Most efficient engine type?

aproctor

aproctor

aproctor

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When people talk about a cars power output they generally refer to its displacement which obviously has a direct effect on power.

I was wondering does the type of engine have any direct impact?

I know that balanced engines such as V6s and V12s are smoother than lets say a V10 but is a straight 6 any better than a flat or V config?

Seems a bit of an odd question but i have never seen it asked.

This is what i was trying to say.

Robbie G said:
This is how I read the op:

'What effect does engine configuration have on power output, all other things being equal?'.

For example, for two 3 litre six cylinder engines with the same number of valves, same cam profiles etc...does having for example a v6 config produce more power than having a l6 config.

The smoothness thing I read as an aside.
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I'm no expert but a V6 isn't naturally balanced, an inline 6 is though. Doesn't necessarily make it any smoother though tbh. There are a million and one factors which affect the power of an engine, number of cylinders is pretty far down the list.
 
Balance is pretty low on the scale of things to cause inefficiency in an engine

If you want efficiency you are chasing making the combustion process better as that is the most inefficient part of the engine
 
aproctor said:
Don't forget valve timing.

Seriously though, go and derail your own thread.
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I'm not derailing any thread, you asked about engine efficiency ...

And actually being able to accurately control the duration of valves being open would be a factor in making an engine efficient (and by efficient I assume we mean fuel/power/mpg)
 
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rypt said:
I'm not derailing any thread, you asked about engine efficiency ...

And actually being able to accurately control the duration of valves being open would be a factor in making an engine efficient (and by efficient I assume we mean fuel/power/mpg)
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Read the OP or FO. :)
 
aproctor said:
Read the OP or FO. :)
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I did, the title was "most efficient engine type" ... to which my reply was (to echo Clarkey) that the layout has far less of an impact than other things.

You may be talking about 1-2% power difference, when you can gain 5% fron good crank design, good oil pump design ... and far more if you find a way to control combustion better (or even use 'knock' to your advantage)
 
Well your opening post confused me totally. The title asks about efficiency, and then you go on to talk about engine balance as though it were somehow relevant?

Are you asking if engine cylinder configuration has an impact on efficiency? Or do you mean something else by engine "type"?
 
Atkinson for petrol is good. Will pull 210g/kWh BSFC as a objective measurement in the Prius 1.8 - the old 1.5 only peaked at 225g.

The question hasnt been asked before as the post is so ambiguous it prompts a range of interpretation.
 
6 cylinder engines have lots of interesting things making them different.

A 90 degree V6 like the Rover K V6 that can be built on the old Rover V8 production line needs a heavier 6 journal crankshaft. A 60 or 120 degree V6 (known as a natural V6) can use a lighter 3 journal crankshaft. An inline 6 needs a 6 journal crankshaft almost twice as long, so heavier than either V6. All 3 have the same length of camshaft in them (ish), the V6s having twice the number of pulleys and some more bearings. Generally the inline 6 is used for smoothness (not that a V6 is rough, inline 4s are much worse) and a V6 for packaging. When designing a new motor a V6 doesn't present enough more opportunity for power/efficiency over an I6 to be a deciding factor.

Flat 4s are interesting too, a "flat four" like in a beetle or a plane is smooth, but inefficient since it is constantly pumping air back and fourth in the crank-case in the direction of the crank. A "boxer" like Subaru's is much rougher and unsuitable for aircraft but more powerful, partly because the air is moved back and fourth between the pistons in the direction of the con rods. Like pushing 2 beanbags back and forward through a narrow door vs shaking 2 bean bags left and right either side of the door.
 
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ajstan said:
V6 smoother than V10? That a fact? I thought that in general, the more cylinders, the smoother the engine.
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V6 is one of the smoothest engine configs according to a well informed source. (one of senior sound proofing engineers at Jag/Land Rover.);)

Just wanted to know more about it, although my OP was gash.
 
no_1_dave said:
A V8 is smoother then a V6 because the V6 has an odd number of cylinders in each bank.
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I don't think so. I forget the physics now, but I once calculated that the one of they momentum contributors had a factor of 3 in it. The result of the maths, which again, I forget, was that engines with an even multiple of 3 cylinders were the most balanced. Beyond that, many other factors come into play.
 
This is how I read the op:

'What effect does engine configuration have on power output, all other things being equal?'.

For example, for two 3 litre six cylinder engines with the same number of valves, same cam profiles etc...does having for example a v6 config produce more power than having a l6 config.

The smoothness thing I read as an aside.
 
Robbie G said:
This is how I read the op:

'What effect does engine configuration have on power output, all other things being equal?'.

For example, for two 3 litre six cylinder engines with the same number of valves, same cam profiles etc...does having for example a v6 config produce more power than having a l6 config.

The smoothness thing I read as an aside.
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Pretty much spot on.

Sorry i could not articulate this in the OP. (Edited).
 
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