91z4me

Has anyone made a flat 4 before?

35 posts in this topic

I have never owned or ridden in a flat engined vehicle but have found myself very intrigued recently by them, both the Porche flat 6s, Corvair flat 6's, and also the Subaru 3.0 and 3.3 flat 6's.

Has anyone ever made a flat 4, a flat 6 with 2 cylinders chopped off? Would this design not be as or more stable than an I4 or a boxer 4 (like the Subaru 4's)?

What about flat 8s, they sound like they would be very well balanced and be as low as flat 6's and they would have more area of combustion?

Would not a flat 4/6/8 engine architecture be the most cost/engineering effective series of engines to build and package? Why aren't/haven't there been more out of the V (play on out of the box, I know it is not funny my bad) engine designs and if so what were they? I know of the Wankel rotor and the Miller cycle derivitives of Otto cycle engines.

Just looking to expand my knowledge of cars a little bit.

If it amuses you to answer or discuss feel free if not then let it slide. Thanks for listening to my rambles. :)

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I have never owned or ridden in a flat engined vehicle but have found myself very intrigued recently by them, both the Porche flat 6s, Corvair flat 6's, and also the Subaru 3.0 and 3.3 flat 6's.

Has anyone ever made a flat 4, a flat 6 with 2 cylinders chopped off?  Would this design not be as or more stable than an I4 or a boxer 4 (like the Subaru 4's)?

What about flat 8s, they sound like they would be very well balanced and be as low as flat 6's and they would have more area of combustion?

Would not a flat 4/6/8 engine architecture be the most cost/engineering effective series of engines to build and package?  Why aren't/haven't there been more out of the V (play on out of the box, I know it is not funny my bad) engine designs and if so what were they?  I know of the Wankel rotor and the Miller cycle derivitives of Otto cycle engines.

Just looking to expand my knowledge of cars a little bit.

If it amuses you to answer or discuss feel free if not then let it slide.  Thanks for listening to my rambles. :)

uhm.... Subaru's boxer 4 is a flat 4. It's just a different way of saying the same thing.

It's the same distinction as a Wankel engine compaired to a Rotary engine.

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uhm.... Subaru's boxer 4 is a flat 4.  It's just a different way of saying the same thing.

It's the same distinction as a Wankel engine compaired to a Rotary engine.

I thought subbies was vertical pistons that were split making it a || || || || design and that the crank case was all weird about it. Am I wrong?

Edit: Just looked it up and I'll be damned it is a true flat 4. Kinda cool is that the only one of its kind out there?

Edited by 91z4me

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I thought subbies was vertical pistons that were split making it a || || || || design and that the crank case was all weird about it.  Am I wrong?

Edit:  Just looked it up and I'll be damned it is a true flat 4.  Kinda cool is that the only one of its kind out there?

Hardly

edit: ugh.... while the flat-4 page I directed you to looks fairly acurate.... I clicked on the Wikipedia entry for the V16... and they call the V16 in the Cadillac Sixteen a Northstar V16.... which it isn't.

Edited by Oldsmoboi

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Hardly

edit: ugh.... while the flat-4 page I directed you to looks fairly acurate.... I clicked on the Wikipedia entry for the V16... and they call the V16 in the Cadillac Sixteen a Northstar V16.... which it isn't.

Hmm...So lots in the past but very few now.

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Subaru used to advertise that their boxer engines had a lower center of gravity than an I4, which makes sense. The downside, I assume, would be that a boxer engine would be comparatively wider. There also may be some NVH differences, but I haven't ridden in a Subaru that was in good shape, so I cannot really say that they're smoother or rougher than a comparable I4. Boxers (at least Subarus) also have rather strange sounding exhausts.

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Kinda cool is that the only one of its kind out there?

Volkswagen has offered them for....um...nearly 70 years. Italians made them as well.

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Volkswagen has offered them for....um...nearly 70 years. Italians made them as well.

I knew you would come into this thread you seem to like 'different' cars and technologies. :P

Are there any modern flat engines besides Porches and Subbies?

As far as length of an I4 vs a boxer I would imagine the boxer is shorter because the cylinders can overlap a little because they are on opposite sides of the crankshaft.

The engine would be wider but not wider than a transversly mounted engine.

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I knew you would come into this thread you seem to like 'different' cars and technologies. :P

Are there any modern flat engines besides Porches and Subbies?

As far as length of an I4 vs a boxer I would imagine the boxer is shorter because the cylinders can overlap a little because they are on opposite sides of the crankshaft.

The engine would be wider but not wider than a transversly mounted engine.

a subi engine isn't mounted transversly.

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91z4me As far as length of an I4 vs a boxer I would imagine the boxer is shorter because the cylinders can overlap a little because they are on opposite sides of the crankshaft.

Cylinder bores do not and cannot overlap on the same side of the engine for obvious reasons. There would not be a bore spacing difference (and thusly an overall front-to-rear dimension difference) --all else being equal-- between a 'flat' design and a V design. Height & width would differ greatly, tho.

The engine would be wider but not wider than a transversly mounted engine.

90-degree IBC V-8s are nearly square F-t-R vs. width (slightly longer than wide). A Corvair flat 6 is definately wider than it is F-t-R- go to 4-cylinders and the difference grows.

Tucker proposed a mid-engine flat six driving each rear wheel off the ends of the crank with torque converters at each wheel. That powertrain program was supplimented by another more-conventional rear-engine flat 6- data is scarce on exactly how well the first worked but then again; development had hardly started.

In modern, smaller cars, flat 6s do not add to packaging efficiency, in general. The main 'advantage' is a greatly reduced height, but when is this a primary concern for packaging? 90-degree V-type offer the most compact dimensions for a given cylinder count & displacement range.

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91z4me As far as length of an I4 vs a boxer I would imagine the boxer is shorter because the cylinders can overlap a little because they are on opposite sides of the crankshaft.

Cylinder bores do not and cannot overlap on the same side of the engine for obvious reasons. There would not be a bore spacing difference (and thusly an overall front-to-rear dimension difference) --all else being equal-- between a 'flat' design and a V design. Height & width would differ greatly, tho. …

Depending on the angle of the V and the crank design a boxer engine can be shorter than a V-engine with the same number of cylinders. Not much shorter, not more than half a bore-spacing. Height, width, balance and commonality with another engine are the primary reasons for choosing a particular block angle, sometimes even for an I4. Hence the popularity of 90 degree V6s and V10s based on 90 degree V8s, instead of the more natural 60 and 72 degrees. Edited by thegriffon

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I clicked on the Wikipedia entry for the V16... and they call the V16 in the Cadillac Sixteen a Northstar V16.... which it isn't.

Fixed.

Also fixed: Cadillac V-16 entry.

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Depending on the angle of the V and the crank design a boxer engine can/ be shorter than a V-engine with the same number of cylinders. Not much shorter, not more than half a bore-spacing. Height, width, balance and commonality with another engine are the primary reasons for choosing a particular block angle, sometimes even for an I4. Hence the popularity of 90 degree V6s and V10s based on 90 degree V8s, instead of the more natural 60 and 72 degrees.

That angle of this possible V-type engine would have to be so narrow that the bottoms of the bores would interfere with bores on the other bank, requiring increased bore spacing and a longer crank. Sure, this is possible in theory, but even a 45-degree V-type doesn't encounter this problem. I am not aware of a V-type IC automotive engine with a degree of less than 45.

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To add to all of the info Balthazar mentioned there's one

more huge benefit for flat or "boxer" engines: lower

center of gravity. This is esp. beneficial to cars like the

Porsche 911 & WRX.

& BTW, as you've probably figured out, the VW/Porsche

flat four (pancake motor) is also a "boxer". It's just 6 of

one and half dozen of another. The legendary Porsche

917 had a flat (boxer) 12 cylinder motor, depending on

the tuning & boost from the turbos they made huge

horsepower... as much as 1100-1300.

There's been a few other exotic boxer engines. The 80s

Ferrari Testarossa was a great example of this.

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I clicked on the Wikipedia entry for the V16... and they call the V16 in the Cadillac Sixteen a Northstar V16.... which it isn't.

Fixed.

Also fixed: Cadillac V-16 entry.

yea i just checked as well... and if my memory serves me correctly it was 2 LS6's crammed together?

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Depending on the angle of the V and the crank design a boxer engine can be shorter than a V-engine with the same number of cylinders. Not much shorter, not more than half a bore-spacing.

A horizontally opposed engine is a vee engine...with a 180-degree bank angle. Except at particular angles (due to the width of the head) will a vee engine of less than 180-degrees be wider than a flat engine. The two designs should be the same length (assuming all internal dimensions are the same, there's no reason why bore spacing couldn't be the same), but a flat engine is just about as wide as you're going to get.

That angle of this possible V-type engine would have to be so narrow that the bottoms of the bores would interfere with bores on the other bank, requiring increased bore spacing and a longer crank. Sure, this is possible in theory, but even a 45-degree V-type doesn't encounter this problem. I am not aware of a V-type IC automotive engine with a degree of less than 45.

Volkswagen has a series of vee engines (V5 and V6) that are designed with 15-degree bank angles.

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A horizontally opposed engine is a vee engine...with a 180-degree bank angle. Except at particular angles (due to the width of the head) will a vee engine of less than 180-degrees be wider than a flat engine. The two designs should be the same length (assuming all internal dimensions are the same, there's no reason why bore spacing couldn't be the same), but a flat engine is just about as wide as you're going to get.

Volkswagen has a series of vee engines (V5 and V6) that are designed with 15-degree bank angles.

The new 3.6 L RV6 is supposed just over 10 degrees. From memory Rover was at one stage wrking on a narrow-angle V6, but the KV6 seems wider, if a little lop-sided or a V6. Edited by thegriffon

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A horizontally opposed engine is a vee engine...with a 180-degree bank angle.

Is an inline six also V-type with a zero degree bank angle? :P;)

Thos VW engines with 10 or 15-degree banks must have increased bore spacing to the point of almost making them comparable to an inline. What was the supposed advantage of building them so narrow??

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Thos VW engines with 10 or 15-degree banks must have increased bore spacing to the point of almost making them comparable to an inline. What was the supposed advantage of building them so narrow??

The "inline vee" six-cylinder Volkswagen engines are said to be about as long as a four-cylinder inline engine.

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Is an inline six also V-type with a zero degree bank angle?  :P;)

Thos VW engines with 10 or 15-degree banks must have increased bore spacing to the point of almost making them comparable to an inline. What was the supposed advantage of building them so narrow??

near the smoothness of an I6 in the space of an I4.

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We must not be talking 'apples-to-apples'. Something is radically different to allow such close spacing on such a narrow bank angle.

The only way I can see to make a 15-degree V-6 with the same size bores as a comparison inline 4 and have the block be shorter is to have long rods & very short strokes to avoid bore/piston interference. This runs counter to the target optimum bore/stroke ratio, tho with electronics I suppose a great deal is possible.

Again- VW isn't building smart-sized cars for these V-6s- what is the packaging problem these motors answer? Because if the overall dimensions aren't at least 20% smaller, the engineering dollar could've been spent much better, elsewhere.

Any links to a cut-away drawing?

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We must not be talking 'apples-to-apples'. Something is radically different to allow such close spacing on such a narrow bank angle.

The only way I can see to make a 15-degree V-6 with the same size bores as a comparison inline 4 and have the block be shorter is to have long rods & very short strokes to avoid bore/piston interference. This runs counter to the target optimum bore/stroke ratio, tho with electronics I suppose a great deal is possible.

Again- VW isn't building smart-sized cars for these V-6s- what is the packaging problem these motors answer? Because if the overall dimensions aren't at least 20% smaller, the engineering dollar could've been spent much better, elsewhere.

Any links to a cut-away drawing?

Have you ever changed the spark plugs on the "back" bank of a V6 on a transversely-mounted engine? It's not fun. The narrow bank angle allows for more space around the engine for crash protection, serviceability, and ease of assembly.

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