends equal more flow no matter what the pressure. The gas does care about changing direction. Fluid dynamics explains this. The fact that the gas is moving at speed means that upon ecountering a turn it suffers centripetal force and all the gas want to compress against the outside wall of the piping therefore increasing friction against the walls dramatically.

When I was getting my bachelor's we did an experiment in the fluid dynamic's class to clear up some doubts that had risen from this fact, I was one that doubted it. We took a 1" diamtube with 4 90deg bends and the same total lenght and a .75" tube with no bends and hooked them up with several intruments like airflow meters and pressure gages in different points along each pipe and the results where astonishing. the .75" flowed the same amount as the 1" and if you do the math the .75" is equivalent to a 2-1/4" diam pipe when compared to a 3"one. Not only that but the flow of the .75" was less turbulent meaning it was constant whereas the tube with all the bends you could see the pressure equipment ocssilating.

It is true however that one 2.5" pipe with one exit will be outflowed by one that divides into 2 2.5" exits. But a 3" with half bends will definatly offer less resistance, even if you divide the 2.5" into four pipes youre still forcing the gases through at 2.5" pipe first....

Chris

 

I had the same class at MIT. That experiment only holds true if the chamber (Tube) is not under pressure.

In that experiment the only factors are, the rate the gas is introduced and the turbulent flow picked up along the way.

If the chamber is presurized it picks up resistance as soon as it enters the chamber, Some turbulent flow can be picked up as it is propelled but that is negligable. The gasses are only going to leave the chamber at a rate dictated by the exit area or restriction.

At least we agree on a 3 inch with two exit areas will out flow one with a single


I just read your post again and I think by "presure" you are refering to the rate of the gas being intoduced. I'm talking about the positive presure of the chamber after the gas is introduced

 

True, if the chamber is pressurized it does pick up resistance as soon as it enters but when I said pressure I was reffering to the same pressure you are reffering to, the bends cause a pressure increase because they post a resistance to the flow and since the gas has to be forced through the resistance it must gain a little pressure to do so. This quantities are very small but they do pose resistance.

We do agree that a dual 3" will flow more than a single 3" but it must be made clear that this is asuming that the total pipe length is the same and that the dual 3" splits into two 3" pipes(not two 2.5" ones) and that it doenst suffer more bends than the single 3" which is usually the case when comparing the HKS single to other dual 3" exhausts on the market. In reality, muffler choice(straight through, muffled, baffled or non baffled) is as big a factor too.

 

Hello guys!
As promissed here is a link to a video of the car with the hks single exhaust and my turbo kit that will be on sale shortly. The car still needs to be tuned in the midrange and I didnt go past about 7000rpm which is when it really wakes up so bear with me. This is just meant to be a teaser. I just wanted to show you what a bigt turbo rx8 sounds like with the hks single....Enjoy:

http://www.youtube.com/watch?v=jqg3U7YkN68


did anyone say effortless flames?

Chris....Esmeril

 

cool clip.. but get the fuel tuned. The explosions don't help with the catback lifespan

the turbo kit looks really nice too

 

doesnt sound very different than an NA with Legamax and racepipe IMO, nice little gurgle to it..

http://s79.photobucket.com/albums/j1...rent=Fire2.flv

excuse the commentators, guys.....

 

The fuel just needs to be tuned in the part throttle range, the explosions are happening after full throttle runs so I think they are not going anywhere...I dont really mind if they stay

Chris

 

it's too rich when you let off the throttle. you can tune it out.. it's fun for a while, but gets annoying because sometimes instead of a giant flame, it can have a slow burning fire look to it, and people will yell and scream that you're about to die because your car is on fire.

 

The video really doesnt do it justice(converted from camcorder to digital). In person its a totally different sound, I have heard a legamax in person and it sounds nice but you can still hear the mumbled factory Rx8 sound, the Single hks without a cat and with the turbo actually sounds like my friends FD(alot of gurgle ) until you go really high in the rev range, then its just plain beautiful :D.

Chris...Esmeril

p.s.Funny commentators....haha

 

well I do love HKS and look forward to hearing it in person soon!

The flames are from my NA Interceptor X.....dumps on decel

 

nice! yes it has that gurgle to it, that turbo really quieted the single side down alot! very nice!