A bored-out Merlin or V-1710?

The early Allisons DID run at 2,600 rpm due to the early nosecase .... true. I donlt think they struggled to do so at all. The main parts were designed for the same safety margins as the ones made in 1945 .... 4,000 rpm, but the early nosecase was one of the limiting parts. They work .... but aren't really good for more than about 950 - 1,100 HP without some risk of failure. They got "improved."

From your comment about the propeller not caring ... you don't understand ... Allison cared. They knew the props were good for about 1,800 rpm or so, give or take a bit, and also knew the original nosecase, the prop, and some accessories weren't. The rotating parts in the main crankcase WERE good for 4,000 rpm. With progressive improvement, they went to 3,000 rpm and later to 3,200 rpm (crank speed). The 12-counterweight crank was made to reduce harmonic vibration, not to increase design speed. It did and does that effectively.

You CAN turn them 3,600 rpm and Joe has run one at 105 inches MAP (+36.9 psi of boost). If anyone has the money and wants to run one at Reno, he can do it quite well, assuming a good airframe and a suitable prop that can handle the rpm. To date, nobody has wanted to proceed. Joe figures 2,950 HP at the prop is possible with race-specific reliability at Reno.

That's OK, he still has around 135 Allisons including maybe 15 - 16 G models available. The rest aren't any particular model. You can turn them into an E or F model with a simple nosecase change. The E runs a driveshaft and the F has a propeller on the prop shaft. He even has one PT boat engine complete with flywheel ready for the V-drive connector shaft.

Only the G-series have to start out as a G. He still has G-series rods left, too, but no individual G-series rods. They go as a set of 12 or stay put in the shop.

The Allison is robust and reliable if built right and operated right. I wish someone had let Allison make a 2-stage supercharged engine properly, but it never happened due to official indifference and the impending end of the war coupled with the arrival of the jet age. It isn't the first machine with great potential to be less than fully developed and won't be the last.

But the development it got was good. If you get an 80 series or later Allison from Joe you get a good, sound, reliable, long-lasting engine. For a stock warbird, what more can you want? Even if you have a Spitfire, you're cruising at 250 knots or less in the USA below 10,000 feet, usually 235 or thereabouts. So it doesn't matter much how fast it WILL go and the Allison will cruise around bit longer than a Merlin without major work assuming proper operation and normal maintenance for both engines.

In use, they are both reliable and robust, but have differing maintenance requirements. I'd take either one if I could and, if I had the money, my first warbird would be a Spitfire IX, though I'd not sneeze at a Mk V or any other Merlin mark. I'd avoid the Griffon just because it has fewer people qualified to work on it than either the Allison or the Merlin, fewer spare parts available and it turns the other way. Otherwise, no issues with it ... well ... maybe a shortage of Rotol props.

If I had a LOT of money, my second warbird would be a Bearcat or Tigercat, followed by the one I didn't have after choice number two was in the hangar.

An Allison powered warbird would be down around number 4 or so. It would be a P-40, preferably an N model or maybe a Yak-3. It might be hard to convert a Yak-3 into a 2-seater and still have it look like a Yak-3. I had a really good time when I took a ride in our P-40N, and Matt didn't pull more than 3 g or so during the flight ... but I might like to do so if I were doing the flying.

Cheers.

Greg, please don't get me wrong on this: I'll stop debating on whether the V-1710 was designed for 4000 RPM. I was expecting some hard data that would prove or disprove that figure, but after 5 posts we don't have anything like. Instead of that, we can read usual text flood describing what V-1710s were capable in 21st century, how Merlin has Allison-produced parts now, how we can buy a V-1710 or a whole aircraft if we have plenty of money etc.
Not trying to be rude or whatever.

Well Tomo,

Joe's original data is at his shop as I said, as are his pictures on the wall. I don't really have the access I used to. The design stuff is not in the maintenance, overhaul, or operators manuals .... it is in Allison documentation.

So ... I'll stop telling you what is says until someone posts something wrong about the Allison. It had its problems, most but not all of which were addressed. In point of fact, the Allison ended the war as a solid engine but had some early troubles not entirely of Allison's making. Some WERE of Allison's making, like the issue with the intake tract. The fix was EASY but took longer than it should have due to the fuel aromatic issue clouding the tests. The early "fix" worked in Indiana, but not once it got to the UK. I bet that made for some sleepless night back in Indiana untli they figured it out.

The Merlin also has issues but things got addressed a bit more quickly at Rolls-Royce. In my mind, the war might have had something to do with the responsiveness of Rolls Royce. One thing is for sure, nobody was threatening to invade Indianapolis, Indiana by force from 25 miles away across the channel! And Rolls had a supercharger genius in Sir Stanley Hooker. Both circumstances combined to make finding a fix for problems a bit more of a priority at Rolls-Royce.

So it isn't surprising that the Merlin had accessories developed in advance of the Allisons. The supercharger was in what is called the accessory housing ... at least on an Allison. The basic rotating hardware for both is similar with the Allison having the slightly stronger components, but there is nothing whatsoever wrong with the Merlin if it is flown at stock power levels or up to a 50% boost from stock. Much more than that and you run into strength issues, as you might expect when "hot rodding" most piston engines.

Altogether they were two decent engines, with the Merlin getting the historical nod as the "best" of the Allied V-12's, and I won't dispute that here; it was. The US War Department never allowed Allison to develop an integral 2-stage unit for the V-1710. To be more precise, they would not fund it, even when the higher-altitude nature of the ETO became clear. That is our own fault and there is nobody to blame but the USA.

As for the ease with which book specs could be exceeded, I can take the example of the P-40. There is a toggle switch in the cockpit. It is spring loaded to the center and you can flip it up or down. No matter what constant-speed rpm you have set you can easily change that by blipping the switch. Blip up and the rpm increases by 200. Down decreases by 200.

So, a guy in some trouble had EASY options. 3 blips up and push the throttle forward a bit and he goes from 57 inches and 3,000 rpm to 75 inches and 3,600 rpm. Might be frowned upon in official circles, but it happened in combat. My bet is it was no more difficult for the Merlin guys to do the same thing, but I don't really know as much about the Merlin engine control setup. You wouldn't stay there once the combat was over, but getting there was EASY.

I also bet it was just as easy for the guys flying Messerschmitts, too.

Maybe that's why there is so much disparity when looking at comparative performance tests. They might blip their own planes a bit and fly the Messerschmitt to specs ... and vice versa for the Germans doing similar testing of captured Allied planes.

The most amazing thing to me is the diverse designs that arrived at almost identical performance at many points in the envelope.

GregP said:

All Allisons were designed for 4,000 rpm from the outset. They were run at 3,000 rpm due to other considerations including the propellers and the attached components. But the crankshafts were good to go at 4,000. They went from 6 counterweights to 12 ti reduce harmonics, not to increase the rpm. When they DID increase it to 3,200, the new Allisons coming off the lines were using the 12 counterweight cranks, but the early cranks could do it, too, if the props and auxiliary devices could handle it. They would, of course, vibrate a bit more, but they could do it.

All piston engines are air pumps. Put more air through them and they make more power. You can do it with bore, but an rpm increase usually accomplishes a lot more a lot sooner. You can also do it with a charge pressure increase (boost). A combination usually makes for the most dramatic power increases.

As an interesting aside, Joe Yancey builds Allison for all applications and he has maybe 15 or so in Europe on tractors for the tractor pull crowd. Some of those guys are turning them 4,600 rpm! And they are doing it reliably.

Click to expand...

Amazing, so they are doing higher piston speeds than Formula 1 engines at 20,000rpm......Wow wonder what they are made of ... unobtanium perhaps?
Or 'unlimited money', couple of minutes of that then off to a complete rebuild.....

The reality, including F1 engines, is that maximum piston speeds hasn't changed that much over the decades.
And the Merlin piston speeds is about the max you can obtain with some sort of reliability.

A 4,000rpm Allison for a combat aircraft is a fantasy......nice fantasy though.....

It isn't a fantasy, thank you very much.

The rotating parts were capable of 4,000 rpm as a safe speed in a dive. If you actually DID that in flight, you'd probably stretch the prop or shed a blade or blades, and I doubt they'd allow that situation to continue for more than a few seconds before they realized they were in some danger. In aircraft use most Allisons were limited to 3,000 rpm and that is a fact, not a claim, but several later models were cleared for 3,200 rpm in flight. That's crankshaft rpm, not prop rpm, and I didn't make up the numbers. Those models would be the E27, F32, G6 (R/L), and G9 (R/L).

The tractors that run aircraft engines in Europe almost always run much higher rpm than stock, but not for very long periods of time. They would NOT last if they tried to do it for any long stretch of time, but a 20 - 30 second run at high rpm is not only possible, it is a very common occurrence. Many types of short duration engines out-do Formula 1 engines. You can find a lot of them at any dragstrip where they run Top Fuel cars of any sort.

They won't survive a Formula 1 race, but have no problem making 8,000 HP for 4 seconds.

Piston speed isn't very important for drag race engines. It comes into play if you want reliability and long engine life. At 3,000 rpm I get a corrected piston speed for an Allison of 3,162 ft/min or 16.06 m/s. They usually had a time limit for 3,000 rpm operation. It also works out to a BMEP of 247 psi which, while it is near the limit for a naturally aspirated engine, isn't out of line for a supercharged engine. Merlins made a BMEP of around 360 psi after about 1942 or so.

If you think these are out of line, then how do do you account for the fact the the Merlin made MORE HP with the same stoke, also at 3,000 rpm? They turn modified Merlins at 3,600 rpm for 8 laps around the Reno race course and those engines live. That's a CPS of 3,795 ft/min or 19.3 m/s. They significantly outperform anything Formula 1 has ever done ... and they do it every year. You might remember Formula 1 is a FORMULA engine, not the best that can be built. This year they are limited by regulation to 15,000 rpm but they have proven they can do more than 19,600 rpm if allowed to do so. I'm not a fan of the 2.4 liter V-8's that are artificially limited to 15,000 rpm this year.

You should come watch the fantasy happen in September at Reno. Steven Hinton gets at least one or two laps in each year at 510+ mph and then slowly backs off enough to win at a race average of somewhere near 480 mph or so at a BMEP of 513 psi! Show me a Formula 1 that gets to more than half of that number.

Maybe it has something to do with the fact that the Reno guys don't have anything to do with the FIM or artificial Formula 1 rules, a situation many a Formula 1 team wishes they were in about now.

I'd bet Daniel Ricciardo is high on top of THAT list.

GregP said:

I'm not a fan of the 2.4 liter V-8's that are artificially limited to 15,000 rpm this year.

Click to expand...

They are 1.6l V6s with turbo and hybrid energy recovery systems, including electric turbo-compounding.

They may be limited to 15,000rpm but they are fuel flow restricted and do not operate that high anyway.

GregP said:

You should come watch the fantasy happen in September at Reno. Steven Hinton gets at least one or two laps in each year at 510+ mph and then slowly backs off enough to win at a race average of somewhere near 480 mph or so at a BMEP of 513 psi! Show me a Formula 1 that gets to more than half of that number.

Click to expand...

The current 2014 V6 engines should be getting close to 500psi BMEP with their restricted fuel flow (100kg/hr). That is ~630hp from 1.6l at 10,500rpm (power drops off at, or shortly after, 10,500rpm as friction rises but fuel flow remains constant).

At maximum power with turbo compounding the F1 engine will give ~715hp @ 12,000rpm and have a specific fuel consumption of ~190g/kW/hr.

GregP said:

Maybe it has something to do with the fact that the Reno guys don't have anything to do with the FIM or artificial Formula 1 rules, a situation many a Formula 1 team wishes they were in about now.

I'd bet Daniel Ricciardo is high on top of THAT list.

Click to expand...

Nobody in F1 has anything to do with the FIM - since M stands for Motorcycle. The rules are made by the FIA, but the engine rules were created in consultation with the engine manufacturers.

And Dan Ricciardo should be pissed at his team for not following the FIA's instructions, as other teams had.

And, btw, the BMW M12 Turbo of 1985/86 gave ~850hp @ 11,500rpm for a BMEP of 640psi. That is in race trim. In qualifying trim it was >1200hp, a BMEP >900psi.

Hi Wayne,

Yeah, typo on the displacement. I don't know the bore and stroke or REAL power levels of any of the current F1 engines. They aren't published as far as I know. As I understand it, Ricciardo's team had telemetry that said they were OK on fuel flow but the FIA had their own telemetry that said otherwise. Seems like a really simple thing to check ... run them both side by side and measure the flow with calibrated test equipment! How hard can it BE? C'mon, FIA, get it RIGHT for once. They miss often enough.

And they never even got to any BMEP much over 220 psi unless they were running turbos, which were banned until this year. I admit I was comparing the supercharged Merlin / Allison to the naturally-aspirated F1 engines. Call it editorial license. When they DID run turbos, especially the qualifying engines, they didn't last very long ... maybe an hour and a half for race engines and 30 minutes for qualifying engines. Merlins and Allisons were getting BMEP's of over 350 psi and were flying 6 hours and longer missions and getting 250 - 450 hours between overhauls. No F1's at ANY time ever got much of a long engine life. Even today, when they have RULES for long life, it is defined as 2 races ... or is it 6 engines for the season?

The Merlins and Allisons are impressive, at least to me.

The ROTATING parts of the Allison were designed for 4,000 rpm safety. They did NOT run the engines at 4,000 rpm. I have known an owner to hit 3,600 for a short time and 3,400 for 2 or 3 laps around Reno in a P-40, but never 4,000 rpm except in a tractor where they hit 4,600 for a short pull, maybe 15 seconds or so. Short-duration abuse is well tolerated by both Allisons and Merlins ... long-term abuse is NOT. Good engines, both.

By the rotating parts I mean the crankshaft, main bearings, the rods and rod bearings, the pistons and rings, the camshafts, the valves and valve springs. I'm pretty sure the F-type nosecase was, too, but NOT the early long nosecase. I am not aware if the supercharger and accessory case items were designed for that rpm or not, nor any of the other accessories and would not care to speculate without looking into it further in Joe's documentation. So maybe, maybe not. It's not a big subject in my mind and I decline to put the time and effort into it unless there is a reason. In this case, there isn't ... the engines run at 3,000 - 3,200 rpm (certified) and are safe if they overspeed a bit. Anyone who disagrees ins't an Allison owner / operator or they would KNOW. I'm not here to prove it to anyone ... ask an Allison owner. Down in the Australia / New Zealand area, ask Graham Frew. He flies a Yak-3 with a Yancey Allison in it.

I am aware of a prop runaway in a P-40 in which the blades got stretched and became unairworthy, but am NOT aware of the rpm it reached. A runaway usually happens when the constant-speed function fails and the blades that WERE running just fine default into takeoff pitch while at high speed or high power. It is almost always fatal to the engine, but was not in the case I know of. The pilot had good reactions and throttled back in time to avoid losing blades. Naturally a new (at least to the aircraft) Curtiss Electric prop was NOT cheap.

Even the decals are expensive!

GregP said:

Yeah, typo on the displacement. I don't know the bore and stroke or REAL power levels of any of the current F1 engines. They aren't published as far as I know. As I understand it, Ricciardo's team had telemetry that said they were OK on fuel flow but the FIA had their own telemetry that said otherwise. Seems like a really simple thing to check ... run them both side by side and measure the flow with calibrated test equipment! How hard can it BE? C'mon, FIA, get it RIGHT for once. They miss often enough.

Click to expand...

The bore of the V8s was maximum 98mm - so that is what they used (strok just slightly less than 40mm). The V6s have a maximum bore of 80mm, meaning a stroke of 53mm.

Power for the V8s was ~750-760hp. Estimates for the 2014 engines vary between 600 and 650hp. So I chose, roughly, the middle.

I doubt that you would really know the power of the Reno engines either.

As for the Red Bull disqualification, the rules require the fuel flow to be measured by the standard FIA fuel flow meter, which the FIA monitor. The FIA instructed Red Bull to lower the fuel flow rate during the race, Red Bull did not and relied on their own fuel maps. In other words, they cheated - ie went outside the rules - and were caught.

GregP said:

And they never even got to any BMEP much over 220 psi unless they were running turbos, which were banned until this year. I admit I was comparing the supercharged Merlin / Allison to the naturally-aspirated F1 engines. Call it editorial license. When they DID run turbos, especially the qualifying engines, they didn't last very long ... maybe an hour and a half for race engines and 30 minutes for qualifying engines. Merlins and Allisons were getting BMEP's of over 350 psi and were flying 6 hours and longer missions and getting 250 - 450 hours between overhauls. No F1's at ANY time ever got much of a long engine life. Even today, when they have RULES for long life, it is defined as 2 races ... or is it 6 engines for the season?

Click to expand...

The best of the wartime Merlins had a maximum BMEP of 320psi, which would last for no more than 15 minutes (and only rated for 5 minutes). They did not run at high BMEPs for extended periods of time. The Merlin 76 at 1710hp had a BMEP of 275psi.

The Current F1 engines will be at 400psi+ for the majority of the race, most of qualifying and the practice sessions. And they have to do this for 4 race meetings (5 engines per driver per year).

Pretty stupid to regulate fuel flow. Just give them a certain amount of fuel and you have it all done. If they run out ... the fuel flow was too high and I bet they wouldn't do THAT more than once. Bernie Ecclestone just wants to have absolute control. Thanks for the bore and stroke data. I don't usually bother with the current year, and they usually release that data for F1's of ... say ... 4-5 years ago. I look at F1 power, BMEP, etc. about once every 3 - 4 years. I suppose with the turbos this year they have more torque and it hits harder like a typical turbo. I liked the racing MUCH better when they had to refuel during pit stops. The no refueling and less noise from them is making me less than happy with F1 and I haven't watched one since Australia. The cars are ugly, the engines too quiet, and the rules too restrictive. Instead of racing, it is beginning to be nothing more than a boring Formula race instead of the pinnacle of auto racing. The only thing more boring is a NASCAR oval track race. At a minimum, NASCAR still has to refuel during pit stops. At LEAST F1 is still on road courses that turn both right and left!

After being a diehard fan for 40+ years. My interest in it is waning due to the regulations and idiot decisions they make.

I'd love to watch some of the other European open-wheel series, but they don't carry them on US TV.


About Reno, yes, they KNOW the power of the two top modified Merlins (Strega and Voodoo). They know rpm, manifold pressure, and airspeed. The guys who do the figuring are experts like Pete Law and Mike Nixon and they can calculate that out VERY accurately. Pete helped design most of these planes and has run the props through wind tunnels to get the REAL data on them.

Pete's written estimate for Strega's speed in level flight at specific rpm and manifold pressure was off by by less than 0.1%, and that's pretty darned close by almost any standard. I have heard the power number (I'm not the only one by any means) and was asked not to pass it on. They can't run at that level for 8 laps anyway, so the high-power laps are lap 1 and 2, after that the modified Merlins are throttling back because they are heat soaked and would otherwise grenade.

The radial guys usually run fastest on the last 2 laps when they move to FULL power and nitrous (if they RUN nitrous). They all decline to say if they run nitrous, but when the exhaust turns dirty brown on the last two laps and the Nitrous truck stops by the pits ... the conclusion isn't difficult. Rare Bear has not used Nitrous since Rod Lewis bought it. It has also been about that long plus one year since Rare Bear won the Gold Race. Maybe they SHOULD be running nitrous, huh? It's a tough call when YOU have to pay the bill for being wrong!

It's my guess that the mighty R-3350 is just about done since they are pretty much out of main bearings. Not QUITE done yet, but the guys who still have one running probably want them to STAY running for awhile. I could be wrong on that guess ...

Greg, the fuel flow is used to control power and promote efficiency.

Without the fuel flow limit they could use some pretty silly power numbers during qualifying, or at certain stages during the race. And with the fuel cap and no fuel flow limit there would likely be more fuel saving going on.

These engines don't behave like typical turbo units either. The turbo is connected to a motor generator unit, which can use the excess power of the exhaust to generate power which can be sent to the other MGU, which is connected to the engine, or to the battery. Or the MGU can be used to spin up the turbo, making lag almost non-existant.

They have a much broader power band than the V8s, plus up to 160hp kick from the MGU connected to the crankshaft, and are coupled to chassis with 15% less downforce. This makes them a handful to drive.

btw, there hasn't been another race since Australia, the next one being in Malaysia, today.

Yeah, it's losing it's allure to me rapidly.

I'll stick for another one or two races and if it's not good racing, I may wait until the Formula 1 Racing Association is not under Bernie to see another one. What I, for one, want to see is good racing where the whole team needs to work together to win. Two second pit stops simply mean they have removed pit stops as variable in winning to a much larger degree than I wanted to see. I could not give a damn about the electric motor ... it has no place in racing. It is one of the reasons I'm souring on F1.

The electronics are neat, but also have no place in real racing either. The drivers are running around in moving video games. Just one opinion, and probably not in the majority.

But I think any mid-80's turbo car with the 1,000+ HP engines, modern tires, and modern brakes suspension would run rings around this group of crates. It's bad when 35 - 30 year old cars made more power, looked better and sounded better.

Bring back Can-Am and engines that SOUND like engines!

If we continue this, maybe it should go in the "Off-Topic" area ... before we get slapped for being ... off topic AGAIN.

Aw well, back to airplanes. As far as I know, Steven Hinton and Voodoo will be back at Reno this year with some extra speed from some aerodynamic mods. Good to hear!

Someone in here was metioning that they weren't too sure about the 3-engine Allison tractor.

Here's a video:

View: https://www.youtube.com/watch?v=g7kJF-LjosU

World record.

Bernie Ecclestone does not control anything in the F1 for some time now...