chilled

What are the pros and cons of an i6 engine versus V6 configuration?

I asked this question in another thread but didn't get an answer.

BMW for 6 cylinder engines tend to use an I6 configuration. Most current manufacturers use either V6, flat 6 or boxer 6 (there is a subtle distinction I believe between flat/boxer).

From first principles, an I6 would have few cam shafts, and a greater outer surface area for disipating heat compared to V6 (or at least low angle V6's). But a V6 would generally be more compact?

C7BLE

is the boxer engine not horizontally opposed?

Horza

Yep.

So is a flat six.

I believe that makes them the same

ge2

I thought they were the same too

Have flat plane cranks got anything to do with it?

I'm not sure about all the pros and cons of the the different configs but I can say the engine layout in my Legacy makes it feel like there's something much smaller under the bonnet when you're throwing it about.

Horza

I suppose it's mainly down to the manufacturer.

Flat engines and V engines are more complex(expensive) to build as a straight engine block is machined from one billet.

Flat engines(and to an extent, V engines) take up a lot more room across the engine bay but crucially, can be mounted significantly lower in the chassis, improving dymanics and lowering the centre of gravity.

Horses for courses I suppose, every design has good and bad points. You just design around the compromises.

Though it's interesting that BMW can use a combination of engines in the same range. Now that's good engineering

Ultra_Nexus

I6 engines are incredibly balanced - more than V6/F6.

Have a look at crankshafts from V/F6 engines compared to I6 engines.

Also, you have 4 cams instead of 2, complex manifolds, and duplicates of many items.

Logitudinally, V/F engines will allow better F/R weight distribution which can be critical for some cars.

Dembo

I thought a flat 6 was a normal inline 6 on its side: i.e. all the pistons the same way and one set of valves at one end, whereas a boxer is effectively a 180 degree V6, so two sets of valve gear.

But I'm quite possibly wrong.

I miss having a V6. Bloody cheapo 4-cyl crap.

fluffyninja

Flat six is longer and can have issues with tortional vibration (typically above straight 8)
V/flat configurations are shorter (overlap of cylinders) but you double number of cylinder heads(most expensive bit of engine) and double the valve train (more drag on the engine)

Survey S2000

I weatched a programme once about the V6 engine. Was a long time ago but if i recall initially all 6cylinder engines were straight 6's. The V6 arrangement was later created to over come under bonnet space issues.
This meant that a V6 could be used were only a traditional 4 would fit. All be it at the cost of complexity and more expesive part costs

JamieS2K

I know sod all about engines but I do know that my flat 6 has no cambelt, in fact no rear engine Porsche has a cambelt. So there is a saving