exhaust very loud........
01-10-2010, 09:40 AM
#26
Registered
A bit about exhausts and RX-8 specific experience.
Ff your exhaust is too loud you don't have to restrict it with anything other than mufflers. This is not rocket science guys. The renesis does not do anything spectacular that makes it require some elaborate solution. This is how you'll want to do it if your looking for power and a decent exhaust note: Run your system as unrestrictive as you can and then muffler it to reduce noise. 3" is plenty for stock n.a. motors. 2.5" is plenty if you're using the stock exhaust manifold.
If making or having made your own headers be aware of locating your O2 sensor too close to the exhaust ports. At wide open throttle your Exhaust Gas Temperatures (of an n.a. motor) will see 1,600 F. This can cook your O2 sensor which is a key component to run your engine. We replace our 02 sensors every two years in our race cars because they see so much heat. Perhaps a very well versed and experienced engine tuner can comment on their experience with O2 sensors. Please refrain from commented on this subject unless you have some hard data. This will eliminate the spread of false info on this thread.
You way want to keep in mind that our race cars using a professional built but bone stock engine pretty much either idles or runs ***** out from 6,500 to 8,700 rpm. MazdaSpeed Intake, highly custom and professional tune, headers and 93 octane gas---the same stuff that some of your run sans exhaust.
The benefit of stainless steel headers (vs. mild steel or "carbon steel") is they will handle these higher temperatures that a rotary produces (not just an RX-8 but other rotary designs as well). We have built and tested seveal header designs and made a few out of mild steel because the cost is much less and we wanted to make some different sizes/configurations to hunt for some power. I've excluded details and would be happy to provide to anyone however the idea of making headers out of mild steel is that they are quick, easy and cheap. They don't last for **** but allow you to try varied primary lengths, and primary runner tubing sizes (1.5" up to 2" as an example). After 12 hours of racing we blew/burnt a hole in the side of a set of mild stell headers. Mild steel is that which you would typically make a roll cage out of. S.S. is generally about 4X the cost of mild steel +/- and used for exhaust. Below is a link to some various metals, their temperature limits, etc.
I've had approx 15 Renesis exhaust systems made using various exhaust configurations, # of mufflers and muffler placement, tubing size (O.D.) etc. In fact, as I write this my buddy Pete called me and we are meeting over at the shop to make yet another exhaust system for a new #31 RX-8 race car we will be campaigning in World Challenge this year.
Two good mufflers will reduce your exhaust volume but still retain that "tone" that some of your street dudes want/like. Put these in-line and they will silence more than a "Y" that goes to two mufflers (which we have ran). A long collector header with low restriction mufflers may get your thrown out of some local HPDE events. Keep in mind that several events (and most professional) have sound limitations and they will check you with a decibel reading device. Often these guys (rotraries included) will carry a set of turn down/turn away tips to have the exhaust flow AWAY from the sound check meter. Happens all the time.
If you talk to a very high performing muffler engineer or muffler company they will tell you a few things:
- A "straight through" muffler design will make more power than one that turns, bends and zig-zags.
-The larger the size AROUND the exhuast pipe the better the muffling qualities. In other words a 2.5" diameter exhaust pipe that enters a muffler follow by a 5" diameter size muffler will work better than a 2.5" exhuast entering a 4" diameter muffler.
-There are various internal packing designs and materials used to "muffle" or reduce sound. LAVA ROCK is a material sometimes used.
-There are such things as "qualifying mufflers" for racing that don't last very long but make a few more ponies.
-A Borla, Magnaflow or Flowmaster are all good brands of mufflers and come in various shapes and sizes and are readily available. They come in various levels of sound deadening and often don't rob much power as you quiet down your exhaust note.
-A good muffler shop can weld you something up inexpensively
-The rear of the exhaust still sees a fair amount of heat but nothing like that just off the motor. You could use mild steel back there but your subject to rust.
-SS doesn't rust (one of it's primary benefits and frequently used as exhaust material for this reason).
-Headers for a Renesis make power.
-Headers for a Renesis that mate up to the stock location of the downpipe and/or the same location that the stock exhaust manifold terminates make MUCH LESS power than those that have longer primatry tubes. These are the majority of headers on the market today and make a handful of hp.
-The cost of a high performing header using a "merge" style collector is in the collector----not the tubing that connects to the flanges on the engine block and mates up to a merge collector. This is because the cost of the material is much less expensive but the labor involved in making these style collectors is big. Go to the link below and look at the various collectors. The longer and more gradual the collector (which will make more power for our RX-8's I'll suggest to you based on tons of testing and thousands of dollars of header material and labor effort) will cost you more. Go here to see some examples.
http://www.spdexhaust.com/pdfs/02-11...Collectors.pdf
SPD (above) is a very well known exhaust component supplier. Many people use them.
A bit on headers for the RX-8:
The cost of the RX-8 headers on the market today (several made of S.S.) is driven by their collectors. The collector is where the cost is (or is not if the collector is a tiny, sharp bending, power robbing design) Look at these collectors. These are easy to make and often available off the shelf. They are low cost when compared to a longer 14-18" collector. This is because of the very intricate cutting and welding involved. More fabrication time = more cost. The cost of our collectors is WAY more than those aftermarket headers available to everyone on this forum. They also make a ton more power. Our typical exhaust system will run about $2,400 parts and labor and will make 210 rwhl hp on a purely stock and good compression motor. I have more data to back this up then you care for and anyone that wants to refute this be prepared to put your tail between your legs and wimper like a puppy.
There you have it---some information on exhausts and sound with some emphasis on effective header design and material choice.
Some of you may email me after I do one of these header posts (at least it has happened in the past). We do sell headers and they are $1,300 and require some modification to the stock engine. I offer this so you don't think these items are cheap and contact me so I guess I'm trying to same you some time.
You'll find various pictures of headers, exhausts and the underside of our cars here:
http://www.meyer-motorsports.com/Home/Home.html
Go to PICTURE GALLERY and surf around.
Happy rotoring
Ff your exhaust is too loud you don't have to restrict it with anything other than mufflers. This is not rocket science guys. The renesis does not do anything spectacular that makes it require some elaborate solution. This is how you'll want to do it if your looking for power and a decent exhaust note: Run your system as unrestrictive as you can and then muffler it to reduce noise. 3" is plenty for stock n.a. motors. 2.5" is plenty if you're using the stock exhaust manifold.
If making or having made your own headers be aware of locating your O2 sensor too close to the exhaust ports. At wide open throttle your Exhaust Gas Temperatures (of an n.a. motor) will see 1,600 F. This can cook your O2 sensor which is a key component to run your engine. We replace our 02 sensors every two years in our race cars because they see so much heat. Perhaps a very well versed and experienced engine tuner can comment on their experience with O2 sensors. Please refrain from commented on this subject unless you have some hard data. This will eliminate the spread of false info on this thread.
You way want to keep in mind that our race cars using a professional built but bone stock engine pretty much either idles or runs ***** out from 6,500 to 8,700 rpm. MazdaSpeed Intake, highly custom and professional tune, headers and 93 octane gas---the same stuff that some of your run sans exhaust.
The benefit of stainless steel headers (vs. mild steel or "carbon steel") is they will handle these higher temperatures that a rotary produces (not just an RX-8 but other rotary designs as well). We have built and tested seveal header designs and made a few out of mild steel because the cost is much less and we wanted to make some different sizes/configurations to hunt for some power. I've excluded details and would be happy to provide to anyone however the idea of making headers out of mild steel is that they are quick, easy and cheap. They don't last for **** but allow you to try varied primary lengths, and primary runner tubing sizes (1.5" up to 2" as an example). After 12 hours of racing we blew/burnt a hole in the side of a set of mild stell headers. Mild steel is that which you would typically make a roll cage out of. S.S. is generally about 4X the cost of mild steel +/- and used for exhaust. Below is a link to some various metals, their temperature limits, etc.
I've had approx 15 Renesis exhaust systems made using various exhaust configurations, # of mufflers and muffler placement, tubing size (O.D.) etc. In fact, as I write this my buddy Pete called me and we are meeting over at the shop to make yet another exhaust system for a new #31 RX-8 race car we will be campaigning in World Challenge this year.
Two good mufflers will reduce your exhaust volume but still retain that "tone" that some of your street dudes want/like. Put these in-line and they will silence more than a "Y" that goes to two mufflers (which we have ran). A long collector header with low restriction mufflers may get your thrown out of some local HPDE events. Keep in mind that several events (and most professional) have sound limitations and they will check you with a decibel reading device. Often these guys (rotraries included) will carry a set of turn down/turn away tips to have the exhaust flow AWAY from the sound check meter. Happens all the time.
If you talk to a very high performing muffler engineer or muffler company they will tell you a few things:
- A "straight through" muffler design will make more power than one that turns, bends and zig-zags.
-The larger the size AROUND the exhuast pipe the better the muffling qualities. In other words a 2.5" diameter exhaust pipe that enters a muffler follow by a 5" diameter size muffler will work better than a 2.5" exhuast entering a 4" diameter muffler.
-There are various internal packing designs and materials used to "muffle" or reduce sound. LAVA ROCK is a material sometimes used.
-There are such things as "qualifying mufflers" for racing that don't last very long but make a few more ponies.
-A Borla, Magnaflow or Flowmaster are all good brands of mufflers and come in various shapes and sizes and are readily available. They come in various levels of sound deadening and often don't rob much power as you quiet down your exhaust note.
-A good muffler shop can weld you something up inexpensively
-The rear of the exhaust still sees a fair amount of heat but nothing like that just off the motor. You could use mild steel back there but your subject to rust.
-SS doesn't rust (one of it's primary benefits and frequently used as exhaust material for this reason).
-Headers for a Renesis make power.
-Headers for a Renesis that mate up to the stock location of the downpipe and/or the same location that the stock exhaust manifold terminates make MUCH LESS power than those that have longer primatry tubes. These are the majority of headers on the market today and make a handful of hp.
-The cost of a high performing header using a "merge" style collector is in the collector----not the tubing that connects to the flanges on the engine block and mates up to a merge collector. This is because the cost of the material is much less expensive but the labor involved in making these style collectors is big. Go to the link below and look at the various collectors. The longer and more gradual the collector (which will make more power for our RX-8's I'll suggest to you based on tons of testing and thousands of dollars of header material and labor effort) will cost you more. Go here to see some examples.
http://www.spdexhaust.com/pdfs/02-11...Collectors.pdf
SPD (above) is a very well known exhaust component supplier. Many people use them.
A bit on headers for the RX-8:
The cost of the RX-8 headers on the market today (several made of S.S.) is driven by their collectors. The collector is where the cost is (or is not if the collector is a tiny, sharp bending, power robbing design) Look at these collectors. These are easy to make and often available off the shelf. They are low cost when compared to a longer 14-18" collector. This is because of the very intricate cutting and welding involved. More fabrication time = more cost. The cost of our collectors is WAY more than those aftermarket headers available to everyone on this forum. They also make a ton more power. Our typical exhaust system will run about $2,400 parts and labor and will make 210 rwhl hp on a purely stock and good compression motor. I have more data to back this up then you care for and anyone that wants to refute this be prepared to put your tail between your legs and wimper like a puppy.
There you have it---some information on exhausts and sound with some emphasis on effective header design and material choice.
Some of you may email me after I do one of these header posts (at least it has happened in the past). We do sell headers and they are $1,300 and require some modification to the stock engine. I offer this so you don't think these items are cheap and contact me so I guess I'm trying to same you some time.
You'll find various pictures of headers, exhausts and the underside of our cars here:
http://www.meyer-motorsports.com/Home/Home.html
Go to PICTURE GALLERY and surf around.
Happy rotoring
01-13-2010, 11:45 AM
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http://www.youtube.com/watch?v=waA3uvTJOTg
i tink this clip shows a rx-8 with very loud tone... but sad it was not speeding... but i love the low loud rumble...
wat u guys think... from 7.40 min to 7.50min...
i tink this clip shows a rx-8 with very loud tone... but sad it was not speeding... but i love the low loud rumble...
wat u guys think... from 7.40 min to 7.50min...
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