manifold pressure regulator after WEP

[saburo_cz]

Hi,

manifold pressure regulator works during normal engine operation corectlly

but

 

when i engage WEP then it stops working.

I tried to fly with engine setting 46inHg/2700, before WEP regulator keeps manifold pressure from sea level to critical altitude.

I repeated it after i engage WEP and manifold pressure started to go down immediately i started to climb.

 

Do not know if it is bug or feature, can someone clarified it please.

 

And one request related to WEP.

During repair plane after flight, WEP gate is not secured back and remains open after plane repair. Can you changed it to normal initial condition?

[Yo-Yo]

Hi,

manifold pressure regulator works during normal engine operation corectlly

but

 

when i engage WEP then it stops working.

I tried to fly with engine setting 46inHg/2700, before WEP regulator keeps manifold pressure from sea level to critical altitude.

I repeated it after i engage WEP and manifold pressure started to go down immediately i started to climb.

 

 

If you stayed at 2700 - where do you think the regulator can find pressure to stabilise?

[saburo_cz]

OK, i did some more tests and.

 

When i use WEP and than continue in flight at lower engine settings (for example max. continuous), manifold pressure regulator starts working when manifold pressure is set at least 47inHG.

If WEP is not use, manifold pressure regulator starts working at 42inHg, which is correct i think.

(RPMs are not important in this, does not matter if 2400 or 3000 or somewhere between)

 

So, my question is, is this movement (5inHG) of lower limit for manifold pressure regulator OK or not?

Thanks

[grafspee]

Throttle

 

I have small issue with throttle, after breaking stop wire the throttle start working extremely weird, you have to add throttle a little bit to hold MP while climbing, which is complete different before breaking wire, can we get this thing sorted out somehow ?

[saburo_cz]

I tried report this 3 years ago.

May be, you will get better answer then i got...

 

https://forums.eagle.ru/showthread.php?t=179736

[BIGNEWY]

Merged threads.

 

I dont have an answer for you but I will try to find out.

[grafspee]

I tried report this 3 years ago.

May be, you will get better answer then i got...

 

https://forums.eagle.ru/showthread.php?t=179736

 

Yeah in p-51 boost regulator kick in at about 41" when you break wire in p-51 its shifting this starting point up, which should not be the case.

When you t/o at 46", as soon as you start climbing MP is droping no matter is it 2700rpm or 3000rpm(stop wire broken) = boost regulator is not working

When you t/o at 46", as soon as you start climbing MP is holding no matter is it 2700rpm or 3000rpm(stop wire intact)(it will not hold up to crit alt but it will hold mp at least to 8k ft) = boost regulator is working.

Something fishy here.

When you break stop wire in p-51 it is even more pain to fly p-51 because you have to monitor your mp like in old old planes,

Since every power setting is set on verge of engine limits this mean that if i allow engine run at 47" 2700 rpm knock will start damaging it, in combat 90% of time i fly at 46'2700 so with crippled boost regulator after breaking stop wire it is imminent engine death.

I added track with 46" initial climb 2700 rpm i didn't touch throttle up to 12k ft when stop wire was broken. When stop wire is intact you set 46" at take off and you don't need to touch throttle up to 8k ft and plane holds 46" on the track i fall to almost 30".

I had problem with holding 46" at take off roll.

p-51StopWireBroken.trk

p-51StopWireIntact.trk

Edited November 13, 2019 by grafspee

[grafspee]

I tried report this 3 years ago.

May be, you will get better answer then i got...

 

https://forums.eagle.ru/showthread.php?t=179736

 

Nop, i got worse, i got no response.

[Yo-Yo]

Sorry, I missed this thread now. I checked, yes, this behaviour is present, and the reason is that historically the engine was created for the earlier B or C version we were going to make first.

This planes had special handle for WEP that plays a trick with the pressure bleeding air to atmosphere, so instead of 67" the regulator gets 61".

This is the same we have for FW 190A-8 now. It works but has not its red button in this modification.

As we were very short in time making the Mustang, we used this mechanics instead of increasing MP set, it was our first piston plane, and we wanted to keep as many travel for 61" range as we can, it was a lot of discussion how to make this stop - dead zone, range scaling, etc. We thought that P-51 will be used mostly for pilotage, formation, etc, where the increased throttle range is critical.

So, whatever the reason was, it was done. And, in fact, as you pull this invisible red handle instead of breaking the seal you can not push it back. So, the lower margn of effective control is shifted up - from 41 to 46.

Generally, this trick does not differ from the MP setting readjusting - the first man noticed it after 4 years passed. And it is not so harmful, because there is no way to overboos at 2700 even if you have MP about 50-52".

As the Spitfire is flying with the full range of 67", now we can make just a dead zone and a seal.

[grafspee]

Sorry, I missed this thread now. I checked, yes, this behaviour is present, and the reason is that historically the engine was created for the earlier B or C version we were going to make first.

This planes had special handle for WEP that plays a trick with the pressure bleeding air to atmosphere, so instead of 67" the regulator gets 61".

This is the same we have for FW 190A-8 now. It works but has not its red button in this modification.

As we were very short in time making the Mustang, we used this mechanics instead of increasing MP set, it was our first piston plane, and we wanted to keep as many travel for 61" range as we can, it was a lot of discussion how to make this stop - dead zone, range scaling, etc. We thought that P-51 will be used mostly for pilotage, formation, etc, where the increased throttle range is critical.

So, whatever the reason was, it was done. And, in fact, as you pull this invisible red handle instead of breaking the seal you can not push it back. So, the lower margn of effective control is shifted up - from 41 to 46.

Generally, this trick does not differ from the MP setting readjusting - the first man noticed it after 4 years passed. And it is not so harmful, because there is no way to overboos at 2700 even if you have MP about 50-52".

As the Spitfire is flying with the full range of 67", now we can make just a dead zone and a seal.

Thank you for answer.