Where can I get a "Long Tube" Header for my RX-8?
08-09-2012, 08:53 PM
#52
if you dont mind me asking--what size primary tubes are those and i am pretty sure you have a merge collector in there? Its a 12 degree one isnt it?
venturi works better than straight?
May as well ask some stupid questions here.
since we have zero overlap pulse wave tuning the exhaust is really not an option like engines with overlap. But arent they still of use?
The exhaust pulse from the rotary is stronger and the ports open and close faster than the recips valves--wouldnt this mean that a larger primary tube that is as straight as possible as far as possible before turning be the best?
In my case I am pushing more than 100hp of exhaust out per port--is a 2 inch tube big enough?
Any help is appreciated
venturi works better than straight?
May as well ask some stupid questions here.
since we have zero overlap pulse wave tuning the exhaust is really not an option like engines with overlap. But arent they still of use?
The exhaust pulse from the rotary is stronger and the ports open and close faster than the recips valves--wouldnt this mean that a larger primary tube that is as straight as possible as far as possible before turning be the best?
In my case I am pushing more than 100hp of exhaust out per port--is a 2 inch tube big enough?
Any help is appreciated
08-14-2012, 10:58 AM
#56
All I know is that my exhaust works and makes power. Beyond that I will leave all debate to my "betters", as I am too busy racing.
OD- as there are no valves, much like a port-timed 2-smoker the exhaust is much more critical than most will suspect. Length, taper, expansion, backpressure, its all important and just like on a two-smoker you can change an engines characteristics to a large degree with the exhaust and how it is "tuned". UNLIKE a typical four-stroke exhaust, which is fairly simple and easy to understand.
My primaries are 2", and that is a proper merge collector with 3" exit, the taper cone is 3 to 4" and is a specific degree of taper- I wont bore you with the math involved to get the degree of taper, partially because Im lazy and partially because a simple google search will net a lot of information on building tw0-stroke exhaust theory. The large chamber is 4", and then tapers again down to 3" and uses a combination of length and those little mufflers to provide a small measure of backpressure to assist the scavenge effect. Not sure how well the mufflers/length do their job but the theory is sound.
The thing to always remember when tuning an NA rotary is that it has more in common with an old-school port-timed two-smoker than ANY four stroke piston engine.Those inclined to do so please feel free to argue that notion all you want, then go prep a car and come race it and prove your theory... put some skin in the game, as they say.
OD- as there are no valves, much like a port-timed 2-smoker the exhaust is much more critical than most will suspect. Length, taper, expansion, backpressure, its all important and just like on a two-smoker you can change an engines characteristics to a large degree with the exhaust and how it is "tuned". UNLIKE a typical four-stroke exhaust, which is fairly simple and easy to understand.
My primaries are 2", and that is a proper merge collector with 3" exit, the taper cone is 3 to 4" and is a specific degree of taper- I wont bore you with the math involved to get the degree of taper, partially because Im lazy and partially because a simple google search will net a lot of information on building tw0-stroke exhaust theory. The large chamber is 4", and then tapers again down to 3" and uses a combination of length and those little mufflers to provide a small measure of backpressure to assist the scavenge effect. Not sure how well the mufflers/length do their job but the theory is sound.
The thing to always remember when tuning an NA rotary is that it has more in common with an old-school port-timed two-smoker than ANY four stroke piston engine.Those inclined to do so please feel free to argue that notion all you want, then go prep a car and come race it and prove your theory... put some skin in the game, as they say.
08-16-2012, 02:52 PM
#59
thanks for the posts everyone, some good info. dWalker your exhaust reminds me somewhat of the header used by the Swift guys.. is that a 15 degree collector?
2 inch primary pipes--ok. 3 inch collector--ok
I know my engine is different, being FI and all, but I think I am learning a little.
Ray--it was Racing beat that told me about the exhaust pulses being that way. I guess when I said "closes faster" then that can be very subjective and confusing--sorry about that.
Waiting patiently--well trying anyway.
Lol--wouldnt want a cam like that. Although it is advantageous to have very little overlap in a SC engine.
2 inch primary pipes--ok. 3 inch collector--ok
I know my engine is different, being FI and all, but I think I am learning a little.
Ray--it was Racing beat that told me about the exhaust pulses being that way. I guess when I said "closes faster" then that can be very subjective and confusing--sorry about that.
Waiting patiently--well trying anyway.
Lol--wouldnt want a cam like that. Although it is advantageous to have very little overlap in a SC engine.
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