Boost Gauge Readings

[emfrat]

Just lately, I have been finding some boost gauges which seem to be working backwards.
I know have far too many addon aircraft installed, but on some, when I start things up, the boost gauge shows a mildly positive figure, and as I increase the throttle setting, it moves up to something like plus 6lbs. On the recently downloaded ones I am talking about, the gauge before start shows about minus half a pound, and when I start the engines, this moves to about minus 4 pounds, and never gets into the plus range even at full throttle.
Could someone tell me what I should be seeing?

TIA
MikeW

[DaveB]

Hi Mike

Well.. you certainly shouldn't see it go into the minus as you open the throttle. My guess is that the programmer has cocked up mate so I'd get in touch with him. Boost gauges will generally (if not always) read in the minus at idle then move progressively into the plus as the throttles are opened. Boost to throttles.. RPM to Prop Pitch
It's impossible to say exactly what you should be seeing without knowing the aircraft concerned but it definately aint you are seeing :think:

ATB

DaveB :tab:

[Garry Russell]

My first thought is are you using FS.9 or FS X and is the aircraft a full native and the panel the correct one for that aircraft model :think:

Mixing and matching can give odd results

Like Dave says, if you tell us which aircraft then someone might have an answer

Garry

[SkippyBing]

Not really up to speed on this sort of thing, but is there a difference if you have superchargers fitted?

[petermcleland]

Not really up to speed on this sort of thing, but is there a difference if you have superchargers fitted?

Yes Skippy...Turbochargers will provide a positive Boost up to their critical altitude...In the case of my Turbo A36 the boost rises on take-off, after a pause for turbo to cut in, up to 35 inches of mercury. This is maintained at full throttle up to 18,100 feet and it then slowly declines with further climbing. With a normally aspirated engine, before startup the gauge should read atmospheric pressure (Say 29.92 inches of mercury). As the engine bursts into life the boost will drop down sharply as the inlet manifold pressure is reduced to below atmospheric by the suction effect of drawing air into the engine. The boost gauge will then rise with opening the throttle to a maximum on take-off. Then as the aircraft climbs away at full throttle the MP will drop steadily as altitude is gained.

[DaveB]

Hi Skip

Dunno the answer to that mate. I'm certain that Ed modelled superchargers on his Spit 16 and the boost/map on that doesn't work backwards as I remember. Could be wrong though and not for the first time It would ultimately help if we knew the detail :think:

ATB

DaveB :tab:

[SkippyBing]

Peter,

Thanks for that, I've only really flown normally aspirated pistons and I'm never really sure if I'm thinking things through correctly when I add a turbo!

[DaveB]

I'm sure Peter's post wasn't there when I posted.. must have snuck in under radar

Comments taken as read really. A supercharger will delay the inevitable and make it happen higher up but I thought this guy was saying his boost gauge on the as yet unknown model moved into minus when he opened the throttle which ain't where the thread is at now. It still sounds like a programming error to me

ATB

DaveB :tab:

[Garry Russell]

Yep

Starts minus half a pound then gets lower with thottle up :think:

Garry

[nigelb]

Could be somthing as simple as the wrong sign (+ or -) in the .air file. Just had a quick look and record 505 has an entry for boost gain. For example, on the Avro York the boost gain is 3.541203. Now I have no idea if this is the right tree I am barking up, but I do think if that value were negative, it could screw the gauge reading up.

Nigel²