Merlin - prop pitch, boost and mixture problems

[reflected]

I noticed that the coarser I set the propellor, the higher the boost goes without me touching the throttle.

Can somebody explain why? Is it accurate? I don't remember reading about this anywhere and it's not like this on the AccuSim FSX Spitfire either.

It's especially confusing knowing that it's not adviseable to use low RPM and high power because it's a big stress to the engine. But then, in order to lower the boost I have to throttle FAR back.

Also, I have a problem with weak mixture.
1) the lever animation is inverted.
2) I climbed up to 24,000 feet and set the mixture to weak (RPM below 2,600, Boost below +2) and my machine started shaking. Why? Is it that "weak" was too rich that high up, and auto rich was actually leaner? It worked fine at lwoer altitudes. Isn't it a bug?

Thanks!

[ZaltysZ]

Originally Posted by reflected

I noticed that the coarser I set the propellor, the higher the boost goes without me touching the throttle.

Can somebody explain why? Is it accurate? I don't remember reading about this anywhere and it's not like this on the AccuSim FSX Spitfire either.!

In short: You put load on engine, RPM decreases, so air usage of engine drops, but it does that more than output of supercharger. I don't have Accusim, but I think I saw the same in their videos.

[Robo.]

Originally Posted by reflected

I noticed that the coarser I set the propellor, the higher the boost goes without me touching the throttle.

Can somebody explain why? Is it accurate? I don't remember reading about this anywhere and it's not like this on the AccuSim FSX Spitfire either.

Yes it is accurate as far I know, this is one of the features slightly wrong in the AccuSim pack. RPM and MFP are depending on each other and it's discussed on AccuSim forums, too. If you're flying at say +4lbs. boost (Merlin III and XII with ) and 2300RPM and then coarsen to 2100RPM, your boost should (and in CloD will) rise a wee bit. Just as rising your boost will affect your RPM. That's why we're supposed to adjust your boost and RPM in certain order to achieve desired power on early Merlins.

Later marks have had automatic boost control or different (and 2-stage) superchargers.

Originally Posted by reflected

It's especially confusing knowing that it's not adviseable to use low RPM and high power because it's a big stress to the engine. But then, in order to lower the boost I have to throttle FAR back.

Low boost = throttling far back. Maybe I don't understand what you're asking, but you're right. Early Merlins generally liked higher boosts (by design). You don't want to fly low RPM high boost (that's why you have to throttle back) or vice versa, high boost and RPM too low. Spark plugs dude, spark plugs...

Originally Posted by reflected

Also, I have a problem with weak mixture.
1) the lever animation is inverted.
2) I climbed up to 24,000 feet and set the mixture to weak (RPM below 2,600, Boost below +2) and my machine started shaking. Why? Is it that "weak" was too rich that high up, and auto rich was actually leaner? It worked fine at lwoer altitudes. Isn't it a bug?

Yeah mixture as such and high alt performance and behaviour are completely off as in 1.05. Spitfires have got that lever reversed, it is only correctly animated in Rotol Hurricane, and it's not having the effects it should have on fuel economy, engine temperature and performance. There were some limit on minimum RPM and MFP, but I don't remember that from the top of my head. Your RPM might be slighly on the high side. As for MFP, you should not be physically able to get auto lean + low boost combination due to the throttle and mixture levers being linked together.

I will try the high alt behaviour in 1.05, what I know from previous versions it's a pain regarding glykol temps, she was so much easier to cool up there, but in CloD, the temp are really high even high up...

edit - slepping

[reflected]

Ah OK, thanks for the info!

So apart from the high alt performance and the mixture, which are bugged, it's all accurate.

Is it also why my engine starts coughing whenever I throttle back on landing (high RPM, low boost), or when I start applying full throttle on takeoff?