Inverted V engine vs. V engine

[DonL]

I have found some very interesting report and flying Test from Daimler Benz.
And it was totaly new for me that there was a Spit tested with an inverted german engine.

At 18.05.1944 a captured Spitfire V was tested with an normal production DB 605A from DB at Echterdingen. The trials were made without weapons and some very interesting results.

The DB guys were truly amazed about the water cooling system of the Spitfire and the very small surface of the watercooler. It was half (50%)as small as the water cooler from a Bf 109G but only less then 4% effective.
In flying condition the water cooler and water cooling system was good enough for the larger DB 605, but there were some problems at warm up and roll up at the ground.

THe oilcooling system of the Spitfire was too small for the DB 605 and the test crew had some major problems at the test trials with full power climbing, because the engine was to fast to hot (oil) for a full power climb. Only at high altitudes the engine could flown permanent with full power.

From the DB crew was stated that the merlin 45 was generally approved for higher temperature (oil and water).

But also with this handicap and not a full power climb, the Spit V with DB 605A was very significant faster in climbing then a Bf 109G.

The other very interesting summary was, that the Spit V with DB 605A was much much faster above the full output performance (6700m), by comparison to a Spit V with Merlin 45 that was tested in Rechlin.

Spit V with DB 605:
6700m ----> 610km/h (full output perfrormance)
7000m-----> 609km/h
7500m ----> 605 km/h
8000m -----> 600 km/h
8500m ----> 595 km/h

Spit V with Merlin 45 (testflight Rechlin)

6200m -----> 605km/h (full output perfrormance)
6700m -----> 601km/h
7000m -----> 598 km/h
7500m -----> 590 km/h
8000m -----> 578 km/h
8500m -----> 560km/h

The power drop and the lost of speed was much slower with the DB 605A compared to the Merlin 45

The report is only available in german.
http://cms.klassiker-der-luftfahrt.de/sixcms/media.php/58/Spitfire_Versuchsbericht.pdf

I can translate parts of the test if someone is interested.

 

[wuzak]

I think the DB605 would have better altitude performance than the Merlin 45 because of the rated altitudes of the two superchargers, and the fact that the Merlin 45 has a single speed single stage supercharger, the DB605 had a variable speed supercharger.

 

[Tante Ju]

I read report. It says: loss of performance with Merlin is greater, because compare to DB, Merlin has insufficient displacement. So loss power is quick above nominal altitude.

This make sense - Merlin obtains power by supercharging, very hard supercharging to DB.. compared, manifold pressures.. FAR greater on Merlin. So when this pressure falls, above nominal altitude.. its again a wheezy 27 liter engine vs. a big 35 liter engine with bigger "lungs".

Also I can think - DB has high compression ratio. RR has low - 6 vs 7.5 on DB.. this is advantagous for DB at altitude. Engine does more work on same amount of oxygene..

 

[Mustang nut]

Merlin obtains power by supercharging, very hard supercharging to DB.. compared, manifold pressures.. FAR greater on Merlin. So when this pressure falls, above nominal altitude.. its again a wheezy 27 liter engine vs. a big 35 liter engine with bigger "lungs".

Also I can think - DB has high compression ratio. RR has low - 6 vs 7.5 on DB.. this is advantagous for DB at altitude. Engine does more work on same amount of oxygene..

I thought the compression ratio was chosen based on manifold pressure. The higher the manifold pressure the lower the compression ratio or you get detonation, or am I wrong?

 

[Tante Ju]

Yes, you are right.. both manifold pressure and compression work against detonation.. I do not know why this was choosen.. but high compression - better output at all altitude (slightly - this is DB style), high manifold pressure - better output until supercharger can deliver air for it to burn more fuel.. this is RR path.

I only understand from discussion I have read this may be cause of notice in DB report - Merlin Spit loose performance faster in altitude than DB Spit.. I think power was not so different in M45 and D605 as first think.. but M45 loose it faster in altitude.

 

[wuzak]

Yes, you are right.. both manifold pressure and compression work against detonation.. I do not know why this was choosen.. but high compression - better output at all altitude (slightly - this is DB style), high manifold pressure - better output until supercharger can deliver air for it to burn more fuel.. this is RR path.

I only understand from discussion I have read this may be cause of notice in DB report - Merlin Spit loose performance faster in altitude than DB Spit.. I think power was not so different in M45 and D605 as first think.. but M45 loose it faster in altitude.

Because the supercharger was a single speed single stage unit with a critical altitude of about 18,000ft. After that altitude the power drops off fast. With the two stage unit the critical altitude is higher.

 

[Tartle]

It would be interesting to compare the Merlin 61 in the Spitfire IX which has a two speed supercharger...designed to deliver a higher high altitude performance to combat the FW190... the Spitfire performance site has this report on the Spitfire IX. The Merlin 45 was meant to be a quick development to restore parity of the Spit with the Me109 models introduced in the Autumn/winter of 1940, whilst the Spitfire III was developed with the 9 inch longer Merlin XX. The Hurricane II got first supplies of M.XX in order to improve the odds for that aircraft as Hurricane I was losing out.

People are confused by the superiority, or not, of \/ or /\. The main issue is that this was a fight for superiority between two development teams, two supply chains and two military forces, all making political decisions. Essentially Kranzberg's first law applies: Technology is neither good nor bad, neither is it neutral. It turned out that the most innovative development of what was needed, when it was needed went to the R-R team and the system that allowed people to do things they had been told not to do and then focus on delivering them; whilst the BMW team, etc, seem to have had more constraints on what they should do.
It is likely, in my opinion, that the \/ and a mechanically coupled supercharger plus improving fuel ON was better than the /\ plus a hydraulic supercharger plus uncertain supplies of improving ON fuel... but the difference was not as big as we might have thought... but a perspective 70 years on might not be how it seemed at the time!

 

[Tartle]

It is the charge that counts.... the higher overall compression of the charge (=air+fuel, if carburetted), allows more bmep to be generated which equals more horsepower. so a low compression ratio engine plus a high pressure ratio supercharger will behave similarly to a high compression ratio plus lower pressure ratio s'charger as it is the temperature and pressure in the combustion chamber that, for a given fuel, determines the onset of detonation... to a first order.

 

[wuzak]

It would be interesting to compare the Merlin 61 in the Spitfire IX which has a two speed supercharger...designed to deliver a higher high altitude performance to combat the FW190... the Spitfire performance site has this report on the Spitfire IX.

The IX would eventually be built in standard (Merlin 61 or, later 70), LF (Merlin 66) and HF (Merlin 70). The Merlin 66 was the low altitude two stage engine, with a critical altitude in MS around 7,000ft, compared with over 11,000ft for the M70. Similarly the critical altitude in FS gear was 18,000ft for the Merlin 66 and 24,400ft for the Merlin 70.

 

[Tartle]

Thanks Wuzak!
The 66 came about when the Luftwaffe realised that although at very high attitudes the Spitfire IX neutralised the FW190... at 18,000 to 22,000ft (if memory serves me well!) the DB engine gave their aircraft better performance...so they decided to operate at this altitude, not higher. This resulted in cropping the impeller on the Merlin 61 to enable the Spitfire to match performance at a lower altitude... in the Egyptian theatre Spitfire IXs had not been introduced so Ronald Harker, who was out there to get service feedback for RR, contacted Derby and asked how to get more power at 6,000ft by enabling +18 lbs boost to be used ... take 3/4" off the diameter, which the local machine shop did to three Merlin 45 of the Spit V and testing showed that this gave them full boost at the required altitude.. the Merlin 50 was born!
The charge story is set out in this paper.

 

[Readie]

And then came the Griffon which beat all DB's hands down.
Which in a circular way goes back to my original point that there is the right way to have an engine and the wrong way. RR was right, and the rest is history.
There have been many blind alleys with engine development and although they had merits they couldn't cut the mustard in the real world. Wankel, Wartburg to name a few.
Cheers
John

 

[rednev]

Which in a circular way goes back to my original point that there is the right way to have an engine and the wrong way.
Cheers
John[/QUOTE]

What greatness might have been achieved if only they had not put the engine in the tiger moth the wrong way.
Might conceviabley gone on to be one of the great planes of history oh well opportunity lost.

 

[DonL]

And then came the Griffon which beat all DB's hands down.

I don't see this clear advantage!

DB 603N 1944/45; C3 fuel; two stage supercharger, dry weight 950kg; 2800PS!

Jumo 213J 1944/45, B4 fuel, two stage supercharger, dry weight 920kg; 2240PS!

 

[Shortround6]

I don't see this clear advantage!

DB 603N 1944/45; C3 fuel; two stage supercharger, dry weight 950kg; 2800PS!

Jumo 213J 1944/45, B4 fuel, two stage supercharger, dry weight 920kg; 2200PS!

Refresh my memory please?

How many of each were built and what planes were they in service with?

Post war (1949) French built Jumo 213 was rated at 2300hp for take off but weighed 960kg dry with a single stage supercharger. Using 100/130 fuel.

 

[DonL]

Both were production ready and had several 1000 hours Teststand at the end of 1944!

How many of each were built and what planes were they in service with?

You should look at the german situation at the begin 1945.

Anyway about what do we talking here?

I think about engine design!?

So I will compare what was developed!

And it was Readie's statement that inverted was the wrong way and the Griffon will beat all DB engines"Hands down"!
I can't see this with the knowing of all engines that were in development and production ready.

Post war (1949) French built Jumo 213 was rated at 2300hp for take off but weighed 960kg dry with a single stage supercharger. Using 100/130 fuel.

Seriously you want to compare the development department from Junkers with some unknown french company?
Was this French built Jumo a 4 valve engine like the Jumo 213J?
Sorry but the Jumo 213EB from 1944 with C3 fuel and two stage supercharger, dry weight 920kg had already 2000PS with a two stage supercharger.

 

[Shortround6]

Both were production ready and had several 1000 hours Teststand at the end of 1944!


You should look at the german situation at the begin 1945.

Anyway about what do we talking here?

I think about engine design!?

So I will compare what was developed!

Test stand and so called "production ready" are not the same as in service. See R-R Vulture, Napiar Sabre, Wright R-3350 and P&W R-4360 for engines that were "tested and Production ready" that gave several years of trouble upon being introduced to service.

Seriously you want to compare the development department from Junkers with some unknown french company?

This unknown french company? Arsenal de l'Aéronautique - Wikipedia, the free encyclopedia

By the way they also developed a co-axial countra rotating propeller gear box for the Jumo 213, Used Jumo 213 cylinder blocks to make an H-24 cylinder engine and by 1953 had built and "tested" a compound 213 using an exhaust turbine to feed power to the crankshaft.

Now maybe the French engines were heavier because they couldn't get (in 1948-53) the raw materials/alloys the Germans had access to in 1944 (sarcasm) or maybe there is a difference in what is included in "dry weight" but the idea that you can go from three valve heads to four valve heads and add a complete stage to the supercharger and increase peak rpm by 450rpm and add not one kilogram of weight to the engine needs an awful lot of swallowing.

I can't even find sources that agree on what the Jumo 213J was (one source says an armored engine for ground assault??)or even if it was ever built, at least in English.

I may not agree with Readie on the inverted thing without more proof but using near fictitious engines (or test engines vs service engines) as a rebuttal doesn't help things.

 

[Tartle]

...and don't forget the trials and tribulations of the first production Merlins with their ramphead cylinder design that cracked very quickly; measures had to be taken that were a challenge to the production machine and the real answer did not appear until the two-piece head designed at Derby but first in production at Packard on the Merlin 28... which was a XX with the new head; Derby were next with the Merlin 61, first one despatched Christmas Day 1941. So the questions we need to ask are:
Has the engine got potential at test stage; did it deliver at service potential stage; did it deliver in-service. The Napier Sabre is an engine with potential that had huge manufacturing problems that had to be overcome not by Napier but first by Bristol (sleeve-valves) and then by English Electric who bought Napier's and took the development programme by the 'scruff of the neck' to get the development engineers to concentrate on today's tactical issues rather than tomorrow's strategic ones. The maintenance burden on the RAF was so high in the autumn of 1944 that a great deal of new engines were being made for replacement in-service as the numbers coming back were causing problems for the overhaul teams.. but it had to be done.
I am not sure what the DB situation was so I cannot make a comparison, other than to say the complexity of the engine has an influence too.
The Griffon had the benefit of being 5 years later than the Merlin and with no shadow factories to support had features that were major improvements, some of which made their way into the late-model Merlin 100 series..the end feed main bearing lubrication system being one of the most effective.
Daimler Benz certainly evolved their main bearing design going from plain to roller to plain bearings as the war and mark number progressed (help needed from DB experts!). Was some of this due to oil aeration challenges as bearing loads and operating altitudes increased... but it really is about good technology choices in the first place together with a supportive organisation and willing 'customers' = success!

 

[Tante Ju]

And then came the Griffon which beat all DB's hands down.

Cheers
John

I do not agree with this. The Griffon was in class of DB 603, Jumo 213. I do not see how it was beter engine. In 1943, available was single stage Griffon, produce in small numbers. Certain no better than 603A or 213A, probably inferior in altitude.

In 1944 produce is 65 series Griffon. This is good engine, excellent high altitutude output but had bearing faults, engine life was very very short, and so few produced I do not know even counts compare. Maximum output is about 2000-2200 HP, depend on use of fuel, again similiar to wide produced 213A or small series 213E type, or 603L series. Like Merlin to 605, the Griffon is very fuel inefficient compared to DB.

In end 1945 there is engine like 603N like DonL said, and Griffon do not compare, inferior all respects IMHO. So I think issue is not so clear as you place.

 

[Juha]

Hello Tante Ju
it is how one definite "small numbers", there were some 850 Fairey Firefly Mk Is and IIs, powered by Griffon Mks IIB or XII, 100 Spit Mk XIIs powered by Griffon Mk II or IV, plus several prototypes, cleaerly more than 1000 single-stage early Griffons were produced during the WWII. And yes, Griffon was a "thirsty" engine.

Juha

 

[Tante Ju]

Juha, you are right. I was mind only Mark XII series Spitfires. Fireflies, I was complete ignorant of them!
In my mind, 1000 engine is rather limited in production. Same true for 603 and 213 production - for 1943!