ENGINE BALANCE: Inline 6 vs. Odd fire V6 vs. 90 degree V6 vs. 60 degree V6

Summary

In this video, the host explores engine balance, comparing the inline-six engine with its V6 counterpart. The video delves into primary and secondary engine imbalances, explaining how they affect performance and engine smoothness. It highlights how the inline-six's even firing interval and perfect balance make it a great engine, while the V6, though more compact, presents challenges such as odd firing intervals and balance issues. The video then describes how engineering advancements like the Alfa Romeo Busso V6 addressed these issues to create a smooth, compact V6 engine. The host promises to explore more engine comparisons in future videos.

Takeaways

• 😀 Primary engine imbalance is caused by unbalanced mass in the reciprocating assembly, mainly the pistons, while secondary imbalance occurs due to varying piston speeds during the stroke.
• 😀 Primary imbalances happen once per engine revolution, while secondary imbalances occur twice per revolution. Primary imbalances are usually more noticeable and impactful.
• 😀 An inline six-cylinder engine is known for its perfect primary and secondary engine balance, making it smooth and well-suited for performance.
• 😀 Inline six engines are perfectly balanced because each pair of pistons cancels out the forces of the others, eliminating rocking motions.
• 😀 The main problem with inline six engines is their length, which makes them difficult to fit into vehicles, especially when mounted transversely.
• 😀 A V6 engine is created by splitting an inline six engine into two banks of three cylinders arranged in a 'V' shape, making the engine more compact.
• 😀 The ideal angle between the two banks in a V6 is 120 degrees, ensuring an even firing interval and minimizing imbalance in firing order.
• 😀 V6 engines often suffer from primary imbalance because the pistons in the two banks share crankpins, and there is no mirroring like in inline sixes.
• 😀 Odd-firing V6 engines, caused by inappropriate bank angles (like 90 degrees), lead to rough engine operation due to uneven firing intervals.
• 😀 Buick's solution to this issue involved creating a V6 with a 90-degree bank angle and using offset crankpins to ensure even firing intervals and smoother operation.
• 😀 The secondary balance in a V6 is naturally handled by its design, as it essentially combines two inline threes, where each bank's pistons are out of phase with each other.

Q & A

What is the main focus of this video?

The video compares the E96 inline six-cylinder engine with its nemesis, the V6 engine, and explores engine balance concepts in-depth, such as primary and secondary imbalances.

What is the difference between primary and secondary engine imbalance?

Primary imbalance is caused by an unbalanced mass in the reciprocating assembly, mainly due to pistons, and occurs once per engine revolution. Secondary imbalance arises because the piston moves at different speeds during the top and bottom half of the stroke, occurring twice per revolution.

How does the inline six-cylinder engine achieve balance?

The inline six-cylinder engine achieves perfect primary and secondary balance due to its even number of pistons, which cancel out each other's forces, and its pistons move in pairs to ensure no single pair is at the same part of the stroke as another.

Why is the inline six-cylinder engine difficult to fit under a vehicle’s hood?

The inline six-cylinder engine is long, making it hard to mount transversely under a vehicle’s hood, especially in smaller engine bays.

How is the V6 engine different from the inline six-cylinder engine?

The V6 engine is a more compact version of the inline six-cylinder engine, with two banks of three cylinders mounted at an angle, making it shorter and easier to mount transversely in vehicles.

Why is a 120-degree V6 engine impractical?

A 120-degree V6 is impractical because it’s too wide for a compact design, making it almost as bulky as a flat-six engine, but with a taller profile.

What did Buick do in 1961 to improve the V6 engine design?

In 1961, Buick created the Fireball V6 by reducing the number of cylinders from their V8 engine, but this resulted in a rough odd-firing engine due to an inappropriate bank angle of 90 degrees.

What is an 'odd firing' engine?

An odd-firing engine has an irregular firing interval, meaning the spacing between the firing events is not equal, which causes rough engine operation.

How did Buick resolve the odd firing issue in their V6 engine?

Buick resolved the odd firing issue by introducing a split crankshaft with a splay angle, offsetting the crankpins to create an even firing interval and ensuring smooth engine operation.

How did Alfa Romeo improve their V6 engine in terms of balance?

Alfa Romeo improved their V6 engine by using flywheels and crankshaft pulleys with offset weights, which rotated at the speed of the crankshaft, to balance the primary forces and eliminate the need for additional balancing shafts.