P-47 boost with altitude and max turbo rpm?...

[Guest deleted@50488]

Has anyone tested the need to reduce ( retard ) the "boost" lever to maintain constant MP during climb up to critical level and specially above around 12,000', according to the following video:

 

Also, when approaching max turbo rpm is it required to significantly reduce it ?

 

Edited October 30, 2019 by jcomm-il2

[RedKestrel]

2 minutes ago, jcomm-il2 said:

Has anyone tested the need to reduce ( retard ) the "boost" lever to maintain constant MP during climb up to critical level ?

Also, when approaching max turbo rpm is it required to significantly reduce it ?

 

Above critical altitude I believe you can overspeed the turbo. That is at around 25000 feet or more though, so it doesn't often happen.

On climbs to maintain constant MP I set the throttle position and then control with the turbo lever if needed.

[Legioneod]

You shouldn't really need to retard the turbo lever to maintain mp pressure, if anything you'll need to increase turbo as you go higher to maintain MP up to critical altitude. This is due to the engine driven supercharger not being able to maintain a constant MP above a certain altitude. Manuals state it's around 7,000ft but I remember the devs stating that in-game the supercharger is only really good up to 3,000ft.

I don't usually use the turbo until my throttle cannot maintain the MP that I want, once my throttle is full forward I'll engage the turbo and use it to regulate my MP.

Edited October 30, 2019 by Legioneod

[Guest deleted@50488]

From the video linked above one should notice the difference in power if the turbocharger AND the throttle are always synced.

 

As much as 300 HP ! A difference like that would be noticeable when flying high, chasing the bombers at angels 20+

 

I don't have IL-2 GB installed right now, so I can't test it.

[Legioneod]

40 minutes ago, jcomm-il2 said:

From the video linked above one should notice the difference in power if the turbocharger AND the throttle are always synced.

 

As much as 300 HP ! A difference like that would be noticeable when flying high, chasing the bombers at angels 20+

 

I don't have IL-2 GB installed right now, so I can't test it.

I never fly with them connected so I couldn't say if it's modeled or not. something like that should be modeled though, wouldn't be too hard to test imo.

[RedKestrel]

4 hours ago, jcomm-il2 said:

From the video linked above one should notice the difference in power if the turbocharger AND the throttle are always synced.

 

As much as 300 HP ! A difference like that would be noticeable when flying high, chasing the bombers at angels 20+

 

I don't have IL-2 GB installed right now, so I can't test it.

That doesn't seem right, the manual tells you to never let the turbo get ahead of the throttle. You can only have the turbo equal to or behind the throttle in that regime, so unlinking the throttle from the turbo should only be necessary when cracking the throttle on the ground for startup, and for delinking it and moving the turbo back above critical altitude to avoid overspeeding. So where would the loss of horsepower come from? It sort of implies there are situations where reducing the turbo would increase horsepower....

[Legioneod]

39 minutes ago, RedKestrel said:

That doesn't seem right, the manual tells you to never let the turbo get ahead of the throttle. You can only have the turbo equal to or behind the throttle in that regime, so unlinking the throttle from the turbo should only be necessary when cracking the throttle on the ground for startup, and for delinking it and moving the turbo back above critical altitude to avoid overspeeding. So where would the loss of horsepower come from? It sort of implies there are situations where reducing the turbo would increase horsepower....

Having the turbo and throttle interlinked is less efficient due to the engine driven supercharger and turbo supercharger both drawing power to operate. If you have the controls interlinked you'll reach higher MP before the throttle is in the full forward position and as a result you're really using two superchargers to do what one alone could do. As a result you're running the engine less efficiently and losing (wasting) power.

 

I'll record a video later to try to show what I mean. It's kinda hard to explain but makes sense once you see it.

 

Best way to operate the P-47 is to advance the throttle full forward and use turbo to maintain MP, it's more labor intensive but will give you the most power for a given altitude.

Edited October 31, 2019 by Legioneod

[ZachariasX]

31 minutes ago, RedKestrel said:

So where would the loss of horsepower come from?

It requires about 300 hp to spin the first stage supercharger coupled to the engine. This supercharger does only run efficiantly at high rpm. This is why you want the throttle wide open first and only then start to compensate by using the turbocharger as needed. If you understand this, lever settings are obvious.

 

The linkage comes handy as settings on the throttle valve have immediate effect on power output, while adjusting the wastegate and thus modulating the turbo rpm are slow in responding. Formation flying is a poster boy use for a situation, where you want quick power changes. Then you can link the levers. But it you want power (or economy), then don't.

[RedKestrel]

2 minutes ago, ZachariasX said:

It requires about 300 hp to spin the first stage supercharger coupled to the engine. This supercharger does only run efficiantly at high rpm. This is why you want the throttle wide open first and only then start to compensate by using the turbocharger as needed. If you understand this, lever settings are obvious.

 

The linkage comes handy as settings on the throttle valve have immediate effect on power output, while adjusting the wastegate and thus modulating the turbo rpm are slow in responding. Formation flying is a poster boy use for a situation, where you want quick power changes. Then you can link the levers. But it you want power (or economy), then don't.

Thank you, that's a helpful explanation.

16 minutes ago, Legioneod said:

Having the turbo and throttle interlinked is less efficient due to the engine driven supercharger and turbo supercharger both drawing power to operate. If you have the controls interlinked you'll reach higher MP before the throttle is in the full forward position and as a result you're really using two superchargers to do what one alone could do. As a result you're running the engine less efficiently and losing (wasting) power.

 

I'll record a video later to try to show what I mean. It's kinda hard to explain but makes sense once you see it.

 

Best way to operate the P-47 is to advance the throttle full forward and use turbo to maintain MP, it's more labor intensive but will give you the most power for a given altitude.

Yeah, that is the way I fly the P-47, I don't bother with the interlink much as I don't do much formation flying. Plus moving the levers makes me feel more like a real pilot ?

[Venturi]

Actually the reason why it is more efficient to have throttle full forward and adjust MP with turbo (or with RPM if in S/C only planes - within reason given detonation parameters IRL) is that the throttle "butterfly" is increasing turbulence and resistance in the intake airstream when partly closed. When open, it is more laminar and resistance is reduced.