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Does the 2004 have a balance shaft belt?

I searched, but found little discussion. But the dealer said something (just a quick blub)...

In checking parts prices, I was looking at Rock Auto, and while they listed numerous timing belts for the '04 (different brands and product lines), they only had one listing for a "balance shaft belt"...

Right now, I am assuming its somethign I don't need to worry about for a 105k service...

Thanks
 

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There's no balance shaft belt on these engine's unlike some Accords. Only one hidden belt in there which of course is the timing belt. I don't think the motor has a balance mechanism, maybe because it's a 6 cylinder?
 

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My understanding has always been that balance shafts are incorporated to deal with vibration problems. I believe that the best designed engines do not use them. I think of it as a patch or rather, dealing with the symptom rather than the problem when balance shafts are added. One of Saab's most troublesome engines, the 2.3 had them and its 2.0 bulletproof predecessor did not. It is strictly a "few cylinder" problem so I doubt that any six would have them.
 

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Balance shafts are used in larger 4 cylinder motors...typically over 2.0litres. An H22 (2.2l) and H23 (2.3l) prelude engine has one as does an F22 (2.2l) and F23 (2.3l) Accord engine. B16 (1.6l) and B18 (1.8l) civic and integra motors do not.
 

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An inline 6 is better balanced than a V6. Acura may have added a balance shaft to compete with BMW's I6 - one sweet motor!
 

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Not that this is the forum but I don't think that the 3.5RL has a balance shaft. I always thought it was the same architecture as our ody motors. (J35).

My math says this.

The ideal crank angle is 720 degrees/number of cylinders. That means a 4 cylinder engine's ideal angle between cylinder banks is 180 degrees - like a Subaru boxer engine. An 8 cylinder engine's ideal angle between banks is 90 and a 6 cylinder is 120 degrees. Since 120 degrees is not very compact for an engine bay, they use a 60 degree angle because a V6 fires every 120 degrees and 120 is divisble by 60 and therefore balances out. There are some V6s that use balance shafts but I am not sure which ones.
 

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Balance shafts are used to counteract vibrations from the intrinsic imbalances of the individual cylinders. If we consider only the primary and secondary balance forces, the following applies:
1 cylinder: primary and secondary shake
2 cylinder, parallel, 180 degree crank; primary/secondary rock, secondary shake
2 cylinder, parallel, pistons in phase: see 1 cylinder
2 cylinder, opposed, 180 degree crank: all forces cancel (bmw motorcycles..)
3 cylinder, parallel, 120 degree crank throws: primary and secondary rocking
3 cylinder, 180 degree crank: primary/secondary shake
4 cylinder, 180 degree crank: secondary shake
4 cylinder 90 degree crank: primary rock
5 cylinder, 72 degree crank throws: primary, secondary rocking
6 cylinder, inline, 120 degree crank throws: smooth
6 cylinder, 90 degree V, common crank throws: primary and secondary rotating couples, uneven firing impulses
6 cylinder 90 degree V, offset crank throws: primary and secondary rotating couples, primary and secondary rocking couples
6 cylinder 60 degree V: primary and secondary rotating couples, primary and secondary rocking couples.
6 cylinder, 180 degree V, opposed pistons: smooth.
7 cylinder inline: primary/secondary rocking couples
8 cylinder inline, 90 degree crank throws: smooth
V-8, 90 degree throws: primary rocking couple (with balance weights on crank ends, smooth operation)
V-8, flat crank: secondary rotational vibration (increased power due to better spaced exhaust pulses in each bank's manifold)
Flat 8, flat crank: smooth
V-10, 90 degree V: primary rotating couple (countered with crank weights), secondary rotating couple
12 (inline or 2 banks) smooth operation
Radial, 2 or more cylinders: smooth operation. Radials are usually odd numbers of cylinders (3 or higher) to get evenly spaced firing impulses.

There is simply not a way to design a V-6 engine to have smooth operation and even firing impulses, regardless of cylinder bank angle (90 vs 60) or arrangement of crank throws, unless you use balance shafts.
 
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