10.06.2008, 03:50
I can't speak in terms of historical documentation, I've none on engine performance with the tropical filters aside from generalised references.
The British vokes filters for example, notably affected engine performance, it has been said. I imagine them as a sort of air cleaner style filter which can offset as much as say, 100hp and is enough to notice the difference, though not enough to obsolete the model. Climb rate and sustained manoeuvres would be the most telling difference with such a relatively minor drop in performance, top speeds and acceleration would be little affected under most conditions.
For example, in an automotive race engine (where my own experience lay) you can get around 5% power offset (+/-) just playing around with your air filter and of course the most modern and advanced, or best are as good as having no filter at all, on the dyno. I should think supercharging may enhance the effect of filters (for good or ill).
This being said the Emil filter looks to me more like a vokes style unit, working all the time. The later one used on the Friedrich onwards is the open/closed style intake filter, that is a simple radial filter with a bypass valve at the front that cancels any performance reduction once altitude is gained and the bypass valve opened. It is however a matter of course, in engineering terms some power output is lost with the added restriction of an intake filter, the amount dependent on the efficiency of the filter.
Again in engineering terms there should be no dramatic decrease in maximum boost pressure with use of an intake filter which is not entirely choking the engine (my estimate with a good look at the Me-109F/G style one is that it should not at all). However it is a matter of record that for example, soon after the introduction of the DB-605 it was cleared for 1.42ata 5-10min boost, but following an early spate of reliability issues, particularly in Africa (and including the loss of Marsielle to engine trouble in his newly acquired G-2), this clearance was rescinded back to 1.35 for sustained maximum boost. Then it was cleared again, then rescinded again, and finally cleared for 10min boost in Aug43 with no further modification (hence the improved performance of the G-6 late, with 1550PS from the DB-605A-1 at 2km). The details go something like that, from memory of what Kurfurst and others have mentioned citing historical documentation.
So in my estimate, as an informal race engineer you should lose around 3-5% with the filter closed on the F/G type sand filter and none at all with it open. On top of this, the 605 engine was probably restricted to a 1.35ata max in the hot African environment as an advisory (due to the period it was used there), although 1.42ata should still be available for the normal 1min take off and emergency limit. The engine itself however, as was later proved by history was perfectly capable of operating at 1.42ata for up to ten minutes, but this was only permanently cleared by the RLM in 08/43. There is no empirical reason I can see this (boost pressure) would be diminished by the filter I'm looking at right now, at worst you might have a momentary lag on engine acceleration with it closed.
Again in my estimate you might lose as much as 5-8% with the Emil style filter, and about the same with the British vokes filters, at the larger end of the scale due to their more restrictive design (I believe an accurate comparison between vokes and German filters would be comparing a car exhaust muffler to an exhaust resonator, or a motorbike exhaust with and without fibreglass packing but still performing some filtration either way).
And yes, the desert sun would heat up filters, which heats up the induction charge and goes a long way to overheating the engine faster. I take air filters off at race meets, use a heat plate under the carbs and pipe a bonnet scoop right to them, to keep it as cool as possible for that one or two extra horsepower and minute or two better longevity on cooler running in the first place. It makes a big difference when the competition is a close match. Hell the way I sand the ports picks up a horsepower per cylinder and it makes a noticable difference (more than one competitor told me my car, with its specs shouldn't perform the way it did).
Hope this helps in lieu of documented historical information, which I think might be hard to come by.
The British vokes filters for example, notably affected engine performance, it has been said. I imagine them as a sort of air cleaner style filter which can offset as much as say, 100hp and is enough to notice the difference, though not enough to obsolete the model. Climb rate and sustained manoeuvres would be the most telling difference with such a relatively minor drop in performance, top speeds and acceleration would be little affected under most conditions.
For example, in an automotive race engine (where my own experience lay) you can get around 5% power offset (+/-) just playing around with your air filter and of course the most modern and advanced, or best are as good as having no filter at all, on the dyno. I should think supercharging may enhance the effect of filters (for good or ill).
This being said the Emil filter looks to me more like a vokes style unit, working all the time. The later one used on the Friedrich onwards is the open/closed style intake filter, that is a simple radial filter with a bypass valve at the front that cancels any performance reduction once altitude is gained and the bypass valve opened. It is however a matter of course, in engineering terms some power output is lost with the added restriction of an intake filter, the amount dependent on the efficiency of the filter.
Again in engineering terms there should be no dramatic decrease in maximum boost pressure with use of an intake filter which is not entirely choking the engine (my estimate with a good look at the Me-109F/G style one is that it should not at all). However it is a matter of record that for example, soon after the introduction of the DB-605 it was cleared for 1.42ata 5-10min boost, but following an early spate of reliability issues, particularly in Africa (and including the loss of Marsielle to engine trouble in his newly acquired G-2), this clearance was rescinded back to 1.35 for sustained maximum boost. Then it was cleared again, then rescinded again, and finally cleared for 10min boost in Aug43 with no further modification (hence the improved performance of the G-6 late, with 1550PS from the DB-605A-1 at 2km). The details go something like that, from memory of what Kurfurst and others have mentioned citing historical documentation.
So in my estimate, as an informal race engineer you should lose around 3-5% with the filter closed on the F/G type sand filter and none at all with it open. On top of this, the 605 engine was probably restricted to a 1.35ata max in the hot African environment as an advisory (due to the period it was used there), although 1.42ata should still be available for the normal 1min take off and emergency limit. The engine itself however, as was later proved by history was perfectly capable of operating at 1.42ata for up to ten minutes, but this was only permanently cleared by the RLM in 08/43. There is no empirical reason I can see this (boost pressure) would be diminished by the filter I'm looking at right now, at worst you might have a momentary lag on engine acceleration with it closed.
Again in my estimate you might lose as much as 5-8% with the Emil style filter, and about the same with the British vokes filters, at the larger end of the scale due to their more restrictive design (I believe an accurate comparison between vokes and German filters would be comparing a car exhaust muffler to an exhaust resonator, or a motorbike exhaust with and without fibreglass packing but still performing some filtration either way).
And yes, the desert sun would heat up filters, which heats up the induction charge and goes a long way to overheating the engine faster. I take air filters off at race meets, use a heat plate under the carbs and pipe a bonnet scoop right to them, to keep it as cool as possible for that one or two extra horsepower and minute or two better longevity on cooler running in the first place. It makes a big difference when the competition is a close match. Hell the way I sand the ports picks up a horsepower per cylinder and it makes a noticable difference (more than one competitor told me my car, with its specs shouldn't perform the way it did).
Hope this helps in lieu of documented historical information, which I think might be hard to come by.