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XyZspineZyX
11-07-2003, 02:41 PM
I've some data indicating that the compression ratio in both DB601 and DB605 engines was 7.5:1 in the left bank and 7.3:1 in the right bank.

Anyone can explain me why?

Thanks!


<center>http://www.uploadit.org/files/170903-G55_Firma.jpg </center>

XyZspineZyX
11-07-2003, 02:41 PM
I've some data indicating that the compression ratio in both DB601 and DB605 engines was 7.5:1 in the left bank and 7.3:1 in the right bank.

Anyone can explain me why?

Thanks!


<center>http://www.uploadit.org/files/170903-G55_Firma.jpg </center>

XyZspineZyX
11-07-2003, 02:55 PM
Nobody knows for sure, there are a couple of possible answers :

-assymetric air pressure in cylinders due to left mounted supercharger
-design feature to eliminate torque to some extent, or make the engine smoother running

etc.

Look for the Luftwaffe massege board, IIRC there was a good discussion about this!




Vezérünk a Bátorság, K*sérµnk a Szerencse!
(Courage leads, Luck escorts us! - Historical motto of the 101st Puma Fighter Regiment)

Flight tests and other aviation performance data: http://www.pbase.com/isegrim

XyZspineZyX
11-07-2003, 02:58 PM
Vo101_Isegrim wrote:
--design feature to eliminate torque to some extent,

Thanx!
Actually, that was my "theory"...


<center>http://www.uploadit.org/files/170903-G55_Firma.jpg </center>

XyZspineZyX
11-07-2003, 06:28 PM
Vo101_Isegrim wrote:
-
- Nobody knows for sure, there are a couple of
- possible answers :
-
--assymetric air pressure in cylinders due to left mounted supercharger
--design feature to eliminate torque to some extent, or make the engine smoother running


..... Your ideas make good sense. The only reason I can think for an engine to possess differing compression ratios would be to equalize pressure in the combustion chambers. In a low rpm four stroke engine (2500-3000 rpm), the longer intake runners feeding the opposite bank of cylinders quite possibly produced a more efficient ram effect. This would have created an imbalance in the amount of air delivered to the respective banks of the engine.

A similar case existed in the Chevrolet Mk IV V8 engine in racing usage. Due to the cylinder head design, four intake runners were slightly greater in length than the other four. This created an imbalance in the fuel/air charge delivered to the cylinders. It was solved by adjusting the lengths of the fuel injection air intakes so that overall passage length was the same for all eight cylinders. This equalized the ram effect and balanced out the combustion chamber pressures. In a case where it was not easily possible to fiddle with runner lengths, cylinder chamber pressures could still be adjusted by altering compression ratio in the affected cylinders. Elegant solution.

Very interesting.


Blutarski

XyZspineZyX
11-07-2003, 07:11 PM
BLUTARSKI wrote:
- Very interesting.


Indeed!


<center>http://www.uploadit.org/files/170903-G55_Firma.jpg </center>