Would a Hemi-head Hispano-Suiza 12 beat RR, DB, and AL?

[stoxm73]

HS-12Y looks very promising when it was first run in 1932. However, its later development left far behind its peers like PV-12, V-1710, and DB601.

If it could get enough funding and applied some new technologies such as Hemi-Head, Desmodromics, and fuel injection.

The Hemi-Head cylinders will tolerate more compression ratio and air intake pressure

The Desmodromics eliminate bounce allowing more REVs

The advantage of fuel injection were demonstrated by DBs

So, combine them together into HS-12 will most probably create a powerful engine before 1940. Such engine given a reasonable supercharge may output 1200 hp/6 psi/87 octane, letting D.520 dwarf 109 and spitfire.

 

[GregP]

Using modern knowledge, you can easily design an engine, with H-S-type features, that you could call an Hispano-Suiza that could outperform the others. That is a "what-if."

In what-if land, you can do anything, and it might even be plausible. But, we all know it didn't happen.

The 1945 engines were the last gasp of the big piston engines. All that were made after that, except maybe the civil transport Merlins, were simply fulfilling contracts that were allowed to lapse. The jet engine was coming on strong.

 

[wuzak]

No.

HS 12 cylinder engines of the 1930s were lightly built, so couldn't take extra compression and boost.

Which of the Merlin, V-1710 and DB601 had desmodromic valve actuation. Daimler-Benz used in their F1 and sports car racing engines, but that was the mid 1950s.

All these things will, most likely, compromise one of the main features of the HS 12s - the ability to fit a motor cannon.

 

[wuzak]

And I am trying to think of a hemi-head engine in WW2 that was successful. At the moment I am drawing a blank.

 

[stoxm73]

Using modern knowledge, you can easily design an engine, with H-S-type features, that you could call an Hispano-Suiza that could outperform the others. That is a "what-if."

In what-if land, you can do anything, and it might even be plausible. But, we all know it didn't happen.

The 1945 engines were the last gasp of the big piston engines. All that were made after that, except maybe the civil transport Merlins, were simply fulfilling contracts that were allowed to lapse. The jet engine was coming on strong.

Hemi-Head, Desmodromics, and fuel injection are not new technologies. They are all initiated before 1930.

 

[Snautzer01]

So why did they not use it?

 

[swampyankee]

HS-12Y looks very promising when it was first run in 1932. However, its later development left far behind its peers like PV-12, V-1710, and DB601.

If it could get enough funding and applied some new technologies such as Hemi-Head, Desmodromics, and fuel injection.

The Hemi-Head cylinders will tolerate more compression ratio and air intake pressure

The Desmodromics eliminate bounce allowing more REVs

The advantage of fuel injection were demonstrated by DBs

So, combine them together into HS-12 will most probably create a powerful engine before 1940. Such engine given a reasonable supercharge may output 1200 hp/6 psi/87 octane, letting D.520 dwarf 109 and spitfire.

It's rather interesting that neither hemispherical combustion chambers nor desmodronic valves are particularly common in production engines, likely as neither have the benefits that their proponents advertise. The same considerations apply to sleeve valves.

 

[pbehn]

It's rather interesting that neither hemispherical combustion chambers nor desmodronic valves are particularly common in production engines, likely as neither have the benefits that their proponents advertise. The same considerations apply to sleeve valves.

Desmo type valve actuation was patented in 1898, they do have advantages in high revving conventionally aspirated 4 strokes, I doubt they would be much of an improvement on a WW2 supercharged aero engine.

 

[GregP]

Regarding post # 5, we all know that.

But Honda came up with a formula to allow ANY number of cylinders from 2 on up to have perfect primary balance. We also have Throttle body and digital fuel injection that ensure all cylinders get a perfect mixture, which was a big issue in WWII. There is nothing special about hemispherical heads that can't be matched with properly-designed conventional technology. We also have variable timing electronic cams and newer metals for valve seats. We have electronic crankshaft position sensing for self-adjustable timing, very efficient turbochargers and superchargers, and a host of other modern inventions.


Using these, they can get 900 horsepower from a 1.6 liter Formula 1 engine today and make it last 3 races or more, so I'm relatively sure we can come up with an engine to outperform the Merlin et al. Having owned a Ducati, I am familiar with Desmo valve actuation. It is OK, even good. But, was it better than what we were using for the speeds we were turning? No. Spring valves don't start to float until after a certain amount of inertia, typically around 7,000+ rpm. We weren't even CLOSE yet. If you are looking at valves, why not use air valves like Formula 1? And we certainly weren't looking for a sprint engine. We were looking for a good-performing engine that offered long, reliable service, not a sprint engine that could catch anything and then had to be replaced.


It is a "what if" since that engine never materialized, which was my point altogether. Could we do it? Yes. Did they? No. Ergo, what is the point in discussing an engine that was never designed, never built, and never ran? If you design by committee, you never get finished and never produce anything.

 

[Shortround6]

The Hispano had a number of problems and a trick cylinder head wasn't going to solve them.

And you do need a new cylinder head and a new intake system. The valves were parallel to the bore. they were also in line with the crankshaft/cylinder block. This limited their size, but without changing the production machinery and design the bore spacing was fixed. You can't angle the valves for and aft, there isn't room (ar at least much room)

This a Hispano V-8 but the V-12s weren't much different and the early V-12s were designed to be built using V-8 production machinery.
Note the simplicity of the valve gear. one cam in each head, no rocker arms, no cam followers.
The later V-12s put the intake on the same side of the head as the exhaust in order to leave the inside of the V clear for the cannon.
Please note that "Hemi" heads are very large compared to some other valve arrangements and often rather heavy.

Valve float was not a real problem in aircraft engines as high rpm was not needed. There was no artificial displacement limit. Let me repeat that.

There was no artificial displacement limit!

there was no rules organization like in car or motorcycle racing establishing classes based on engine size.
There was no best 990 cu in engine or best 990 cubic in fighter.
You needed more power? you made a bigger engine.
A large but light low revving aircraft engine was usually much less trouble than a small, high revving but heavy engine. Please note than many WW II engines offered over 1 hp per pound which car engines took (for the most part) into the 50s to achieve.
The Merlin ran at 3000rpm pretty much from the first to last.
The R-2800 went from 2600rpm to 2800rpm in about 5 years but from 1850hp to 2800hp.

I would also note there may have been thousands if not tens of thousands of engines using hemi heads. depends on your definition of Hemi.

supposed to be a piston from an R-1820. anda cut away

If not a true hemi it is pretty darn close.

The 12 cylinder Hispano didn't get counter weights on the crankshaft until they tried to go over 2400rpm.
The 12 cylinder Hispano was nearly the displacement of a Griffon and weighed several hundred pounds less than a Merlin.

You are going to need a crap load of technology to get it to survive making competitive power.

 

[Sid327]

Didn't they discover that a hemispherical head,

and the use of domed pistons made an engine more prone to knock or detonation, hence the move to flat top pistons and a pent roof head?

 

[Shortround6]

So, combine them together into HS-12 will most probably create a powerful engine before 1940. Such engine given a reasonable supercharge may output 1200 hp/6 psi/87 octane, letting D.520 dwarf 109 and spitfire.

You forgot to specify altitude. The higher rpm route is pretty much out. The 12Z engine was good for 2500rpm instead of 2400rpm and it used counterweights on the crankshaft.
The Russian M-105 engines all were beefed up and gained weight. They also reduced the bore by 2mm to help strengthen the engine. Post war Spanish and Swiss Hispano engines (or derivatives ) gained several hundred pounds.


The use of fuel injection making more power is debatable. The Hispano didn't quite get the boost in power due to lower intake temperature charge that the Merlin got by spraying the fuel into the supercharger inlet (German engines got none) but the Hispano used 6 carburetors (one for every two cylinders) and might well have had better fuel distribution than the Merlin even if not quite as good as the German engines. German engines used a mechanical fuel injection system and all cylinders got the same amount of fuel regardless of the amount of air they got. With those long intake ducts not all cylinders on either the Merlin or the DB/Junkers engines got the same amount of air. The German fuel injection was somewhat adjustable in that the injector pumps did have a range of adjustment but the amount of fuel could only be adjusted for one condition. By that I mean they had the pumps in a rack and by rotating each pump in the rack a greater or lesser amount of fuel could be sent to the individual injector nozzle, the individual pumps were then locked down and when more power was called for (throttle opened up) all the pumps were turned at the same time so pump 6 which may have been set a bit richer than pump 2 at idle (or test rpm) was turned the same amount and was proportionally richer at full throttle. Airflow through the manifolds was not perfectly proportional at all rpms.

You are going to get arguments as to whether the fuel cooling allowed more power than the German injectors or not. RR figured the effect of the fuel cooling lowered the intake temperature 25 degrees C at about 6lb of boost.

Hispano Suiza used a really crappy supercharger and one account claims the superchargers got hot enough to blister the paint on them. Some of the 1939-40 engines were getting a new supercharger from an outside company that performed better.

 

[rinkol]

And I am trying to think of a hemi-head engine in WW2 that was successful. At the moment I am drawing a blank.

Many radial engines would have used a hemi head or something close to it. One of the main advantages is that it maximizes the possible size of the valves in a two valve cylinder head. This was an important issue for two row radial engines if one was to keep the complexity of the valve gear manageable. The complexity of the valve gear is less of an issue in an inline engine: it is relatively straightforward to use one or two overhead cams to operate a pair of intake and exhaust valves for each cylinder.

 

[wuzak]

Many radial engines would have used a hemi head or something close to it. One of the main advantages is that it maximizes the possible size of the valves in a two valve cylinder head. This was an important issue for two row radial engines if one was to keep the complexity of the valve gear manageable. The complexity of the valve gear is less of an issue in an inline engine: it is relatively straightforward to use one or two overhead cams to operate a pair of intake and exhaust valves for each cylinder.

Yes, I misspoke.

I was only thinking of in-line engines.

 

[Sid327]

................You are going to get arguments as to whether the fuel cooling allowed more power than the German injectors or not. RR figured the effect of the fuel cooling lowered the intake temperature 25 degrees C at about 6lb of boost. ............

RRHT ''The Merlin In Perspective - The Combat Years. Page 46: ''Cyril Lovesey indicates that the latent heat effect of the evaporation of fuel in the blower improved the compression ratio by about 7% compared with inlet port injection.''