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Hanglands
09-22-2006, 09:31 AM
Hi,

I just read that the Daimler Benz 605 engine had different compression ratios in each line of cylinders. Something like 7.3:1 on the left, and 7.5:1 on the right. Turns out the DB603 did too.

As far as I can make out, the 601 had the same compression ration on all cylinders, as did the Merlin, and other contemporary engines.

So why did the 605 and 603 have this difference in compression ratio? I cant seem to find out anywhere

Kurfurst__
09-22-2006, 11:52 AM
I've seen a few explanations, but no definiete ones : it's supposed to be a practice to smoothen out engine running, and also some suggest the reason was the sidemounted supercharger. Probably the latter, it sound reasonable.

WB_Outlaw
09-22-2006, 04:26 PM
This is just a guess but like Kurf said, maybe the supercharger charged one bank a bit more due to location and/or intake design.

--Outlaw.

Hanglands
09-22-2006, 04:44 PM
Thanks for the answers guys.

So, the compression ratio is set differntly to compensate for the resistance in the intake manifold?

Im no engineer, but Im guess it means that as the supercharger intake is on the left, the supercharger is on the left, and so the intake manifold pressure is higher on the left hand side of the engine. To get to the right hand side of the engine it has to overcome the resistance of the extended intake manifold and so loses pressure which is compensated for by a higher compression ratio???

Thank you once again.

Sergio_101
09-22-2006, 06:25 PM
Originally posted by Hanglands:
Thanks for the answers guys.

So, the compression ratio is set differntly to compensate for the resistance in the intake manifold?

Im no engineer, but Im guess it means that as the supercharger intake is on the left, the supercharger is on the left, and so the intake manifold pressure is higher on the left hand side of the engine. To get to the right hand side of the engine it has to overcome the resistance of the extended intake manifold and so loses pressure which is compensated for by a higher compression ratio???

Thank you once again.

Good question, no official answer here.
But I suggest it has to do with compensating
for another variable such as cam timing, intake
runner length, coolant flow, or canceling out a vibration issue.

But I got to think it's a cooling issue.
I have no clue as to the coolant flow path
for a DB-605 and I can not find it here or on line.
I can tell you that cylinder head temp is
a very important factor in controling detonation.
If one bank runs hot, the compression can be
dropped a tad to offset a detonation problem
and have a minimalised power and effinency loss.

Sergio

luftluuver
09-23-2006, 09:20 AM
Yes I can see that some are not engineers and even failed their highschool science. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

The outlet of the supercharger was one tube that fed an 'O' shaped manifold. The manifold is tapered to compensate for the pressure drop lost to the cylinders closest to the s'charger.

http://aircraftwalkaround.hobbyvista.com/db605/DB%20605.JPG