Engine detonation

[Kalin]

Since the previous update by air temperature at or below 12C and MANIFOLD PRESS. above 26 I am hearing a strange sound from the engine wich I suppose is detonation.
After applying carb heat the sound stops. But how to make a proper take off without carb heat on hot?

Thanks!

[Taguilo]

Since the previous update by air temperature at or below 12C and MANIFOLD PRESS. above 26 I am hearing a strange sound from the engine wich I suppose is detonation.
After applying carb heat the sound stops. But how to make a proper take off without carb heat on hot?

Thanks!

Just let CHT rise to proper values before increasing throttle too much/too fast.
Wait at least for 15 C to avoid detonations, and to 100 C before doing engine runup.

Tom

[DAVIDF]

It doesn't seem to matter how long you let the engine warm up, the detonation sound/exhaust flame effect always come back if you use anything above half throttle.
I might be doing something wrong, but it does seem like something might be broken. It never did this prior to this latest patch.
Using FSXA here.

[Kalin]

Same here! And can't find a logic when it will start. Sounds like bug. Also FSXA user.

[DAVIDF]

If this could be looked at then that would be great.
As it stands the plane is very annoying to use becasue of the racket it makes and the constant belching smoke.

I came across a forum thread on the internet from a real Beaver pilot who was asking what might be making his plane misfire on occasion.
The resounding answer that came back was to ground the plane and get the engineers involved.

Thank you.

[Taguilo]

. Sounds like bug.

It is not.

Detonations are randomly provoked if, for example, engine is cold started (CHT below 50 C) and throttle is above 70 %, or SAT ambient temp (current temp-ISA) is below 10 C and CHT is below that.

So throttle should be kept low (below 50 %) until engine is warm enough.

BTW, to be sure that engine is detonating, just go to external view and check for short flames coming out of the nozzle.

Tom

[DAVIDF]

Hi Tom,
Definately detonating. The flame effect is visible from the exhaust and matches the sound effect.

So on a hot Summer day how long does an engine warm up take? Longer than the 20 odd minutes I patiently gave it?
The temp gauages had topped out into the green by then, but still anything even slightly more than half throttle and it starts to bang. That can't be correct and it did not do this before the recent patch.

Perhaps some interlinked logic is being derailed by a bad data feed from something else.
How is the detonation effect coded? What exact criteria makes the effect fire? If I know that then I can test.

I know the detonation effect is intended, but I don't think it is working properly.

[Taguilo]

Hmm, sounds weird, yes.

You say then it happens after the latest update right? I will check that.

Tom

[DAVIDF]

My last update before this one was from mid-May...so I think I've missed a few of the intermediate patches.
Don't want to mislead, but previously the misfire wasn't evident.
The versioon I have installed now is from the 19th of June.
Kalin might have a different patch history, but he/she too has only noticed this since a 'recent' patch. I notice that Kalin's first post on this is dated 17th of June though, so it can't have started in the most recent patch. in that case.
Sorry to have confused the issue.
Which install did you first see the problem in Kalin?

[Taguilo]

I checked it and works as expected.

From Beaver's POH:
"AT AMBIENT TEMPERATURES BELOW STANDARD ALTITUDE TEMPERATURE (15 C/59 F AT S.L.) WITH CARBURETOR AIR AT COLD, OVERBOOSTING AND DETONATIONS ARE POSSIBLE AT MAP SETTINGS BELOW THE NORMAL MAXIMUM PERMISSIBLE. THEREFORE, TAKE OFF MAP MUST BE REDUCED BY 2% PER 11 C (20 F) BELOW STANDARD, IF ENGINE LIFE IS TO BE PRESERVED."

Are you taking Carb Heat into account? Always keep it in the green sector (above ~ 4 C).

Tom

[Kalin]

I saw this in the manual, but I can't undetstand it
Culd you explain the proper procedure? Should we take off with carb heat on in this situation?

[Taguilo]

Should we take off with carb heat on in this situation?

Yes you should.
Actually there is no ON-OFF on Carb Heat gauge, but instead a green sector in where you need to stay, mostly in cold weather (below 10 C) if you don't want to hear sporadic detonations.
With lever in top most position there is no heat applied, though air temp, because of compression, is always colder than ambient.

You can control heat by moving the lever, or you can hit FS's shortcut key (H by default) to make the lever postion at an optimum for current situation.
Also remember that you can apply carb heat in hot weather to reduce CHT (as mixture becomes richer) ; just avoid going over the red line.

Tom

[Kalin]

Thank you, Tom! Now everything is clear!

[DAVIDF]

Thank you for you patience Tom.
Let me confess that I've just discovered that the Summer's day I was testing in was June in the Sim, but Active sky was set to historic weather for February and was injecting cold (but sunny clear) weather. A glance up at the cabin thermometer (outside temp) showed actual temperature was only about 4 degrees C and not the 27 degrees I was expecting. The sim experience only goes so far. Maybe I need to hook up some AC to blow cold air on me!
Carb heat lever down sorts out the detonation. And No problems in actual Summer weather conditions of course!
Sorry for my stupidity and thanks again.

[Taguilo]

No prob David,

You know, when working with different updates something might become messed, so it is always worth giving a check.

Tom