PurpleCherokee said:
Ok so I have a question for 5-90 then. How do you differentiate well balanced and smooth to vibration free? Seems like smooth should be vib free. But mine's definately not. The MOORE motor mounts don't help either. So where are the vibs coming from??
Any internal combustion engine will have vibrations in normal operation - that's just the nature of the beast. "Smooth" means you don't notice them as much as you otherwise would (if you want "vibration free," get a turbine engine.)
Having the MORE engine mounts probably does
not help - anytime you take a flexible mechanical coupling and make it more rigid, it will transmit more vibration. I used to fab up engine mounts out of tube stock for bracket racers - but these weren't dual-duty cars set for the week-end at the drags. The things were trailered there and back, and the mounts removed and inspected two or three times a year (usually replaced annually, at least.) You can make a mount out of tube stock or solid stock - but expect it to be even worse (the MORE mounts seem bad because they're using polyurethane busings - instead of a latex elastomer - and they anchor to more of the engine. I presume you're tlaking about the "bomb-proof" mounts that spread all over the sides of the block?)
Eliminating vibration is the challenge facing luxury carmakers - I know Porsche actually used a "hydraulic" mount for a while, where engine coolant was circulated through the mount and used as a cushion instead of elastomer. I believe that also made the engine mount a maintenance item - no, thanks.
There are a number of factors that go into NVH reduction (Noise, Vibration, Harshness) in the engine bay - the AMC242 casting was revised twice in the block in an effort to improve NVH response. Both times, it got lighter (that seems to be the main thing - reducing weight reduces inertia.) The ChryCo LA block was "precision cast" in later years for the same reason - the "precision casting" allowed them to use less material for the same results, meaning less weight, meaning less inertia, meaning ...
However, as long as we continue to use the internal combustion engine in the Otto cycle, the Diesel cycle, or the Wankel cycle (or even the Crower cycle, if it comes to pass...) engine vibration is still going to be a reality. I believe even the Stirling cycle engine (which uses an external heat source) is subject to NVH, as are the old EC steam engines (think "steam locomotive" and you've got it. Or any other "steam engine" used to generate motion.) Some engine patterns are going to be better than others, and when you get into V-block engines, the headaches get even larger (that's why there are two different versions of the General Motors 90-degree V6, why automakers shifted over to a 60-degree V6, ... Eight-cylinder V-block engines are usually done at 90 degrees, some were done at 45. And, there's always the horizontally-opposed engine,
a la Volkwagen/Porsche/Subaru, W-blocks, V-blocks with an odd number of cylinders and a
very close bank angle, ... Don't forget opposed piston engines as well, and any number of other configurations. Even a sixteen-cylinder V-block Hemi that was run
upside down for an aircraft application, although I don't recall which at the moment...)
Otto cycle - four-stroke gasoline-fuelled heat engine cycle. Ignition with an electric spark
Diesel cycle - four-stroke oil-fuelled heat engine cycle. Ignited by compression.
Bank Angle - the angle between the centrelines of the cylinder bores, when the cylinder bores are not in line. Typically done with an even number of cylinders, but has been done with an odd number as well (five, mainly.)
Horizontally Opposed - an engine in which the cylinder banks have a "bank angle" of one hundred eighty degrees, making them directly opposite each other. Notable examples were the Volkswagen beetle (four-cylinder) and early Porsche (four- or six-cylinder.) Typically air-cooled, since water-cooling something like that is a royal pain (keeping it sealed is worse.) NB: Bank angle may be adjusted, in some cases, in response to packaging concerns. An eight-cylinder, for instance, can be run with a bank angle of 45/90/135/180 degrees with relative simplicity, and the engine gets shorter (top to bottom) as the bank angle increases. Six-cylinder engines can be run at 60/120/180 degrees. You get the idea.)
"Well balanced" means that the engine won't shake itself to bits underhood, although vibrations (there will always be some) may or may not be transmitted to the chassis by way of the mounts. "Vibration free" don't happen - but it get approached by a combination of mount design, cylinder/firing even timing, cylinder arrangement, and the like.
