Engine Power/Aircraft Speed

[Elf1606688794]

With the throttle firewalled, 100% RPM and whatever fuel setting is default, I'm at 7000 RPM and 58 MP. I'm at 482 feet with default weather and I'm doing 305 knots TS.

With no wind, my ground speed is 305 mph.

When I drop the RPM to 2500 and with the throttle at Mil power MP drops to 32 and I'm doing 177 knots TS and  slowly dropping. I'm also slowly losing altitude.

I'm at default setings for cowl flaps, mixture, intercooler and oil cooler. Mapping those commands to my throttle (Virpil) doesn't seem to be working. I'll have to write down all those keyboard commands and try using those.

.trk attached.

F4U_Test.trk

[felixx75]

7000 RPM is surely a typo (should be 2700).

The keybinds for the coolers work for me without any problems...

Edited July 10 by felixx75

[Elf1606688794]

7000 RPM is not a typo. I have it mapped to the flaps lever on my Virpil throttle and when I move the lever it's as if I was using the RPM handle that can get the engine way past the 2700 it's supposed to be maxed at. I'll see if I can grab a screen shot.

If I use the keyboard commands I can open/close the cowl flaps easily. If I try using the hat switch it's mapped too then it's no joy.

[felixx75]

2 hours ago, Elf1606688794 said:

7000 RPM is not a typo. I have it mapped to the flaps lever on my Virpil throttle and when I move the lever it's as if I was using the RPM handle that can get the engine way past the 2700 it's supposed to be maxed at. I'll see if I can grab a screen shot.

If I use the keyboard commands I can open/close the cowl flaps easily. If I try using the hat switch it's mapped too then it's no joy.

Ok, but then hopefully you realise that 7000RPM is a bug. The maximum permitted RPM in a dive is 3060. The engine would not survive 7000RPM for half a second...

[Elf1606688794]

I was pretty sure it was a bug when I noticed the rpm gauge spin around twice while making the video, After I stopped recording I moved the lever back and forth to verify what I just saw.

This leaves me in an interesting position where I can't tell how many RPMs I'm actually running. I'll have to wing it (pun intended). I suppose.

Edited July 12 by Elf1606688794

[Templar560]

On 7/12/2025 at 5:33 AM, Elf1606688794 said:

I was pretty sure it was a bug when I noticed the rpm gauge spin around twice while making the video, After I stopped recording I moved the lever back and forth to verify what I just saw.

This leaves me in an interesting position where I can't tell how many RPMs I'm actually running. I'll have to wing it (pun intended). I suppose.

I think this is now fiixed in today's update.

[cw4ogden]

Still feels slow after first patch, at sea level at least.  Max manifold pressure I can obtain is 53 maybe 54.  Tried making the throttle a slider but I don't think it's axis related.

2700 rpm, water injection on, All cooling systems closed, 50 percent fuel - Max level speed 283 knots

[Saxman]

1 hour ago, cw4ogden said:

Still feels slow after first patch, at sea level at least.  Max manifold pressure I can obtain is 53 maybe 54.  Tried making the throttle a slider but I don't think it's axis related.

2700 rpm, water injection on, All cooling systems closed, 50 percent fuel - Max level speed 283 knots

283 kts IAS is 342mph TAS at 500ft. That's very close to the 1D's rated speed at sea level (350mph). That could easily be the difference between being even slightly out of trim, or just a bit nose up.

Edited Thursday at 07:25 PM by Saxman

[cw4ogden]

36 minutes ago, Saxman said:

283 kts IAS is 342mph TAS at 500ft. That's very close to the 1D's rated speed at sea level (350mph). That could easily be the difference between being even slightly out of trim, or just a bit nose up.

Not sure how you are calculating that.  I get about 330mph true, when converting 283 KIAS to True airspeed and subsequently converting to mph, 20 mph less than the quoted 350 mph, which is also low depending on sourcing.  

...

And that's leaving aside how artificial it feels trying to actually accelerate to that speed in level flight.  To achieve 283, I'm diving to 300 or so, then holding level flight to see when the airspeed stops bleeding off.  I've yet to get it above 265 knots or so without needing a dive to get over the "invisible wall" this module feels like it has with respect to acceleration.

And being slightly out of trim, which I wasn't or slightly slight nose up, which I wasn't, might account for a reduction of  few knots at best, not a 20 knot reduction in top speed.  

Edited Thursday at 08:01 PM by cw4ogden

[Invisibull]

21 hours ago, cw4ogden said:

Not sure how you are calculating that.  I get about 330mph true, when converting 283 KIAS to True airspeed and subsequently converting to mph, 20 mph less than the quoted 350 mph, which is also low depending on sourcing.  

...

And that's leaving aside how artificial it feels trying to actually accelerate to that speed in level flight.  To achieve 283, I'm diving to 300 or so, then holding level flight to see when the airspeed stops bleeding off.  I've yet to get it above 265 knots or so without needing a dive to get over the "invisible wall" this module feels like it has with respect to acceleration.

And being slightly out of trim, which I wasn't or slightly slight nose up, which I wasn't, might account for a reduction of  few knots at best, not a 20 knot reduction in top speed.  

Yes, that's right - it's right around 330 mph and I agree that you can't seem to get there unless there's at least a slight dive first. The bigger issue, according to the speed trial documentation, is up at 22.8 K' - I should be seeing 250 kts ias (395 mph tas), but I haven't been able to get over 220 kts. That's a 12% shortfall of performance. This is at 11,197 lbs, trimmed out as close to perfect as I can get it, no wind, in high blower, 2700 RPM, 54" manifold and 20C.  It's early yet and I have no doubt this will be remedied in short order. 

[Saxman]

47 minutes ago, Invisibull said:

Yes, that's right - it's right around 330 mph and I agree that you can't seem to get there unless there's at least a slight dive first. The bigger issue, according to the speed trial documentation, is up at 22.8 K' - I should be seeing 250 kts ias (395 mph tas), but I haven't been able to get over 220 kts. That's a 12% shortfall of performance. This is at 11,197 lbs, trimmed out as close to perfect as I can get it, no wind, in high blower, 2700 RPM, 54" manifold and 20C.  It's early yet and I have no doubt this will be remedied in short order. 

Just an FYI, please be careful when presenting these kinds of documents. BuNo. 2155 was a fairly early Birdcage model. In fact it was the third production machine (first production Corsair was BuNo. 2153.

[Invisibull]

23 minutes ago, Saxman said:

Just an FYI, please be careful when presenting these kinds of documents. BuNo. 2155 was a fairly early Birdcage model. In fact it was the third production machine (first production Corsair was BuNo. 2153.

Here's some test results from Aug 1945 with an F4U-1D, which you'll notice, is 10 mph faster, even though it's with a combat loadout, so roughly 1000 lbs heavier than the Birdcage when it was tested. 

http://www.wwiiaircraftperformance.org/f4u/f4u-1d-acp.pdf

 

 

[westr]

5 hours ago, Invisibull said:

Yes, that's right - it's right around 330 mph and I agree that you can't seem to get there unless there's at least a slight dive first. The bigger issue, according to the speed trial documentation, is up at 22.8 K' - I should be seeing 250 kts ias (395 mph tas), but I haven't been able to get over 220 kts. That's a 12% shortfall of performance. This is at 11,197 lbs, trimmed out as close to perfect as I can get it, no wind, in high blower, 2700 RPM, 54" manifold and 20C.  It's early yet and I have no doubt this will be remedied in short order. 

Well so far it’s not been acknowledged yet as an issue or discrepancy by Magnitude. Im not expecting anything to soon. 

[Invisibull]

28 minutes ago, westr said:

Well so far it’s not been acknowledged yet as an issue or discrepancy by Magnitude. Im not expecting anything to soon. 

All we can do is provide the primary sources and hope for the best. Hope springs eternal! 

[captain_dalan]

On 7/24/2025 at 9:55 PM, cw4ogden said:

Not sure how you are calculating that.  I get about 330mph true, when converting 283 KIAS to True airspeed and subsequently converting to mph, 20 mph less than the quoted 350 mph, which is also low depending on sourcing.  

...

And that's leaving aside how artificial it feels trying to actually accelerate to that speed in level flight.  To achieve 283, I'm diving to 300 or so, then holding level flight to see when the airspeed stops bleeding off.  I've yet to get it above 265 knots or so without needing a dive to get over the "invisible wall" this module feels like it has with respect to acceleration.

And being slightly out of trim, which I wasn't or slightly slight nose up, which I wasn't, might account for a reduction of  few knots at best, not a 20 knot reduction in top speed.  

 

21 hours ago, Invisibull said:

Yes, that's right - it's right around 330 mph and I agree that you can't seem to get there unless there's at least a slight dive first. The bigger issue, according to the speed trial documentation, is up at 22.8 K' - I should be seeing 250 kts ias (395 mph tas), but I haven't been able to get over 220 kts. That's a 12% shortfall of performance. This is at 11,197 lbs, trimmed out as close to perfect as I can get it, no wind, in high blower, 2700 RPM, 54" manifold and 20C.  It's early yet and I have no doubt this will be remedied in short order. 

Am I doing something wrong?

My sea level tests:
 

50% internal fuel. 56-59 MP, 2700RP, experimenting with fuel mixture. 
Without water injection, I get 303-304 knots ASL, which translates to 348-350mph or 563kmh. Seems right on the money there, if that chart is correct.
With water injection, I get 317 knots ASL, 365 mph or 587kmh.
I'm still not sure which fuel mixture works best, and to use when, but the numbers appear close to what they should be. I can take her up to 320 knots in a shallow dive. 

Why do you think we have such different results? Are your cowls tucked in? 

[Invisibull]

Here's what you should be seeing at sea level with the parameters listed in the doc below - 358 mph / 1.150779 mph/kn ≈ 311.10 knots. Best I could get was about 302 knts. The disparity is even more pronounced at 19,900 as I stated above. Edit: Just noticed that the empty weight for our Corsair is listed as 9903. Maybe that's where the missing 9 knts are going? 

 

 

 

Edited Saturday at 03:21 PM by Invisibull

[Saxman]

39 minutes ago, captain_dalan said:

I'm still not sure which fuel mixture works best

For the R-2800-8W it should be Auto-Rich for takeoff, but otherwise leave it in Auto-Lean.

[cw4ogden]

50 minutes ago, captain_dalan said:

 

Am I doing something wrong?

My sea level tests:
 

50% internal fuel. 56-59 MP, 2700RP, experimenting with fuel mixture. 
Without water injection, I get 303-304 knots ASL, which translates to 348-350mph or 563kmh. Seems right on the money there, if that chart is correct.
With water injection, I get 317 knots ASL, 365 mph or 587kmh.
I'm still not sure which fuel mixture works best, and to use when, but the numbers appear close to what they should be. I can take her up to 320 knots in a shallow dive. 

Why do you think we have such different results? Are your cowls tucked in? 

For me at least, I'm not getting anywhere near 59 inches of manifold pressure.

[Invisibull]

I get 57" and about 302 kts at sea level at the weight of 12088 lbs. As far as I can tell, there's no water injection implemented yet. 

[felixx75]

11 minutes ago, Invisibull said:

I get 57" and about 302 kts at sea level at the weight of 12088 lbs. As far as I can tell, there's no water injection implemented yet. 

if you get 57" MP at sea level, there is no reason to assume that water injection is not implemented. WEP is MIL + water injection. And that should give you pretty much 57“ MP (57.5” to be exact).

[Saxman]

3 hours ago, Invisibull said:

I get 57" and about 302 kts at sea level at the weight of 12088 lbs. As far as I can tell, there's no water injection implemented yet. 

ADI is implemented, it's just not being tied to the throttle like it's supposed to be and is instead a separate button press. At least it wasn't before the patch. If they changed that it wasn't in the notes.

[Invisibull]

2 hours ago, felixx75 said:

if you get 57" MP at sea level, there is no reason to assume that water injection is not implemented. WEP is MIL + water injection. And that should give you pretty much 57“ MP (57.5” to be exact).

Yes, it might be implemented, but without the wire or need to activate the water injection - it's still def a WIP 

3 minutes ago, Saxman said:

ADI is implemented, it's just not being tied to the throttle like it's supposed to be and is instead a separate button press. At least it wasn't before the patch. If they changed that it wasn't in the notes.

The button press changes nothing, so it seems to not be implemented yet. As said in another post, the lack of a wire to inhibit travel of the throttle makes it pretty obvious that it's still a WIP. 

[captain_dalan]

8 hours ago, cw4ogden said:

For me at least, I'm not getting anywhere near 59 inches of manifold pressure.

What is your throttle setting? I get 59 by pushing it all the way forward.

9 hours ago, Invisibull said:

...Edit: Just noticed that the empty weight for our Corsair is listed as 9903. Maybe that's where the missing 9 knts are going? 

 

Could be. At least those pylons we haul around must be worth some extra weight, on top of drag.

3 hours ago, Invisibull said:

 

The button press changes nothing, so it seems to not be implemented yet. As said in another post, the lack of a wire to inhibit travel of the throttle makes it pretty obvious that it's still a WIP. 

It absolutely is implemented. I have it on one of my HATs. That's how I got to 317 knots (in the second part of the video) and 320 in a shallow dive to the deck. Make sure your binding is working. 

Edited yesterday at 12:19 AM by captain_dalan

[captain_dalan]

8 hours ago, Saxman said:

For the R-2800-8W it should be Auto-Rich for takeoff, but otherwise leave it in Auto-Lean.

That's the middle position, right? 

[captain_dalan]

Latest test, no video this time around. 
Gross weight 12176lbs, 6 rockets and 48% fuel, the closest I could get to that chart.

2700RPM, 59 MP, auto lean = 305 knots ASL, 351mph or 565mkh
2700RPM, 59 MP, auto lean, water injection on = 314 knots ASL (managed to push it to 315 by decreasing the MP a bit to 37-38),  or 361mph or 582kmh.
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