Advantages of V-twin over an inline four

Hi,

Been asked another question - and me neither having enough mechanical knowledge nor a big ego stopping me from putting it out as a question on this forum - again sending it out to the experts.

I've been asked what is the advantage of a v-twin vs. an inline four in motorbikes. All I could think of was if Ducati is doing twins in most of its bikes; something must be right about these.

Thanks,

Bottom end torque, helpfull engine braking (if you think it's helpfull,... I do), generally lighter (not as much metal), MUCH nicer sound (IMHO ) and before my SV I only road in-lines, and they're not as wide which along with other geometry makes them (well SV's anyway) great track bikes.

Twins tend to develop power/torque lower down the rev range than IL4's. That's the most basic "difference". However, as engines get bigger this becomes less noticeable.

Twins tend to have narrow engines than fours unless it's a "transverse" engine (across the frame rather than in line with it).

Fours tend to produce more power for a given engine size, but generally tend to rev higher to achieve it. For example, the GSXR600 produces more BHP and torque than the SV650, but needs to rev much higher to make it happen.

[Sid Squid]

Neither has an advantage as such, they both have their good points of course. Assuming you mean only those V-twins that are fitted longditudinally - SV, Firestorm, Ducati, Harley, Aprilia, but not Guzzi - then:
A V-twin is compact laterally, but can be less easy to fit to a motorcycle frame due to it's length. Arranged in a conventional way, (that is; a 90 degree twin on a single crankpin), then torque can feel good as at any given time a piston is moving. Generally it's accepted that twins, any layout, 'feel' good - this can be hard to quantify of course.
The downside is efficiency, with good design the more cylinders you have the more piston/valve area there is, as an engine is essentially a pump the more easily the gasses are moved in and out of the engine, and the more area the pistons have for the gasses to act upon, the better.
More cylinders give that, thus twins aren't efficient.
If you're thinking of Ducati's racing success, remember that until a few years ago in Superbikes, Ducati had quite a capacity advantage, twins had a 1000cc limit, fours 750cc, since that's been evened out it hasn't all gone Ducati's way as it once did. In GPs Ducati's bike is a four cylinders, (in a 'V'), within reason the more cylinders the better.
In theory perhaps the best engine configuration for a bike would be a V-four - the advantages of both engine types.

[Luckypants]

Originally Posted by Sid Squid

In theory perhaps the best engine configuration for a bike would be a V-four - the advantages of both engine types.

I'm now feeling all smug

Originally Posted by Sid Squid

In theory perhaps the best engine configuration for a bike would be a V-four - the advantages of both engine types.

As long as it's not weighed down with ABS, touring screen, V-Tec, GPS, Luggage, CAMRA stickers, pipe, slippers and a beardy bloke with a flip-up helmet and a beer belly - thereby undoing all the hard work Honda put into making the engine more efficient.

You meant the vision of beauty that is the VFR750R RC30, didn't you... please tell me you did?

[Luckypants]

Originally Posted by Lozzo

As long as it's not weighed down with ABS, V-Tec, Luggage and a beer belly

OI!

Originally Posted by Lozzo

You meant the vision of beauty that is the VFR750R RC30, didn't you... please tell me you did?

Nah, he means an RVF750 RC45 mate!

Originally Posted by toonyank

generally lighter

How sure about that are you?

[johnnyrod]

The twin has longer gaps between the power pulses so in thoery gives more grip. It was enough for the racing boys to mess around with the firing order of 4-cylinder bikes. I still maintain that you can feel the difference when you feed to power on with it cranked over.

Originally Posted by johnnyrod

The twin has longer gaps between the power pulses so in thoery gives more grip. It was enough for the racing boys to mess around with the firing order of 4-cylinder bikes. I still maintain that you can feel the difference when you feed to power on with it cranked over.

This always intrigued me - there may be longer gaps but surely the pulses must be bigger?