V4 engine

[Gettingonabit]

Its my understanding the I6 is the best balanced having both primary and secondary imbalance cancelled out - that must be a serious consideration as well.

there would still be vibratory forces from the valve motion
conventionally this is ignored ....
but Mr Duckworth said (of the DFV) these forces were greater than the well-known 2nd order imbalance of a flat crank V8

V6 balance will be very close to the straight 6's if it has 6 crank throws positioned such that a full number of proper webs is needed
so producing a longer and heavier engine than we would want ie the old Ford UK 60 deg Essex and similar Cologne engines
there is a small 2nd order rotating couple but no 2nd order rocking couple

since, V6s had larger bank angles allowing overlapping throws, eliminating webs and giving shorter crank to match natural block length
overlapping or near overlapping throws won't avoid the 2nd order rocking couple
the larger bank angle might help a bit, its main benefit is to even firing order without the length and weight of the old Ford
and less engine height of course

anyway imo the V4 is better in a racing car than in the road car, but is a bit downmarket to give F1 gloss to car makers

All true of course. My post was aimed more at road applications i.e. 'Facts Only' mention of the new JLR engine family.

[riff_raff]

The crank stroke is a major consideration. Small displacement MC engines use both V4 and I4 configurations without any real problems.

[J.A.W.]

The crank stroke is a major consideration. Small displacement MC engines use both V4 and I4 configurations without any real problems.

MC engines have also used O4, O6 & I6 configurations in mass production units.

The Yamaha I4 mill used in Superbike & Moto GP racing..
.. mimics the V4 crankshaft inertia torque/firing profle by running a 90`crankpin set-up, rather than the typical 180`type.

This also produces a more pleasant dynamic feel for the everyday rider, which is an attraction for the V4 layout.
180`I4's generally require a complex, power-robbing balance shaft to quell the unpleasant buzzy/busy resonant feel.

[Tommy Cookers]

.......The Yamaha I4 mill used in Superbike & Moto GP racing..
.. mimics the V4 crankshaft inertia torque/firing profle by running a 90`crankpin set-up, rather than the typical 180`type.
This also produces a more pleasant dynamic feel for the everyday rider, which is an attraction for the V4 layout.
180`I4's generally require a complex, power-robbing balance shaft to quell the unpleasant buzzy/busy resonant feel.

yes, crossplane crank I4 Yamahas have perfect balance ie the notional primary and secondary balance of forces and moments
(though no doubt there's some obscure small secondary rotating couple eg as in V8s, and other forces being ignored as usual)
so are unlike normal 4's secondary (2x engine frequency) force imbalance, treated by elastic mounting and/or balance shafts

the downside of the crossplane I4 is the uneven spacing of firing-related forces (would/need a V4 be so uneven ??)
this is bad in a road vehicle for both operator and crankshaft
but good at race rpm as the crossplane crank gives even spacing of inertial (rpm-related) forces
inertial forces on the crankshaft become large at high rpm, firing-related forces remain rather constant and are lower frequency
and these forces (both) drive piston 'sidethrust' friction
but remember the firing-related forces are higher in a high-boost engine than in N/A

if the Yamaha was a 2 stroke the firing intervals with this crossplane crank would be even and spaced at 90deg
40 years ago their road-derived race 2 stroke I4s had conventional 'flat' cranks and so used paired firing (ie spaced at 180deg)

EDIT while unsuccessfully trying to find what crankshaft arrangement a 90 deg V4 road car might use .....
I find that road motorcycle V4s (including the 1930s Matchless) almost all use(d) a 180 deg (2 throw not normal I4 flat crank)
and feel vindicated that ......
race Honda RC30s and RC45s used 360 deg (aka 0 deg) cranks and consistent uneven intervals 90 deg, 270 deg, 90 deg, 270 deg
(not the road bike V4 normal 180 deg, 90 deg, 180 deg, 270 deg that is the same as the Yamaha I4 crossplane gives)
ANOTHER EDIT - the 360 deg used in the above and the RC30 VFR 400s mentioned after this by another poster ....
is all about minimising engine width (probably with plenty of bigend width in the rods), has 2 throws, 4 webs and 4 main bearings
the so-called 180 deg crank used in the normal engines incl (earlier) RC21 and RC23 VFR 400s is like a conventional I4 ('flat') crank
ie 4 throws, 8 webs, and 6 main bearings
what differences between these wrt primary drive ? - immaterial
the race-model 360 deg crank is all about getting the smallest engine
the road Ducati 'GP race-replica' is similar, but has 1 throw at 70 deg to the other
so giving 180 deg, 160 deg, 180 deg, 200 deg firing intervals (I guess), but a small imbalance of primary forces

a 90 deg car V4 would need a crank like the cross-plane I4 yamaha's, this would give equal firing intervals and no primary force imbalance
4 throws, 6 or 8 webs, 3 or 5 main bearings

[nokivasara]

Isn't a V6 better for F1/racing than a V4 simply because of greater valve area?
More cylinders = more valve area

For bikes and road cars that's not as important but for racing I'd think that they need all the space they can get for valves.

[bdr529]

race Honda RC30s and RC45s used 360 deg (aka 0 deg) cranks and consistent uneven intervals 90 deg, 270 deg, 90 deg, 270 deg
(not the road bike V4 normal 180 deg, 90 deg, 180 deg, 270 deg that is the same as the Yamaha I4 crossplane gives)

It's the same 360 deg Crankshaft and Firing order #1 @ 90 deg.; #4 @ 270 deg.; #3 @ 90 deg.; #2 @ 270 deg
used on my VFR400R also known as Honda NC30

[J.A.W.]

Interestingly enough, although Honda & Ducati both run V4s in Moto GP, ( & have produced 'race replica' versions for road use)
they dont race them in WSBK, & the latest World Championship was won by Kawasaki ( I4),
- albeit with Aprilia winning the final races, somewhat ironically, since they are as of now, out - of WSBK factory racing!