Ruf's 8-cylinder Porsche 911

[Stotty]

Heh, flat 6's don't sound good then?

996 Rally Car with FVD Exhaust

1971 991S, Walter Rorhl, The 'Ring in reverse

Re: the original post; 2 thoughts immediately spring to mind...

1) a V8 is likely to be longer than a flat 6 and therefore could move the weight balance of the car even further rearwards

2) a V8 will have more of its weight higher up, which isn't a good thing for handling

I'd be surprised if this is the direction Porsche go in the future. As has already been said, it's muhc more likely they'll go for smaller capacity turbocharged engines to meet ever stricter emissions and consumption targets.

 

[ExigeEvan]

Now everyone's saying this is the path for the future of 911s, yet, all the rage in the industry is about turbocharging smaller engines for fuel efficiency. Then again, many would believe the 911 has reached the absolute max potential for its current ethos, rear-engined RWD flat-6, so perhaps something else is needed for the sake of moving forwards.

I guess the problem with the 911 range is that it is very much built around the engine and drivetrain configuration.

For example to start introducing forced induction to the Carerra line up would lead to confusion with the Turbo. Or if they were to add hybrid electric motors to the front wheels it would distorte the line between the traditionally 2 wheel drive and 4 wheel drive cars.

So yes, changes will have to be made, but it'll mean a big shake-up for the line-up.

 

[Omnis]

Awful driver in that Rally 996.

 

[Stotty]

I didn't post it for his driving skills, I posted it for the noise.

If you want to see skills, watch the 2nd video.

 

[homeforsummer]

Too bad that being a flat-plane crank it will most likely sound crap like modern Ferarris, but I'd still like to see this thing in action.

Err... think this is a personal preference thing. And I don't think I'm the only one here who thinks a Ferrari flat-plane V8 sounds awesome...

EDIT: And, I can't really see Porsche going towards V8s with the 911. This is a RUF, remember. It's in no way whatsoever a representation of the direction Porsche are heading, no more than any other tuner decides where any factory car is headed.

 

[Jim Prower]

It won't sound bad, but keep in mind that I have trouble distinguishing a Ferrari Flat-plane engine from a tuned 20V 4A-GE...

 

[Neal]

It is pretty unlikely Porsche will start increasing engine size and cylinder count in the 911 with the current CO2 legislation. BMW will be fitting a twin turbo V8 in the next M5 and it is rumoured Ferrari will be fitting a turbo V8 in its F70 so that they will meet the required CO2 levels.

As has been said it is more likely that Porsche will turbo charge smaller capacity engines but this does confuse the range when if there are turbos that aren’t a Turbo!

The boxer layout Porsche use does have its advanatges so a V8 would have a negative effect on weight placement, does anyone know why a boxer 8 is more problematic than a boxer 6 or 4?

 

[TheCracker]

The boxer layout Porsche use does have its advanatges so a V8 would have a negative effect on weight placement, does anyone know why a boxer 8 is more problematic than a boxer 6 or 4?

I can only think that size and weight distribution would be the issue, especially in a rear-engined car.

The Porsche 908 sports prototype was a boxer 8.

 

[Venari]

Prepare for madness.

Too bad that being a flat-plane crank it will most likely sound crap like modern Ferarris, but I'd still like to see this thing in action.

Current Aston Martin V8 Vantage is a flat plane crank. I can make a 1969 Fiat 500 sound like a V16 with enough plumbing.

A Vee has shared crankpins - piston pairs reach TDC one half revolution apart. A flat has separate crankpins - piston pairs reach TDC whenever you want them too, but usually the same time.

Boring, but technically correct. 180-degree Vee != Flat

Cough. Actually, it does.

180-degree Vee = Flat​

... but also...

Boxer = Flat​

The equation you're looking for is:

180-degree Vee != Boxer​

I'm sure someone will knock up a Venn diagram, given time.

Moving on, this 8-pot clearly has two banks of cylinders at 90 degrees. Sadly, that's not relevant. If the crank has 4 crankpins, it's a Vee. If it has 8 crankpins, it's a flat. I don't care enough to find out, but other flat-plane crank 8 pots - Esprit V8, TVR AJP8, most V8 Ferraris since ever - are all vees.

*sucksteeth* Number of crankpins (and angle of vee) is completely irrelevant for V-motors. Most of them share crankpins per pair of cylinders, 'tis true, but a V8 could have eight crankpins if it really wanted. In fact, to get 120deg ignition intervals on a 90degree V6 engine, it would have 3 crank pins, but each has 30deg offsets machined into them so the conrods are not mounted on concentric surfaces! Arg!

Now a boxer-8 must have 8 throws... unless maybe it has 5, three of which were very long. I'm not sure of the balancing and bearing arrangement of such a wacky device, however!

does anyone know why a boxer 8 is more problematic than a boxer 6 or 4?

It's not, really. Boxers require more intricate crankshafts than V-motors (generally) and they require supporting inbetween, thus a Porsche boxer-6 is a 7 bearing engine. A Chevy V8 is a five bearing engine, just like many modern inline 4s. However, there are 3-bearing i4s, and I'm sure in the murky past, there were three bearing V8s too.

I can only think that size and weight distribution would be the issue, especially in a rear-engined car.

The Porsche 908 sports prototype was a boxer 8.

I'd agree with that. A flatplane 90deg V8 will* be a lighter and less complex engine than a boxer-8.

Right, everybody clear now?

* All other things being equal.

 

[Keef]

Now everyone's saying this is the path for the future of 911s, yet, all the rage in the industry is about turbocharging smaller engines for fuel efficiency. Then again, many would believe the 911 has reached the absolute max potential for its current ethos, rear-engined RWD flat-6, so perhaps something else is needed for the sake of moving forwards.

My opinion is that Porsche's next step should be lighter and smaller cars. Then they could go back to smaller engines and not max out what they've got now.

 

[homeforsummer]

My opinion is that Porsche's next step should be lighter and smaller cars. Then they could go back to smaller engines and not max out what they've got now.

Same. Wouldn't surprise me if the next Boxter was a flat-four.

 

[Neal]

Right, everybody clear now?

* All other things being equal.

Clear enough for me matey

 

[Radracing]

The boxer layout Porsche use does have its advanatges so a V8 would have a negative effect on weight placement, does anyone know why a boxer 8 is more problematic than a boxer 6 or 4?

I think it would be an advantage with regards to the Boxter or Cayman layout rather than the rear engine 911's weight placement. The problem would be how they could make it fit without cutting out the engine bay just to make it fit.

 

[Omnis]

It won't sound bad, but keep in mind that I have trouble distinguishing a Ferrari Flat-plane engine from a tuned 20V 4A-GE...

Well that's perfectly fine because I can.

 

[Paulie]

Current Aston Martin V8 Vantage is a flat plane crank. I can make a 1969 Fiat 500 sound like a V16 with enough plumbing.

Whaaaaaaaaa?!?!?! I didn't know that about the V8 Vantage, that car sounds awesome. So does an Alfa Romeo 8C, but I always thought that was a Ferrari V8 converted to a cross-plane crank and a little more displacement?
Either way, so perhaps cross-plane crank V8s can sound just peachy then, I'm more interested to see this RUF in action now.

Additionally, with equal length headers a 600+hp cross-plane crank pushrod 5.0L V8 can be made to sound very high pitched and monotonous similar to a Ferrari, much to my dis-taste.

 

[Keef]

Weird as hell. Sounds like a 4 cylinder. I think it's got more to do with fuel delivery and timing than the exhaust itself. NASCAR engines are carbed with equal length headers and still have a rumble grumble, except at 9k where they sound pretty ridiculous.

 

[Paulie]

Nope, it's entirely the exhaust, everything else is category controlled AFAIK. They used to sound like everyone else then switched to equal length headers and, ta-da, the note from the video above.

 

[analog]

A 180 degree V is not a boxer per se, Ferrari called it's 180 degree V12 used in both the BB and the Testarossa a boxer engine, although it is widely accepted this is not correct.
Why they chose to call it a boxer is probably to accentuate the fact they created a flat V12 as opposed to their regular V12's to avoid confusion.
They created a flat V engine to reduce the lenght of the total car by fitting the transmission underneath the engine, anyway i'm not very technical myself so here's Wiki explaining the difference between V and boxer somewhat;

"A flat engine is an internal combustion engine with multiple pistons that all move in the horizontal plane. The most popular and significant layout has cylinders arranged in two banks on either side of a single crankshaft, generally known as "boxers". There is a widely-used but technologically less significant form consisting of a straight engine with two, three, four or more cylinders canted 90 degrees into the horizontal plane.

The concept of the boxer was patented in 1896 by engineer Karl Benz, eight years after he started producing the world's first successful cars. Flat engines are commonly described as horizontally opposed engines but must not to be confused with opposed-piston engines, which are mechanically quite different."

Hope to clarify the argument somewhat, although there are probably more detailed descriptions of the difference between boxer and flat-V, but they are not the same essentially.

 

[Jim Prower]

To further clarify, An Opposed-piston engine is one of these..

Instead of one crank and two cylinders, there's two cranks and one cylinder.

 

[Paulie]

Forgive the off-topic-ness, but Ferrari's engine was a boxer.......

 

[Keef]

To further clarify, An Opposed-piston engine is one of these..

Instead of one crank and two cylinders, there's two cranks and one cylinder.

With two pistons. Crazy. They make their own combustion chamber. It would be easy enough to get the cranks timed, but imagine what would happen if you revved it a little too high!

 

[TheCracker]

Forgive the off-topic-ness, but Ferrari's engine was a boxer.......

They called it a boxer, but it wasn't one technically.

A Ferrari Berlinetta Boxer is one of a series of cars produced by Ferrari in Italy between 1973 and 1984. They used a mid-mounted flat-12 (180° V12, not actually with a Boxer crankshaft) engine, replacing the FR layout Daytona, and were succeeded in the Ferrari stable by the Testarossa.

Flat-12 engines are generally not true horizontally opposed engines (boxer), but rather 180° V-engines. A true boxer has one crank pin per piston, while in the 180° V-engine, two opposing pistons share the same crank pin.

 

[Neal]

The below article and diagram makes sense to me but I don’t understand how both pistons share the same crank pin, what am I missing?

Source - http://www.e31.net/engines_e.html

Boxer-Engines

In boxer engines the pistons are not aligned upright or in V-shape, but lie horizontally opposed. This type of engine not only achieves an extraordinary low centre of gravity but also runs perfectly smooth and free of vibrations - regardless of number of cylinders.
As you can see in the following picture, a pair of pistons are not only always in the same position but also move with the same speed - only into different directions so that all vibrations are cancelled.

A boxer-engine runs always smoothly.

 

[Famine]

The below article and diagram makes sense to me but I don’t understand how both pistons share the same crank pin, what am I missing?

That they don't - Boxer engines have one crankpin per piston. Boxer4 = 4 crankpins, just like a straight four but unlike a V4 (which has 2). Boxer6 = 6 crankpins, just like a straight six but unlike a V6 (which has 3).

 

[Neal]

That they don't - Boxer engines have one crankpin per piston. Boxer4 = 4 crankpins, just like a straight four but unlike a V4 (which has 2). Boxer6 = 6 crankpins, just like a straight six but unlike a V6 (which has 3).

I misread TheCraker's 2nd wiki

Thanks Famine I finally get it...slightly embarrassing as the info was in the source I quoted!

 

[Famine]

I only posted it on Tuesday morning...

 

[Neal]

I know, I was being increadibly slow and then read the wiki quote as boxers share a crank pin. It didn't help that I was looking at the below diagram for a V8 and thought the links between the crank arms were crank pins X million!