A&Q about 350Z
Q:
I just read a piece about the RX-8, and while the HP and torque numbers are impressive for the stated displacement, I was wondering....
It appears that displacement is measured based upon the maximum volume of one combustion chamber per rotor, resulting in a displacement of about 1.3l. But it actually has six combustion chambers, so to my mind it has a displacement of about 3.9l.
I've got the part about it taking three revolutions of the "crankshaft" for a single combustion chamber to go through the intake; compression; combustion; and exhaust "strokes; but in that 1080º spin, a single rotor has three combustion chambers going through those four "strokes".
A two stroke engine goes through the the intake; compression; combustion; and exhaust cycle in only 360º, while a four stroke takes 720º, but their displacements are both measured the same way; i.e., maximum volume of a combustion chamber multiplied by the number of combustion chambers.
Why are rotary's measured differently?
TomR
-Z- Enjoy the ride.
A:
I believe it's 2 combustion cycles per one of a cylinder engine.
Yes they're 1.3l, but should be thought of as 2.6l, but not like it matters because it has the torque of a 4 cylinder and the fuel consumption of a new v8....
Mario
1976 280Z - Dad's Z (turbo swap?)
1978 280Z - Stock Rebuild | 5 Speed | Twice Pipes | Gutted
1982 280ZX - Turbo | MSnS-E | 5 Speed | Large NPR IC
BROKE: Will build computers, webpages, networks, MS units, troubleshoot computers for money
A:
>It appears that displacement is measured based upon the maximum
> volume of one combustion chamber per rotor, resulting in a displacement
> of about 1.3l. But it actually has six combustion chambers, so to my mind
> it has a displacement of about 3.9l.
Mario is right, it's more like 3.1 or something, there is a formula for calculating the active chamber size. The 1.3L is a misnomer marketing ploy.
A:
rotary is crap .
73' 240z: F54 4.2L, OS Giken LY DOHC Crossflow head, 17:3comp.ratio, N33, Tripple SU's, T10 Hybrid Draw-Through TT @ 47pds, Roots&Centrifugal Type supercharger, 3-2-1 headers, Centerforce 4 clutch, 6oz flywheel, R300 differential, Super-Hicas
A:
rotory is cool if you like your car to rev like a sport bike and produce the smae amount of tq which isnt gonan get you no where ina 3000lb car and as stated use gas up the butt - although jermay of top gear said it was a bit weak it was one of the easiest "sports cars" ever to drive and you were still able to have fun with it
sure i would take a tt 3rd gen rx7 as the turbos help make up for lack of tq but pistions are doing the job for me oh ya and you dont have to get your motor rebuilt every 5 miles
70 yay!
77 parts
81 compressed parts
86 compressed it handles
00 mercury cougar omg wtf : \ girl has to have something to drive
- owned
74.5 why did i sell you
81 1st car $425 found out s130s dont handle stock
82 good
84 BMW 325e omg never again
A:
Since Mazda is the only manufacturer using them, they can call them whatever they want without anyone complaining or contesting. The amount of power they put out for their weight is imressive though, and the power is rediculously smooth. I have a problem with overevving them because it feels like it will just keep going. They are noisy (not in a good way) and get terrible gas milage.
1972 240Z always in progress
***WARNING*** MY POSTS MAY CONTAIN SARCASM
A:
The how stuff works web site explains Wankel rotary engines pretty well. As I understand it, the Mazda RX-8's engine has 2 rotors with 2 spark plugs per rotor.
What I don't understand is why they get such lousy gas mileage given all their favorable attributes such as the engine being smaller and lighter and has less moving parts than a reciprocating engine.
A:
People brag about the foney HP/L and about how efficient they are. In reality they are very unefficient, 18mpg out of a so called 1.3L? Yep thats efficent, not to mention to emissions problems. Not to mention it uses oil from the factory, it has to burn oil in order to keep the apex seals lubed. There are websites out there that explain that it's listed displacement isnt accurate. In reality it's the equivlant to 2.6l piston engine.
The only thing rotory engines are good for are it's small size and being different. Once you start throwing turbos and stuff like that on it the small size and weight become pretty pointless.
My favorite thing rotory guys say, "I'll never throw a rod". To that I say, I'll never have to replace apex seals or rotor housings.
---
Justin T
72 240Z L28, 5-speed
77 280Z 5-speed (t-boned 8-25-04)
80 280ZX automatic(retired)
A:
Mario,
A reciprocating piston four stroke six cylinder hits ignition every 120º, and a six chamber rotary (two rotors) hits ignition every 180º; so I can see some logic in calculating the displacement of a rotary engine by multiplying the gross displacement by a factor of .666; that is until I remember the two stroke engine.
I understand why race sanctioning organizations might place differing displacement limits on differing types of engines; but why does the rotary engine get a pass on the standard displacement measurements?
TomR
-Z- Enjoy the ride.
A:
As far as having to rebuild rotary engines every 5000 miles...thats not true..I have a 90 Gxl with around 160,000 miles on it...from what i can tell most people don't do the research into the required maintanance of a rotary engine so maybe thats why everyone says they only last 5k miles?
79 280zx N/A 2+2
280zx N/A: Parts car THE RUST MONSTER!
90 Rx-7(FC3S) N/A:TurboII Swap when I'm not broke...
A:
.
If my reply sounds offensive, TAKE IT AS HUMOR !! MUUUUHAHAHAHAHA !!
.
...'77 280 ZEE-EEK.....If it's got Wheels.....It's gonna Cost Ya ! !
A:
>from what i can tell most people don't do the research into the required
> maintanance of a rotary engine so maybe thats why everyone says they
> only last 5k miles?
Yes, required maintenance like replacing the apex seals.
hehehe.
A:
Another issue I’ve found with them is they run hot. Reason being you have a larger surface area to mid sized combustion chamber to loose heat to opposed to the large chamber vol. to smaller surface area of a piston. This is turn cause a lot of energy to be lost to heat in a wankel. Neat idea, Id like to see the design put into a super charger (if it hasn’t already).
79' 280zx aka "rusty"
A:
The combustion chamber is a very poor shape for good gasoline combustion. Leading to bad gas milage.
A:
Not a lot of facts here, besides the technical data introduced to figure out the displacement. I don't have the exact specifications to back me up, but 1.3ltr is almost exactly 2.6ltr in a standard piston engine.
As for reliability.. rotaries are just as reliable as gas engines.
However, the 3rd gen RX-7 has NUMEROUS problems unrelated to the rotary portion of the car that cause it to fail, 1 being EMS, 2 being extremely poor cooling system that actually HEATS up the engine due to the poor exhaust system. For instance, if you add an exhaust and intake to a stock 3rd gen, the EMS doesn't compensate, you run lean, you blow up. Very little tolerance.
Many turbo FC's have 160k+ on stock engines. Many n/a rotaries have over 250k.
The main reason rotaries are so far behind is because only weak mazda R&D's them. There are lots of technical reasons but this is the foundation. Right now they just aren't efficient with fuel and they don't want to spend the $$$ to fix it. I don't blame them personally.
19[TT]91
My TT beauty is gone.
2[00]2 Honda 954RR
Suzuki 1200 S; sportscar eater
19[I4]94 Integra GSR Sedan
Long live the Z...
aka SAHTT
A:
zlover,
Can you provide further information regarding the displacement measurement?
Why, and/or how, is a 1.3l rotary the equivilent of a 2.6l piston engine?
Thanks for any help.
BTW, I really don't care about reliability or other issues concerning the rotary engine. I'm not planning on buying one. I just don't understand the standards for measuring displacement.
TomR
-Z- Enjoy the ride.