Author Topic: RR Merlin vs the DB series (Read 9461 times)

Angus · « **Reply #60 on:** November 19, 2002, 08:34:19 AM »

Quoting Niklas here:

"P.S Ok, it took the allieds 6 years to beat germans fighting in completly inferior material and numbers. Somehow i could also live with the conclusion you can draw out of this point of view"

Well there.
This is stupid Niklas, and does not belong to this thread. Stupid in definition, stupid in material and stupid in conclusion. Like the de-limbed black knight swearing and threatening with the words " come back you coward, I will bite your heels" you try to hold your pride whatever the cost.
You skid out of the debate and into another. Maybe time to start another thread with your header?
puhhh

Staga · « **Reply #61 on:** November 19, 2002, 09:20:55 AM »

It sounds like Angus didn't get kind of answer he liked to hear

O.K...

Merlin is best aero engine ever built.

There

gripen · « **Reply #62 on:** November 19, 2002, 11:37:57 AM »

Niklas,
I wonder what data you have on the V-1650-3, late P-51Bs had the V-1650-7 which fits your (questionable) data better. With +16lbs boost V-1650-3 did probably around 26k without RAM and around 30k with RAM. There is several good source books available and mentioned above, please get some of them to avoid continous mixups with the ratings.

The report I saw stated that the supercharger of the P-51 (no model specified) was "out of comission" and therefore they could not do high altitude tests (I have no idea what that means).

I don't know if you fully understand the word "test" it is not same thing as "comparison". We can use test data for comparisons but the values should be comparable.

Yes, RR lists critical altitude of the Merlin 66 as 16k without RAM and that means that at 10km it would produce roughly 800hp. But it appears that the values in the DB 605A manual are given with some sort of RAM effect (actually some German reports on the BMW 801 give unrammed and somekind of rammed output in the charts, see Bingham's book). So values appear to be not comparable.

But in the case of the test flight data we have very well comparable data because the planes operate roughly at same speed range. Even intake systems were quite similar. To put it shortly; in the real world conditions the Merlin 66 outperformed the DB 605A clearly at all altitudes.

And I wonder your comment: "Noone would know the climb speed, the aircraft and so on." Well, I have very similar and actually even more detailed data (conditions, MAP curves etc.) on the Bf 109G-2 than the above mentioned data on Spitfire IX. This data is for 1,3ata because 1,42ata boost was not used in the FAF G-2s. And in this data FTH of the climb speed is pretty much exactly same as mentioned for the 1,3ata in the DB 605 manual. And all this is roughly supported by several german measurements and actually by the DB 605 manual which you don't want believe or another possibility is that you are not able to understand it (after reading your theories about the DB605AS, it seems that later possiblity is more likely).

As noted in my last post, the slip of the supercharger or the lower peak output curves of the DB 605AS has very little to with the RAM effect as you tried to argue in your earlier post. The size of the inlet was increased simply to get a better RAM effect; you talked about the DB 605AS not about the DB 605ASM.

What next?

gripen

niklas · « **Reply #63 on:** November 19, 2002, 01:18:24 PM »

"Yes, RR lists critical altitude of the Merlin 66 as 16k without RAM and that means that at 10km it would produce roughly 800hp"

Thank you.

"But it appears that the values in the DB 605A manual are given with some sort of RAM effect (actually some German reports on the BMW 801 give unrammed and somekind of rammed output in the charts"

I have this 801 chart, but with dynamic pressure crit. alt is over 6km, while engine tops out in all sources below 6000. Strangely the power listed in most sources go along with the dynamic pressure curve. So most sources list "bad" altitude and "bad" power.
But even in german sources you won´t find the 801 listed with an altitude of over 6km, so this actually confirms my opinion that the DB is listed also without RAM.

With the climb speed i wanted to say that the 605 also was used in slower flying bombers or so (Say He-177 in the double engine variant).

"The size of the inlet was increased simply to get a better RAM effect"
Sure about this? Actually i doubt that. Because pressure is independent from the inlet size. In same way you have at the bottom of vessel filled with liquid always the same pressure at a given level, regardless of the shape.
No no, it was really a problem that at high altitudes the volume flow for the new engine consuming more air up there became to high.

niklas

gripen · « **Reply #64 on:** November 19, 2002, 01:43:29 PM »

Niklas,
Why did you not thank at first time? I gave you a source and all the needed information.

The chart in the DB manual claims dynamic pressure just as the BMW chart ie it means that the DB chart is with some sort of RAM effect just like the other curve in the BMW chart.

The test flight data also clearly proves that the DB chart contains some RAM effect because the total RAM effect is certainly more than 100m, at climb speed (about 400km/h true at FTH) it should be more than 500m. Another possibility is that the inlet system of the Bf 109G was far inferior if compared to the inlet system of the Spitfire. Later possibility is quite unlikely.

You don't seem to have much idea about dynamic airflow in the inlet. It's not a static system as you argue.

gripen