H-6 versus V-6
 

I have always wanted to know what makes an H-6 engine better than a V-6. I know that our engines are horizontally opposed but what makes that better? Does it make any more power? I know Subaru and Porsche both make horizontally opposed engines but when somoene asks me what kind of engine i have and i say H-6 their always like what are you talking about. I was just wondering what the major differences were and which was better (of course whatever an svx has is better) .:D

Smoother running due to the horizontal design.

I believe that the biggest positive aspect of the flat engine is the low center of gravity. The motors can sit lower in the chassis. Other than that, I don't think flat motors make more power or do anything else that much better. If they did, everyone would use them!

One design doesn't make more power than the other, but they both have inherent pluses and minuses...

H-6 engines are flatter and can fit in 'vertically challenged' engine bays. Due to their zero interference, if belts break, no internal damage is done to the moving parts.

V-6 engines are taller but take up less lateral room.

Both engine designs can utilize variable valve timing, and both have been developed to outputs exceeding 100bhp per L.

...just my $0.02 ;)

-Chike

Not all flat motors are non-interference....

Small airplane and helicopter manufacturers have been using flat engines for decades. With airplanes I think its helps to keep the nose lower for better visibility. From what I understand a flat engine has less vibration, since the opposing cylinders tend to cancel each other out. This eliminates the need for "balance shafts" and what not.

Horizontal engines also need less oil pressure to operate, since oil never has to flow uphill.




Dave

True! Subaru doesn't make any non-interference engines anymore:(



None that I know of anyway.




Dave

I thought the EJ20t in the wrx was non interfering.

If I remember correctly, an H-6 is the most 'perfectly' balanced engine.

Works for me.

-Mark

Nope. From the 2.0 Turbo Service Manual:

"Disengagement of more than three timing belt teeth may result in interference between the valve and piston"



Dave

I think the EJ25 is interference too. I'd be willing to bet the EZ30 is. it's tough to make a CR close to 11:1 and still have it non-interference.

can't horizontally-opposed engines function upside-down? isn't this one of the draws for aeronautical (wrong word?) uses?

I also heard that the boxer engines are subject to piston slap

V-6 & V-8 engines can also have piston slap as well. It's a common problem in SVT Lightnings which have the 5.4L Triton V-8...

-Chike

The H-6 engine has lower main bearing loads because the power stroke is counter acted partially by an over lapping power stroke on the other side. This helps keeps the crank in the middle of the bearings.

The V-6 just tries to drive the crank out thru the oil pan.

Sort of. Aviation engines designed for inverted flight have special oil and fuel systems that other airplanes do not have. But the overall horizontal design does do very well with inversion.



Dave