A V8 ? THAT'S CUTE

Matthew Kennedy said:

Yep, and inline engines are terrible for aviation use because they're large and heavy for a relatively small amount of displacement.  A V12 is far less than double the size of an inline six, but has double the cylinders and displacement.

Aero piston engines generally try to minimize the amount of crankcase and crankshaft required for the most displacement, because those are the heavy parts.  Long inline and V engines are also poor choices if air cooled, so those are generally large, high performance water cooled engines.

One of The reasons the V12 is most commonly used for airplanes is because it produces a narrow frontal area for its power. When Rolls Royce developed the V12 they put a man in a chair and used the space from his feet to  his shoulders as the maximum area they could build in.  

Unlike a six cylinder which needs an intake on one side and exhaust on the other side limiting total displacement.  A V12 could be fed air and fuel in the V. From either the supercharger in front or rear of the engine.  

How compact is a V12? Well the Jaguar V12 which can be bored and stroked to 10 &1/2 liters or about  700 cu inches.

Is about 20 inches wide. Yes that includes the exhaust manifolds.  That’s just one of the advantages of a 60 degree V over a more common 90 degree V

To make a 700 cu in V8 is at least a foot wider to the exhaust manifolds  and anything with the valves splayed to make power might be another foot over that! Times the total height of the motor. Let’s for the sake of argument assume 3 feet. 

So 6 sq feet more frontal area is a massive amount of drag if you’re trying to go 400 mph. 

In  addition  the more narrow V of 60 degree’s provides added stiffness over the 90 degree V 

All radial engines use massively more frontal area than water cooled  engines. While an air cooled engine is simpler and shorter than a water cooled engine it does have it’s own issues.  Bulk being chief among issues, Also oil consumption 50 gallon oiling systems being the norm.   

The 4360 corncob is a 4 row  36 cylinder radial engine  that is more than twice as heavy as the Complete Rolls Royce Griffin which made 2450 horsepower compared to the Corncob at 3700 hp. But two Griffons would make 4900 horsepower.  One other point The Roll Royce engine was ready before the start of WW2  while the 4360 corn cob wasn’t until nearly the very end of WW2 

rslifkin said:

V12s were also probably a good balance of displacement vs physical dimensions for making lots of power fit into the available space.  An I6 would have needed bigger cylinders, making it longer (and if it's crossflow, not much narrower anyway). 

Exactly. When Rolls Royce developed their V12 prior to WW2 they put a man on a chair up to his shoulders was all the frontal area allowed.  Hence the V12. Considering they got a version of their V12  up to 2450 horsepower  that’s pretty impressive. 

A Jag V 12 which will go to 700 cu In is only 20 inches wide at the exhaust manifolds. Another advantage of that 60 degree V over a 90 degreeV. Is stiffness.  The  cylinders overlap in the crankcase for more of the stroke with the narrower V. 

alfadriver said:

In reply to codrus :

Assuming the firing order on a bank is even, you are correct. Not sure what book Frenchy gets his info from. 

 

Look at the firing order of a V8 engine.   the reason headers make such a big difference is because adjacent cylinders fire anywhere from 90 to 270 degrees.  Now try to design a V12 with 90 degree separation to have adjacent cylinders fit on even spacing.  

Or you can use a 60 degree V engine and have them fire 60-120 -180 apart.  It’s not the weight of the piston /rod assembly. It’s the firing order that provides the smoothness. 

In reply to frenchyd :

So a shared pin 90 degree V12 does NOT have a second order harmonic, as you originally stated, it's just odd-fire. What is your first hand experience with odd-fire V12 engines to know  just how much vibration this effect does, or does not, create in one?  Seems to me that the way the power pulses would overlap and blend with that many cylinders, it might not actually be much (or effectively any) worse than the effects of power pulse separation on an equivalent I6 at that point...Which is to say, of minimal concern in an automotive application.

For example, the shared pin 90 degree V10 that was used in the BMW M5 also utilizes the inherent primary mechanical balance benefits of all shared pin 90 degree V engines, rather than the 72 degrees that would provide an even-fire engine but which would also require a balance shaft for mechanical balance, yet even being odd fire it is still sufficiently smooth to excel in that high-performance-luxury application...And I would expect a shared pin 90 degree V12 to be even more smooth running overall than that.

Talking about de-railing and while talking to a wall. 

Haven't you figured out that I will fact dump about aviation as often as possible? 

frenchyd said:

alfadriver said:

In reply to codrus :

Assuming the firing order on a bank is even, you are correct. Not sure what book Frenchy gets his info from. 

 

Look at the firing order of a V8 engine.   the reason headers make such a big difference is because adjacent cylinders fire anywhere from 90 to 270 degrees.  Now try to design a V12 with 90 degree separation to have adjacent cylinders fit on even spacing.  

Or you can use a 60 degree V engine and have them fire 60-120 -180 apart.  It’s not the weight of the piston /rod assembly. It’s the firing order that provides the smoothness. 

 

Sigh...  I would point out that you are wrong, but you would just ignore that, again.  

V8's and V12's are not the same thing.  So vibrations you get in V8's- wether flat plane or standard even firing V8, would not be seen on a V12.  Unless you did some crazy firing order just to make it uneven.  I would have thought that you knew that, but it is apparent that you don't.

You CAN have an un even firing V12, and as long as each bank was itself even firing, you would still have a smooth V12.  That's how physics work.  Two even I6's put together in any manner, given an even firing set up, result in a smooth V12.

Yes, it's the firing order that matters- and in THIS case, it's the firing order of each I6 that matters.

BTW, it's pretty funny that you reply to a post that you already replied to.

I know it *seems* crazy, but I do have some experience with a 90deg V12.  Which was made up of welding parts from two modular V8's together.  Thankfully, that was later changed to being developed off of the duratec v6 based V12, which was pretty awesome.  Coolest car I ever worked on.  And it restored Aston Martin back to decent health.

Appleseed said:

Haven't you figured out that I will fact dump about aviation as often as possible? 

I know now! But, you aren't the wall I'm referring to lol.

Yeah, I know.  Still fun to watch.

Back to discussing our god

While I agree with an earlier poster about being easier, cheaper and likely all-around better to turbo an LS engine, I can't help but desire something like a Jaguar XJS or 740il V12, ESPECIALLY in an old muscle car. So many of those things had to be able to fit the inline 6s of the era, and considering how far technologies have come for ECUs, proper cooling and ability to fabricate parts I always keep an eye out for those. Do they have much of an aftermarket?

In reply to GIRTHQUAKE :

They do have an aftermarket, not cheap though. Unless you go with Chevy parts in your jag v12. I will swap an m120 (Mercedes v12) into something one day. 

GIRTHQUAKE said:

Back to discussing our god

While I agree with an earlier poster about being easier, cheaper and likely all-around better to turbo an LS engine, I can't help but desire something like a Jaguar XJS or 740il V12, ESPECIALLY in an old muscle car. So many of those things had to be able to fit the inline 6s of the era, and considering how far technologies have come for ECUs, proper cooling and ability to fabricate parts I always keep an eye out for those. Do they have much of an aftermarket?

The Jaguar V12 is particularly well served. Here in America by Welch and Moss Motors  for parts in general.  Plus a few others. 

For racing parts by Rob Beere racing  and AJ6 engineering.  Plus since so much on a Jaguar came from America in the first place it’s relatively  easy to use American things like transmissions. Most Jaguar V 12’s had either a GM Turbo 400 or the same unit with overdrive..  switching to a manual gearbox amounts to nothing more than buying the correct bell housing and gearbox.  

Wheels have the same bolt hole pattern as a Corvette/ Camero   

Good news?  It’s narrow 20 inches wide from exhaust manifold to exhaust manifold .  Little long.  34 inches from back of bell housing to front of pullies.  Although that includes a couple of pullies that may not be needed.  

It’s either 366 inches or most common 326 inches with a whole lot of torque. And around 300 horsepower stock.  It will go out to 700 cu inches. With 450 inches achieved with a simple bore and offset grinding of the crankshaft.  

Money wise a decent V12 can be purchased as low as $500 but even a the last best engines sell around $2500. In running condition.  Seldom have I ever opened one up and found it needs much. A valve job, new rings, a quick hone and maybe bearings.  

They came carbureted or most were fuel injected( and made a little more power and fuel mileage). If you want more power it’s easy to find. Plug and play?  Try AJ6 engineering. Or go the Megasquirt route. There are street engines that make 600 horsepower plus. 

spitfirebill said:

In reply to frenchyd :

Japan did produce v12 engines based on the Daimler Benz design.  

Oh?  I wasn’t aware of that.  That’s interesting,  What Japanese  aircraft used them?  

Kawasaki Ki-61 Hien (Tony)

Kawasaki used a licensed built Daimler Benz DB601, called Ha-40.

How interesting! I assume it was towards the end of the war?  I’ll have to check it out.

Edit; A German Mercedes-Benz designed  inverted V12  only 873 were built from about 1936-1944? but crankshaft failure was common as was the difficulty of getting parts. 

Exact numbers of aircraft using that engine seems a little confusing. One variant used two engines  linked together.  And it’s highly unlikely that over 400 aircraft were built to use that engine.  Thus aircraft production would have been less than 1/2 of 1%  of total Japanese aircraft production during WW2  however only that engine would fit in the aircraft carrier submarine the Japanese’s built 

Well  found!