daimler benz 605

[danielp]

does anybody know the reason why on a lot of literature of the daimler benz engines it list one compression ration for the laft cylinder bank and another for the right bank ?

[kettbo]

I've seen this too.
I think it has something to do with the Flux Capacitor

Seriously, I believe I have a resource for this for an exact answer, but I recollect ducting and supercharger efficiency

[HoHun]

Hi Danielp,

>does anybody know the reason why on a lot of literature of the daimler benz engines it list one compression ration for the laft cylinder bank and another for the right bank ?

Since the supercharger is mounted on the port side of the engine (you might have noticed the forward-facing air intake on pictuers of the Me 109, fore example), the ducting to the starboard side is longer and has to bend around the engine, which I understand results in a slight drop in charge pressure for the starboard cylinder bank.

If my understanding is correct, the compression ratio should be a bit higher on the starboard bank. If it's actually higher on the port bank, I must have screwed up somewhere

Regards,

Henning (HoHun)

[danielp]

I am kind of confused now. yes the daimler benz has the intake and super charger on the port side. the jumo series has it on the starboard side but i have not seen to my recollection different compression rations associated with them. would not the inefficency's also effect them as well or did jumo run the plumbing differently.

and I had read somewhere that it had to do with the windage internally of the oil being thrown to one side and that it would accumulate more on one bank than the other and leak into the combustion chamber and require the different compression because it would add to the fuel being burned in the side.

[wilbur1]

Originally Posted by danielp

I am kind of confused now. yes the daimler benz has the intake and super charger on the port side. the jumo series has it on the starboard side but i have not seen to my recollection different compression rations associated with them. would not the inefficency's also effect them as well or did jumo run the plumbing differently.

and I had read somewhere that it had to do with the windage internally of the oil being thrown to one side and that it would accumulate more on one bank than the other and leak into the combustion chamber and require the different compression because it would add to the fuel being burned in the side.

I dont know if this will help but here goes, in automotive when you have two separate banks of cyl, the one farthest away from your pressure point usually has higher comp to help with pressure loss in the intake tract, in the case of mazda, they did it to help combat detonation from higher intake temps. Hope that helps.

[jerryw]

Danielp, you have just about answered your own question! The reason for the different compression ratios in the left and right cylinder banks was due to the difficulty experienced by DB in controlling the oil consumption in the inverted V-12 engine.
In the DB 601/5, the crankshaft spins anti-clockwise (as seen from the rear) and due to the windage, shape of the engine and gravity, more oil gets sprayed into the LHS bank compared to the RHS. (Remember, these engines had three-row roller bearings in the con-rod big-ends which allowed more oil to pass than conventional shell bearings.)
This excess oil would get past the piston rings and into the combustion chambers. If too much oil gets mixed with the fuel it lowers the octane rating and causes detonation. Thus they had to lower the C.R. of the left hand bank cylinders. It was a very crude solution to the problem.
The different CR's had NOTHING to do with the side-mounted supercharger!!

[Eric Decamps]

DB 601/605

It' an interesting answer but there isn't difference between the two cylinder block in the DB 601!
DB 601 engine manual shows one C.R of 1:6,7 for the two!

Best regards!

Eric

[seesul]

ask here LuftArchiv.de - Das Archiv der Deutschen Luftwaffe and I´m sure you´ll get your answer in one day...
If you want I could ask there, just let me know...

[Denniss]

DB603A manual shows 1:7.3 on the left side and 1:7.5 on the right side. Similar variable ratios are shown in DB605 manuals or data tables. The separate compression ratio may have not been used in the DB 601A/B, Aa/Ba and N/P series. It was probably introduced with the DB601E/F/G with 1:7.0 left and 1:7.2 right.

[Eric Decamps]

I Can confirm that none of DB601 model had different CR!
This modification was introduced in DB 603 and in the next models.
After reading technical documents and the book of Kyrill Von Gersdorff "Flugmotoren und Strahltribwerke", it appears that this CR was used to correct the small drop in manifold pressure in the R cylinder block owing to the design of the induction manifold. (See personal photos; the induction manifold connecting the R cylinder block is longer, so drop in manifold pressure for the R block and so increase in CR to correct it).
Don't forget! German engineers worked to improve the performances of the DB 601 E with minor modifications!
(Increase of RPM, altered valve timing to increase volumetric efficiency, increasing bore with existing cylinder center, repositioning of the sparks plugs and... different CR between the two blocks)


Best regards

Eric

[jerryw]

The explanation in the von Gersdorff book is, like many given on this forum, is just guess work and it is WRONG. How could there possibly be "a small drop in manifold pressure on the right side, etc" if the two halves of the manifold were JOINED at the front!
The compression ratios for the cylinder banks on the DB601 engines were the same because the engine had gone into production before the problem was recognized.

[HoHun]

Hi Jerryw,

>How could there possibly be "a small drop in manifold pressure on the right side, etc" if the two halves of the manifold were JOINED at the top!

Air is a gas.

Regards,

Henning (HoHun)

[mad_max]

Different lengths and different angles in the manifolds would effect airflow to the cylinders. Yes a small difference in pressure/airflow will show itself.

[jerryw]

If you thought the induction piping of the DB 601 was a bit lop-sided, have a look at this sketch of the intake tubes for the Junkers 211A (from Flight, 1940).
Entry to the "I" section is distinctly offset and the cylinder head common rails receive their feeds from very odd entrances.

[kool kitty89]

Was the supercharger always on the port side (left when viewed from behind) of the Jumo? I seem to rember seeing intakes on the starboard side for the 211.



Edit: Nevermind, It's inverted... :embarassed: Thus that diagram is of the bottom of the engine. Pics like this don't help either: