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I really love that front end! It still conveys aerodynamic sleekness, adding a touch of subtle sharpness, without the aggressive bulk and gaping holes of the Mazdaspeed and C-West kits we've been seeing so much.
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"Reina"
1993 RX-7, Silverstone Metallic, Base Model
291 RWHP @ 0.9kg/cm^2
"But before you start mentally calculating how much more power a turbo version of the Renesis engine will punch out, we have to tell you that relatively cool exhaust gas from turbocharged rotary motors prevents efficient catalytic conversion, making it unlikely we'll see one soon, if ever."
So here's my question: why not put the turbo fans in the exhaust pipe AFTER the catalytic converter? That way emissions would still be low and you'd still get turbo power. Are there any problems with this layout?
Car and Driver is talking no turbo from the factory. It will be very hard for Mazda to get the turbo renesis to pass emmisions standards. The idea of putting the turbines after the cats will not help the emmisions problem and will drastically effect the performance of the turbo, its not the turbo that cools the gases, the turbo unit itself gets very hot and the compression of air creates heat also, that is why you must cool the intake charge before it goes back into the engine. The amount of additional fuel and air your pushing through the motor to make horsepower keeps the motor from heating up quickly from start up and that is where the FI motor has an increased amount of unburned hydrocarbons. The faster an engine can get to full operating temperature the better for emmisions and if you have noticed the newer cars operate at a lot higher temp than ever before to help burn the fuel more completely. And as any hot rodder should know heat is the arch-nemesis to horsepower.
Originally posted by vipeRX7 Car and Driver said at:
"But before you start mentally calculating how much more power a turbo version of the Renesis engine will punch out, we have to tell you that relatively cool exhaust gas from turbocharged rotary motors prevents efficient catalytic conversion, making it unlikely we'll see one soon, if ever."
So here's my question: why not put the turbo fans in the exhaust pipe AFTER the catalytic converter? That way emissions would still be low and you'd still get turbo power. Are there any problems with this layout?
um, first, they're flat wrong: rotary emissions are higher tempurature and higher energy than any comparable piston engine.
second, there'd be no advantage to putting the cat before the turbine (which'd be impossible anyways, unless someone can create a 2" long CC): the problem with a turbo'd engine is that you get a TON of uncombusted HC's (that big *** backfire) when you lift off the throttle at really high boost... the AFM tells the computer a LOT more air is coming than what does, and you end up with a mega rich cycle, throwing it all out into the exhaust... that's mega HC emissions.
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Originally posted by SPDFRK The amount of additional fuel and air your pushing through the motor to make horsepower keeps the motor from heating up quickly from start up and that is where the FI motor has an increased amount of unburned hydrocarbons.
um... what??
the problem isn't that the motor takes longer to warm up (which it wouldn't/doesn't), it's that the cats take time to warm up no matter if it's FI or not: this was the achilles heel of all previous RX-7's, where they'd have a pre-cat which'd warm up really really fast (from those very hot exhaust gasses) so that it could help the always-high HC emissions while the main cat (which is better at doing that than the pre-cat) warmed up for a minute or two.
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Originally posted by SPDFRK heat is the arch-nemesis to horsepower.
...not always. an engine will always operate best in a certain range, but yes, too hot is bad, but not hot enough bad too.
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Originally posted by SPDFRK It will be very hard for Mazda to get the turbo renesis to pass emmisions standards.
it'll be no harder than it was for an RX-7 to get through, and that one had perhipheral ports as opposed to the RENESIS's side ports: they could do it if they wanted, which they may not... the wider rotor'd motor is happening, like it or not.
it'll be no harder than it was for an RX-7 to get through, and that one had perhipheral ports as opposed to the RENESIS's side ports: they could do it if they wanted, which they may not... the wider rotor'd motor is happening, like it or not.
Two small points:
1. Emissions are much stricter now than 8 years ago.
2. I think everyone would like wider rotors. The reason forced induction is so widely talked about is we are all looking for extra power for the 1.3 liter engine in the RX-8 that many of us have already ordered. That's why this is the aftermarket section of the forum.
thanks SPDFRK and wakeech for clearing up my turbo question. My mistake was thinking that the turbo fan in the exhaust was what made the exhaust cool. I guess I can still look forward to aftermarket turboed RX-8s :D
... zoikes, that'd be interesting to learn about... i'd love to know why
probably same reason the rx-7 had it. the precat (lil cat) took care of some hydrocarbons and had the advantage of really hot air, and the cat got much cooler air and handled the rest of the exhaust. (or something like that)
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-nate
freedom is just another word for nothin' left to lose, nothin' and it's all that bobby left me
Originally posted by lefuton probably same reason the rx-7 had it. the precat (lil cat) took care of some hydrocarbons and had the advantage of really hot air, and the cat got much cooler air and handled the rest of the exhaust. (or something like that)
But both the 7's cats were after the turbos. I didn't know the WRX has one before the turbo. Is this true?
In the 7, while cold, the main cat is ineffective at catalyzing hydrocarbons properly. The pre cat was designed to heat up quickly and take care of emissions as the larger main cat warmed up. Once the main cat is operational, the pre cat is for the most part useless. This is why many owners can run a downpipe, yet still pass emissions.
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"Reina"
1993 RX-7, Silverstone Metallic, Base Model
291 RWHP @ 0.9kg/cm^2
Originally posted by evel333
In the 7, while cold, the main cat is ineffective at catalyzing hydrocarbons properly. The pre cat was designed to heat up quickly and take care of emissions as the larger main cat warmed up.
NASA developed a new catalyst to work in the cold of outer space. Apparently automotive applications will show up on the market within a year. There's hope yet.
Besides cold emissions, the other turbo/rotary issue is back pressure. It kills rotaries plain and simple.
Turbines do cool the EGT of an engine. They're both exhaust and thermally driven. You'll see about 250 degrees of difference between EGT's just aft of the exhaust port and those say 4" behind the turbine on a rotary. After gasses exit the turbine they also expand and cool rapidly, slowing them down. By shrinking the exhaust after the turbo, you speed up velocity, but backpressure goes up. That's why turbo guys run huge exhaust systems.
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Michel
95 RX7 single turbo Enzo killer :-)
zoikes, that'd be interesting to learn about... i'd love to know why 
thx for the backup
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