Thursday 8th February 2007

Subaru unveils new boxer diesel

Turbo-diesel flat-four claimed as world-first

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Subaru's turbo-diesel boxer

Subaru said it's about to unveil what it called the world’s first horizontally-opposed turbo-diesel engine.

The company will be debuting the engine at the 77th Geneva International Motor Show next month, along with an entire, all-wheel-drive drivetrain.

Subaru said it "believes passionately" in its boxer engines which are more compact than in-line units and provide a much lower centre-of-gravity. This reduces body roll for safer cornering and also enhances handling precision.

Due for its first vehicle application early next year, Subaru claimed its boxer turbo diesel to be a highly rigid unit with low levels of noise and vibration, eliminating the need for a balancer shaft. Other benefits include compactness and strong pulling power at low engine speeds with high-rev throttle-response.

[FestivAli]

High rev throttle response? Wouldn't people like to see that in a diesel. If Subaru can make an oil-burner that'll run past 6000rpm and feel sporty, I believe they could be onto a good thing.

[Mr Whippy]

High rev throttle response, well my diesel has good throttle response at high revs. Whoopie dooo.

The noise will be interesting though

Dave

[Truckosaurus]

An interesting project. Anyone know if it still is an alloy block?

An Impreza diesel that still had 200bhp and averaged 40mpg would be a winner imho.

[freddytin]

Mr Whippy said:

High rev throttle response, well my diesel has good throttle response at high revs. Whoopie dooo.

The noise will be interesting though

Dave

If it sounds half as good as the supercharged diesel opposed Rootes TS3 engines we are in for a treat.

[NDT]

very interesting to see this.
classically it has been difficult to get a flat four diesel to be as short as the gasoline flat four while still having sensible big-end and main bearing areas.

[collateral]

At last!

I've always wondered why Subaru didn't make a diesel as they have such a history with turbos...this is definitely one to watch

[vpinto]

From what I've read, you'll never see a diesel going past much of the 4.000RPM

5k tops.

That's because of the fuel characteristics, namely the speed the front of the flame achieves.

I believe what they are trying to say is that the engine should have good throttle responses in high revs (for a diesel) which will still be around the same high revs of any other diesel engine.

For me the most interesting thing is that a boxer engine is in equilibrium by nature. Vibrations are the worst nightmare of a diesel engine (inline or V or W or whatever).
Having a diesel engine without this vibrations would be fabulous.

Regards,
Vítor

[annodomini2]

vpinto said:

From what I've read, you'll never see a diesel going past much of the 4.000RPM

5k tops.

That's because of the fuel characteristics, namely the speed the front of the flame achieves.

I believe what they are trying to say is that the engine should have good throttle responses in high revs (for a diesel) which will still be around the same high revs of any other diesel engine.

For me the most interesting thing is that a boxer engine is in equilibrium by nature. Vibrations are the worst nightmare of a diesel engine (inline or V or W or whatever).
Having a diesel engine without this vibrations would be fabulous.

Regards,
Vítor

True, its quite possible with a modern diesel and Common rail to achieve 7000rpm, however the engine doesn't produce much torque above 5k and becomes pointless trying to use it above this speed.

[La Bollocks]

Fuel economy versus performance will be interesting for a diesel boxer.

[mafioso]

Bit random, but while we're talking about engines, is the Subaru Boxer engine any similar to the Porsche Boxer engine!? Or is it just a coincidence that they have the same name??

[dsf3g]

mafioso said:

Bit random, but while we're talking about engines, is the Subaru Boxer engine any similar to the Porsche Boxer engine!? Or is it just a coincidence that they have the same name??

The term "boxer" describes the engine's design. A boxer engine is like a "V" shaped engine (with two banks of pistons in a "V" shape) except that instead of being "V" shaped with a 45 degree angle, the two banks of pistons lie flat at a 180 degree angle and move in opposite directions outward and to the sides. Also since the acceleration of one bank of pistons is counteracting the other bank on a common plane, boxer engines tend to run more smoothly than "V" style engines.

[Mr Whippy]

vpinto said:

For me the most interesting thing is that a boxer engine is in equilibrium by nature. Vibrations are the worst nightmare of a diesel engine (inline or V or W or whatever).
Having a diesel engine without this vibrations would be fabulous.

Aren't all the BMW sixes just as good, if not a bit better?

Ok they are longer, but for a proper front engine rwd setup that works fine anyway...

Dave

[havoc]

dsf3g said:

mafioso said:

Bit random, but while we're talking about engines, is the Subaru Boxer engine any similar to the Porsche Boxer engine!? Or is it just a coincidence that they have the same name??

The term "boxer" describes the engine's design. A boxer engine is like a "V" shaped engine (with two banks of pistons in a "V" shape) except that instead of being "V" shaped with a 45 degree angle, the two banks of pistons lie flat at a 180 degree angle and move in opposite directions outward and to the sides. Also since the acceleration of one bank of pistons is counteracting the other bank on a common plane, boxer engines tend to run more smoothly than "V" style engines.

However, just to throw a spanner in the works, there are also 'horizontally opposed' engines, which IIRC are different to boxer engines, although not sure how...possibly in the way the crank works.

[pesmo]

Opposed have twin cranks. They can be made quite compact despite this. Terminology does tend to get muddled though with these designs

wiki

http://en.wikipedia.org/wiki/Opposed_

Edited by pesmo on Thursday 8th February 14:45

[havoc]

pesmo said:

Opposed have twin cranks. They can be made quite compact despite this. Terminology does tend to get muddled though with these designs

wiki

http://en.wikipedia.org/wiki/Opposed_

Edited by pesmo on Thursday 8th February 14:45

Thanks pesmo - I was thinking of the flat-V then! (Not the 'opposed engine')

[choufangpi]

A "boxer" engine IS a horizontally opposed engine. Boxer is just the commonly used term, like when people say "Hoover" when they mean vacuum cleaner.
A BMW straight 6 probably is as well, or better, balanced but for different reasons. With the horizontally opposed engine you lose the weight and added complexity of the balancer shaft.

[Mr Whippy]

The Deltic railway locomotive's triangular opposed engine is pretty mid-boggling!

Bloody huge too when your stood next to one

Dave

[Tris.E]

Turbo-diesel flat-four claimed as world-first dont think so vw had them in the first td transporters they were like beetle engine with added water jackets and a turbo.
I know this because i had to fit new heads to one years ago.

[bothari]

vpinto said:

From what I've read, you'll never see a diesel going past much of the 4.000RPM

5k tops.

That's because of the fuel characteristics, namely the speed the front of the flame achieves.

I might be wrong, but I'm under the impression that this is caused mostly by the difficulty in injecting fuel fast enough into each cylinder during the burn cicle.
The great thing about common-rail diesels is precisely this: since you have a large metal tube with injectors bolted on to it instead of a large number of little pipes going to each cylinder, it's easier to crank up the pressure, allowing more fuel into the cylinder each time.

This allows a higher rev-ceiling.

[shoestring7]

choufangpi said:

A "boxer" engine IS a horizontally opposed engine. Boxer is just the commonly used term, like when people say "Hoover" when they mean vacuum cleaner.
A BMW straight 6 probably is as well, or better, balanced but for different reasons. With the horizontally opposed engine you lose the weight and added complexity of the balancer shaft.

Its not quite as simple as this: http://en.wikipedia.org/wiki/Boxer_en

A true boxer engine is different to a 180 degree V engine.

SS7