Lagg supercharger modes

[SCG_motoadve]

Mode 2 I can see how MP increases above 3,200.

Mode 1 only makes it having less MP at high alt.

 

So why not leave the Supercharger in mode 2 all the time?

At low alt you switch between gear 1 and 2 and nothing happens.

So if you keep it at gear 2 all the time then you have the best performance at all alttitudes, so what is gear 1 for?

 

Is it a bug in the game or what was the purpose of it in real life?

[Jade_Monkey]

Good question, i wonder what the drawbacks of leaving stage 2 at low altitudes are too. Anyone?

[216th_Lucas_From_Hell]

As far as I understand it's just that: you'll be running the engine harder and getting more power.

 

The catch is that this produces more heat, and to counter that you need to open both radiators more thus neglecting whatever minor additional gains you could get from that.

[JtD]

Stage 2 consumes more power from the engine in order to compress the intake air to a higher degree than stage 1. In order to not damage the engine at low altitude, the resulting higher boost will just be throttled down again to the maximum the engine can take. But you don't get the power you put into compressing the air back at this point, it is just wasted. Leaving the engine in stage 2 at sea level will cost you about 100hp at full throttle, which is about 10% of the available power.

 

It costs a lot of performance, which you can check in game, just fly it in stage two at top speed at sea level or anywhere up to about 2km and then switch to stage one, you will see that the plane accelerates. It should gain around 15km/h.

 

Another point is that the 100hp that go into compression essentially all get turned into heat eventually, and you can damage the supercharger or other intake components if the engine is not designed for this abuse. Not sure if/how this is modelled in game.

Edited October 12, 2017 by JtD

[SCG_motoadve]

Stage 2 consumes more power from the engine in order to compress the intake air to a higher degree than stage 1. In order to not damage the engine at low altitude, the resulting higher boost will just be throttled down again to the maximum the engine can take. But you don't get the power you put into compressing the air back at this point, it is just wasted. Leaving the engine in stage 2 at sea level will cost you about 100hp at full throttle, which is about 10% of the available power.

 

It costs a lot of performance, which you can check in game, just fly it in stage two at top speed at sea level or anywhere up to about 2km and then switch to stage one, you will see that the plane accelerates. It should gain around 15km/h.

 

Another point is that the 100hp that go into compression essentially all get turned into heat eventually, and you can damage the supercharger or other intake components if the engine is not designed for this abuse. Not sure if/how this is modelled in game.

Yep , I just tested it and it works as you said.

 

I was expecting a increase or decrease of MP in the instrument readings.

[Jade_Monkey]

Thanks for clarifying!!

[ZachariasX]

By leaving in stage 2, you have so much compression that soon after you pass 50% throttle lever travel, you have excess manifold pressure and you will blow the engine. It is a very dangerous thing to do.

 

Think of supercharger gearing like gearing in a bicycle. You theroretically could leave it in the longest gear, but unless you go fast (high altitude) it is actually more work than in a shorter gear. This waste (mentioned by JtD) makes you slower down on the deck in high gear.

 

Ideally, the gearing of your compressor turbine is such, that at your (rated) altitude, throttle fully open produces max. permissible (rated) manifold pressure.

 

The longer the gearing is, the less efficient your engine will be down low (with a similar comressor turbine). This is the reason why we have the LF and the F Spitfire variants. They are just custuom tailored to the indended working altitude. The P–51 Merlin engine was explicitly geared to have the critical altitude of the 2nd stage at the flight level, at which they were supposed to escort the bombers.

 

It can however be beneficial doing the opposite of what the OP suggested, namely running low gear at high altitude. This namely in cruise flight, when you only need part of the power. If you can reach intended power output on the lower gear at altitude, you will save fuel, as you lose less power in turning the compressor at higher speeds. This was done and is good practise.

 

It is of note that this comes at a reduction of manifold temperature. In the B–17, it is beautiful how you can contol manifold temperature with the adjustment of the supercharger rpm.

 

Yes, it is a cool topic.

Edited October 12, 2017 by ZachariasX

[6./ZG26_Klaus_Mann]

So much disinformation out here. 

 

First of all: All ingame Aircraft are "using" the Supercharger ALL of the time. This isn't Mad Max. How else would you expect your Engine Intake Pressure to be higher than your surrounding Atmospheric Pressure?

 

Also: NO: You can't overboost in Second Gear. You have Wastegate, and that just blows excessive Pressure out of the System. 

 

YES, all ingame Aircraft are supercharged. (Who even started all of these myths?). Some Aircraft can change the Ratios at which the Supercharger Spins in Relation to Engine RPM. 

That is what most people call "Shifting the Supercharger", "Switching the Supercharger on" and whatever else NONSENSICAL, MISLEADING terminology they come up with. 

 

Switching it to a higher Speed simply means it CAN deliver more Air at the expense of Power. All excess air is just blown off through the Wastegate Valve. 

The Amount of Power the Supercharger requires is constant at a constant RPM. Running it at high RPM eats more Power than it does at low RPM. 

If you Switch up too early you just produce a lot of excess Pressure for NOTHING. 

 

No, the Point to shift is NOT when MAP starts dropping. Imagine your Altitude as a X Axis and your Power on the Y-Axis. Per Supercharger Gear you have a distinctive Power Curve. Peak Power is created at FTH for each Gear. 

For example: A Theoretical Engine Produces 

• 1st Gear: 1000hp at 0m; 1100hp at 1000m; 1200hp at 2000 (FTH, now MAP drops); 1000hp at 3000; 800hp at 4000m
  
• 2nd Gear: 700hp at 0m; 800hp at 1000m; 900hp at 2000m; 1000hp at 3000m; 1100hp at 4000m (FTH)
  
• Although MAP drops at 2000m, only when shifting at 3000m do you gain Power again. 
  

For example this Bristol Engine. The Shifting Point is where the Power Curves intersect. You can'T see that however on the MAP Gauge and have to trust the Manufacturers Data

 

Edited October 12, 2017 by 6./ZG26_Klaus-Mann

[Finkeren]

By leaving in stage 2, you have so much compression that soon after you pass 50% throttle lever travel, you have excess manifold pressure and you will blow the engine. It is a very dangerous thing to do.

This is false. For one thing, there are safety systems in place to prevent too high pressure in the air.

 

In addition: Manifold pressure does not measure the pressure in the induction system. It actually measures the suction of the cylinder as it draws air in for the next stroke. No matter what pressure the air is at it doesn't directly show in the manifold pressure, only insofar as it helps the engine develop more power and therefore create more suction.

[6./ZG26_Klaus_Mann]

Same for our Aircraft, Mainfold Pressure Reading comes from just before the Inlet Valve. Add to this Picture the Supercharger just behind the Throttle. 

 

[JG5_Schuck]

Read this....... all you need to know!

 

http://www.pacificaviationmuseum.org/pearl-harbor-blog/superchargers-and-turbochargers/

 

 

 

 

 

NB, there are a few little mistakes in some of the descriptions, but on the whole you'll get the idea.

Edited October 12, 2017 by JG5_Schuck

[BlznSaddles]

Just another note... the P40 does NOT have a wastegate aka blow-off valve. Although it only has a single stage supercharger as well, at low altitudes you can run way too much manifold pressure if you're not careful.

[JtD]

You have Wastegate

No aircraft in game has a wastegate. A wastegate vents exhaust fumes of turbocharged engines so that they don't go through the turbocharger causing higher than required boosts. It has nothing to do with the inductive system.

All aircraft in game control the boost through a throttle.

 

The Amount of Power the Supercharger requires is constant at a constant RPM.

It is not. It very much depends on what it compresses, i.e. air density, temperature, pressure.

[6./ZG26_Klaus_Mann]

It is not. It very much depends on what it compresses, i.e. air density, temperature, pressure.

Yes, I oversimplified.  

 

 

No aircraft in game has a wastegate. A wastegate vents exhaust fumes of turbocharged engines so that they don't go through the turbocharger causing higher than required boosts. It has nothing to do with the inductive system. All aircraft in game control the boost through a throttle.

Yep, I'm wrong. Ok, forget that, it's a Blow Off on the Induction, and a Wastegate or Bypass in the Exhaust. I get confused. 

Edited October 12, 2017 by 6./ZG26_Klaus-Mann