1.3?
08-11-2010, 07:22 AM
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08-11-2010, 10:03 AM
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shenanigans ... my 93 camaro v6 MT gets 21 MPG on my trip to work driving the same speeds as I do in the RX8.... with the rx8 im pushing 15.5 and thats babying the car a bit.... yes while MPG is lower in sports cars the rx8 is low even among the sports cars...
Last edited by mbitterman; 08-11-2010 at 10:14 AM.
08-11-2010, 10:28 AM
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Agreed. I do about 15mpg with a known issue. When everything was healthy I could easily post 22-24mpg any time I wanted to, and my usual thrashing only dropped it to 19.
Check your ignition (plugs, wires, coils), O2 sensor, Cat, and compression. It doesn't take much degradation of any of these and you will start losing mileage quite quickly.
Check your ignition (plugs, wires, coils), O2 sensor, Cat, and compression. It doesn't take much degradation of any of these and you will start losing mileage quite quickly.
08-11-2010, 11:16 AM
#10
In the city when I'm driving however I want I usually get about 16 mpg. On the highway at 80 mph I MAY get 22 mpg but that's absolute best. I do have original ignition coils with ~45K miles on them though 
08-11-2010, 11:36 AM
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really? im getting about 19.. but.. i am mostly highway.. soo...
08-11-2010, 11:40 AM
#12
For 2 rotor engine 13B/Renesis:
When whole engine, and I repeat - when whole wankel rotary egine - all working chambers do the work, there is 3,924 L of displacement
And this is ONLY right measurement, since whole engine did the work, not just part
But this happens after 3 revolutions of e-shaft.
So if you want to compare with 4-stroke piston engine, you compare how much it displaces in 2 revolutions, so 2,616 L.
And for comparing with 2-stroke, you compare displacing in 1 revolution, so 1,308 L.
Many people will try to say otherwise, but it will be plain wrong
When whole engine, and I repeat - when whole wankel rotary egine - all working chambers do the work, there is 3,924 L of displacement
And this is ONLY right measurement, since whole engine did the work, not just partBut this happens after 3 revolutions of e-shaft.
So if you want to compare with 4-stroke piston engine, you compare how much it displaces in 2 revolutions, so 2,616 L.
And for comparing with 2-stroke, you compare displacing in 1 revolution, so 1,308 L.
Many people will try to say otherwise, but it will be plain wrong
08-11-2010, 01:57 PM
#14
2009 RX-8 Touring
Was this thread intended to be a clusterfuck, or did it just end up that way? I'm leaning towards the former. 
It's a 1.3L engine because that's the amount of volume the rotors displace when they hit top-dead-center and bottom-dead-center twice, just like any other 4-stroke engine. The tricky part is that TDC and BDC aren't actually at the top and bottom like they are in a piston engine -- instead, the two TDCs are the long, flattish sides of the rotor housing, and the two BDCs are the short, sharply-curved sides of the rotor housing. That means each rotor face can hit TDC and BDC twice in a single rotation. If you look at the e-shaft's position relative to any one of the rotor faces when it's pointed in the directions I specified, you'll see why I call those positions TDC and BDC.
So anyway, 1.3L is the correct displacement, because all four strokes are completed in a single rotation unlike in a piston engine. Multiplying by 2 is not only not necessary, it's also grossly inaccurate. Yes, that makes comparing engine sizes very difficult, so to that end I suggest a different rule:
A piston engine has to rotate the crank twice to complete combustion, whereas a rotary engine has to rotate the e-shaft three times to complete combustion, so multiply the displacement by 3/2 to get a better comparison of power-generating capacity. That puts the piston-engine equivalent of most rotaries at 1.999L, rounded to 2L for brevity's sake. And you'll notice that the torque numbers line up pretty well, too: if you multiply the torque by 3/2 you end up with a number that looks like it came from a modern 2L piston engine.
It's a 1.3L engine because that's the amount of volume the rotors displace when they hit top-dead-center and bottom-dead-center twice, just like any other 4-stroke engine. The tricky part is that TDC and BDC aren't actually at the top and bottom like they are in a piston engine -- instead, the two TDCs are the long, flattish sides of the rotor housing, and the two BDCs are the short, sharply-curved sides of the rotor housing. That means each rotor face can hit TDC and BDC twice in a single rotation. If you look at the e-shaft's position relative to any one of the rotor faces when it's pointed in the directions I specified, you'll see why I call those positions TDC and BDC.
So anyway, 1.3L is the correct displacement, because all four strokes are completed in a single rotation unlike in a piston engine. Multiplying by 2 is not only not necessary, it's also grossly inaccurate. Yes, that makes comparing engine sizes very difficult, so to that end I suggest a different rule:
A piston engine has to rotate the crank twice to complete combustion, whereas a rotary engine has to rotate the e-shaft three times to complete combustion, so multiply the displacement by 3/2 to get a better comparison of power-generating capacity. That puts the piston-engine equivalent of most rotaries at 1.999L, rounded to 2L for brevity's sake. And you'll notice that the torque numbers line up pretty well, too: if you multiply the torque by 3/2 you end up with a number that looks like it came from a modern 2L piston engine.
08-11-2010, 03:10 PM
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08-11-2010, 03:51 PM
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It's a 1.3L engine because that's the amount of volume the rotors displace when they hit top-dead-center and bottom-dead-center twice, just like any other 4-stroke engine. The tricky part is that TDC and BDC aren't actually at the top and bottom like they are in a piston engine -- instead, the two TDCs are the long, flattish sides of the rotor housing, and the two BDCs are the short, sharply-curved sides of the rotor housing. That means each rotor face can hit TDC and BDC twice in a single rotation. If you look at the e-shaft's position relative to any one of the rotor faces when it's pointed in the directions I specified, you'll see why I call those positions TDC and BDC.
Yes, I know that engine literally Multiplying by 2 is not only not necessary, it's also grossly inaccurate. Yes, that makes comparing engine sizes very difficult, so to that end I suggest a different rule:
A piston engine has to rotate the crank twice to complete combustion, whereas a rotary engine has to rotate the e-shaft three times to complete combustion, so multiply the displacement by 3/2 to get a better comparison of power-generating capacity. That puts the piston-engine equivalent of most rotaries at 1.999L, rounded to 2L for brevity's sake. And you'll notice that the torque numbers line up pretty well, too: if you multiply the torque by 3/2 you end up with a number that looks like it came from a modern 2L piston engine.
A piston engine has to rotate the crank twice to complete combustion, whereas a rotary engine has to rotate the e-shaft three times to complete combustion, so multiply the displacement by 3/2 to get a better comparison of power-generating capacity. That puts the piston-engine equivalent of most rotaries at 1.999L, rounded to 2L for brevity's sake. And you'll notice that the torque numbers line up pretty well, too: if you multiply the torque by 3/2 you end up with a number that looks like it came from a modern 2L piston engine.
As I said previously, during that 3 revolutions of e-shaft, 3,924 L of charge is induced, compressed, burned, expanded and exhausted, really simple
But what you will do now is that you divide 3,924 by 1,5(yours 3/2) to get what is done in same period of time like in 4-stroke engine - 2,616 L during 2 revolutions
Reason why torque values and everything combustion related are not on pair with equal displacement piston engine, is simple. Rotary is not as thermally efficient as piston engines, clear and simple. Not only BSFC is higher, but mainly Brake specific AIR consumption is higher - big problem
Vast area to volume ratio, poor combustion chamber shape etc. all contribute to this.When you compare all out racing NA rotary vs. all out 4-stroke, in terms of torque and brake specific fuel consumption, you will find that rotary can output 83% of torque on same capacity - same airflow, and BSFC will be higher by 20% - in ideal conditions, it can be worse...
Same goes to turbocharged engines, from given compressor, rotary, in ideal conditions can output 83% of power vs. piston engine, again it can be worse for non ported engines...
For your "theory" about 13B/Renesis should be compared with 2000cc 4-stroke based on torque values, then rotary shouldn´t exhibit all its drawbacks - fuel consumption, air consumption, high EGTs...
To the OP, we have to know, what you wanna know
You can call 13B/Renesis like you want, but it will not change physics and fact that when you want to compare - on equal basis, displacement of this engine against 4-stroke piston engine, you have to double Mazdas rating. Excuses about poor torque and that it can´t be compared with 2,6 Liter are just excuses and inability to stand, that rotary is not that efficient
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