I am glad you are happy with the results.
If you had already done a lot of tuning to your AIR file, the only real changes in mine were
Record 505 - Supercharger Boost Gain, Manifold Pressure Limits
Record 508 - Engine Torque versus RPM
Record 509 - Per Cylinder Friction Loss versus RPM.
There were no other changes, so if you just copy these Records over to your AIR file, you have all the changes.
The Propeller diameter should and relevant tables Records 511 and 512 should not affect Engine Power at all.
They affect thrust and performance but not engine output.
If you want the original performance, you can still get it with just a few changes.
Try the following and see if it helps:
1. Reduce the Zero Lift Drag until you get about 295 to 297 MPH.
2. Reduce the Supercharger Boost Gain a bit until the power reduces enough to get down to 320 MPH.
3. If you need to adjust the Service Ceiling, adjust Torque versus Friction as per the Tutorial.
As a Confirmation that the results are good:
Take an engine power and manifold pressure reading at 12,000 feet.
It should be around 1700 HP and 41.0 inches Hg.
My version exceeds both these numbers by a fair amount at 12,000 feet but I needed to do that to get the performance I was looking for.
The numbers match pretty well a little higher at 12,500-13,000 feet which I attribute to Ram effects.....
The net performance changes to my own B-25C were pretty much negligible as compared with its earlier AIR file.
The only real gain was about 80 HP at Take-Off for a touch less speed at altitude.
If I were building a real aeroplane, I would have preferred the earlier version of the engine because the net effect of these changes was negative but I believe it is a bit more realistic for a B-25B/C.
WEP type 3 is probably more realistic. I just don't like the engine damage at 5 minutes 10 seconds.
I also needed more WEP duration for flight testing.
I am also pretty sure that even above critical altitude when WEP has no effect, exceeding WEP time limits will still destroy your engine even though there is no power gain at all.
That part is quite unrealistic if it is true.
Hello Ivan,
Thanks for your additional info. The engines are getting better all the time!
Iīll just do the extra little adjustments to get the previous Sea-Level performance back again.
Cheers,
Aleatorylamp
Earlier this evening I ran just one simple test of the Mitchell.
The earlier version was able to reach
310 MPH at 15,000 feet.
The new version only gets to
301 MPH at 15,000 feet.
The results were a bit surprising and tell me there is more work necessary.
There are some interesting explanations for the unexpected results; They have to do with the fact that the propeller tables are discrete points rather than continuous curves and the interpolation would sometimes arrive at slightly different results than one would expect from a smooth curve.
Next step is to check Sea Level speed. The method of adjustment also depends on how that number has changed.
Update: It turns out Sea Level speed is also lower which means Drag was altered since the test back in 2008. Or I could be working on an incorrect version.
Sometimes itīs not as easy as it seems! At the moment I have quite a few different versions, and it takes a bit of an effort not to get them all tangled up!
Using the latest version I still havenīt been able to reduce the speed range between Sea-Level and Altitude.
I too have to conduct additional trials!
Iīm still at 288 (S.L.) -320 mph (15K ft), when the goal is 296-320 mph.
Of course, increasing torque and reducing Boost gain works, but then the Manifold Pressure values come out too low higher up.
Strangely enough, if I use my own .air file and only introduce the new engine data, the S.L. speed goes up to about 309 mph instead of 296. In this case the culprit is my propeller, which doesnīt work as well as the your slightly cut-down Mitchell-C one!
Well, weīll see what comes out!
Cheers,
Aleatorylamp
I am having some issues with my engine performance as well.
It turns out (it is actually in the notes) that my testing protocols have changed a bit since 2008.
Back then, I was conducting the Service Ceiling and Absolute Ceiling tests with a full fuel load (670 Gallons).
These days, I do it with about half fuel. (Start with 53% and it should drop down very near 50% by the time the test is done.
I found with my changes I was actually getting just over 28,000 feet Service Ceiling.
The Zero Lift Drag was also SLIGHTLY higher than it should be and that was easily corrected.
With a re-edit of the Torque versus Friction Records to bring down the Ceiling, I need to test engine power all over again.
I got a bit of bother myself just now... It was beginning to look promising after lowering Torque and increasing Boost Gain - Iīd just got Sea-level speed at 196 mph and was going to test at 15000 ft when the graphics card went.
Luckily it was not on my main computer but on my re-furbished old dual-core laptop with upgraded CPU, memory and battery. Suddenly the screen filled with short lines! The graphics card is seriously deteriorating... pity about the wasted upgrade! Now Iīll have to get at the HDD data with a USB HDD box.
If itīs not one kicker, itīs another, sent to keep us on our toes...
The auxiliary laptop is dead but I still have another p4 fall-back one - so all in all Iīm not too badly off. Iīm rather suspicious of the sudden failure of the graphics - despite a cooling platform. Programmed obsolescence? I wouldnīt put it past them!
Anyway, with the Baltimore engine tuning, it appears that thereīs a limit to the Boost Gain without it boosting too much above critical altitude, and Iīm finding it impossible to get the planned performance range - i.e. 296 mph with WEP at 500 ft and 44 inches Hg, and 320 mph with about 40-41 inches Hg at altitude. With correct S.L. performance it just falls 5 mph short higher up. The best Iīve managed is 300-317 mph upto now.
Weīll keep trying! Now itīs time to get my biological food from the farmerīs market. Have a nice Sunday! Tomorrow is a Canary National holiday, so that will also be nice.
Sorry to hear about the first laptop. Glad you have another one.
It is funny how we can get attached to computers as if they have some kind of spirit in them.
I would be very upset if my old Pentium 233 were to die completely. It fails intermittently and that bothers me as it is.
Regarding the AIR file, I am wondering a bit why you chose to INCREASE TORQUE as your first step.
Depending on where you are starting from, that is probably not a good first step.
I did suggest adjusting Zero Lift Drag as a first step. Which way to adjust depends on whether your speed was high or low.
After that, the chances were that your speed at 15,000 feet would have been too high because it was correct earlier.
Now depending on which direction you needed to go, you could adjust Supercharger Boost Gain to correct it.
Life would have gotten a bit more interesting at that point because the actual Critical Altitude of the revised AIR file I sent to you was around 12,100 feet or so and you are trying to adjust performance ABOVE the critical altitude.
This would have been time for a service ceiling test and use Torque / Friction to adjust as needed.
Oops, almost forgot.
Late last night, I did some testing with the Mitchell C Air file I had adjusted the night before.
Here are some results:
Sea Level: 1631 HP @ 42.0 inches Hg -- 272 MPH
Sea Level: 1726 HP @ 44.0 inches Hg -- WEP. No speed test was done because this is only a T-O setting.
5,000 feet: 1695 HP @ 42.0 inches Hg
12,500 feet: 1775 HP @ 41.3 inches Hg -- 316 MPH
15,000 feet: 1608 HP @ 37.3 inches Hg -- 310 MPH'
Service Ceiling was not tested but I am estimating it at 26,500 - 27,000 feet from power readings.
I quit testing when I got too tired to remember what to do. I was missing the points where I needed to collect data.
Speed is a couple MPH too high at Sea Level, but I am not planning on adjusting it.
Hello Ivan,
Well, the surviving laptop also got a memory and CPU upgrade, so itīs quite pleasing. Itīs an older single core 1.7 Mhz, and I do hope its programmed obsolescence will have a greater span... If this one goes, I could always buy my daughter a new laptop and use her present one for which WinXP drivers do exist (for AF99, of course)!
Baltimore engines: The thing is that I am working on two different .air files, to try and get the desired 296-320 mph speed range: Your originally MitchellC one, adjusting weight, loading and fuel to the Baltimore, and also my own, with the Mitchell engines and propellers, and they need two different approaches.
Mine gives me a too narrow speed range: 303 mph at 500 ft with WEP (too fast), and 317 mph for 15000 ft (too slow). Yours is somewhat better, but the range is too wide: 288 mph (too slow) at 500 ft and 320 at 15000 ft (quite right).
I also tried a balanced increase of torque and friction to see if there was any difference in the speed range, i.e. what the speed was at altitude with correct speed lower down, but I think this only made it worse on the MitchellC .air file, so I should really use this system on mine!
Speed range was 290-327 mph. Lowering Boost Gain to reduce the 327 mph at altitude then lowers Manifold pressure too much, but I suppose that will have to occur if I want to lower the speed, although Iīve been trying to keep my Manifold Pressure and Horse Power values similar to the ones you are getting.
Update: I just tried the balanced friction/torque increase maneuver on my .air file and got a 2 mph increase in the range. It was 303-317 mph and now itīs 303-319 mph. ...not enough, even though the friction/torque increase was tremendous.
Anyway, weīll see...
Cheers,
Aleatorylamp
Last edited by aleatorylamp; May 29th, 2016 at 14:42.
If you need to adjust Sea Level speed and your engine power is already correct,
Adjust the Drag or Thrust to achieve the proper speed.....
Once you have this, and need to adjust the speed or power at altitude,
Use the Supercharger Boost Gain.
Most of the time this should work pretty well.
At this point, you should test Service Ceiling and balance Torque / Friction to adjust the altitude at which this power level is achieved.
This WILL affect engine power at lower altitudes, but since you are balancing to get the same Sea Level Power, the speed change there should be pretty much negligible.
The speed at critical altitude MAY change a bit, but it should still be near negligible.
The spread from Sea Level power to Critical Altitude power is controlled by Supercharger Boost Gain which is why I was recommending distinct steps.....
If those steps do not work well, there are other ideas but we have not gotten there yet because so far, this AIR file task is actually following the pattern pretty well.
Hello Ivan,
OK, thanks for your patience and insistence on the correct procedure. Indeed I have been using this procedure all along. Sorry that Iīve been insisting on a point which seems not to have been a point anyway! I do apologize.
Because of the very low Manifold Pressure readings I get at altitude when speed is right, I sometimes invert the procedure to see what S.L. speed I would get with the expected Manifold Pressure readings and correct speed at 15000 ft. Of course S.L. speeds are incorrect because I have to change Zero Lift Drag for the trial.
As the speed span is larger in the Baltimore case, and from what you say then, it would be normal to expect lower Manifold Pressure Values values at altitude. That was what was throwing me off all the time.
Anyway, I see Iīm on the right track, and Iīll do the ceiling check and see.
For the time being Iīll use the Mitchell-C torque and friction settings. Mine are a little higher, and I have also done tests with exaggeratedly high settings (of course at the desired Hp).
Incidentally, I did correct critical altitude as I saw youīd done in the .air file youīd sent. I also noticed that one of the things to get the performance more correct is that the Boost Pressure Change Rate is set at Zero. This obviously helps to prevent WEP from shooting up with altitude.
Update:
OK, Iīve just done the normal procedure for the originally Mitchel .air file.
12100 ft: 38.5 Hg, 1628 Hp, 324.0 mph (I was hoping for 41 Hg and 1700 Hp)
15000 ft: 34.3 Hg, 1466 Hp, 320.1 mph (I was hoping for 37 Hg and 1500 Hp)
2nd Update:
I tried the procedure with my own .airfile with the considerably higher friction/torque settings, but for settings that keep Hp below 1800 at altitude, with correct Boost Gain so as not to have a WEP power increase above critical altitude, speed falls very short at altitude, so I prefer to use the .air file coming from your Mitchell-C.
Cheers,
Aleatorylamp
Last edited by aleatorylamp; May 30th, 2016 at 01:09.
I actually am not insisting that you take ONLY the path that I am recommending.
I am still learning as well.
The actual part that I am objecting to is your comment that something is "impossible" when the path to achieve that goal is pretty clear.
Now if there are additional goals, the process becomes a bit more complicated, but I believe it can still be achieved.
The real problem as I see it with the results that you are getting is that your path is a bit scattered for direction.
You adjust numbers that I believe should be used for fine tuning in an effort for major tuning.
The reason I keep recommending a particular path is that I am fairly certain that it brings the result RELIABLY toward the goal whatever that might be. The order of tasks is selected so that there is minimal backtracking as opposed to the jumping around which tends to undo earlier things that may have been satisfactory before.
If your real goal is experimentation, then it is working.
If your goal is to arrive at an AIR file that meets your specifications, then the wandering around will not get you there with any reliability.
There are a few other fine tuning steps but I have not suggested them yet because they only fine tune the basics.
If you use them for major tuning, you will probably get serious unintended side effects.
One of the other issues I need to figure out is a better protocol for conducting climb and service ceiling tests.
If you are also learning then Iīm glad and relieved that it is not a pain for you! It shows that the tuning of the R-2600-13/29 radial engine is an interesting subject for both of us. The Mitchell-C and the Baltimore will definitely benefit from our discussions!
Thanks for your comments and thoughts. The last test results were conducted using your recommendations, and apart from the experimentation bit, which is of course interesting for me to see what happens, the goal is indeed to get a decent air file that will fit the plane.
In reality, the difficulty in reaching the desired numbers at altitude is giving me something to chew on, an a "what if" thought appears. The somewhat vague specifications for the Baltimore are just not specific enough.
The thing that bugs me is the 320 mph top speed specified only for the MKV model, whereas the earlier models were all much slower: MKI/II models with 1600 Hp were quoted with a max. speed of 308 mph at 13000 ft, and the heavier MkIII, with 1660 Hp and 302 mph at 11000 ft. The also heavier MkIIIA/IV with also 1660 max Hp are quoted with a max. speed of 298 - 305 mph at 11500 ft. ...and then comes the MkV, with 1700 Hp and suddenly 320 mph at 15000 ft...
How on earth they get this huge power surge with only 40 Hp extra?!! Was it because they just increased the Turbo Boost and really went for it? This would then indicate that the 320 mph was a WEP speed, and also that the MkV had an additional Boost Gain with WEP - i.e. a small percentage in the Pressure Change Rate parameter. 320 mph is then not a speed attained with Max. Continuous - not non-WEP. Should Maximum Continuous speed at altitude perhaps really only be about 311-313 mph?
The things I am learning about actually have little or nothing to do with the Wright R-2600 or even Engine Tuning in general.
That part is pretty easy at this point. Even the WEP Boost Gain did not really change any of my prior methods.
I was thinking more of the flight testing and creating a testing protocol that is both useful and reliable.
The Reliable part is done but the big question is whether or not the protocol really provides any useful measurements
That is the part I am working on now.
With all the changes over the last couple weeks on the Mitchell-C AIR file, the net result is that there isn't any great performance difference other than having another 80 HP or so available at Take-Off. At this point, I am satisfied with the R-2600-13 engine for the B-25C; I know I can fine tune it in either direction for ceiling without any other significant effects.
Regarding what the performance was on the Baltimore, I think we have gone over the subject a couple times already.
I have done very limited research. You have found more performance tests than I have so perhaps you also have reached some conclusions.
As you have already seen, tuning doesn't take very long if you know your target. Building the model takes much longer.
I have started to build the Baltimore - the muses have come back and the builderīs block is thankfully gone! Letīs see if I can be more successful with the model itself than with tuning the MkV engines for which insufficient information is available.
I may have done more research on the Baltimore than you, but by no means with any more success! The information on the Polish document relative to the different versions, MkI to MkV, ties in perfectly with two other old publications I have found, but what is lacking is more specific engine data regarding WEP power on R-2600-29 on the MkV Baltimore.
How they all of a sudden got 320 mph out of the -29 engine in my opinion implies an increased WEP, giving perhaps about 1800 Hp. For want of more specific information on the engine, one simple solution here would simply be not to build the MkV, but one of the earlier Baltimores, the Mk III for example, which had the -13 engines. This way the 320 mph mystery can be ignored.
Top speed would be fine at around 305 mph. Current flight test results would tie in perfectly well for the R-2600-13 engined Baltimore MkIII (of course), with the Mitchell-C .air file simply corrected for dimensions and weights.
For the moment, I think this will be the best solution.
Cheers,
Aleatorylamp
Hello Ivan,
Out of interest, I tried out some tests for the R-2600-13 powered Baltimore Type B-2 MkIIIA, which is quoted with the following performance:
Vmax at S.L.(500 ft?): 284 mph
Vmax at 11500 ft: 305 mph
After Boost Gain and Drag adjustments, results for the MkIIIA are:
__500 ft: (____WEP) 44.0 Hg, 1721 Hp, 284.0 mph
11500 ft: (non-WEP) 37.9 Hg, 1597 Hp, 305.7 mph
The 4500 and 6700 ft readings are not really of much use given the lack of a 2-speed blower in CFS1, and are included just for information. Then, just for the record:
12500 ft: (non-WEP) 36.4 Hg, 1532 Hp, 305.0 mph
Again, and similarly to the MkV with its 320 mph, the high altitude Manifold Pressure readings here donīt tally very well with the SEFC either, and that would presumably be put down to the lack of a 2-speed blower.
Anyway, at the end it appears that although at first glance it seemed more probable that a MkIIIA tuning would be more exact because of the R-2600-13 engines, perhaps the previous tuning for a MkV adaptation to R-2600-29 engines is also quite acceptable, without any need for any additional WEP Boost, which is quite pleasing, I would say. Would you think so too?
Iīve been re-reading your posts from the last 3 weeks, and thereīs indeed a LOT of information.
One thing that I had meant to comment on is related to your Post #99, where you mentioned the R-2600-13 as being incorrect on the Polish table: Would this mean that the R-2600-13 is SIMILAR to but not EXACTLY the same as the 1700 Hp R-2600-29 ? Perhaps this also explains the Mitchell-Cīs R-2600-13 enginesī having a Cylinder Displacement 0.2 cu.in less, and a Compression Ratio 0.5:1 lower than the one Iīm using - the only one I could find similar to the R-2600-29 was the GR-2600-C14BB. Itīs not a terrible difference, but it amounts to about 1.5 mph at 500 ft.
Incidentally, the R-2600-29 apparently also had a 1850 Hp version, which is interesting.
Then, Iīd forgotten to compensate the 5 mph speed difference between S.L. and 500ft for the IIIA version. It should be 289 mph instead of 284, but thatīs easily fixed.
At the end of the day, the good thing that has come out of all this, is that we will most probably have TWO Baltimore models: An early one without a turret (or perhaps larger Boulton Paul turret, but preferably not), and also the later MkV with the smaller Martin turret, possibly in 2 different liveries, a desert-camo and khakhi-green-camo.
1. As I commented earlier, I do not believe the Baltimore was ever equipped with the R-2600-13 and if it was, it was not the same engine we are seeing the SEFC for. The power ratings are too low for the one described in the Page 112 data table.
I am fairly certain it is a typographical error.
2. Also as I commented, the early R-2600 engines were not all that durable.
The engine obviously had a Take-Off rating at 44.0 inches Hg but I do not believe it was for use after take-off.
I believe that my idea of 42.0 inches Hg as normal maximum is most likely correct.
These engines only had a critical altitude of around 12,000 feet which means that they essentially have no additional boost available post that altitude. in other words, there is no high altitude WEP.
With my Mitchell, I was really going for B-25B level performance to have something capable of flying the Tokyo Raid mission.
I could not get the level of performance I wanted by staying strictly with the SEFC, so I adjusted a bit to get where I wanted.
Additional Detail:
I was getting 26,750 feet service ceiling with my current testing protocol but observed that this altitude was simply impossible (hate that word) to achieve when the aeroplane was flown manually.
I simply cannot trim quickly enough to keep the aeroplane headed in the correct direction for a continuous climb and practical ceiling was more like 24,000 feet or perhaps even lower.
I could get the aeroplane to go way over 25,000 feet but not in a continuous climb and formation flying would simply be hopeless.
So what IS the service ceiling now and how do I test to confirm it?
(The Russian term is actually "Practical Ceiling" which I used a few lines above.)
So, what should your target performance be?
I can't tell you. I have my own opinions, but I have already told you those.
Thanks for your interesting reply! OK, so it isnīt the R-2600-13 engine that was used on the Baltimore, but inferior ones for MkI to MkIV models, and OK too, that the R-2600-19 and the GR-2660-A5B were worse quality engines, for which the performance envelope developed here in this thread is more fitting.
Then, it seems that we can agree that once I fix the S.L. speed for the MkIIIA, this would be good to use for earlier the Baltimores. Then, initially, the faster version of the same .air file would serve for a MkV, as it has the speeds agreed on in our posts. No extra WEP!
There is a slight contradiction regarding the MkVīs R-2600-29, a later edition of the R-2600 engine: In fact, in the article about the R-2600 engine defects, thereīs a comment on aircraft models from other manufacturers receiving a recommendation to change from the -13 to the -29 engines to cure the problems, so the -29 must have been more reliable and better than the -13. That would also explain its vastly improved top speed. Too bad there is no information on it - as I said, I have only found a GR-2600-C14BB. Possibly similar, but who knows?
Update:
As per the other two sources, the engines on the MkIIIA were R-2600-19, and on the MkIII, GR-2660-A5B, both giving 1660 Hp. I can try reducing engine torque in the .air file to get 40 Hp less, hopefully it will not make it more difficult to maintain proper power at altitude and it may be more fitting for the worse engines. Thanks for pointing it out (again).
The plan of making two models using two different adaptations of the Mitchell-C R-2600-13 engine .air file parameters comes from the fact that there are no other SEFCs available. The two modelsī (MkV and MkIIIA) engine performances do not really match ALL the performance details in the SEFC that we have at hand - only some of them coincide, the aim being to correctly reflect the performances given in the documentation on the Baltimore MkIIIA and MkV aircraft types.
Regarding your comments on the Mitchell-B/CīService Ceiling, I still have to do that test on the Baltimore(s). They definitely had a lower ceiling, and I wonder what the outcome will be. For the MkV it was 25000 ft, and for the MkIIIA it was 23300. I suppose the fitting term "Practical Ceiling" would entail the ability to maintain a 100 fpm rate of climb, as you once mentioned. The conditions under which such a test is to be undertaken would be 50% fuel tankage and 50% Bombload, perhaps? ...similar to a rate of climb test, maybe?
Cheers,
Aleatorylamp
Last edited by aleatorylamp; May 31st, 2016 at 11:56.
Hello Ivan, again, OK, Iīve just done it, and contrary to what I was fearing, the results for a 2x1660 Hp MkIIIA/VI Baltimore were unexpectedly easy to arrive at. There are corresponding adjustments to Zero Lift Drag, Oswald factor, Boost Gain (this at only 1.955, which apparently has a side-effect of lowering the set critical altitude), slightly reduced Torque graph and somewhat increased Friction graph, and results are probably (hopefully) looking quite satisfactory:
What is not so pleasing (but irrelevant) are the WEP peaks or surges, but, as you said, WEP would not be used other than at take off, so it can be ignored:
Anyway, I thought this was quite interesting for the 1660 Hp R-2600-19 or GR-2660-A5B engines. Thanks again for prompting me to do it. Hopefully this will be acceptable now.
Update: Problem!
The (irrelevant) WEP surges made me test some other altitudes at non-WEP, just in case.
There are some non-WEP points above 305 mph, just between the 6700 ft and 11500 ft
altitudes where I hadnīt tested before!
Lowering these implies lowering the specified 305 mph for 11500 ft.
Perhaps not so good after all, and itīs not as easy as Iīd first thought!
After this rather unexpected surprise, I decided to try out the MkV .air file, which was correctly giving me 320 mph at 15000 ft and 296 mph at 500 ft, for untested altitudes. Lo and behold! I ALSO get the same peak surge at 10000 ft, this time going up to 326.5 mph. Well well, another kicker!
Maybe I should just quit and built a completely different airplane that will give a decent performance envelope in CFS1, because whatīs the point in building a plane that will do crazy things at illogical altitudes?
Cheers, Aleatorylamp
Last edited by aleatorylamp; May 31st, 2016 at 18:19.
I just noticed that our Posts 143 and 144 were done at nearly the same time and I know I did not read your post until just now.
I will try to address the issues you brought up there.
Are the R-2600-13 and R-2600-29 functionally similar?
At least from a power standpoint, I believe they are identical.
See the attached excerpt from the B-25 Mitchell Training manual.
This is the reason I was willing to use the SEFC from the B-25C/D as a guide for tuning the R-2600-29 in the Baltimore Mk.V.
Are the engines dimensionally the same?
I believe the Bore and Stroke are the same but the compression changed slightly in different models.
This is from memory but I CAN go back and check the dimensions when life slows down a bit over here and I get some time.
I do not believe from a functional standpoint that there will be any significant change requiring additional performance tuning changes in the AIR file though.
It sounds like the R-2600-29 came in multiple versions like the BMW 801D-2 did.
Although the designation didn't change, the equipment DID change for the better with the later versions.
My guess also is that because of the discontinuation of the Baltimore, it may never have seen the better engines.
Don't feel too bad, the same probably applies to the B-25B/C/D using the R-2600-13.
Just to really throw an even bigger wrench into the machine, check out the attached SEFC also for the R-2600-13 but for a different aeroplane. Note that this one actually specifies a Military Power setting and it is the same as the Take-Off setting.
No, they are not identical. It makes you wonder how the -13 may have changed during its production run.
Note also that the original MitchellC engine without WEP is closer to this one from the Vengeance.
So WHICH -29 engine did the Baltimore have? I have no idea but the time period is a pretty good guide.
Ha ha! I donīt feel so bad, itīs just that just when I thought I had it all sussed out, I got this unexpected peak at a completely unexpected altitude...
The two posts were done almost at the same time because Iīd edited them. Sometimes it takes me a while until the penny drops! Iīd missed the main point on the non-existence of the R-2600-13 for the Baltimore, wondering why weīd used the SEFC in the first place, so I edited it. Then, I added the second post so as not to make the first one even longer with the new MkIIIA results, which Iīd thought were so good. Later, I edited that one too, twice in fact, once to include the MkIIIA kicker results, and again to add the MkV ones. So, itīs just as well that you didnīt read them sooner - they would have been incomplete or different. ... Oh, what a long story!
Very interesting, the 2 new attachments you provide. Thanks very much indeed! They are not really a bigger spanner in the works. On the contrary, I feel they would actually tie in quite well with the early MkI/II Baltimores that had their 308 mph top speed at 13000 ft.
The absence of War Emergency and there only being Military Power proves your point on not having WEP for anything else than Take-off. Then, would it be better to use WEP Option 3 once the .air file is not being tested any longer, to destroy the engine sooner, in order to deter simmers from using it while flying?
Thanks also for your clarification as to the similitude between the -13 and the -29. Thatīs 1 doubt fewer. And, we can then also discard the 1850 Hp version of the -29 engine - another doubt fewer!
Incidentally, one of the 2 old document scans Iīd found mentions the R-2600-13 for the MkV! There does seem to be quite some confusion in the original old sources, doesnīt there?
Good, your moral support! So itīs not as bad as would deem dropping the project for want of higher performance envelope precision.
This peak at 10000 ft seems to come from the low Boost Gain setting, and I was thinking of ways around that, but increasing it again to make the peak coincide with Critical Altitude will cause the surges where top speed is correct now, which is exactly what I was fixing.
Thereīs a comment in AirEd Info for the Boost Gain parameter:
>Maximum MP/Ambient Air pressure
>Sets Max Speed/Max Altitude Factor
Well, at least your Mitchell-B/Cīs flight envelope is backed by the information on the new attachment!
OK. Iīll keep on looking for a good way around for the Baltimores! (Can we have ALL 5 of them? - No, please... Ha ha!)
Cheers,
Aleatorylamp
Last edited by aleatorylamp; May 31st, 2016 at 23:05.
Hello Ivan,
Looking at the numbers of the unexpected 10000ft Hp and Speed Peak, an obvious solution comes to mind, which works, but comes at a price: 7 mph lower WEP speed at 500 ft, but exactly maintaining 1700 Hp there. Iīd already lowered it before from 1721 Hp, to improve the situation.
I increased Drag to reduce 500ft WEP speed from 296 mph to 289.1, and raised Boost Gain from 2.085 to 2.24, getting a max. speed of 319.6 mph at 15000 ft with 36.9 Hg.
Then I went down to 10000 ft to check for the bad peak, and although the 1743 Hp Hp peak was still there, the speed peak was gone, speed staying happily at around 319.5 mph.
The next step is to adjust this "solution" to exactly 320 mph at 15000 ft.
A similar solution can be obtained for the MkIIIA/IV .air file, which, with its lower bad speed peak will lose less speed at 500 ft.
So the million dollar question here is: Can we accept this 7 or 8 mph reduction in the previously agreed 296 or 297 mph max. speed for 500 ft? I would say yes, but I would like to know if you would agree.
Thanks in advance for your always valued opinion!
Cheers,
Aleatorylamp
Been off the net all day. on iPad right now.
Power and speed peak is unavoidable: CFS Single Speed Superchargers.
You are only moving it around. It will not go away.
You will see if you test at more altitudes in between.
Hopefully peak is not too much higher.
I don't understand why sea level speed dropped so much.
Performance tuning is to whatever goal you decide.
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