Interesting report on a G-14

[MiloMorai]

Originally posted by mora
Your ignorance is amazing. Why do you think the break in times would be any different?

Enlighten me, oh yee with such  GREAT  knowledge.

Instead of just flapping your gums    , post some info for P&W, R-R, Bristol, Allison, Napier, Wright, Jumo, Fiat, Nakajima, Mitsubishi, Mikulin, Shvetsov, Piaggio, Klimov engines.

[mora]

A Break in of an engine is needed because there are always tolerances when moving engine parts are machined. During the break in period the engine parts are supposed to set together to achieve optimum tightness. The smaller the tolerances are, the shorter the reguired break in period, hence new cars for example don't reguire any break in period because machining tolerances have been lowered in recent decades and oils have been getting much better. I have no reason to believe that German manufacturing tolerances during WW2 were any higher than those used in GB, USA, Soviet Union, Italy, Japan etc.

The duration of the break in period you posted(10h) actually seems quite low and is probably too short to achieve optimum engine life. However during war time conditions this was more acceptable than all the hassle with longer break in.

[niklas]

Even today car manufactors (still) recommend not to exceed 3000rpm the first 1-2000km in a car.

niklas

[Angus]

All engines need a run-in.
For what it's worth though, an old 109 Pilot told me that he was not satisfied with the late DB engines. They would wear out way too quickly he said, and getting to know a captured Mustang with an impressive engine time on the clock, he was very impressed with it. "Our engines were not that good" he said.

I don't know what to read out of it though. The DB design was indeed very good. Was it lack of maintainance and material, and the use of MW perhaps.

I'll try to ask him better later.

[TimRas]

In Gabreski's book (Gabby, A Fighter Pilot's Life), Frank Klibbe tells: " Airplanes were assembled up in northern England, and then flown down to the units. And the engines had to be slow-timed. This meant you had to fly 10 hours of time at low rpms on the engine before you could really open it up to its maximum. So, after each mission I'd jump into this new P-47 and go up to put on an hour or two."

[GScholz]

Angus, are you mixing up MW and GM again? MW was not harmful to the engine, GM was.

[Angus]

GM?
Maybe. MW is Methanol-Water right?
GM is what?

Anyway, not so well in on these exact things, I'm all ears though.
The old guy sort of embarrased me, you see, for these things were being discussed by a group of people, where I gave the impression that the German machinery had always more or less been on the top. He looked at me and shook his head (tsk tsk tsk).
(Actually, he already told me this engine story by then. The pilots would measure the tightness of their cylinders by turning the prop. The late DB's wore up really fast. Therefor he was amazed to check out a P51 with an impressive figure on the clock, yet the prop was totally stiff. He later flew the 51 and was extremely satisfied with it.)

[GScholz]

Yes, MW is water-methanol, which is harmless to the engine. GM-1 is nitrous oxide, which is very corrosive. Technically the DBs were more advanced than the Merlins, much more advanced in fact. However given the state of Germany's supply and production problems late in the war the engines were not made with the specified quality of materials and production, in fact a great deal of research went into studies of how to use cheaper/more abundant materials in production. This gave the engines a shorter life and a higher risk of malfunctions. However this was less important to the Germans as they were fighting over their own territory. The Allies OTOH needed reliable long-life engines because their planes were flying for several hours every sortie, and they were flying over enemy territory.

[phookat]

Originally posted by GScholz
Yes, MW is water-methanol, which is harmless to the engine. GM-1 is nitrous oxide, which is very corrosive.

Hmm, are you sure about that?  I thought it was the opposite.  Coming from a car perspective...if you want to run a methanol-powered car, you have to make sure your fuel system etc is stainless steel to avoid corrosion.

Nitrous, OTOH, requires no such precautions.  Squirt it in, and let the N2 split from the O in the cylinder as the piston rises.  And of course spray extra fuel to burn with the extra O.  You still have to worry about preignition just like a forced-induction engine, but no corrosion problems AFAIK.

That's why Nitrous upgrades to cars are fairly common, while methanol injection is not.

[Wotan]

No water-methanol is injected into the eye of the supercharger where it evaporates cooling the charge. This cooling allows a higher pressure  before fuel would detonate. Its not injected into the cylinders and its not a fuel additive or fuel itself. It is not burnt.

Methanol is added to keep the water from freezing. I believe it evaporates faster then water.

GM1 couldn't be run below 7000m.

[HoHun]

Hi phookat,

>Nitrous, OTOH, requires no such precautions.  

Both the Germans and the British also experimented with liquid oxygen, which was quite corrosive. Nitrous oxide was preferred because it was trouble-free in that regard.

>Coming from a car perspective...if you want to run a methanol-powered car, you have to make sure your fuel system etc is stainless steel to avoid corrosion.

I'm not sure whether that helps, but the MW50 system was separate from the normal fuel system. The MW50 (50% methanol-water mixture) was sprayed into the supercharger air intake, were it would evaporate. I guess the high speed of the intake air might reduce the corrosive effect in the intake system.

>That's why Nitrous upgrades to cars are fairly common, while methanol injection is not.

I guess car owners like to get more running time out of their engines than WW2 fighter pilots, anyway :-)

MW50 reportedly was hard on the spark plugs, which had to be changed frequently. Other than that, it seems to have been mostly trouble-free, too.

Oh, running an MW50 tank dry would have busted the engine, but as a pressure sensor cut out the extra boost if MW50 supply was exhausted, that was not a real problem.

Regards,

Henning (HoHun)

[phookat]

Originally posted by Wotan
No water-methanol is injected into the eye of the supercharger where it evaporates cooling the charge. This cooling allows a higher pressure  before fuel would detonate. Its not injected into the cylinders and its not a fuel additive or fuel itself. It is not burnt.

Methanol is added to keep the water from freezing. I believe it evaporates faster then water.

So this is really water injection, with "antifreeze" added.  Understood.

But regardless, if methanol goes into the compressor side of the SC, it goes into the cylinders, and it *does*get burned.  I would imagine that the SC would have to be stainless or something to avoid corrosion.  Maybe the rest of the intake and cylinders would not be affected as much if the methanol is a gas...but I doubt it.  Still think it would be subject to corrosion.  But even if the cylinders/intake weren't more corrosion resistant, as HoHun says, the engines weren't supposed to run 200,000 miles like a car.

Originally posted by Wotan
GM1 couldn't be run below 7000m.

Probably just because of head cooling considerations.  Intercooling/watercooling doesn't work as well for pure nitrous, since the pressure build-up (and the resultant heat build-up) happens inside the cylinder rather than in the intake/plenum.

[phookat]

Originally posted by HoHun
Both the Germans and the British also experimented with liquid oxygen, which was quite corrosive. Nitrous oxide was preferred because it was trouble-free in that regard.

Yes, makes more sense to me.

Originally posted by HoHun
I'm not sure whether that helps, but the MW50 system was separate from the normal fuel system. The MW50 (50% methanol-water mixture) was sprayed into the supercharger air intake, were it would evaporate. I guess the high speed of the intake air might reduce the corrosive effect in the intake system.

Yes, I'll admit that's possible.  Both the fact that there is much less of it (cooling injection rather than main fuel), and the fact that it is gaseous mitigate (but don't eliminate) the corrosiveness.

You can get methanol additives for cars too (say 3% fuel volume, or so).  But even at that small percentage it is recommended that you run the tank down as quickly as possible.

Originally posted by HoHun
MW50 reportedly was hard on the spark plugs, which had to be changed frequently.

Hmm, that's a little suprising.  Do you know if that was from fouling/carbon build-up, or corrosive effects?

Originally posted by HoHun
Oh, running an MW50 tank dry would have busted the engine, but as a pressure sensor cut out the extra boost if MW50 supply was exhausted, that was not a real problem.

Cool.  Yeah, seems like these German engines were pretty far ahead of their time, as far as engine management functions.

[Staga]

Heh I know only one car which did use methanol-water mixture: it was 60s Oldsmobile Jetfire.
Car had turbocharged V-8 and just like german engineers guys in GM thought that MW50 would be answer to detonation problems at higher boosts.
IIRC these systems could be driven dry without boost cut and engines weren't too  happy getting full boost without methanol-water mixture.

[VO101_Isegrim]

Originally posted by HoHun

Oh, running an MW50 tank dry would have busted the engine, but as a pressure sensor cut out the extra boost if MW50 supply was exhausted, that was not a real problem.

Regards,

Henning (HoHun)

I didn`t know that, even though I suspected it didn`t just go boom if MW was suddenly not injected (damaged lines, for example). Are you sure it worked that way ? I will add that to my site, don`t want to put rubbish in there not even by accident.