Please, Mazda. Give us a three rotor?
02-22-2007, 11:28 PM
#51
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MDS will completely close the valves, which causes the air in the piston to work like a gas spring, getting much of the energy back on the expansion strokes. Keeping the valves open would cause the engine to act as an air pump.
02-23-2007, 06:39 AM
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Originally Posted by ckape
MDS will completely close the valves, which causes the air in the piston to work like a gas spring, getting much of the energy back on the expansion strokes. Keeping the valves open would cause the engine to act as an air pump.
02-23-2007, 12:42 PM
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For clarification on the various sequential shut down systems, the pumping effect losses are negligible inside the cylinder but the extra O2 flushed into the exhaust skews the O2 sensor. Thats why they close off exhaust valves.
The reason why they work so well on piston motors is it forces active cylinders to raise combustion pressures which in turn increases efficiency on the Otto cycle.
I was reminded by a Mazda engineer that the Renesis has no exhaust valves so we won't see an implementation of this on the rotary.
I was also told that there are no major changes coming for the remaining production life of the Renesis and that the next gen rotary has been in the works for over 2 years now, but no clues as to what will be. Then again it might answer why Kennametal has been contracted to fuse some rather lightweight powered metal triangular shaped thingies......
The reason why they work so well on piston motors is it forces active cylinders to raise combustion pressures which in turn increases efficiency on the Otto cycle.
I was reminded by a Mazda engineer that the Renesis has no exhaust valves so we won't see an implementation of this on the rotary.
I was also told that there are no major changes coming for the remaining production life of the Renesis and that the next gen rotary has been in the works for over 2 years now, but no clues as to what will be. Then again it might answer why Kennametal has been contracted to fuse some rather lightweight powered metal triangular shaped thingies......
02-23-2007, 12:57 PM
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Originally Posted by Icemark
Because that would tag the car into Gas Guzzler tax. And while many people would pay it, Mazda would never sell another Gas Guzzler vehicle in the states. That is what almost killed the company all together back in the mid 70's. They have said this over and over and over.
A 3000 lbs car must get better than 16 MPG to avoid gas guzzler tax.
And as far as cooling. That is one of the issues that prevented the FC from getting a 20B (there were running test bed FCs with 20B engines in them). The cooling system needs to be increased by 1/3rd over what a two rotor system would use. There are packaging issues already with the FE, what makes you think that you could cost effectivly increase the cooling capacity??
Then toss in the transmission issues- you'd be back to the R-type 5 speed tranny in order to handle the torque.
I have one that passes every two years just fine with only one monlithic Cat, so why wouldn't it??? It passes with less emissions than new and that it did stock when there was 3 cats.
And if you drive a RX-8 with a stock motor, then you drive a 13B. Go look at the castings on the housings. 13B right on the top... plain as day. Same as it has been since the 70's. Renisis is just the series name of the 13B used in the RX-8
Emissions is not some bug-a-boo science. If you could make a Ford 5.0 V8 motor pass modern emissions, you can get a cleaner burning fuel injected rotary to pass.
The problem with a MDS system on a rotary motor is that both oil and fuel act as lubricants to the rotors. So if you magically cut fuel on one rotor, you cut out half the lubricant to the apex seals leading to increased wear on the seals and housings. Even if you continue to inject (or really dribble) the oil in, then you have the issue of smoking when the oil gets dumped into the exhaust (which the cats hate).
Mazda has been playing with MDS on the rotary engine for the last 5 years with no cost effective solutions. Really the only solution is to kill only one rotor face at a time, but because of the side port design and mixture carry over, you end up with a very very lean rotor face. which must be burned before ejecting it from the motor (so not you have a valve in the intake and a valve on the exhaust that switches open and closed based on MDS and rotor face postion- leading to huge costs and control issues).
Just cutting out one rotor doesn't work, because then there is no lubrication for that rotor. That is different than on a piston engine where the lubricatant is still shot up from the crank to the piston rings even if that piston is "shut off".
A 3000 lbs car must get better than 16 MPG to avoid gas guzzler tax.
And as far as cooling. That is one of the issues that prevented the FC from getting a 20B (there were running test bed FCs with 20B engines in them). The cooling system needs to be increased by 1/3rd over what a two rotor system would use. There are packaging issues already with the FE, what makes you think that you could cost effectivly increase the cooling capacity??
Then toss in the transmission issues- you'd be back to the R-type 5 speed tranny in order to handle the torque.
I have one that passes every two years just fine with only one monlithic Cat, so why wouldn't it??? It passes with less emissions than new and that it did stock when there was 3 cats.
And if you drive a RX-8 with a stock motor, then you drive a 13B. Go look at the castings on the housings. 13B right on the top... plain as day. Same as it has been since the 70's. Renisis is just the series name of the 13B used in the RX-8
Emissions is not some bug-a-boo science. If you could make a Ford 5.0 V8 motor pass modern emissions, you can get a cleaner burning fuel injected rotary to pass.
The problem with a MDS system on a rotary motor is that both oil and fuel act as lubricants to the rotors. So if you magically cut fuel on one rotor, you cut out half the lubricant to the apex seals leading to increased wear on the seals and housings. Even if you continue to inject (or really dribble) the oil in, then you have the issue of smoking when the oil gets dumped into the exhaust (which the cats hate).
Mazda has been playing with MDS on the rotary engine for the last 5 years with no cost effective solutions. Really the only solution is to kill only one rotor face at a time, but because of the side port design and mixture carry over, you end up with a very very lean rotor face. which must be burned before ejecting it from the motor (so not you have a valve in the intake and a valve on the exhaust that switches open and closed based on MDS and rotor face postion- leading to huge costs and control issues).
Just cutting out one rotor doesn't work, because then there is no lubrication for that rotor. That is different than on a piston engine where the lubricatant is still shot up from the crank to the piston rings even if that piston is "shut off".
the oil cooler on the cosmo is smaller than the one on the fc
02-24-2007, 11:47 AM
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Originally Posted by gh0st
they are running a 20b.
http://www.speedsourceinc.com/index....§ion=mazda
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