Boxer engines and oil burning

[BMWTurboDzl]

Does the design of the boxer lend itself to becoming an oil burner vs "I" or "V" layouts?

I can't help but think that because of gravity the bottom of the cylinder bore wears faster than the top and consequently its the top where a gap appears.

 

[SubieRubyRoo]

Do you think that gravity only works at 90* angles or something? I don't think boxers "inherently" burn more oil than other designs; if so would Porsche still keep a massive R&D budget and continuing development? Boxers are inherently balanced, but it is likely harder to get oil off the lower part of the cylinder. I think this is probably what you were thinking.

 

[BMWTurboDzl]

Originally Posted by SubieRubyRoo
Do you think that gravity only works at 90* angles or something? I don't think boxers "inherently" burn more oil than other designs; if so would Porsche still keep a massive R&D budget and continuing development? Boxers are inherently balanced, but it is likely harder to get oil off the lower part of the cylinder. I think this is probably what you were thinking.


Well I would think that an "I" configuration would be less likely to burn because gravity isn't pulling the piston against one wall more than the other. "V" configurations are such were gravity is pulling against the outer piston and the flat layout there's a lot more pull as I opined on my post.

 

[SubieRubyRoo]

Cylinder wall loading due to rod angle will exert FAR more pressure on the cylinder than the weight of a 12 ounce piston will.

Now, if you are thinking about the pistons, and specifically the generally short compression height of boxer pistons and very short skirts, this may have merit. An "I" engine will generally have a much taller deck height, allowing a taller compression height and therefore longer piston skirt for a given crank stroke and rod length. THIS will greatly increase the piston's stability in the bore, which will both increase ring sealing and reduce "cocking" of the piston in the bore, which will help reduce both ring wear and piston/bore wear. Both of those should help "slow" the relative rate in oil consumption, but it's still a "relative" term.

 

[Job]

The big Hall Scott engine used on buses and such was laying flat on it's side. I think it was a famed engine in the day. There are probably some increased wear issues with heavy pistons laying sideways, but probably not on a light weight passenger car engine with light weight Al pistons.
There are also aircraft engines with boxer style and of course VW Porsche. I don't think it is an issue.

 

[BMWTurboDzl]

Originally Posted by SubieRubyRoo
Cylinder wall loading due to rod angle will exert FAR more pressure on the cylinder than the weight of a 12 ounce piston will.

Now, if you are thinking about the pistons, and specifically the generally short compression height of boxer pistons and very short skirts, this may have merit. An "I" engine will generally have a much taller deck height, allowing a taller compression height and therefore longer piston skirt for a given crank stroke and rod length. THIS will greatly increase the piston's stability in the bore, which will both increase ring sealing and reduce "cocking" of the piston in the bore, which will help reduce both ring wear and piston/bore wear. Both of those should help "slow" the relative rate in oil consumption, but it's still a "relative" term.



Thanks !

So are boxers typically over-square?

 

[benjy]

as manufacturers experiment trying for more mpg's oil burners arrive regardless of engine design. from reading the subies oil burners where using low tension rings "trying" for better mpg's as they are not known for better mpg's. now they use an anemic DI 2.0 engine with a questionable CVT. looking on a subie forum one owner had 3 thats THREE cvts replaced under warranty in his WRX at low miles + that indicates a GOOD possibility of failures at higher mileage even with the anemic 2.0. manufacturers use buyers as beta testers as witness by DI issues

 

[JLTD]

How about gravity doesn't return oil to the sump from cylinders (as much) in a boxer....

 

[FA_WRX]

My WRX has 76K currently on it and depending on oil brand burns no more that 1/2 QT over 6K OCI. This is not enough to cause me concern. When I read on blogs about blown transmissions, clutch issues, or excessive oil burning. I wonder how much is driver abuse.

 

[TTK]

Originally Posted by FA_WRX
My WRX has 76K currently on it and depending on oil brand burns no more that 1/2 QT over 6K OCI. This is not enough to cause me concern. When I read on blogs about blown transmissions, clutch issues, or excessive oil burning. I wonder how much is driver abuse.

Yes, and there is probably someone somewhere that has had 3 standard automatic transmissions replaced under warranty. And people who post claims on forums are just claims. We should not take those claims as proof of anything.

 

[emg]

Originally Posted by benjy
ooking on a subie forum one owner had 3 thats THREE cvts replaced under warranty in his WRX at low miles + that indicates a GOOD possibility of failures at higher mileage even with the anemic 2.0.


The WRX CVT is a different transmission to the 2.0 CVT, and is worked much harder by most owners. And there seem to be plenty of high-mileage Subaru CVTs out there that haven't broken yet.

 

[DGXR]

With forced oiling systems and modern materials and technology, the boxer engine design can be just as reliable as any other, it depends on the manufacturer's R&D and commitment to quality. Gravity is negligible for cylinder wear, even considering oil pooling/draining (vertical cylinders have more oil drainout than horizontal or v-angled cylinders). Compression forces and connecting rod side forces are much more factor in piston, ring and cylinder wear.

If oiling systems still depended on splashing, yes the boxer design would be more vulnerable.

 

[RooflessVW]

Boxer engines can burn more oil.

Oil more easily pools in the cylinder heads and can leak into the cylinder. Likewise, oil finds its way to the bottom of the cylinder and stays there longer vs gravity taking it down past the rings.

When mine sits for a few days with Pennzoil Platinum I get a nice puff on cold start.

 

[BikeWhisperer]

I owned a 1994 Subaru with a the 2.2 Boxer engine for 14 years and 160k miles, never burned a drop even when I switched it from conventional to synthetic and went to 6k OCI's at 108k miles.

 

[y_p_w]

I remember bringing my car in to a mechanic (used to work at a Subaru dealer) and he looked at the dipstick on my 2004 WRX. Was telling me that in his experience the boxers sometimes consumed oil from hard cornering. Wasn't sure what to make of it, but he was telling me to keep an eye on the oil level and top off.

 

[barryh]

I've got 12 years of experience running a boxer motorcycle engine and while pooling is sometimes noticeable to an extent that might cause alarm, it doesn't seem to translate into measurable oil consumption. I think what oil does get into the combustion chamber gets there via the engine breather.

The inherent balance of a boxer engine far outweighs any minor foibles.

 

[ARCOgraphite]

Originally Posted by BMWTurboDzl
Originally Posted by SubieRubyRoo
Cylinder wall loading due to rod angle will exert FAR more pressure on the cylinder than the weight of a 12 ounce piston will.

Now, if you are thinking about the pistons, and specifically the generally short compression height of boxer pistons and very short skirts, this may have merit. An "I" engine will generally have a much taller deck height, allowing a taller compression height and therefore longer piston skirt for a given crank stroke and rod length. THIS will greatly increase the piston's stability in the bore, which will both increase ring sealing and reduce "cocking" of the piston in the bore, which will help reduce both ring wear and piston/bore wear. Both of those should help "slow" the relative rate in oil consumption, but it's still a "relative" term.



Thanks !

So are boxers typically over-square?


The Famed EJ253 had a 1.5" crank throw** and small block V8 302 Ford (or Chevy) sized bore of ~ 4" making that engine real revver when you got over 4500 rpm. with the 5m trans.

So yes it was way oversquare. That's the way to make high rpm torque and thus power. Funny its in a Forester !

Ask LoneRanger he must still have his beloved EJ253 powered Forester. It think its a 2009 IIRC.

** 1.5" x 2 = 3.0 in. stroke

 

[SubieRubyRoo]

Originally Posted by BMWTurboDzl
So are boxers typically over-square?


Over-square refers to bore being larger than the length of the stroke, i.e., a 4" bore and a 3" stroke (like Ford 302) is over-square. As a general rule, gas engines will either be square (bore & stroke are equal) or oversquare. Low-speed engines designed for torque are generally under-square because torque is a vector, and mostly driven by the length of the crank stroke. Cylinders can be smaller diameter for a given displacement, because slower engine speeds and long strokes provide a "long" time for cylinder filling, especially as most torque-biased engines are forced induction, which helps cylinder filling as well.

So yes, most boxers are over-square, but this is not significantly different than other gasoline engines in the same displacement class.

 

[Silk]

BMW flat twins will sometimes give a puff of smoke if parkked on the sidestand. A bit random, in 10 years mine has done it maybe half a dozen times. Park your boxer car on the side of a hill and it might do it too.

 

[hpb]

Originally Posted by Silk
BMW flat twins will sometimes give a puff of smoke if parkked on the sidestand. A bit random, in 10 years mine has done it maybe half a dozen times. Park your boxer car on the side of a hill and it might do it too.


I used to ride a BMW K series, that thing smoked hilariously almost without fail if left on the sidestand. It was pretty embarrassing, as the bike was only a couple of years old at the time!