Fw-190F8/U1

[RRAM]

Hohun, thanks, makes sense to me if those numbers are true

Originally posted by GScholz
Why? Wouldn't MW50 be useful at say 20k if the engine had a rated altitude of 25k? If not then why?

of course it would be useful.

The problem you don't seem to grasp is that the BMW801D-2's supercharger critical altitude was at 18500 feet. Over that altitude it's performance fell steadily.

[GScholz]

Exactly what do I not seem to grasp? You twit!

Originally posted by GScholz
MW50 is actually equally useful at any altitude. It's just that the supercharger can't exploit the anti-knocking benefits above its rated altitude, the cooling effect however should be equal at any altitude.

[RRAM]

touche , I think I misread that part. That's the problem of not being english speaker, you know .

However you asked "Why? Wouldn't MW50 be useful at say 20k if the engine had a rated altitude of 25k? If not then why?", and the Fw190's rated alt was 18.5k. Over that altitude the MW50 power gain would be way less than what it gave under it.

 AH's Fw190A5 has no MW50. Low level performances with MW50 should be significantly higher than what they are.
 I concede that the hi alt performance would have a slight increase with MW50, but there's no increase in low alt performance to back up your affirmation. In fact the A5 at low altitudes is, as I already said, up to 10mph slower than what the german charts of a standard Fw190A5 report.

[HoHun]

Hi Rram,

>In fact the A5 at low altitudes is, as I already said, up to 10mph slower than what the german charts of a standard Fw190A5 report.

If you mean the same German charts as posted on this board, they're actually illustrating the effect of compressiblity error on air speed indications.

These charts do not match the German engine charts.

The US flight tests do match the German engine charts.

My conclusion is that the US test is accurate, and the German data (which has nothing to indicate it's from actual flight tests) stems from a simplified calculation.

The simplification consists of substituting the complex thrust-over-altitude function for a fixed power figure. This leads to an exaggeration of low-altitude performance.

Regards,

Henning (HoHun)

[RRAM]

Yep I'm talking about those charts. I know they are calculations rather than coming from actual tests (but I would say that FW engineers had at least some idea of their own's machine performance to not putting incorrect data on those curves, wouldn't they? ).

However I'm surprised about "matching the german engine charts". To which charts are you referring to?. And how those charts prove german reports incorrect and US ones spot on?.

Links, links, I want links!! I'm a compulsive Fw190 chart downloader!!!! I need them all!!!! .


Now seriously, what I do think is that both the german and US charts could be right.

Given the fact that most Fw190A5s on the western front were used for high altitude combat is possible that they were "tuned" on the field to achieve a slightly better hi altitude performance at the cost of a somehow worse low level performance. The captured A5 could be one of those, thus explaining the discrepances between german charts and US reports

Of course this is pure speculation based on no fact at all, so feel free to say "nonsense"...because probably, it is

[senna]

Originally posted by HoHun
Hi again,

>The Jumo 213A gave 1680 HP @ 5.2 km @ 3250 rpm.

>At a cubic volume of 35 L and a boost pressure of 1.42 bar, that gave an airflow of less than 1.66 kg/s. MW50 was added at 0.04 kg/s.

That should give a temperature drop of about 40 K, from which without knowing the intake air temperature (after supercharging) I can't directly calculate the power gain.

It should be enough to justify a 4% power increase easily, though.

Regards,

Henning (HoHun)

Thank you for the explaination.