Detonation

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astaib
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Detonation

Post by astaib »

Hello,

Short question because yesterday on a hot start (at fuel station) I heard a detonation from my engine.

How can I avoid this?
Is it due to hot start?
What do I risk?
Anything to know?

Thank you!!!

Arnaud.
Arnaud
DA40 Star 180 / 40.026 / 2001
Wingtip, landing and taxing LED (Whelen)
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GNS430 NON-WAAS
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Rich
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Re: Detonation

Post by Rich »

Do you really mean detonation or what we often misidentify as a "backfire"? By that I mean air/fuel mixture igniting in the exhaust system.

The latter happens when a cylinder fuel/air charge fails to ignite in the compression cycle, is pumped out in the exhaust stroke and gets ignited by the hot exhaust from the next cylinder. This can happen, for example, if you accidentally switch mags to "off" and back on during a runup. But an overly rich mixture at start could do this also.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Steve
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Re: Detonation

Post by Steve »

That is what I thought - a "Backfire". Interestingly, I've never had one in my DA40 in almost 19 years of operation. Plenty of other airplanes at my home field have them, though.
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astaib
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Re: Detonation

Post by astaib »

OK, thanks.

But can the backfire be as harmfull for the riser and mufflere as when you accidentally switch of the mags during runup?

How to avoid backfire during hot start?

Arnaud.
Arnaud
DA40 Star 180 / 40.026 / 2001
Wingtip, landing and taxing LED (Whelen)
Skitube
GNS430 NON-WAAS
Steam gauges
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AndrewM
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Re: Detonation

Post by AndrewM »

I have read that a backfire can cause cracks in the exhaust and therefore possible carbon monoxide issue. Something to keep in mind for a check at next annual and be careful to ensure you have the CO2 monitor going and potentially a backup.
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astaib
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Re: Detonation

Post by astaib »

AndrewM wrote: Mon Sep 07, 2020 11:34 am I have read that a backfire can cause cracks in the exhaust and therefore possible carbon monoxide issue. Something to keep in mind for a check at next annual and be careful to ensure you have the CO2 monitor going and potentially a backup.
This is exactly my question: the cracks on the exaust system.

How to prevent not to make backfire on a hot startup?

Arnaud.
Arnaud
DA40 Star 180 / 40.026 / 2001
Wingtip, landing and taxing LED (Whelen)
Skitube
GNS430 NON-WAAS
Steam gauges
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AndrewM
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Re: Detonation

Post by AndrewM »

Not sure. I have done many hot starts and never had that occur.
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astaib
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Re: Detonation

Post by astaib »

me too, it only happened rarely, but I don't like to hear this and to risk to damage the exaust system.

Arnaud.
Arnaud
DA40 Star 180 / 40.026 / 2001
Wingtip, landing and taxing LED (Whelen)
Skitube
GNS430 NON-WAAS
Steam gauges
Non certified ADS-b
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Rich
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Re: Detonation

Post by Rich »

I have no magic cure for this. My hot/warm starts are typically to start cranking at full lean mixture and after about a second slowly advance the mixture. Somewhere in there it starts. Works every time.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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astaib
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Re: Detonation

Post by astaib »

This is what I do.
In WOT position.
When it fires, from WOT to idle quickly
Arnaud
DA40 Star 180 / 40.026 / 2001
Wingtip, landing and taxing LED (Whelen)
Skitube
GNS430 NON-WAAS
Steam gauges
Non certified ADS-b
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