A&Q about 350Z
Q:
Sorry to say that I'm completely confused
I always thought that when you have multiple cylinders, then all the cylinders, piston, displacement would all be identical. Now I come to know that even if you don't have identical cylinders, if the displacement is the same, then you can still have the system up and running. Is my understanding correct? Plz educate me.
TIA
Ganesh .R
A:
Let me try to clear up some things here.
Frist the more cylinders you have on a crankshaft the smoother the engine well run. Why? The more cylinders you have the narrower the power stroke cycle is or the closer it is between power cycles.
The engine's RPM is limited by the piston speed. Short stroke, lower piston speed, higher RPM. Long stroke, higher piston speed, lower RPM.
Now the single cylinder engine is on power stroke every 720 degrees of crankshaft rotation. A 2 cylinder is on power stroke every 360 degrees of crankshaft rotation, and a 4 cylinder, every 180 degrees. A V8, every 90 degrees.
Years ago Cadallac, LaSalle and Lincoln had V12 and V16's. The V16 was very smooth running as it had a power cycle every 45 degrees.
Now 2 engines of different mfg. well be different in power because different mfg's. have designed the engine generally for normal daily use. Now some of them have made hi-performance engines out of there engines designed for daily use.
Some engines by there design make better hi-performance engines than others. Why? Because of head design, pistons, intake or exhaust runners, many things taken into account.
Pryor to the OHV V8's Ford had a Arden conversion kit that kicked butt. There engine at that time was a flathead, and GM having some smarts in 1954-55 came out with 2 OHV V8's that ruled and Ford and Chrysler scrambled to catchup.
And now with CAD, Metallurgy and engineering knowledge we have engines far better than anything we ever dreamed of in the past.
Combustion chamber design is better, computers control everything and can be programmed to handle just about anything you can think of, with the aid of fuel injection. Economy is better and power is higher with less displacement and the cars are lighter.
A:
In one engine, all of the cylinders are identical. Same size, bore, stroke, etc. I was comparing two different engines of the same displacement. Let's take for example two different American V8 engines that displace 455 cubic inches. The Buick 455 got its displacement with all 8 cylinders using a 4.3" bore and 3.9" stroke crankshaft. The Oldsmobile 455 got its displacement using a smaller 4" bore and a longer 4.25" stroke (or close to it... I forget). The Buick, since it uses a shorter stroke is capable of higher RPMs. Why? The shorter stroke produces slower piston speeds which reduces inertia greatly.