CEM: noob question time!

[Fredfetish]

I've been playing the British campaign and for the later part you play mostly with the type Ia Spitfire.
What I've noticed is that the plane is really slow.
So, I read about the AI engine management problem and thought “hmmm great don't want to really fiddle with this every second”, but on further investigation, it seems that there are only 3 different settings required:
Low -slow (Rich mixture and fine prop setting, mostly take off speeds)
Low - fast (Rich mixture and coarse prop setting, from vid at about 120 mph)
High - fast/slow (should be coarse prop fast or slow due to thinness of the air and lean mixture ... doesn't really matter since most combat in the game is at low altitude)
In the vid it shows the plane kicking into higher gear at 200 mph with the optimum rpm speed for the later model automatic prop pitching optimized at 3000rpm... which would be my target as well.
So here is the problem... The engine never spins past 3000 rpm on the fine pitch. Even whilst going at 300 mph, if I switch to a coarse pitch, the rpm's instantly drops to 2200 rpm and starts detonating and a huge bleed of airspeed. I’ve dived straight down from 18000 ft with the coarse setting with full trottle and the rpm's never reached 3000. I'm running patch 1.4072. As a result, I obtain a max straight line speed of 320 mph in the Spitfire Ia with the fine prop pitch. (between 0 and 5000 ft) . I quickly checked the manual now, and it seems that this is the correct-ish speed ) (between 450 km ~ 550 km) for the Spitfire at this height, so it seems to me that CEM is just incorrect. (Question markI’ve quickly played with the Me 109 as well and find that the max prop pitch increase of only 10% is viable before the engine starts detonation.
I thought maybe that since I had radiator management on AI that the rpm’s are kept down to prevent overheating, but this is not the case after checking.
Any comments or suggestions anyone?

[Blackdog_kt]

Bdawg and Babi: The engine gauges on all aircraft provide a measure of the same thing, they just use different units. What they measure is the air pressure in the engine's intake manifold. If i'm not mistaken, this is where the fuel metering valve mixes the fuel with the air according to your chosen mixture settings, if there's a lot of air you get more fuel, the engine "sucks" more air to burn because the throttle valve is more open and you get more power. This is probably just before the fuel-air mix enters the cylinders to burn.

How it's measured in engines that use direct fuel injection inside the cylinders i don't know for sure. However, for most intents and purposes manifold pressure shows you how restricted, unrestricted or even force-fed (in the case of supercharging and/or turbocharging) the air supply is into the engine. This is a measure of power, because the engine is essentially a vacuum pump: without the throttle valve all engines would run on full throttle all the time, but that valve can restrict the amount of air that goes into the engine and thus, it starves it of the needed air to burn fuel and decelerates the rate at which the burn cycle occurs, enabling us to reduce power.

The Luftwaffe ones are metric so they use Ata, which is the atmosphere unit (aka bar). Modern general aviation aircraft and American WWII aircraft use inches of mercury (Hg), while Italian ones use the metric equivalent which is millimeters of mercury.
This unit of measure dates back to Torricelli's experiments. Imagine a vertical lab tube filled with mercury with a repository "dish" below it that holds more mercury...if the atmospheric pressure is high, the air pushes down on the surface of the liquid mercury in the dish and forces it to "climb" inside the tube.

1 Ata is the standard air pressure on sea level for a standard weather day (which is defined by a set of further data like temperature and so on, let's not get even more complicated if we don't have to ).
The rough conversion between units is that 1 Ata (or 1000 millibars) = 760mm Hg = about 30 inches Hg (i think it's actually 29.92 inches, on modern dual-unit altimeters the calibration window shows 29.92 inches when you set it to 1000mBar).

You probably realized i left the RAF dials last. This is because

a) The RAF planes automatically adjust the throttles to maintain your chosen manifold pressure. In a USAF or Luftwaffe aircraft, as you climb higher into thinner air you will need to gradually advance the throttle if you want to maintain the same amount of manifold pressure, if you dive to lower altitude into thicker air you will also need to reduce throttle to prevent the pressure from going too high.
In an RAF aircraft you set it once and it will do its best to maintain it regardless of altitude changes. In that sense the power lever in a Hurricane or Spitfire is not controlling the throttle directly, it's controlling the target value of a system that varies the throttle to maintain the selected manifold pressure.

b) The units are relative and not absolute.

This means that while the boost gauge measures manifold pressure in psi it is not the actual pressure in the manifold. What it measures is the pressure in psi relative to the standard pressure on sea level ie, it shows you how far above or below you are from standard sea level pressure.
So, 1 Ata = 760mm Hg = 29.92 inches Hg = 0 psi boost
I think that 1 psi = roughly 2 inches Hg (or is it the other way around? i'm a bit fuzzy at the moment).

In any case, it should be enough to show you that zero boost is by no means low power. It's actually full power on sea level for non-supercharged engines and probably why almost no current day general aviation aircraft use this measuring convention: it's neither intuitive nor satisfying for a general aviation pilot to have a big fat zero indicating full power, since most of these aircraft are normally aspirated (that is, they lack superchargers/turbochargers)

[bDAWg]

hi Blackdog_kt

I found this part you wrote very interesting:

b) The units are relative and not absolute.
"This means that while the boost gauge measures manifold pressure in psi it is not the actual pressure in the manifold. What it measures is the pressure in psi relative to the standard pressure on sea level ie, it shows you how far above or below you are from standard sea level pressure"

I now realize the above bit of info has been written about in the other posts expressed in formulas etc. but the way you put it is easier to understand....it's little bits of practical knowledge like this that will help to fully comprehend the basic principles of boost etc.

there's been much advice given on this subject and to be honest alot of it has been too hard to follow completely...if this was real life and my life depended on it I would make damned sure I did... 100% of it...but it ain't and I just what enough info in order to "fly" these simulated aircraft well enough so that the A.I. or the humans online are not always handing me my ass back

thanks

[Fredfetish]

Anyone?

[Babi]

go to http://forum.1cpublishing.eu/showthread.php?t=21590 for the complete post of Viper2000 (second page). if you are lazy:

Originally Posted by Viper2000

5 - Practical flying

Use throttle to control boost, use propeller control to set rpm, set mixture rich unless you're cruising at reduced power.

At least IRL, problems with CHT or coolant temperature, with oil temperature or with oil pressure will kill most engines much faster than simply running them at high power settings, because the time limits in the manual are intended to allow the engine to achieve its design overhaul life. In general, it has been observed that limits only matter if you realistically expect to use the aeroplane again.

When increasing power, first go to rich mixture, then increase rpm, and then increase power to the desired boost setting.

When decreasing power, first decrease boost, then decrease rpm, and finally weaken the mixture.

You can read recommended settings for some planes in the manual that is in the game folder.

[Fredfetish]

Originally Posted by Babi

go to http://forum.1cpublishing.eu/showthread.php?t=21590 for the complete post of Viper2000 (second page). if you are lazy:



You can read recommended settings for some planes in the manual that is in the game folder.

Done that and it doesn't explain the question that I asked (which I gave a lot of back ground to). Why would the Spitfire Ia fly faster on fine prop setting than coarse? Why doesn't the rpm go above 3000rpm like in the video provided with a fine setting? Based on the information and the answers given it seems like the game doesn't really simulate prop pitch (prove me wrong and I will be happy because I want to learn)

[DrPepper]

Originally Posted by Fredfetish

Done that and it doesn't explain the question that I asked (which I gave a lot of back ground to). Why would the Spitfire Ia fly faster on fine prop setting than coarse? Why doesn't the rpm go above 3000rpm like in the video provided with a fine setting? Based on the information and the answers given it seems like the game doesn't really simulate prop pitch (prove me wrong and I will be happy because I want to learn)

I'm not sure about being faster on the fine setting, I haven't experienced that. But, I get the same thing with the RPMs... I cannot get over that dangerous rpm limit like in the video if I set the pitch fine and crank the throttle full.

The video makes it seem like you can easily wreck the engine doing this, but with full CEM & Heat management the only thing that I have to make sure is the radiator is set correctly... Anything else only affects my speed... Dives, incorrect prop pitch, changing the mixture, throttle wherever I feel like it, nothing seems to make the engine go into dangerous zones.

Doesn't seem right to me. I had seen quite a few people post that they kept blowing their engines so quickly and couldn't get the settings right. I decided not to try CEM & Heat managment for a while because it seemed so hard. Finally when I tried it, I never blow my engine or have oil come up anywhere. Doesn't seem right to me, I think it should be harder.

I'm no ace or anything and can't reach top speeds, but I don't understand why I don't wreck my plane with my horrible engine management. Oh ya, I've tried all variations of the Spit doing this.

[Babi]

Originally Posted by Fredfetish

Done that and it doesn't explain the question that I asked (which I gave a lot of back ground to)

Sorry i mixed up yours and bDAWg's question, at the top of this page.