Large Radial Engines Were About As Good As Can Be?

[kitplane01]

Suppose I gave you year 2020 design technology and a large pile of money for the design process. But when it comes time to build the engines, you are limited to what's available in 1944. So no electronic ignition, no computer controls, only things that could be built in 1944. Would you be able to produce a large radial engine that was significantly better than what they had in 1944?

Think you can make one that's 10% lighter, 10% more fuel efficient, and 50% more reliable?

P.S. Yes, I know the answer is the gas turbine, but I'm not asking about gas turbines. I'm asking about how close-to-optimal large radials from 1944 were.

 

[kitplane01]

My personal guess:

It would be reasonable to make the engine 10% lighter, because you would have a better understanding of which parts were heavily stressed, and less heavily stressed. And maybe slightly better metals. Also, you could put exactly the right reinforcing bits of metal to run at higher boost and higher RPM, which can reduce engine weight.

It would be easy to make the engine a little bit more reliable, because (again) of the computer stress and temperature analysis.

I don't think you could make the engine 10% more fuel efficient. You would be able to understand in-cylinder fuel swirl patterns and make the best fuel injector available in 1944 (or tune the intake/exhaust paths if you still have a carburetor). But I don't think that's enough.

 

[BiffF15]

If you look at the outputs of the Amsoil Engine Masters Challenge I think you would be surprised. In 2019 they got 800hp out of a 440CI LS-4 engine.

I think engine reliability would go up tremendously, along with power, and improvements in valves, valve train, blowers, turbos, waste gates, internal friction that fuel efficiency would also improve.

Cheers,
Biff

 

[Admiral Beez]

I think engine reliability would go up tremendously, along with power, and improvements in valves, valve train, blowers, turbos, waste

I'm not so sure. We're still using 1940's metalurgy and manufacturing. Turbos and superchargers would benefit from 75 years of experience in what works.

Suppose I gave you year 2020 design technology

The only change is we have 2020's design process and extra funding. Funding was not in short supply, at least for US firms.

I suppose we need to define what is 2020 design process as applied to the 1940s? If we don't have computers to aid in the calculations and modeling, are we back to drafting tables and slide rules? What design tech from 2020 can we use and not use? Did we learn more about valve train in the past 75 years that we can apply in 1944 using the manufacturing tech of the time? I like this discussion, I just need more info.

One place to start might be a look at how existing engines, like the P&W R-2800 Double Wasp and Bristol Centaurus are overhauled in the 2000s by both museums and more importantly, racing teams. Unless this entails "unobtainable" alloys or manufacturing processes, whatever is done in 2020 to make these 1940s radials reach their max performance should be applicable in the 1940s. This guy could help us Youtube interview with Ray Anderson of Anderson Aeromotive, Inc. Idaho — Anderson Aeromotive, Inc

 

[Shortround6]

Making it lighter would be almost all up to better materials. They blew up/wrecked a lot of engines in testing them in the late part of WW II. They had pretty good ideas of good shapes because they had a lot of examples of what didn't work.
Better materials would also help reliability and durability (not the same thing) although some of the post war engines were rated at much higher hours than the war time engines.
There has also been a major change in lubrication technology.
However everything is guess work.

I would note that a P&W engineer is supposed to have gotten 3500hp out of a "B" series R-2800 for short period of time on a test stand using a huge amount of boost and copious amounts of water/methanol. The engine survived.

 

[kitplane01]

I'm not so sure. We're still using 1940's metalurgy and manufacturing. Turbos and superchargers would benefit from 75 years of experience in what works.
The only change is we have 2020's design process and extra funding. Funding was not in short supply, at least for US firms.

I suppose we need to define what is 2020 design process as applied to the 1940s? If we don't have computers to aid in the calculations and modeling, are we back to drafting tables and slide rules? What design tech from 2020 can we use and not use? Did we learn more about valve train in the past 75 years that we can apply in 1944 using the manufacturing tech of the time? I like this discussion, I just need more info.

One place to start might be a look at how existing engines, like the P&W R-2800 Double Wasp and Bristol Centaurus are overhauled in the 2000s by both museums and more importantly, racing teams. Unless this entails "unobtainable" alloys or manufacturing processes, whatever is done in 2020 to make these 1940s radials reach their max performance should be applicable in the 1940s.

You can have all knowledge from 2020, including whatever textbooks and design secrets GM has stored away.

I like the idea of looking at how we overhaul old engines, but that's not enough. In this scenario, we could redesign cylinder heads such that every bit of metal is under the right amount of stress, every cooling fin is the exact right size and placement, and inlet/exhaust passageways are designed using computer aerodynamic simulations. Repeat for every single part.

My first thought is that we get a much higher optimal RPM. Better stress analysis and better breathing should make that easy. And assuming you have adequate breathing, horsepower scales with RPM.

 

[kitplane01]

If you look at the outputs of the Amsoil Engine Masters Challenge I think you would be surprised. In 2019 they got 800hp out of a 440CI LS-4 engine.

I think engine reliability would go up tremendously, along with power, and improvements in valves, valve train, blowers, turbos, waste gates, internal friction that fuel efficiency would also improve.

Cheers,
Biff

But how did they do that, and can one get 1,000 reliable hours doing it?

 

[BiffF15]

Okay, look at it this way.

2020 Ford GT-350 (5.2L V8 526HP and 8200RPM redline)(5 years 60k powertrain)
2020 Ford GT-500 (5.2L V8 760HP and 7500RPM redline)(5 years 60k powertrain)

1971 Ford Boss 351 Mustang (5.7L V8 330HP very very conservative and 6150 redline)
1970 Ford Boss 302 Mustang (5.0L V8 290HP@5200RPM and that's conservative)

1966 Ford Mustang K code (4.7L V8 278HP and 6000RPM redline)(Standard V8 warranty 12k/12 months - K code 3k/4 months)

I know there is some good electronic nannies embedded to keep a guy from bombing his engine, but a 5 year warranty on a V8 making 760HP!

Look at the trend in 5 years (1966-71) which is well after WW2, and HP in small block Fords stayed near 1 HP for 1 C.I. (cubic inch).

Fast forward to 2020 and the GT-500 is almost 2HP for each C.I. (assuming 5.7L equals 351 C.I. - I didn't do the math).

Blowers, turbos, and intercoolers have progressed tremendously in the last decade. I think gains in HP would be impressive as would reliability.

Just my opine.

Cheers,
Biff

PS: Full disclosure I own a 1966 Mustang GT 2+2 K code.

 

[kitplane01]

That's interesting .. but hard to know what to make of it.

The modern engines run with many-much electronics (forbidden by scenario) and car engines run at 15% power most of the time.

 

[BiffF15]

Well, I get 2020 tech but not the engine electronics. I would think, especially on the V engines, that a good deal more power could be squeezed out with a gain in reliability. Does that include todays tech for fuels?

Cheers,
Biff

 

[kitplane01]

Well, I get 2020 tech but not the engine electronics. I would think, especially on the V engines, that a good deal more power could be squeezed out with a gain in reliability. Does that include todays tech for fuels?

Cheers,
Biff

If they can make your proposed fuel using 1944 tech at a reasonable cost, go ahead. But they octane they had in 1944 (and their lack of fear of lead) ...

 

[kitplane01]

The first of the cars to be designed and produced post war were about 1948. Electronic controls were introduced by GM in 1981.
So comparing a Cadillac designed in 1948 and 1980 ...

The 1948 engine had a 331 cubic inch, 160 horsepower.
The 1970 engine had 500 cubic inches, 400 horsepower.
The 1976 engine had 500 cubic inches, 210 horsepower (and it got worse after)

So if you figure engine weight is proportional to cubic inches, and you stop sometime before the OPEC crisis, you conclude Cadillac engines got 14% worse.

Arg!

 

[Shortround6]

Don't forget, the WW II engines were rather underrated. To qualify for wep rating the engine had to run 7 1/2 hours at that rating PLUS the rest of the 150 hour type test. Car engines seldom run for more than a minute at a time at full power. Even at Le Mans with that long straightaway.
Type test might be equal to 5-6 24 hour endurance races without ever replacing a major part in the engine.
Modern knowledge will improve things. But those old engines had another design criteria. That was power to weight. A lot of the high power engines were running more than 1hp per pound of engine weight.
What are the weights of those Ford car engines?
The other thing is altitude. Most of those engines were running at part throttle at sea level or take-off.
How much power do the car engines make at 15,000ft? Or pick critical altitude for a specific aircraft engine.
See how much power some of those engines made when set up for hydroplane racing.
Again, modern knowledge will improve things but those engines were pretty high tech not only in their day but compared to race car engines 10-20 years newer. Granted it wasn't supercharged but the engine in the 917 Porsche was the first Porsche engine to make more than 1hp per pound.

 

[kitplane01]

Well, I get 2020 tech but not the engine electronics. I would think, especially on the V engines, that a good deal more power could be squeezed out with a gain in reliability. Does that include todays tech for fuels?

Cheers,
Biff

Any reason why this helps the V engines (like V-8, V-12) more than the radials. Or did you mean V like Allison? And if so, why is Allison more able to be improved?

 

[Admiral Beez]

In this scenario, we could redesign cylinder heads such that every bit of metal is under the right amount of stress, every cooling fin is the exact right size and placement, and inlet/exhaust passageways are designed using computer aerodynamic simulations. Repeat for every single part.

Are we any smarter or more knowledgeable about such things today than we were in the 1940s? Look at any aerospace engineering school today and everyone's using calculators and computers to do calculations that people did in their head and on paper. I just don't know if an aerospace expert of today would have much to offer their 1940s counterpart.

 

[Shortround6]

They used slide rules and mechanical adding machines.

paper and pencil is a myth.

 

[BiffF15]

Any reason why this helps the V engines (like V-8, V-12) more than the radials. Or did you mean V like Allison? And if so, why is Allison more able to be improved?

Kitplane,

The reason I focused on the V12 engines is the "inline" engine has shown tremendous advances in the last 30 years compared to the automotive engine of the early 40s. I look at aviation engines of WW2 as hot rod motors meant to have high performance and acceptable longevity (those two things being the guard rails on your "road"). Radials have not gone through the continued evolution that the inline motors have however its a recip, has a blower or turbo and can benefit at least some.
Auto engines up until the performance explosion of the 60s biased towards longevity over perf. Since the 60s to today look at the power output vice weight, and don't forget that longevity has improved dramatically as indicated by warranties.

The modern GT-350 / 500 engines are aluminum and although larger, are lighter than their predicessors.

Now take todays hot rod know how, and apply it to a Merlin/ Allison / Radial du jor and I would expect increases in power, longevity and fuel mileage. How much is all guess, but giving the Allison a great supercharger alone would increase power / usefulness quite a bit. Add lightened reciprocating mass, improved filters (K&N oil type), better plugs / wires, better lighter turbos / superchargers and improved fuel delivery I would think 10% across the board would be achievable. Add smarter MX practices as well.

Some of your power to weight examples were choked by performance robbing emissions equipment which is not a player on a wartime performance engine.

In the 70s the standard car warranty was 12k / 12 months. Today, cars can get as high as 100k / 10 years. Mileage is up, repairs are down, performance is way up and it's not all attributable to electronics. I would expect a commensurate improvement in aero engines as well.

Just my opine.

Cheers,
Biff

 

[swampyankee]

There is much more known about combustion processes (like it as not, this is almost entirely due to emissions regulations), unsteady flow, especially within cylinders, and materials technology than 75 years ago. There is also much more known about flow in turbomachines, both axial and radial (aka centrifugal).

A program like Kiva (see KIVA) can accurately predict engine performance over a broad range of conditions, including off-design, different fuel characteristics, and different environmental conditions.

An individual skilled user of Kiva could probably replicate all the work done in the US Army's Hyper program in under a year. Using these programs isn't trivial, as users frequently have to write code to model some behavior, like injecting anti-detonation fluid or nitrous oxide, but it's a whole lot easier than building and modifying numerous test engines.

 

[swampyankee]

The first of the cars to be designed and produced post war were about 1948. Electronic controls were introduced by GM in 1981.
So comparing a Cadillac designed in 1948 and 1980 ...

The 1948 engine had a 331 cubic inch, 160 horsepower.
The 1970 engine had 500 cubic inches, 400 horsepower.
The 1976 engine had 500 cubic inches, 210 horsepower (and it got worse after)

So if you figure engine weight is proportional to cubic inches, and you stop sometime before the OPEC crisis, you conclude Cadillac engines got 14% worse.

Arg!

Don't forget that somewhere in that period, GM -- whose advertised power was probably the most inflated of any of the US automakers -- and the other makers switched from SAE Gross, where the engine power was reported with an ideal inlet and exhaust system, and no accessory drive losses, that is the horsepower reported didn't include things that would be present in an installation, like the power needed to drive the radiator fan, the water pump, the oil pump, the alternator, etc, to SAE Net, where actual inlet and exhaust losses are included, as are accessory drives.

 

[pbehn]

This was running in 1944 Lycoming XR-7755 - Wikipedia