Was wondering, do all straight-4 engines have em? if not please give examples of specific types, cheers
franc123,
Feb 12, 4:50am
No its more common that they don't. In terms of mainstream cars its mainly Mitsubishi that uses them.
panicky,
Feb 12, 4:50am
pretty much anything japa that is not a mitsi or a honda
barrylarry,
Feb 12, 5:00am
are they that necessary? or just a smoother engine ride?
dublo,
Feb 12, 5:12am
Honda certainly used them in the 1998 - 2002 2354cc Accords. No doubt they cancel out any vibrations a big four may otherwise have (think 1950s 2 1/4 litre Humber Hawks and similar cars!)
mechnificent,
Feb 12, 5:37am
They are not necesary. Most cars don't have them. The ones that do you can generally leave them disconnected and hardly notice the difference.
Here's how it works. In the case of a single cylinder engine. When a piston and it's connecting rod go up and down it would cause a weight to be thrown up and then down which would cause a bad vibration. To stop that huge vibration we put counter balance weights on the crank, so when the piston and rod are going up, the crank weight is going down. so far so good.
Now here is when the balance shaft comes in.
If the weight of the crank weight is equal to the weight of the piston and rod, when the crank swings to the right as it goes through it's rotation, it swings the bottom half only of the conrod to the right, but the bottom half of the can rod does not weigh as much as the whole piston and rod or the crank weight, and the crank weight which is swinging to the left as the rod goes right, would outweigh the bottom half of the rod and cause a left right vibration. To stop that happening they used to have the weight on the crank slightly less than the whole piston and rod. The had it so the difference in weight was half way between the two and settled for a small vibration up and down and a small vibration left and right. They fit balance shafts to counter that small secondary, twice the crank rev vibration
Hope that makes sense.
phillip.weston,
Feb 12, 10:39am
Many larger capacity 4 cylinder engines run balance shafts to cancel out inherent vibrations that all 4 cylinder 4 cycle (4 stroke) engines have, more specifically the ones with say approx more than 500cc per cylinder.
Most Mitsubishi 4 cylinders of the late 70s, 80s and 90s ran balance shafts and licensed their patent to Porsche Fiat and Saab who used balance shafts in their engines soon after. Toyota and Honda both use balance shafts on their larger capacity 4's as well.
Some people say that disconnecting them will let your engine make a bit more power (how much?), but it might also reduce it's comfort and it's life a bit (again, how much though).
pandai,
Feb 12, 6:54pm
Some cars use unbalanced flywheels instead of a balance shaft. I have a feeling the current model 1L, 3 cylinder, Fiesta is one of them.
skiff1,
Feb 12, 7:24pm
Power?depending on friction and weight, the extra power could be quite a lot as in 2-4%. Comfort? Depends how sensitive to vibrations you are, but other have said the difference was not noticeable. Lifespan? Dunno, it definitely won't help but it the engine is well made and maintained, it probably won't do too much damage. The old adage is "if it's shaking, it's breaking" so if she's skittering sideways out of the garage, it's probably a bad idea. If you can't feel it, it's probably ok? Not an expert, just read a couple of bits and pieces.
mechnificent,
Feb 12, 7:25pm
Hmmm And how does that work exactly ?
timmo1,
Feb 12, 7:46pm
A counter weight 180 degrees from each cylinders' TDC?
mechnificent,
Feb 12, 8:17pm
Well that wouldn't be an unbalanced flywheel.
It might have some effect though. Perhaps making it run as smooth as a straight six.
Ford started offering their new turbocharged 1.0-litre EcoBoost unit in the Focus from 2012. This new engine features several innovations, including the use of an unbalanced flywheel to remove the need to use balancer shafts.
Ha. Thanks fellahs. Saves me having to search. or even worse think about it.
mechnificent,
Feb 12, 9:44pm
Ok. That three cylinder's flywheel is not to make the crank/piston balanced, or to stop vibration, but to counter it's firing order causing a pulsing effect as the cylinders fire from front to back. In a four we fire them 1342 to alleviate it.
tintop,
Feb 12, 9:55pm
or 1432
And of course there are some engines that run 'backwards', or is it that they have the flywheel on the 'wrong' end! lol
ladatrouble,
Feb 13, 5:00am
A 3 cyl engine (eg Daihatsu) has an engine speed balance shaft - an unbalanced flywheel would do the same thing.
mechnificent,
Feb 13, 5:31am
Yeah but the balance shaft isn't to stop vibration caused by the crank and pistons. it's to stop the engine rocking on it's mounts. That's a different thing altogether.
ladatrouble,
Feb 13, 5:42am
No, the 3 cyl doesn't vibrate, but has a bad rocking couple - the best way to solve it is to add it to another 3 cyl engine, making a smooth inline 6. Ride a 3 cyl motorcycle and you can feel it throwing itself around in the frame.
mechnificent,
Feb 13, 5:52am
Ninety degree v is the best configuration. that automatically takes care of that secondary vibration I was talking about in my earliest post. the one describing balance.
sr2,
Feb 13, 6:07am
Henry Royce (and most automotive engineers) would disagree; that's why he chose an in-line 6 for the Silver Ghost, still considered to be one of the smoothest running motors ever made to this day.
mechnificent,
Feb 13, 6:16am
It's physics Sr. read my description of how the balancing works and think about the ninety degree V. Ninety degree motors are wide and that's why they are not popular.
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