RPMs at cruising speed
03-31-2010, 12:18 AM
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RPMs at cruising speed
When I'm in 6th gear and cruising at around 120km/h (so around 75 mph) im revving at almost 4000rpm...is this normal? I know rotaries revs high but this just seems wrong...
03-31-2010, 12:33 AM
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also...im getting just over 300km to a tank of gas...half the tank was from lat summer because I didnt get to finish it before i stored it but i used stabilizer and filled up the other half with 91...
03-31-2010, 09:35 AM
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keep in mind that the only part in the engine that is moving at 4K rpm is the eccentric shaft. the rotors rotate at 1/3 that speed 1,333.33---rpm. this why it is so important to run the car to red-line.
03-31-2010, 09:42 AM
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04-01-2010, 11:19 AM
#12
2009 RX-8 Touring
Here's a comparison for you:
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
04-01-2010, 08:39 PM
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04-01-2010, 10:12 PM
#17
Here's a comparison for you:
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
8.
04-01-2010, 10:27 PM
#18
Here's a comparison for you:
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
It seems an apples-to-oranges comparison.
04-02-2010, 02:03 AM
#19
"I wanna go fast!"
Here's a comparison for you:
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
04-02-2010, 02:54 AM
#20
Registered
Here's a comparison for you:
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
1. I own a VW Passat 1.8t which runs at 3000rpm at 80mph.
2. I own an RX-8 which runs at 4300rpm at 80mph.
3. A piston completes a combustion cycle in 2 crankshaft rotations.
4. A rotor completes a combustion cycle in 3 crankshaft rotations.
5. So, a rotary engine needs to spin 1.5x as fast to produce as much power as a piston engine with comparable displacement.
6. That means my rotary engine is roughly equivalent to a 1.9L piston engine, and it's spinning 1.43x as fast as my 1.8L piston engine.
7. Adjusting for the .1L difference in "virtual displacement" between the two engines, my rotary is spinning 1.35x as fast as my 1.8t to produce the same power, which is well below the 1.5x rule.
You really can't compare power output per revolution, rotor or e-shaft, to a piston motor as there are many other differences and variables.
Automatic (6-sp) RX-8s are geared more for cruising (in 5th & 6th) than absolute accelerative performance, so they run almost 120 mph @ 4000 rpm in 6th.
Last edited by PeteInLongBeach; 04-02-2010 at 03:06 AM.
04-02-2010, 10:02 AM
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04-02-2010, 10:19 AM
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Last edited by nate340; 04-02-2010 at 10:27 AM.
04-02-2010, 05:34 PM
#24
Yeah, the more I think about this, the more ridiculous a direct comparison becomes. The piston engine is more fuel efficient, generally, but the Wankel has a better power-to-weight ratio, a lot fewer moving parts, and less loss to force vector changes within the engine. And this is post-engine drivetrain aside.
The piston engine has also had over twice the development time as the Wankel concept, and in terms of man-years of development that ratio skyrockets when you consider the vast number of piston engine designers and manufacturers over the last 110 years, at least.
The piston engine has also had over twice the development time as the Wankel concept, and in terms of man-years of development that ratio skyrockets when you consider the vast number of piston engine designers and manufacturers over the last 110 years, at least.
