DB vs Merlin vs ??

[Sal Monella]

More on the Pratt Whitney R-2800-C Series engine that was the powerplant in the P-47M and N models.

"During durability testing of the C series R-2800 by Republic, it was decided to find out at what manifold pressure and carburetor temperature caused detonation. The technicians at Republic ran the engine at extreme boost pressures that produced 3,600 hp! But wait, it gets even more amazing. They ran it at 3,600 hp for 250 hours, without any failure! This was with common 100 octane avgas. No special fuels were used. Granted, the engines were largely used up, but survived without a single component failure. Try this with Rolls Royce Merlin or Allison V-1710 and see what happens."

http://home.att.net/~historyzone/Seversky-Republic7.html

 

[wmaxt]

More on the Pratt Whitney R-2800-C Series engine that was the powerplant in the P-47M and N models.

"During durability testing of the C series R-2800 by Republic, it was decided to find out at what manifold pressure and carburetor temperature caused detonation. The technicians at Republic ran the engine at extreme boost pressures that produced 3,600 hp! But wait, it gets even more amazing. They ran it at 3,600 hp for 250 hours, without any failure! This was with common 100 octane avgas. No special fuels were used. Granted, the engines were largely used up, but survived without a single component failure. Try this with Rolls Royce Merlin or Allison V-1710 and see what happens."

http://home.att.net/~historyzone/Seversky-Republic7.html

That is amazing. How about this:

Allison ran the standard V-1710 series engines for a similar period @ 100+ in/hg and 2,300 hp.

http://www.unlimitedexcitement.com/Miss US/Allison V1710 Engine.htm

Today the hopped up Merlins used in race planes use 1710 components.

wmaxt

 

[Sal Monella]

In the field, it was common for the P-47 mechanics to modify the engines to increase output. I heard that some P-47 N's were putting out over 3,000hp at WEP. That extra power must have come in handy when loaded down with fuel and ordinance.

The P-47N's maximum take off weight was 20,700lbs. (twice the maximum take off weight for a Spitfire XIV)

 

[wmaxt]

In the field, it was common for the P-47 mechanics to modify the engines to increase output. I heard that some P-47 N's were putting out over 3,000hp at WEP. That extra power must have come in handy when loaded down with fuel and ordinance.

The P-47N's maximum take off weight was 20,700lbs. (twice the maximum take off weight for a Spitfire XIV)

A Crew Cheif would never tune an engine that far outside the normal spec, it would be irresponsible, but 1 or 2 hundred horses wouldn't suprise me much. The factory will set the best compromise between reliability and max power to ignore it completely was just not done.

My dad was an Air Force Crew Cheif he still cringes at the thought of putting a performance aircleaner in his car! You can also ask Flyboy just how encourging the services are about going beyong the Tech Orders. I know things were a little different in WWII but they were pretty careful what they did.

wmaxt

 

[FLYBOYJ]

You can also ask Flyboy just how encourging the services are about going beyong the Tech Orders. I know things were a little different in WWII but they were pretty careful what they did.

wmaxt

These days you loose stripes (or worse) if you purposely violate a TO or a NAVAIR manual. You have to follow "the book" by the letter, and maintainers are heavily scrutinized by QA folks. Any maintenance action involves a TO or NAVAIR reference, chapter and page when completeing VIS MAFS (Navy Forms) or 781A forms (Air Force).

Recips provide avenues for you to "tweek." Advance ignition timing, shave piston heads, valve timing changes, removing air filters, even shortening of propellers I've heard been tried. Jets are very rigid in their set up and maybe the only thing you might try to play with airframe wise is changing the CG for better cruise speed and performance, but again careful to remain "within limits." For the most part, the only "tweeking" done by maintainers are the developing tools to to the job better....

 

[schwarzpanzer]

I always thought that H style engines were problematic and unreliable? BRM tried a H format in 66/67 in F1 and it was plagued by unreliablity and lack of power...How did the Napier engine differ?

That was a W16 that BRM tried IIRC.

wmaxt:

Today the hopped up Merlins used in race planes use 1710 components.

I didn't know they were interchangeable? What is the most powerful hopped up Merlin?

My dad was an Air Force Crew Cheif he still cringes at the thought of putting a performance aircleaner in his car!

With reason, it's just not worth it. Chavs do it just for the noise really. Plus mixture needs resetting and can cause other problems, for like 1hp is not usually worth the effort.

FBJ:

Recips provide avenues for you to "tweek." Advance ignition timing, shave piston heads, valve timing changes, removing air filters, even shortening of propellers I've heard been tried.

I wouldn't do any of those on a road engine, they'd drastically reduce life expectancy to mere hours! I don't know about the last one though and the valve timing I suppose could be altered.

Jets are very rigid in their set up and maybe the only thing you might try to play with airframe wise is changing the CG for better cruise speed and performance

I don't understand that Could you please explain?

 

[Sal Monella]

wmaxt, you say that two hundred horses wouldn't surprise you much but for a P-47N to get to 3,000+ horsepower, it would only take an increase of 200+ horsepower. (Remember that the C series engine developed 2,800 hp in stock configuration.)

Again, I have read in several places that it was quite common for the P-47 mechanics to soup up their planes. I wish I had a source on this.

 

[the lancaster kicks ass]

well i wouldn't be suprised but again i don't think they'd mod the engine to get any more than an extra 4/500hp outta it, otherwise that's just being stupid..........

 

[cheddar cheese]

I always thought that H style engines were problematic and unreliable? BRM tried a H format in 66/67 in F1 and it was plagued by unreliablity and lack of power...How did the Napier engine differ?

That was a W16 that BRM tried IIRC.

No it was actually a H-16, inspired by the H-24 format used in the Napier Dagger aero engine....But thats for another time...

 

[FLYBOYJ]

Recips provide avenues for you to "tweek." Advance ignition timing, shave piston heads, valve timing changes, removing air filters, even shortening of propellers I've heard been tried.

I wouldn't do any of those on a road engine, they'd drastically reduce life expectancy to mere hours! I don't know about the last one though and the valve timing I suppose could be altered.

Yep - you're not going to get to TBO if you do these "tweeks" but then, to WW2 guys, it didn't really matter. Reducing the Prop tips gave higher RPMs at certain MP settings. Propeller manufacturers actually gave rework tolerances on the props, certain mechanics exploited that to get more power....

Jets are very rigid in their set up and maybe the only thing you might try to play with airframe wise is changing the CG for better cruise speed and performance

I don't understand that Could you please explain?

Setting up a turbine engine involves "trimming" the engine - running it and setting up the fuel control with relation to RPM, Turbine Inlet Temp (TIT ) Exhaust Gas Temp (EGT) and power level positioning. All these setting must fall into place for the engine to be considered operational - there are adjustments on the fuel control that control all of this.

Aircraft tend to fly better with the CG as far aft as possible, but their stalling characteristics are degraded. I know guys who have set up their aircraft so they are always at the "back end" of the weight and balance envelope. I am told they may get an extra 5 or 10 knots out of their aircraft...

 

[wmaxt]

Schwarz,

Youd be suprised at the difference a low restriction air filter can do. On 1 car I had it was worth 1lb boost and 1" to 3" vacume resulting in 2mpg. The electronics can easily adjust these days.

Allison rods in particular are used in race Merlins when going over the 3,000hp mark.

When refering to a 100 to 200hp increase for the 2800 I was talking the 2,000- 2,400hp models. Something the savy Crew Cheif would take into account is the pilot, with a pilot that understands mechanical things tweaking is most productive. If he's ham handed you don't do anything to make it worse, like tweaking it for more power/less reliability.

wmaxt

 

[wmaxt]

As I review some data I ran accross this on the data page of the Allison info.

V-1710-E27 XP-63H 2,980hp - 11,000ft - 100"hg

Thats 1.74 hp/in the 3,000hp 2800s are 1.07 and the Allison was to be a production engine! To be fair they were still having trouble with turbine wheels/exaust temps when the project was dropped for jet programs.

wmaxt

 

[helmitsmit]

Firstly, the 2800 radial and other like it, were 50+litre engines! whereas the Merlin and sabres were only 25-30 litres.

Rolls royce actually tested the merlin at over 3000hp as part of its development. The sabre opperated at 4500rpm where other engines barely made 3000rpm. This is because the sabre used sleeved cylinders live Bristol engines like the Pegasus and Hercules

 

[wmaxt]

Firstly, the 2800 radial and other like it, were 50+litre engines! whereas the Merlin and sabres were only 25-30 litres.

Rolls royce actually tested the merlin at over 3000hp as part of its development. The sabre opperated at 4500rpm where other engines barely made 3000rpm. This is because the sabre used sleeved cylinders live Bristol engines like the Pegasus and Hercules

So they were diferent sizes, I'm not sure what your saying?

My point was that the 1710, in that reincarnation, was to be a production engine at that HP rating. Testing is one thing, the most powerful Merlin rating I've heard about is 2,150/2,200 in the P-51H.

1hp/in has been an engine goal for years, and for engines that last for more than a race is still a very good engine. 1.74 is a very very good engine.

If youve got solid info on the other engines please post it, I'm sure I'm not the only one that would like to see it.

wmaxt

 

[helmitsmit]

My point was that they produced more hp per cubic inch of fuel. The Sabre was the first Hybrid engine

 

[wmaxt]

My point was that they produced more hp per cubic inch of fuel. The Sabre was the first Hybrid engine

Cubic inch, is a term for total displacement of the engine.

Please post data I know many of us would like to compare them.

How do you mean Hybrid?

wmaxt

 

[DerAdlerIstGelandet]

I would either want a DB-605D rated at 2000HP, a BMW-801 rated at 1730HP, a Pratt Whitney R-2800-77 Double Wasp rated at 2800HP, or a Allison V-1710-111/113 rated at 1600HP.

 

[wmaxt]

I would either want a DB-605D rated at 2000HP, a BMW-801 rated at 1730HP, a Pratt Whitney R-2800-77 Double Wasp rated at 2800HP, or a Allison V-1710-111/113 rated at 1600HP.

I'd kind of like the planes to go with the engines.

wmaxt

 

[DerAdlerIstGelandet]

Same here, same here....

 

[helmitsmit]

Sorry I meant hyper engine.

Here is some info I got about the Sabre

The Sabre was a 24-cylinder sleeve valve piston aircraft engine designed by Major Frank Halford and built by Napier Son during WWII. It was one of the most powerful piston aircraft engines in the world, especially for inline designs, developing over 3,500 horsepower (2,200 kW) in its later versions. However, the rapid conversion to jet engines after the war led to the quick demise of the Sabre, as Napier also turned to jets.


Napier Sabre. Note that the exhaust ports from both banks on one side of the engine are ganged into a single row of pipes. Small amounts of cutaway metal also allows one to see some of the complex gearing needed to drive the sleeves and take power from the two shafts into the prop.Prior to the Sabre, Napier had been working on large engines for some time. Their most famous was the Lion, which had been a very successful engine between the World Wars and which, in modified form, powered several of the Supermarine designs to the Schneider Trophy in 1923 and 1927. By the late 1920s it was no longer competitive, and work started on replacements.

They followed the Lion with two new H-block designs: an H-16 engine known as the Rapier, and a H-24 known as the Dagger. The H-block has a compact layout, as it essentially consists of two horizontally opposed inline engines lying one atop another. Since the cylinders are opposed, the motion in one is balanced by the opposite motion in the one on the opposite side, leading to smooth running. However, in these new designs, Napier oddly decided to use air cooling; in service, the rear cylinders proved to be impossible to cool properly, leading to terrible reliability problems.

During the 1930s, designers were looking to the future of engine development. Many studies showed the need for engines that could produce 1 hp per cubic inch (50 kW/L), in order to be able to provide the power needed to equip large aircraft which could carry enough fuel for long-range use. In the US this design goal became known as the hyper engine, and it was clear that this sort of performance would not be easy to achieve. A typical large engine of the era, the Pratt Whitney R-1830 Twin Wasp, developed about 1,200 hp (895 kW) from 1,820 in³ (30 L), so an advance of some 50% would be needed. This called for radical changes, and while many companies tried to build the hyper engine, none were successful.

In 1927 Harry Ricardo published a seminal study on the concept of the sleeve valve engine. In it he stated that traditional poppet valve engines would likely have a hard time producing much beyond 1,500 hp (1,100 kW), a figure many companies were eyeing for next generation engines. In order to pass this limit, the sleeve valve would have to be used in order to increase volumetric efficiency. Halford's office was next to Ricardo's in London, and while Ricardo started work with Bristol Engines on a whole line of sleeve-valve designs, Halford started work with Napier, using the Dagger as the basis of what would become the most powerful engine in the world. The H-block layout's inherent balance allowed it to run at higher RPM, to deliver more power from a smaller displacement (more bangs per second means more power delivered); the sleeve valve would allow these higher RPMs to be reached.

The first Sabre engines were ready for testing in January 1938, although at a severely limited 1,350 hp (1,000 kW). By March they were already passing tests at 2,050 hp (1,500 kW), and by June 1940 the first production-ready versions were delivering 2,200 hp (1,640 kW) from their 2,238 in³ (37 L). By the end of the year, they were producing 2,400 hp (1,800 kW). To put this in perspective, the contemporary 1940 Rolls-Royce Merlin II was generating just over 1,000 hp (750 kW), and the most powerful production engines in the world all developed around 1,200 hp (900 kW).

Problems started to appear as soon as volume production started. Up to that point the engines had been hand-assembled by Napier craftsmen, and it proved to be rather difficult to adapt it to assembly line production techniques. In particular, the sleeves tended to fail quite often, seizing the engine in the process. At that time Bristol were developing their own sleeve valve designs, and their Taurus engine had the same bore. At first Bristol refused to work with Napier, but eventually, under intense pressure from the Air Ministry, they relented, and the problems soon disappeared with the addition of Bristol's well-machined sleeves.

Quality control also proved to be a serious problem. Engines were often delivered with improperly cleaned castings, broken piston rings, and machine cuttings left inside the engine. Mechanics were constantly overworked trying to keep Sabres running, and during cold weather they had to run them every two hours during the night so that the engine oil wouldn't congeal and prevent the engine starting the next day (unlike 'multigrades' today, the oils available tended to become thick at low temperatures, preventing the Sabre from 'picking-up' when started) These problems took too long to straighten out, and for many the engine started to attain a bad reputation. To make matters worse, mechanics and pilots were unfamiliar with the very different nature of this engine, and tended to blame the Sabre for problems which were caused by incorrect handling. This was all exacerbated by the representatives of the competing Rolls-Royce company, who had their own agenda.

The problems were eventually addressed, however, and the engine started to reliably allow higher and higher boost settings. By 1944 the Sabre V was delivering 2,400 hp (1,800 kW) consistently, and the reputation of the engine started to improve. This was the last version to see service, however. The later Sabre VII delivered 3,500 hp (2,600 kW) with a new supercharger, and the final test articles delivered 4,000 hp (3,000 kW). By the end of the war there were several engines of the same power class; the Pratt Whitney R-4360 Wasp Major was at that time producing about 3,055 hp (2,280 kW), but used over twice the displacement, at 4,360 in³ (71 L).

The Sabre's primary use was in the Hawker Typhoon and its derivative, the Tempest. While the former was not the fastest plane in the air, the Sabre engine drove it past anything whilst flying at lower altitudes, where it could reach about 412 mph (663 km/h). At higher altitudes, the thick wing of the Typhoon made it slower, and so it was primarily used as a strike fighter. The later Tempest added a new low-drag wing, and the otherwise similar plane became the fastest propellor-driven fighter of the war, at least for a short time.

[edit]
Specifications
For Napier Sabre II, the first production version:

Bore by stroke: 5.0 by 4.75 in (127 by 121 mm)
Displacement: 2,238 in³ (36.7L)
Compression ratio: 7 to 1
Power: 2,180 hp (1,630 kW) at 3700 rpm
Weight: 2360 lb (1,070 kg)