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Old 06-17-2019, 06:07 AM   #51
grafspee
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Originally Posted by Snapage View Post
Does it say in the P51D manual that you cant use WEP below 5000ft? I know it says that WEP gives little benefit below 5000ft in the DCS P51D manual. I dont remember it saying that WEP below 5000ft causes any more stress on the engine then at any other altidude. There are flight tests that show significant speed improvement at sea level with WEP.

The P51D manual(not DCS manual) says nothing about engine failure. It says that WEP should be avoided because it reduces the lifespan of the engine. It also says that after 5 hours of war emergency time the engine should be pulled for tear-down inspection and reconditioning. Regarding time WEP can be used, all it says is that 95°C oil temp must not be exceded for 5 minutes. It also says that coolant outlet temp should not excede 121°C.

You cant run the DCS P51D WEP for any period of time without engine failure nevermind the 5 hours it says in the manual.
i did some testing recently in dcs i took off at full power after maby 40 second climb i droped to 46"2700rpm than i climbed to something like 5500ft and i rised rpm to 3000 and i broke stop wire to hit 67" and i kept climbing at WEP power up to 35k ft at speed around 220mph this was minimum speed to not exeed temp limits oil and coolant doors were open to max i dont remember oil temp but coolant temp was exactly 121 degree than i level flight at 35k and keept going and nothing happen to engine. later i landed at airport and bring up repair command no timer showed so no damage. Looks like this is it
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Old 06-17-2019, 06:40 AM   #52
Skwinty
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Quote:
Originally Posted by Snapage View Post
Does it say in the P51D manual that you cant use WEP below 5000ft? I know it says that WEP gives little benefit below 5000ft
From the pilots training manual.
"
Remember too, that there's nothing to be
gained by using war emergency power below
5000 feet. Up to that altitude the throttle alone
gives you more than enough power to exceed
the operating limits of the engine. "

It doesn't say you cant use WEP below 5000, but it does increase the risk of exceeding engine limitations.
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Old 06-17-2019, 07:03 AM   #53
grafspee
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Originally Posted by Skwinty View Post
From the pilots training manual.
"
Remember too, that there's nothing to be
gained by using war emergency power below
5000 feet. Up to that altitude the throttle alone
gives you more than enough power to exceed
the operating limits of the engine. "

It doesn't say you cant use WEP below 5000, but it does increase the risk of exceeding engine limitations.
what interests me much more is this "there's nothing to be
gained by using war emergency power below
5000 feet" what the mean by that, when i look at charts for climb or speed preformance actualy WEP at low alt gives the biggest benefits for example at crit alt for 2nd supercharger speed difrence in top speed is only 2mph hardly noticable 61" at 26k and 67" 24k ft but at sea level it something like 11mph same comes with climb.
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Old 06-17-2019, 10:06 AM   #54
Snapage
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Quote:
Originally Posted by grafspee View Post
i did some testing recently in dcs i took off at full power after maby 40 second climb i droped to 46"2700rpm than i climbed to something like 5500ft and i rised rpm to 3000 and i broke stop wire to hit 67" and i kept climbing at WEP power up to 35k ft at speed around 220mph this was minimum speed to not exeed temp limits oil and coolant doors were open to max i dont remember oil temp but coolant temp was exactly 121 degree than i level flight at 35k and keept going and nothing happen to engine. later i landed at airport and bring up repair command no timer showed so no damage. Looks like this is it

If you are constantly climbing then you are not going to be above 61" for very long. And you won't be at 67" for long at all because as you climb your manifold pressure drops until the supercharger kicks in at about 16000ft then you will be at 67" briefly before it drops again as you continue climbing.



As far as I can tell from reading the manual, there is no reason for the engine to seize from using WEP. It will cause extra wear on the engine but as long as you are keeping temps within parameters and using WEP for no more then 5 minutes at a time, you should have no problems with the engine. Especially when the P51D was cleared to 75" with 150 octane fuel with the same engine.
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Old 06-17-2019, 01:42 PM   #55
grafspee
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Originally Posted by Snapage View Post
If you are constantly climbing then you are not going to be above 61" for very long. And you won't be at 67" for long at all because as you climb your manifold pressure drops until the supercharger kicks in at about 16000ft then you will be at 67" briefly before it drops again as you continue climbing.



As far as I can tell from reading the manual, there is no reason for the engine to seize from using WEP. It will cause extra wear on the engine but as long as you are keeping temps within parameters and using WEP for no more then 5 minutes at a time, you should have no problems with the engine. Especially when the P51D was cleared to 75" with 150 octane fuel with the same engine.
you are right but what i was trying to say that temps aren't main reason for engine seizure because i at some point were above red line in coolant temp, there is something different which is killing engine in p-51. i will test it at level flight 6k ft for longer time.
i did read some report test about 150 octane and 75" power settings, test pilots did not report any increase in engine temps during those test, so cooling system is enought to cool p-51's engine.
And output power of the engine is lower at sea level than at 6k ft so the over powering engine isnt a problem here too
i think that at sea level temp of inducted air is high enough to couse knocking and this is killing engine very quick. so at low ambient temps p-51 should be ok
i did test it 6k-7k alt 67"3000 for 3 minutes then i reduced to 46"2700 after a while 30" 2400 it took me another 3 minutes to make close to airfield when i rised rpms to 2700 for landing engine seized temp were totaly ok coolant in green range all the time and oil about 85. engine died after 3 minutes of operation at alt between 6 and 7 k feet.
and it wasnt 67" close to 7k MP droped to 66"
i just did exact 2 flights with stopper in the hand engine seizure happen exact in the same time so it is just simple timer after all. 4:40 min:sec at wep flight took about 14 minutes including force landing at airport
no i will try engage wep but i will climb higher to hit only 61" -> no damage to the engine but fligh alt increased to 9.5k ft
will test 67" at 2nd spuercharger speed.
for me it looks like guaranted engine damage when running 67" no matter alt or speed or coolant or oil temp and on engine limit chart is clearly said that wep can be operated for 5 minutes, and manual thurther says that oil temp can exeed 95 clelcius up to 5 minutes while operating WEP i think this thing need rework for sure.
will test how much time you can run wep with no engine damage

Last edited by grafspee; 06-18-2019 at 12:43 PM.
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