Exhaust diameter and power
05-10-2007, 01:05 PM
#26
Pfft...both yous guys dont hold a candle to muh uber knowledge of <INSERT_THINGI_HERE>...so its eviltwinkie FTW regardless!!
Tis time this thread got toasted...
And with that...this thread now dies...
Eviltwinkie - Toasting more threads than all the threadkillers combined since 1902...
Tis time this thread got toasted...
And with that...this thread now dies...
Eviltwinkie - Toasting more threads than all the threadkillers combined since 1902...
05-10-2007, 01:34 PM
#27
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05-10-2007, 01:40 PM
#28
Before you get flamed...I was also once a non-believer like you...then I searched and found the answers...
SCAVENGING EXISTS!! ITS BEEN PROVEN!! AND YES ON THE RENNY
kthxbi
SCAVENGING EXISTS!! ITS BEEN PROVEN!! AND YES ON THE RENNY
kthxbi
05-10-2007, 02:01 PM
#29
I read his absurdly long post wherein it contained the answer. I trust the rotary gods...and god singular in regards to that information.
https://www.rx8club.com/showthread.p...ght=scavenging
05-10-2007, 02:07 PM
#30
Registered
Scavenging from the standpoint that the moving exhaust gasses exiting the engine themselves help pull in more intake air during overlap is not going to happen. This is what we technically consider scavenging. However if we keep the exhaust gas velocity such that it leaves the chamber at a lower pressure than ambient outside air, which is very possible, when the intake ports open, the air in them will have a stronger pull and get moving faster. Obviously you can't do this at all rpm's at one time so proper sizing is critical but it's very possible.
A built in EGR effect isn't going to happen if we don't keep any air in the chamber. Remember that since we can really only make this happen over a narrow rpm range, at lower rpm's we will still have a built in EGR effect of sorts but not at high rpms where we will get a "scavenging" like benefit. The rotary has never had emissions issues at higher rpm's anyways.
A built in EGR effect isn't going to happen if we don't keep any air in the chamber. Remember that since we can really only make this happen over a narrow rpm range, at lower rpm's we will still have a built in EGR effect of sorts but not at high rpms where we will get a "scavenging" like benefit. The rotary has never had emissions issues at higher rpm's anyways.
05-11-2007, 09:58 AM
#33
In other news...I reviewed a good chunk of your postings and did not really seem to run into anything in regards to scavenging...I know alot of the exhaust stuff you've done but nothing that really covered that aspect specifically...I miss something? Care to point a finger (and not the one you normally point...heh) in the direction?
05-11-2007, 10:20 AM
#35
I have no doubt...But I dont like to assume anything and would prefer finger pointing...heh...again...not with the one he normally uses...
05-11-2007, 10:26 AM
#36
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05-11-2007, 10:35 AM
#37
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I know Speedsource is using 3" header back, but they don't say if they gained or lost power in the lower rev range, and clearly for the ST cars they are only concerned with gaining power in the upper RPMS.
05-12-2007, 12:17 AM
#39
Sonic, the boost is not instant with an S/C as the ability of the S/C to move air is directly linked to the speed of the crankshaft/e-shaft. The quick boost you speak of is really a benefit credited to the turbo system. Generally, S/C's are better for M/T's and T/C's are better for A/T's.
All I will say, at this point, is that I disagree with your understandings of the transmission types/boost methods and combos thereof.
All I will say, at this point, is that I disagree with your understandings of the transmission types/boost methods and combos thereof.
But your right, I do have a lot to learn. I'm very open to learning more...
Mazda's stock muffler is 60mm (2.3 in) and the Mazdaspeed muffler is 65mm (2.5 in)... In the case of the Mazdaspeed muffler, you would think Mazda would go bigger if there was something else to be had. The Mazda techs and R-Magic guys I've talked to, thought it was wise to stay 65mm/2.5in for NA.
If 3" pipe was the magic number to greater HP, it would be crazy for Mazda not offer a Mazdaspeed muffler that size (though Mazda is just not doing justice to the RX-8 with Mazdaspeed upgrades).
Should I toast this thread now...or just whip out the bread and load it up....
Last edited by sosonic; 05-12-2007 at 12:19 AM.
05-12-2007, 07:11 AM
#40
Bummed, but bring on OU!
Sonic, the boost is not instant with an S/C as the ability of the S/C to move air is directly linked to the speed of the crankshaft/e-shaft. The quick boost you speak of is really a benefit credited to the turbo system. Generally, S/C's are better for M/T's and T/C's are better for A/T's.
All I will say, at this point, is that I disagree with your understandings of the transmission types/boost methods and combos thereof.
All I will say, at this point, is that I disagree with your understandings of the transmission types/boost methods and combos thereof.
05-12-2007, 11:57 AM
#41
Registered
sosonic: If you ever get the chance go measure the outlet size of the stock exhaust manifold. That should explain why Mazda only went so large with their muffler.
I have measured the exhaust runner (not port) area in the Renesis plates and added the total area up. They add up and just barely fall short of being the equivalent of a single 3" pipe but are larger than a 2.5". They'd be slightly larger than a 2.75" if we could find one. 3" is the closest you can get.
However saying that, it is my opinion (until I test it to actually verify it) that the exhaust runners don't need to be so large as the ports themselves can't flow as much as the size of the runners imply they could. I believe that at some point in the future we will see some new exhaust sleeves appear that are designed in conjunction with the size and shape of the ports to promote smoother flow through the exhaust ports and when we do the total exhaust runner area out of the plates will decrease. At least on the outer ports. I see a day coming when everything is done properly and built to work together that the total exhaust pipe area needed to go out the back of the car will be 2.5". Remember that even a race built peripheral port 3 rotor only needs a 3" exhaust pipe and they make twice the power!
Another reason that I see a smaller pipe being all that is neceesary in the future is that when the exhaust ports are open, their flow is not steady. The exhaust speed fluctates and pulses. Both exhaust ports will always be open to some extent at the same time as the others but their flow at those corresponding times will be different. Therefore you don't need as large of a total area. You need more than a single but not as much as both added up. With some proper exhaust port and sleeve work this will become a reality.
For now I'd stick with a 3" pipe out the back as I'm not a fan of getting smaller again after you've made a pipe larger. Only in the case of a collector will I agree with this. Just something to think about.
I have measured the exhaust runner (not port) area in the Renesis plates and added the total area up. They add up and just barely fall short of being the equivalent of a single 3" pipe but are larger than a 2.5". They'd be slightly larger than a 2.75" if we could find one. 3" is the closest you can get.
However saying that, it is my opinion (until I test it to actually verify it) that the exhaust runners don't need to be so large as the ports themselves can't flow as much as the size of the runners imply they could. I believe that at some point in the future we will see some new exhaust sleeves appear that are designed in conjunction with the size and shape of the ports to promote smoother flow through the exhaust ports and when we do the total exhaust runner area out of the plates will decrease. At least on the outer ports. I see a day coming when everything is done properly and built to work together that the total exhaust pipe area needed to go out the back of the car will be 2.5". Remember that even a race built peripheral port 3 rotor only needs a 3" exhaust pipe and they make twice the power!
Another reason that I see a smaller pipe being all that is neceesary in the future is that when the exhaust ports are open, their flow is not steady. The exhaust speed fluctates and pulses. Both exhaust ports will always be open to some extent at the same time as the others but their flow at those corresponding times will be different. Therefore you don't need as large of a total area. You need more than a single but not as much as both added up. With some proper exhaust port and sleeve work this will become a reality.
For now I'd stick with a 3" pipe out the back as I'm not a fan of getting smaller again after you've made a pipe larger. Only in the case of a collector will I agree with this. Just something to think about.
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