Mazda 6 Forums banner

21 - 24 of 24 Posts

·
Registered
Joined
·
2,883 Posts
Rx8 Displacement = 1.3L, 2.6L, and 3.8L

Rx-8s are smaller and put out 200+ horses lol
Actually the Rx8 engine is bigger than the 2.3 and 2.5L engines, and is comparable to 2.6L piston engines that fill the streets.


The inventer of the first Wankel engine decided to ignore many years of convention, when defining the engine's displacement. He based it on:
  • the size of the displaced volume in one "chamber" or cylinder (.65L)
  • the number of chambers in a rotor housing that fire in one rev (1)
  • the number of housings. (2)
disp = .65L/chamber x (1 chambers fired)/(output shaft rev)/ housing x 2 housings
disp = 2 fired chambers per rev of output shaft.

That gives the current Rx8 engine 1.3L disp in one rev, based on that clever old dude.


If you use that logic with a 3L V6 engine, with 2 heads:
  • a single chamber displaces (.5L)
  • number of chambers per head that fire in one revolution (3)
  • number of heads (2)
That gives the 3L duratech 1.5L disp in one rev, based on the Wankel logic.


So to match the chambers fired per rev for a fair comarison of hp output, there are 3 choices:
  • rate per wankel logic, in one rev: 6S=1.5L
  • rate per 99% of cars on road, in 2 revs: Only wankel changes to 2.6L >Best
  • rate per total swept volume. Only wankel changes to 3.8L in 3 revs.
The Wankel engine is exactly like the Otto cycle 4 stroke engines that dominate the roadways:

intake, compression, power, and exhaust strokes

What makes it unique is

1) No Pistons going up and down. Instead a rotor that rotates on an eccentic "throw" of the crankshaft, at 1/3 crank speed, and has no shocking, reversing direction of motion.

2) the port style intake and exhaust, progressive opening and closing events ... no valves or valve train

3) the chambers are dynamic, vs the commmon head and chamber for normal 4-strokes. The wankel housing has a fixed, rotor TDC position, where the spark plugs are fired. One of the rotor's identical 3 faces define a moving "cylinder" for the compression and expansion strokes.

4) because of the shared combustion chamber (like the pocket in a head), it is the most compact design for all 4 stroke engines.
http://en.wikipedia.org/wiki/Wankel_engine

.
 

·
Registered
Joined
·
683 Posts
Goooogle!

The first gen is a 2.3L and the second gen is a 2.5L, how would the smaller engine be more powerful?

2.3-160
2.5-170

Sent from my iPhone using AutoGuide.com App
Honda S2000 has a 2 liter making over 200 hp.

Id love to have that motor in my mx5.

Unicorns! Without a honda badge!
 

·
Registered
Joined
·
540 Posts
Well my cousins car was purchased from brand new and maintained at mazda everytime and yet the engine still died out at 138k kms.
And my friends brother rebuilds JDM car engines (purchases car with broken egine and rebuilds the engine) and 50% of the cars he buys are rx-8s at 150kms.
I love the look of the car but the engine kinda scared me off

Sent from my SGH-I747M using AutoGuide.Com Free App
Rotary engines drink oil like a mall santa drinks lite beer, tell him to put oil in evrey 1500 miles, about a quart, if you do that they will live forever they burn oil intentionaly, if you dont lube them properly they blow up
 

·
Registered
Joined
·
2,883 Posts
Rotaries do have a very small amount of oil injection into the 6 distinct chambers, but they also have fuel dilution of the oil. Continuous rings do a better job of sealing the pistons, vs ring segments and corner seals used to form a ~rectangular seal on the rotor.

If the car was serviced by a dealer, they likely chose the "normal" oil change intervals of 7500 miles or 6 months, vs the"severe" intervals of 3 months or 3000 miles. That makes a big difference in engine life, if the car is driven hard, as a long change interval allows fuel dilution of the oil beyond acceptable levels, in many cases. FD owners like myself typically change oil every 2000 miles.

Long oil change intervals have a 2nd, negative impact on engine life. I often change the oil and filter, then run the car until oil is hot, and come back and drain and refill again. This is because the typical oil change only includes 3.7 Q of oil, and the rebuild capacity is 7 Quarts, with a lot of oil left in the oil cooler(s) and the big supply hoses. With a normal single drain, ~50% of the fuel diluted oil remains in the engine. Doing the 2nd change, you have more like 75% new oil in the system.


.
 
21 - 24 of 24 Posts
Top