Cat back exhaust for N/A
07-29-04, 12:25 AM
#1
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Cat back exhaust for N/A
Hi, I currently purchased a 1986 rx7 se. It needs an exhaust. Im seriously leaning towards a single exit exhaust for weight reasons. No I dont plan on racing the car, but I figured anything I could to save weight would be good, for that occasional race I do get in. I was looking at the corksport exhaust. I was wondering if this exhaust is loud??? How good does it fit???????? Am I better off with a custom bent exhaust system??????? What other single exit exhaust systems are out there?????
All information is appreciated.
ae86ny@yahoo.com
All information is appreciated.
ae86ny@yahoo.com
07-29-04, 12:46 AM
#2
Rotary engine victory
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WOW creepy you live in newburgh, ny i live in newburgh, in but anyway..... teh apexi n1 comes in singel and dual. good system from waht i have hered. but i would go w/ duals. the weight or one muffler isnt worth having your car look unballanced. if u go duls and r worried about weight. drop the spare tire and have a can or slime tire stuff in the car w/ u at all times.
07-29-04, 08:37 AM
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How much do you want for the header??? What brand is it????? Is it new or used????
Ok, well then how about dual exhaust systems. Ivee seen quiet a few different ones. The one I saw most recently is one from Borla. How is that exhaust system??? Also, what brand of header do most of you use?????
ae86ny@yahoo.com
Ok, well then how about dual exhaust systems. Ivee seen quiet a few different ones. The one I saw most recently is one from Borla. How is that exhaust system??? Also, what brand of header do most of you use?????
ae86ny@yahoo.com
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07-29-04, 10:58 AM
#8
Rotary Freak
almost everyone on the forum that runs a header runs a racing beat one if i were you id look into the racing beat catback and apexi N1 but does anyone know the size of tubing apexi uses for there dual N1 catback
07-29-04, 11:13 AM
#9
If volume is an issue...
Headers on an NA make your car loud. No matter how quiet everything else is, you car will be loud.
Same is true for running a single exhaust. You really need both mufflers to quiet the thing down. If you ran headers and a single muffler, your ears might bleed...
I might suggest sticking with headers but getting some good dual mufflers, and make sure to stick a presilencer in there to quiet it down a tad. If you have emissions and you need a cat, you're gonna need some custom work since the RB headers aren't made to hook into stock replacement cats. Any muffler shop could handle it easily, though.
Headers on an NA make your car loud. No matter how quiet everything else is, you car will be loud.
Same is true for running a single exhaust. You really need both mufflers to quiet the thing down. If you ran headers and a single muffler, your ears might bleed...
I might suggest sticking with headers but getting some good dual mufflers, and make sure to stick a presilencer in there to quiet it down a tad. If you have emissions and you need a cat, you're gonna need some custom work since the RB headers aren't made to hook into stock replacement cats. Any muffler shop could handle it easily, though.
07-29-04, 12:18 PM
#11
Rotary Freak
Originally Posted by 1987RX7guy
Racing beat, Greddy PE, Borla, ApexI Dual n1
In that order from good to shitty.
anything else i wouldn't touch.
In that order from good to shitty.
anything else i wouldn't touch.
07-29-04, 12:47 PM
#12
Racing beat has hard data that proves that a N/A car with a mostly stock intake and mosty stock fuel injection (aka, no performance carb conversion and/or perf porting.) Gets little to no gain from a header. Being a mechanical engineer i firmly agree with and am not surprised by their findings.
Further any gains you get from a header will not be noticable if still running a cat AT ALL on these cars.
The main way a header allows more engine output (power) is how it handles exhaust pulses, backpressure, and how they effect exhaust valves. These cars have no exhaust valves. Thus scavanging effect is generally not as important to a rotary engine. Typical headers that achive the most power gains are long equal tube length that have very well manufactured/engineered colectors. They maintain as much velocity pressure as possible. When velocity pressure is converted to standard pressure via system resistance (cat, muffler, to many bends, small pipes, etc.) it creates back pressure in the system. Further headers allow the exhaust to collect so that the exhaust pulese "line up" and thus do not produce the power robing random pressure fluctuations and differences in a typical stock manifold. The sience of rotary engine exhaust is much simpler than other vehicles and rotaries respond much more dramatically to simple reduction in backpressure. But they do not have as much response as a piston engine to tuning of the exhaust pulses. Simply put the less exhaust a rotary has the better. Where as you can actually get more power out of a pistion engine with a properly tuned exhaust system (pipes can be better than open exhaust).
The obvious side effect of just running no exhaust is noise.
The only true gains of a header on our cars comes from the simple fact that it provides a much more smoth transition from the exhaust ports to the exhaust. system than a stock manifold.
Again, the stock manifold when compared with some other vehicles stock manifolds isnt that bad.
Case in point, I own a 2003 toy tundra (daily driver) i put a less restrictive duel cat back exhaust system. And, though it sounds great it realy didnt improve performance much IF AT ALL. Where as my racing beat downpipe presilencer and cat back duel system on my RX produced LOTS of gain. Mainly due to removal of the cats but also the freeer flowing mufflers has a little bit to do in helping power.
Further RX-7s from my experience don't suffer any noticable low end torque loss from a free flow exhaust system. Again due to the fact that they are a valveless rotary multi-combustion-chamber system.
I also put headers on my tundra and gained over 20 ftlbs of torque and about 20 hp. The scavanging effect on 8 cylinders and the fact that the stock manifolds were a HORRIBLY inefficient design made this possible.
In short, headers for rotary engines arn't worth the money unless its a fully carburated N/A race car with some serious port work.
The best thing you can do for gains from an exhaust system is live in a no-test state and chuck the cat.
Rotaries adhere to the simplest of exhaust theory "reduce losses in the system (restrictions) and you will reduce loss of power output. (more HP)
Further any gains you get from a header will not be noticable if still running a cat AT ALL on these cars.
The main way a header allows more engine output (power) is how it handles exhaust pulses, backpressure, and how they effect exhaust valves. These cars have no exhaust valves. Thus scavanging effect is generally not as important to a rotary engine. Typical headers that achive the most power gains are long equal tube length that have very well manufactured/engineered colectors. They maintain as much velocity pressure as possible. When velocity pressure is converted to standard pressure via system resistance (cat, muffler, to many bends, small pipes, etc.) it creates back pressure in the system. Further headers allow the exhaust to collect so that the exhaust pulese "line up" and thus do not produce the power robing random pressure fluctuations and differences in a typical stock manifold. The sience of rotary engine exhaust is much simpler than other vehicles and rotaries respond much more dramatically to simple reduction in backpressure. But they do not have as much response as a piston engine to tuning of the exhaust pulses. Simply put the less exhaust a rotary has the better. Where as you can actually get more power out of a pistion engine with a properly tuned exhaust system (pipes can be better than open exhaust).
The obvious side effect of just running no exhaust is noise.
The only true gains of a header on our cars comes from the simple fact that it provides a much more smoth transition from the exhaust ports to the exhaust. system than a stock manifold.
Again, the stock manifold when compared with some other vehicles stock manifolds isnt that bad.
Case in point, I own a 2003 toy tundra (daily driver) i put a less restrictive duel cat back exhaust system. And, though it sounds great it realy didnt improve performance much IF AT ALL. Where as my racing beat downpipe presilencer and cat back duel system on my RX produced LOTS of gain. Mainly due to removal of the cats but also the freeer flowing mufflers has a little bit to do in helping power.
Further RX-7s from my experience don't suffer any noticable low end torque loss from a free flow exhaust system. Again due to the fact that they are a valveless rotary multi-combustion-chamber system.
I also put headers on my tundra and gained over 20 ftlbs of torque and about 20 hp. The scavanging effect on 8 cylinders and the fact that the stock manifolds were a HORRIBLY inefficient design made this possible.
In short, headers for rotary engines arn't worth the money unless its a fully carburated N/A race car with some serious port work.
The best thing you can do for gains from an exhaust system is live in a no-test state and chuck the cat.
Rotaries adhere to the simplest of exhaust theory "reduce losses in the system (restrictions) and you will reduce loss of power output. (more HP)
Last edited by RockLobster; 07-29-04 at 12:53 PM.
07-29-04, 01:24 PM
#14
Nurse I need 1300cc's NOW
i have borla on my na with a rotory performance hi flow cat. its louder than im used to .. but i got used to it. comparied to all the other rx7 aftermarket exhaust ive heard so far. the borla is the quieter and i think the cheapest so far to
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