DB 600 compression ratios

DB Compression ratios.

It is often asked, “why wasn’t this uneven oil consumption a problem with the DB 601 (or DB 600, for that matter)”.
The answer is, it probably was but it needs to be remembered that the DB 600 series engines were designed and put into production very quickly and so, it is quite possible that the problem took some while to filter back to the manufacturer. It may well have been a fact that overhauled DB 601 engines were fitted with low compression pistons in the left-hand bank.
The original hand books and data sheets would, of course, only mention the single compression ratio figure.
It would be an interesting exercise for the Bf 109 experts to check if photos of Bf 109’s in service had dirtier, sooty exhaust stains on the left side of the cowling as compared to the RHS.

If the different compression-ratios are being quoted the wrong way round that would explain my confusion!

Sorry, don’t have any REFERENCES but I still find it a surprising conclusion.

Can the difference in oil contamination between the cylinder blocks have been that significant? Why wasn’t it a problem on the DB601 that had an identical layout but also a single common compression-ratio?

Maybe it’s a sixty-year-old wind-up by the Daimler-Benz engineers! :diablo:

DB CR’s

Some books list the figures as, for example, 7.5/7.3 while others give the figures the other way round!
The left hand bank would have the lower CR.
This was a problem of oil consumption, or more precisely, a problem due to UNEVEN oil consumption according to the conversations the Rolls-Royce engineers had with the D.B. people very shortly after the War’s end.
If anyone has a REFERENCE to dispute this, please post it.

Interesting to read one’s thoughts from a past thread!

I don’t think this is a problem of oil consumption, in a conventional sense, when oil consumption of large aero-engines is measured in litres-per-hour!

Possibly fuel/air charge oil contamination is a better description.

Considering the distribution of crankcase oil between the cylinder blocks; instinctively I would think that the block on the side with the ‘downward’ rotation of the crank would get more oil. Is this the case?

DB603 crank rotates anti-clockwise, as seen from cockpit, (propeller clockwise) so more oil should end-up in left-hand cylinder block, as seen from cockpit. So according to ‘detonation’ theory left-hand cylinders should have lower compression-ratio.

Except that the compression ratio of the left-hand cylinders is higher (7.5:1) than the right-hand cylinders (7.3:1).

Or are the left-hand/right-hand cylinder blocks the other way round? :confused:

DB 600 series differential compression ratios.

Attached is a copy of page 4 of a 6 page article I did on this topic some time ago.
This particular page quotes the only concrete reference I’ve ever come across pertaining to the matter.
The different CR’s were introduced because of an OIL CONSUMPTION problem, not off-set supercharger or articulated con-rods (which the DB 600 series engines never had).

Thanks Galdri,but it`s a lot of fanciful thinking,no references,and no `factual` info.

Not a new topic. Search is your best friend.
http://forum.keypublishing.co.uk/showthread.php?t=71140&highlight=Benz+engine