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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...
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it is normal, it's around 4k rpm
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^ Damn if she keeps drinking that water her boobs are gonna bust!
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Um, yeah, normal. It revs to 9k, you know. Really only 3k for the rotors, no big whoop.
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Originally Posted by Razz1
(Post 3494101)
^ Damn if she keeps drinking that water her boobs are gonna bust!
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our 6th gear is too short
^and... lol |
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...
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you're fine
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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.
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Originally Posted by Pico
(Post 3494387)
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.
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^ Yep, even at 9k redline the rotors are only spinning 3k.
I cruise at 4k in 6th which is right at 80 mph (well, actually a bit slower since going with 265x35 tires). |
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. |
Originally Posted by Huey52
(Post 3494407)
^ Yep, even at 9k redline the rotors are only spinning 3k.
I cruise at 4k in 6th which is right at 80 mph (well, actually a bit slower since going with 265x35 tires). I'm running 265/35 as well. Add another 2mph to the already +2 mph the speedo is off already.. |
Originally Posted by Dale8000
(Post 3494097)
When I'm in 6th gear and cruising at around 120km/h (so around 75 mph) im revving at almost 4000rpm...is this normal?..
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Originally Posted by zoom44
(Post 3496017)
How could it not be normal? seriously stop and think a moment. what in the world could possibly make the engine spin at a different rpm at a given speed in a given gear?
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what? how would it differ with an AT? rpm x gear = speed
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Originally Posted by fyrstormer
(Post 3495915)
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. 8. :Eyecrazy: |
Originally Posted by fyrstormer
(Post 3495915)
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. It seems an apples-to-oranges comparison. |
Originally Posted by fyrstormer
(Post 3495915)
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. |
Originally Posted by fyrstormer
(Post 3495915)
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. 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. |
Originally Posted by zoom44
(Post 3496757)
what? how would it differ with an AT? rpm x gear = speed
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Originally Posted by Dale8000
(Post 3494097)
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...
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Originally Posted by nate340
(Post 3497293)
i herd something interesting the other day, that if your leading spark plugs are gone then the engine has to spin twice as fast as it normally would in order to produce sufficient power to cruise at the desired speed. just saying. ;)
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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. |
Originally Posted by zoom44
(Post 3496017)
How could it not be normal? seriously stop and think a moment. what in the world could possibly make the engine spin at a different rpm at a given speed in a given gear?
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