Author Topic: Interesting report on a G-14 (Read 1960 times)

GScholz · « **Reply #45 on:** August 16, 2004, 05:14:36 PM »

How is methanol corrosive? It is just alcohol. Methanol is used to clean engine parts for oil/grease. Water OTOH is corrosive to iron alloys, but as long as the engine is lubricated properly and run for a while without water injection, it should not be a problem. Water is only corrosive if it is allowed to stay in the engine for a while, and normal lubricant oil should protect the engine parts. Every engine swallows water now and then, and the air can be very humid sometimes. Never hurt an engine as long as it has oil.

VO101_Isegrim · « **Reply #46 on:** August 16, 2004, 06:10:27 PM »

Pretty much as Gscholz said; Jane`s WW2 Aircraft says that an unspecipied (i think the jumo213 or the DB 605D) German engine needed to be checked after 50 hours of operation for signs of corrosion, if MW50 injection was used. That`s quite a long time for a wartime engine, chances were that the engine was already destroyed by the time the check would be neccesary - even with very low loss rate, ie. 2%.

phookat · « **Reply #47 on:** August 16, 2004, 06:21:59 PM »

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Originally posted by GScholz
How is methanol corrosive? It is just alcohol. Methanol is used to clean engine parts for oil/grease.

Not sure what the exact chemical process is, but I do know it is a concern with car engines. Hell, I know for sure it affects RC engines. They run on methanol, and if you leave fuel in the engine for a while it will rust solid.

It might just be the hydrophobic nature of methanol, but I think it is more than that.

GScholz · « **Reply #48 on:** August 16, 2004, 06:53:19 PM »

Alcohol will suck every last bit of humidity out of the air, and if left in the engine the water will corrode the metal. The alcohol itself is harmless.

phookat · « **Reply #49 on:** August 16, 2004, 07:01:58 PM »

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Originally posted by VO101_Isegrim
Pretty much as Gscholz said; Jane`s WW2 Aircraft says that an unspecipied (i think the jumo213 or the DB 605D) German engine needed to be checked after 50 hours of operation for signs of corrosion, if MW50 injection was used. That`s quite a long time for a wartime engine, chances were that the engine was already destroyed by the time the check would be neccesary - even with very low loss rate, ie. 2%.

Yeah, given the low percentage of methanol, I can believe this. I'd definitely say GM-1 (nitrous) isn't corrosive though. Otherwise we'd have a lot of dead Honda Civics out there.

phookat · « **Reply #50 on:** August 16, 2004, 07:03:09 PM »

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Originally posted by GScholz
Alcohol will suck every last bit of humidity out of the air, and if left in the engine the water will corrode the metal. The alcohol itself is harmless.

Yeah you're prolly right, now that I think about it.

Wotan · « **Reply #51 on:** August 16, 2004, 07:59:00 PM »

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

My understanding is that with the higher boost the engine ran hottter and the plugs would foul. Carbon would build up and thus no spark.

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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

Well methanol evaporates faster then the water. Water wont accumulate due to the speed of SC and heat eng. You can get metal wet without corrosion as long as doednt stays in contact over time. Oil / lubricants protect most of the metal anyway.

The amount of heat and air will quickly evaporate the water.

MiloMorai · « **Reply #52 on:** August 16, 2004, 08:09:41 PM »

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Originally posted by Wotan
My understanding is that with the higher boost the engine ran hotter and the plugs would foul. Carbon would build up and thus no spark.

Think you have that reversed. 'Cold' plugs tend to foul. That is why the P-51s would increase their revs and boost after cruising for awhile. An engine that is 'lugging' fouls with carbon.

At higher boost and revs, the plug gap would be eroded.

phookat · « **Reply #53 on:** August 16, 2004, 08:51:52 PM »

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Originally posted by Wotan
My understanding is that with the higher boost the engine ran hottter and the plugs would foul. Carbon would build up and thus no spark.

No, it's quite the opposite in cars...cold and rich causes carbon build-up. Heat can also damage plugs, the glazing and cracking etc...but I'd have thought the MW injection would mitigate that. That's why HoHun's comment on spark plugs surprised me.

Oh well... Minor point anyway.

Quote

Originally posted by Wotan
Well methanol evaporates faster then the water. Water wont accumulate due to the speed of SC and heat eng. You can get metal wet without corrosion as long as doednt stays in contact over time. Oil / lubricants protect most of the metal anyway.

The amount of heat and air will quickly evaporate the water.

Yup, understood.

HoHun · « **Reply #54 on:** August 17, 2004, 01:17:43 AM »

Hi Isegrim,

>Are you sure it worked that way ?

I just re-checked it, and it may be that I'm wrong. The diagram I remembered as showing the cut-out actually shows a solenoid-activated warning lamp for indicating low MW50 level.

Either there's another diagram with a cut-out I can't find right now, or I confused the warning lamp with a solenoid-activated cut-out.

Regards,

Henning (HoHun)

HoHun · « **Reply #55 on:** August 17, 2004, 01:26:41 AM »

Hi Phookat,

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

No idea. Maybe the electrodes burned away due to the higher temperatures in the combustion chamber?

Von Gersdorff et al. quote 15 - 30 h spark plug life, probably based on typical engine handling (opposed to pure MW50 operation).

Regards,

Henning (HoHun)

Wotan · « **Reply #56 on:** August 17, 2004, 01:45:40 AM »

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Maybe the electrodes burned away due to the higher temperatures in the combustion chamber?

Thats what I meant.

MiloMorai · « **Reply #57 on:** August 17, 2004, 04:47:29 AM »

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Originally posted by HoHun
Hi Isegrim,

>Are you sure it worked that way ?

I just re-checked it, and it may be that I'm wrong. The diagram I remembered as showing the cut-out actually shows a solenoid-activated warning lamp for indicating low MW50 level.

Either there's another diagram with a cut-out I can't find right now, or I confused the warning lamp with a solenoid-activated cut-out.

Regards,

Henning (HoHun)

On the right side of the lower panel there was two lamps and a switch. One lamp (red) was the 'low fuel' warning and the other was lamp (white) was for 'rear tank switch over'. The switch was fuel guage selector. Is this 'rear' tank the one under the pilot or the aux. tank?

@ Crumpp

Tech description 284, dated 28.11.44

"Based on the requirement to increase a/c range without degrading its aerodynamic efficiency, provision has been made for the mounting of a protected fuel tank within the rear fuselage. After Aug-Sept 1944 all A-8 a/c will be delivered with the fuel tank. If required, instead of the 115l fuel tank, an un-protected MW tank of either 115l or 140l capacity, or a GM1 tank of 85l capacity, can be installed. At the present time, however, it is planned that the standard A-8 will be produced only with the auxliary fuel tank".

Angus · « **Reply #58 on:** August 17, 2004, 10:04:02 AM »

I always heard that Methanol had some bad aspect with corrosion.
But what exactly, I don't know.