2L 4Cyl. vs. 2L 8Cyl What's more fuel efficient?

[UltArc]

Originally Posted by drmiller100

should have explained - heat is lost to surface area, power is made by PSI pushing on the piston times the length it effectively moves (stroke, sort of).

so, there is a square/cube thing going on - for a given CC, the fewer pistons you have, the less surface area you have for heat to be lost to.

air gets in and out of the combustion area through valves, which are effectively limited by the circumference of the valves, times the number of valves, with bonus for more lift and longer lift. too long of lift, and you lose economy.

I was going to chime in and say I'd like a boxer style 8 cylinder. I think it wold be pretty cool.

[Allch Chcar]

Originally Posted by serialk11r

Old Mechanic, how about flat-4 engines? I know Subaru doesn't use balance shafts, and the EJ25s are pretty rev friendly I believe (although that may be because they have a somewhat short stroke).

The thing about the EJ25 is that a stock crank will physically destroy itself past 8k RPM. I don't know if it's just the huge bores or the firing order. But it's for that reason I don't believe the flat four is any more smoother than a straight 4. The EJ25 is the one with the problem though since the JDM EJ20 will rev to 8k no problem.

As for big 4 bangers, one of the old Mercedes racing engines was huge compared to today's 4 bangers. 5.9L Mercedes 35hp

[Duffman]

Originally Posted by Allch Chcar

But it's for that reason I don't believe the flat four is any more smoother than a straight 4.

Flat 4 is naturally balanced (like an inline 6) whereas a inline 4 is not.

[tjts1]

A flat 2 is also just as balanced as a flat 4 or flat 6. Any combination of multiple of 2 cyls at a 180 degree Vee is inherently balanced.

[drmiller100]

Originally Posted by tjts1

A flat 2 is also just as balanced as a flat 4 or flat 6. Any combination of multiple of 2 cyls at a 180 degree Vee is inherently balanced.

that is why harley motors don't vibrate at all and can turn such high rpm's......

oh. wait......

(that was sarcasm folks - harley's vibrate like a housewife's spin cycle and have a VERY low upper RPM limit....)

[tjts1]

Originally Posted by drmiller100

that is why harley motors don't vibrate at all and can turn such high rpm's......

oh. wait......

(that was sarcasm folks - harley's vibrate like a housewife's spin cycle and have a VERY low upper RPM limit....)

I think you're having trouble figuring out the difference between a 45 degree Harley Davidson engine and a smooth 180 degree flat twin such as BMW. Let me help you with that.

Harley


BMW boxes 2 cyl

[some_other_dave]

Originally Posted by UltArc

I was going to chime in and say I'd like a boxer style 8 cylinder. I think it wold be pretty cool.

How about a 1.5 liter one?

Porsche 804 - Wikipedia, the free encyclopedia

It was also made in two-liter and 2.2 liter forms.

-soD

[UFO]

I've been on both cycles. I love the BMW, smoothest twin on the planet. I hate the Harley, roughest twin on the planet. I'd rather ride a single cylinder. The person who thought a V twin with odd firing to share the crank throw is certainly roasting down somewhere in the planet's core.

[tortoise]

So, the ultimate in ICE fuel efficiency would be a single. You could start with an end combustion chamber off the head from a Chevy 5.3 liter LS truck engine, a stroke of about 4.5 inches would give you 50 cubic inches, about right to power a light car. You'd probably want counterrotating balance shafts.

[pete c]

Originally Posted by tjts1

I think you're having trouble figuring out the difference between a 45 degree Harley Davidson engine and a smooth 180 degree flat twin such as BMW. Let me help you with that.

Harley


BMW boxes 2 cyl

yup, the harley sound is the result of perhaps the worst possible 2 cylinder layout in existence. the bmw boxer is perfectly balanced, but, sounds crappy to my ear. there is another layout, the 90 degree V twin used by various sport bike makers such as ducati. IMO, this layout, in addition to being balanced is my favorite engine soundtrack, followed closely by a 90 degree v-8 and the inline 6 which probably is the perfect engine layout, if there is such a thing.