- 62
- Tønsberg, Norway
- mathias-gj
How big is the engine on the RX-7 when it's 654x2 cc 
Mazda RX-7 engine
- Thread starter The Car Tuner
- 21 comments
- 4,367 views
- 1,899
Its a trick question, because rx-7 engines blow up.
- 26
- tonybarbados
It displaces 1.3 litres , but it is rated as a 2.6 litre engine due to the way each rotor fires twice for every rotation of the con-centric crank shaft . ;-)
- 62
- Tønsberg, Norway
- mathias-gj
- 1,233
- Patra
- Rotorist
This unique engine was invented by the German engineer Felix Wankel and it is used mainly in light airplanes as it is very light, high output and revving with zero vibration. It's way of working resembles with a 2-stroke engine but it makes everything in a full turn of the rotor. So, it's displacement is 1.3lt in RX7 and RX8. Some, when trying to compare it with 4-stroke engines double its displacement. This is useless because wankel motors have almost nothing in common with other motors. Ports instead of valves, rotors for cylinders, not camshafts for instance. Did i tell you how much I like wankels?
- 1,173
- Drex81
Amazing engines. Simply amazing.
- 86,832
- Rule 12
- GTP_Famine
For every revolution, each of the three spaces created by the rotor will go through an intake/compression phase, a compression/ignition phase and an expansion/exhaust phase - so by definition each rotor chamber will fire three times for each rotation. However, that's for each rotation of the rotor. The shaft itself will rotate three times for each rotation of the rotor, leading to one chamber firing once for each revolution of the shaft.
The reason we double the capacity for equivalency is because each chamber fires once for each shaft revolution - whereas in a four-stroke piston engine each chamber (or "cylinder") fires once for every two shaft revolutions (down [intake], up [compression/ignition], down [expansion], up [exhaust]).
We triple the cylinder count for equivalency simply because each chamber contains three spaces.
So a rotary is equivalent to a 4-stroke piston engine of twice the capacity with three times the number of cylinders - the 654x2cc 13B rotary is thus the equivalent of a 2.6 litre, 6 cylinder engine.
- 1,233
- Patra
- Rotorist
All this theory about equivalent engines doesn't have meaning for us. There is no comparison in fact. Wankel is what it is. The displacement of its rotors' house is 654cc X 2=1308cc. Only meaning of this this theory existed for racing so as to categorize rotary powered vehicles in order for them not to play without opposition...
- 62
- Tønsberg, Norway
- mathias-gj
The RE Amemiya RX-7 Aspara Drink engine is 654x3 cc. Are it a 4000 cc engine or a 2000 cc engine
- 451
The RE Amemiya RX-7 Aspara Drink engine is 654x3 cc. Are it a 4000 cc engine or a 2000 cc engine
The way I read Post #9, I'd say 4 litres and 9 cylinders.
- 26
- Indianapolis, Ind/ USA
- White_Zeal
- White_Zeal
- 62
- Tønsberg, Norway
- mathias-gj
ok so it looks like this
Nice engine
Nice engine
- 1,092
- Ecchi_BANZAII
- 1,899
Its just a shame that these engines are all born to die
You see in the GIF above? Where the peaks of the triangle meet the oval housing? Well thats called the 'apex' seal, and over time it wears out. There is nothing you can do to stop the wear. Its a design flaw. Needless to say all Rx-7's have a shelf life of maybe 75k miles before the seals need to be replaced
Thats why so many knuckleheads are putting v8's and v6's and such in to rx-7's.. because unless youre the type of guy who likes to remove and dissasemble a motor once a year, the wankel just isnt for you
You see in the GIF above? Where the peaks of the triangle meet the oval housing? Well thats called the 'apex' seal, and over time it wears out. There is nothing you can do to stop the wear. Its a design flaw. Needless to say all Rx-7's have a shelf life of maybe 75k miles before the seals need to be replaced
Thats why so many knuckleheads are putting v8's and v6's and such in to rx-7's.. because unless youre the type of guy who likes to remove and dissasemble a motor once a year, the wankel just isnt for you
CodeRedR51
Premium
- 55,281
- United States
How much experience do you actually have with these motors? Because it sounds like zero. Gee, apex seals are no different than piston rings which also wear out over time. I have seen naturally aspirated Rotary engines last for well over 100k miles, including some around 200k miles. They do take more care and upkeep that a normal piston engine, but they can last just as long if not longer.
- 341
- Auckland
- RZRX7
I agree with you they have no experience. Been building rotary engines now going on 20 years. If a backyard mechanic does a bad job of building a piston engine does it last? I think not. Too many people doing "I think I know what I'm doing" backyard builds and mods on rotaries which give it a bad reputation.
Rotary engines last, just depends who works on them!
Happy owner of a FD3S RX-7 Type RZ '96, FC3S RX-7 '87 and a rare JC COSMO Type SX '92 20b triple rotor.
- 60
- New York
- Ruthless_Clipz
The Car TunerThe RE Amemiya RX-7 Aspara Drink engine is 654x3 cc. Are it a 4000 cc engine or a 2000 cc engine
Yes the 3 in 654x3 means there are 3 rotors & 654x3=1,962 which rounds up to 2000cc which in turn translates to 2.0 liters making the engine a 20B unlike the 1308 aka 1.3 13B wankel engine.
- 379
- PNW
- Zenmervolt
While I agree with you that the previous poster's comment about only a 75,000 mile life expectancy for Wankel engines was ridiculous, an engine lasting "well over 100k miles" is mediocre at best. Short of abuse, neglect, or a very rare manufacturing defect you won't be getting blow-by past piston rings even at upwards of 300,000 miles. If you've got a piston engine where the rings are shot at 150,000 miles, then you've got an owner who did something wrong (never changed the oil, let the oil run out, ran the wrong viscosity, let the engine overheat, etc). An engine being able to last to "around 200k miles" in a street car is a bit like a runner being able to do a 10-minute mile. It's not bad, but it's also not really impressive.
I like the Wankel, it's a really neat little engine, but it's horribly inefficient (in terms of fuel consumed per horsepower generated) and the emissions just plain aren't as clean as the traditional Otto-cycle engines. Even with the massive improvements made by Mazda to the new Renesis design, the Wankel still lags behind piston engines in both emissions and fuel consumption.
CodeRedR51
Premium
- 55,281
- United States
I think you misunderstood what I was saying.
