Difference in RPM between between Bf 109 E-7 and Bf 110 E-2

[kramer]

Why there is a difference in RPM between DB-601A in Bf 109 E-7 and Bf 110 E-2?

In Aircraft Flight and Technical Specifications both should have   

Quote

Boosted power (up to 1 minute): 2400 RPM, 1.4 ata

And at the game Bf 109 E-7 have 2600RPM with 1.4 ata.

What's the reason?

[FlyingH]

As the 110 is a much heavier machine I´d guess it puts a lot more strain on the engine thus the restriction in time and revs!

[Bremspropeller]

Probably a different prop-diameter, but the same reduction gear.

[Finkeren]

40 minutes ago, FlyingH said:

As the 110 is a much heavier machine I´d guess it puts a lot more strain on the engine thus the restriction in time and revs!

 

The weight of an aircraft can’t really put more “strain” on the engine in any way.

[kramer]

But in "manual" topic there is 2400RPM for Bf109E-7 also. And automation in game gives you 2600RPM with 1.4 ata.

[ATAG_kiwiflieger]

I think the Bf 110 E-2 had DB601B engines - almost the same as a DB601A, but different reduction gear, something like 1:1.88 on the B vs 1:1.55 on the A.

 

Some 110s also had the DB601P, the changed-reduction gear version of the DB601N, used in the 109 E-7N and F-2.

 

I guess that might explain it?

[kramer]

Not exactly because there is an info in E-7 section it should be 2400RPM with 1.4 ata and there is 2600RPM with 1.4 ata.

[=TBAS=Sshadow14]

AFAIK Different super charger.
1 holds boost better at higher RPM (thermal efficiency) (just like my car makes 14psi boost @ 5000rpm and by 7200 rpm it tappers off to 9psi as the turbo goes past its efficient range.)

without a visible power curve its hard to tell 
Or the factory specs stating the reason ?

 

Edited August 11, 2018 by =TBAS=Sshadow14

[69th_chuter]

Wow.  The question is why does the 109E-7 have a higher engine redline than the 110E-2 in game versus the game showing them using the same DB601A engines (technically they can't, the 110 prop is 12% bigger, the equivalent engine would be the B, the same engine with lower gearing).  Neither prop ratios or superchargers by themselves are going to change the redline.  A quick look at real data seems to show the 109E-7 as having the DB601A, DC601Aa and DB601N engines, the Aa should (?) be the likely version for in game.  That engine had a nominal redline of 2500rpm (the A had a 2400rpm limit).  The 110E-2 had the DB601P (just a lower geared DB601N) engine with a redline of 2600rpm.  I'm not sure what's up with the game.

 

All tach readings are crankshaft so prop gearing, again, isn't a factor.

[IckyATLAS]

3 hours ago, chuter said:

Wow.  The question is why does the 109E-7 have a higher engine redline than the 110E-2 in game versus the game showing them using the same DB601A engines (technically they can't, the 110 prop is 12% bigger, the equivalent engine would be the B, the same engine with lower gearing).  Neither prop ratios or superchargers by themselves are going to change the redline.  A quick look at real data seems to show the 109E-7 as having the DB601A, DC601Aa and DB601N engines, the Aa should (?) be the likely version for in game.  That engine had a nominal redline of 2500rpm (the A had a 2400rpm limit).  The 110E-2 had the DB601P (just a lower geared DB601N) engine with a redline of 2600rpm.  I'm not sure what's up with the game.

 

All tach readings are crankshaft so prop gearing, again, isn't a factor.

If I am correct the  RPM mentioned above is the engine crankshaft rotation speed. What was the propeller rotation speed, or the gear ratio? 

[69th_chuter]

The 109E had a 1:1.55 ratio (1548:2400 and 1612:2500) and the 110E had 1:1.88 ratio (1382:2600).

 

Fun Facts:  Prop tip speeds for the 109E7 are 553mph (2400rpm) and 576mph (2500rpm) and for the 110E are 575mph (2600rpm).

Edited August 13, 2018 by chuter

[RedKestrel]

Guys, I think OP is saying that the aircraft tech specs say 2400 RPM but you achieve 2600 RPM in game. So the tech specs may be wrong.

[69th_chuter]

12 hours ago, RedKestrel said:

Guys, I think OP is saying that the aircraft tech specs say 2400 RPM but you achieve 2600 RPM in game. So the tech specs may be wrong.

 

 

Yes, the in game tech specs are wrong on several counts, not the least of which is the callout for the DB601A in the 110E.

[6./ZG26_Klaus_Mann]

The E-7 simply has the RPM Increase for better Full Throttle Altitude, so it's really only useful above 5.5k. 

 

Edited August 15, 2018 by 6./ZG26_Klaus_Mann

[kramer]

So automatic mode should allow only 2400RPM below 5,5km and 2600RPM above 5,5km.

At the game it allows 2600RPM even below 5,5km.

Thnks for the document.

[6./ZG26_Klaus_Mann]

Incorrect. Full Throttle (1.4 ata) is meant as Take-Off Power only, and after  Lift Off and clearing Obstacles at below 200kph is to be reduced to normal Climb or Cruise Settings. 

At Full Throttle below 200kph the Propeller barely manages 2100 to 2400RPM, and is reduced right after Take-Off, so Limiting RPM after that is no longer necessary. 

Even in Combat you aren't supposed to use more than 1.3ata which is at 2400RPM as per Standard.

 

All you do as you get higher and want to maintain 1.3 is to just move the Lever further Forward without exceeding 1.3ata while increasing RPM. 

[kramer]

So without disengaging automatic device pilot was not able to pull 2600RPM lower then 5,5km? Or he had to be carefull not to exceed 2400RPM and regulate ata/RPM manually below 5,5km even with automatic device?

Edited August 17, 2018 by kramer

[6./ZG26_Klaus_Mann]

The Device did not adjust RPM by Altitude. It wasn't necessary. The 2600RPM were bound to Absolute Full Throttle only, raising gradually from 2400 to 2600 from the 1.3ata Position to the 1.4ata Position where before the Kommandogerät would simply allow for 2400RPM at 1.3 as well as 1.4ata. 

Because 1.4 ata were intended purely for Take-Off Power, and all other flight to be at 1.3ata and less, limiting RPM was not necessary. 

On Take-Off the Propeller mounted was unable to achieve more than 2400RPM as it's finest Pitch was still too coarse, so below 200kph 2600RPM were simply not achievable, and such a Limitation thus not necessary. 

 

So you just used the Automatic Device normally, and only moved it over the 1.3ata Position above 5.5k ONLY to maintain 1.3ata, as the higher RPM allowed it to maintain this Boost at Higher Alitude.

 

As we all know. the Amount of Fluid a Centrifugal Compressor can move grows exponentially with RPM, while Air Requirement of the Engine only grows Linearly with RPM. So adding more RPM means you can normalize the Engine for Higher Altitude. 

 

[kramer]

So:

1) for take-off you can go full throttle because you won't exceed the RPM due to lack of speed

2) Below 5,5km you have to be careful and restrict yourself manually not to exceed 1.3ata and 2400RPM, you shouldn't go full throttle

3) Above 5,5km you can go full throttle and 2600RPM for short amount of time

correct?

Edited August 17, 2018 by kramer

[6./ZG26_Klaus_Mann]

True, except you don't have to be careful about Point 2. Just leave it in Automatic, and 1.3 ata will maintain 2400rpm low down. And in Emergencies you can go Full Throttle, but you have 1 Minute and not a Second more. 

Not really a lot of Care has to be taken. 

[kramer]

So to conclude there is just a mistake in manual which say: Boosted power (up to 1 minute): 2400 RPM, 1.4 ata. It should be 2600 RPM.

 

And in case of Bf110E-2 you have still one minute with 1.4/2400RPM. 

[6./ZG26_Klaus_Mann]

Well, it was never part of any of the Manuals, as the E was replaced by the F at the same time. 

 

The Ingame Manual is correct in so far as the 1.4/2400 is the desired Take-Off Setting and not to be used afterwards. The Time Value (1 Minute) is also given for the Take-Off Setting only, and at 2600RPM is considerably shorter, as it is not really an existing Powersetting. 

[kramer]

Interesting. Thanks for the details anyway.