Why aren't there more V-configuration 4-cylinder engines? There's plenty of in-line 4's, and even a few flat-4's. Why not V-arranged lumps?

 

my guess would be that it is out of primary and secondary balance.

 

If memory serves me correct there used to be a V4 in a mk2 cortina

 

There are alot of V4 bikes. the Yamaha Vmax 1200, Honda VFR...

 

The old ford Zephers were V4 and we used to have some V4 supercharge amoured landrovers in the army

 

Cost too much to build, when balanced against offering no real benefit. Most mass produced models have 4-cyl engines, therefore why build an engine which has two heads, 4 camshafts etc etc when an inline is cheaper and does the job.

 

tell that to subaru they have 2 heads 4 camshafts etc etc

 

...possibly the same reason some firms choose V6s over lin-line 6s? I'm not necessarily thinking of economy. Why would 'sporting' 4-cyl engines be more likely to be in-line (or flat) than V-config?

 

As said, balance, cost, packaging (not good for front wheel drive) transverse layout.

Saab used to have a V4 as (i think) Lancia did as well - although the Lancia was a narrow angle V4 like the VW engines.

As for 6 cylinder engines, either configuration has its benefits.

Straight six has perfect balance, but a long crank leading to distortion problems, and a long block leading to packaging problems. V6 has balance problems, but is obviously much shorter so better packaged.

D

 

Yes we could tell that to Subaru, as there engines are more expensive to build and service, but their configuration was chosen for engineering reasons also, so the additional cost in this case can be ignored. And thats the reason why Subaru engines are the exception to the norm.

But the vast majority of cars on our roads have tranversely mounted 4-cyl engines with front wheel drive, and in that case the economic arguement does come into play. The additional costs multipied by the numbers of cars produced, just do not add up.

For motorcycles its a different matter, the numbers of engines being built is a fraction of the total for cars, plus with a bike you need to consider the packaging of the engine in the frame, sometimes a V4 is better, so you can ignore the additional costs.

As for inline 6 and V6 engines, then the type of engine chosen is more critical. An inline 6 does have primary balance and in theory is preferable, which is the argument BMW use for sticking with it.

But 6-cyl in a line means you are going to have a long engine to try and squeeze under the bonnet, and it can cause packaging problems (particularly for front wheel drive tranverse applications), so many makers use a V6 to make it easier to fit. Mercedes remember use to have an inline 6 petrol engine, but moved to V6 for packaging, which was a minor **** up for the C-class and ML-class, when they realised they couldn't then put their inline-6 320 CDI engine in either of them, as its too long to fit under the bonnet.

 

Could always throw in the VW VR6 engines. A V6 formation in line!!!! (15degree angle ). Then there's their VR5 engine. Ignore the last cylinder and you've got a V4

 

I'm going to show up my lack of mechanical knowledge here, but can someone explain the 'balance' argument against the V4s?

 

Lancia pioneered narrow angle V engines. They used narrow angle V engines in the 1920's and 1930's, but the most recent was the Fulvia. Single crankshaft, single block, single head, but block not perpendicular to the head.

 

If it hasn't been mentioned already, the subaru flat4 was designed (or a happy coincidence) to have a very low centre of gravity thus helping the handling of the car !

 

Yes....but's it's waaayy out infront of the front axle which doesn't do the weight distribution and turn-in any favours

 

If I can remeber correctly, v4's are one of the worst possible engine designs, for both unbalanced forces and moments arent they?

Seem to recollect a lot of v4 engines need balance shafts to try and resolve these problems.

 

Trying to remember my advanced dynamics notes from the past...

Theres two main issues in engine design with regard to balance, imbalance of forces and imbalance of moments (overturning effects or twisting effects) - classic example being the way a powerfull v8 engine will rock the car when revved due to a secondary harmonic imbalance of moments.

An engine at its simplest is a rotating shaft propelled by a series of impulse forces.

It's from these forces that an engine can be inbalance or out of balance depending on how the force is applided on the crankshaft in relation to the configuration of the engine.

The fact the force is applided at a distance away from the shaft centre (the conrods and shape of crank) gives rise to the in or out of balance moments.

Both the forces and moments can be worked out mathematically depending on the crankshaft length, the angle of the pistons in relation to the crankshaft, the firing order and the length of the pistions.

Unless you've studied mechanical engineering the maths is too complex to go through simply, it gave me a headache anyways!

Any engine will have a natural frequency, which can be worked out.

When an engine is severly out of balance it will vibrate at its worst when the natural frequency is reached- this is known a primary inbalance. At this point the crank bearings, the crankshaft and the pistons are at their most stressed, as the engine literaly tries to rip itself apart.

If it has a secondary imbalance the vibration occurs at twice the natural frequency, the same with third (3 times natural frequency) and so on..

Engine designers deliberately do their best to design out the severity of the vibration through counter balance measures - crankshaft shape, heavy flywheels, counterweights on the crankshaft pulley etc. Raising the natural frequency of the system beyond the working rpm range of the engine is also a common tactic.

This is probably why v4 engines were more common in the past- lower rpms?

In the worst cases such as V4 engines balance shafts are used.

As has already been stated, from a dynamics viewpoint straight six engines are the best (hence bmw's infatuation with them).

 

My mate (mettalurgist) did actually tell me exactly why V4's are prone to this and v6's and v8's less so.

I switched off halfway through, woke up at the end hearing him say "that's why you don't have V4 engines"...aha! I took him to garage where just so happened to be parked was a Honda VF700. Started it ran it, revs to 11K an d is quite smooth, and both of us could be damned if we see where the balance shafts were on the engine - if they are any, unless it has very clever counterbalancing on the crank.

But then, Honda have a knack for these things (as well as woefully complex gear driven OHC's ). As did Yamaha (V-Max).

 

Balance shafts are common on v4 bike engines.

V4's are not too bad as bike engines, as they have shorter conrods than car engines if I remember rightly? (so they can use higher revs, gives more power but lower torque) so the effect of the outbalance isnt as severe as it's magnified less.

 

The thing is though, I've checked the workshops manuals on a VFR engine, and although there is a countershaft it's in the transmission and is independant of the crankshaft (i.e not directly driven). The only other place on the engine I could fathom that a counter balance could be is on the camshaft idler gear set.

I'll have to take it apart to rebuild it and find out