Engine back firing

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BigT-65
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Engine back firing

Post by BigT-65 »

While taxiing, particularly while reducing the throttle to slow down, I get a lot of back firing from my P-47. I am also constantly getting mechanic messages saying that I have detonation damage. What am I doing wrong? Where should I have my mixture set when taxiing? i am finally getting to where I can land this airplane very well, I now need to get this back firing under control.
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Jacques
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Engine back firing

Post by Jacques »

On ground for warm -up, taxi, takeoff and climb I keep the mixture fully forward at Full Rich or Auto -Rich. If I’m using Full Rich, I move it back to Auto Rich once I’m in the climb. Auto Lean I may or may not use after I’ve leveled off. It depends on if I’m doing touch n go’s or settling in for a longer flight.

With regards to the backfiring on taxi, are you using your boost lever at all on the ground?

And are you moving the throttle slowly when applying and decreasing power?

I can’t really think of too many reasons why you would have backfiring while taxiing around. I mean other than that kind of the nature of this beast- there’s always little puffs that come out when applying power and reducing. Mainly just keep your throttle movement slow and steady.



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Last edited by Jacques on 17 Jul 2018, 23:56, edited 1 time in total.

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BigT-65
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Re: Engine back firing

Post by BigT-65 »

Jacques wrote:On ground for warm -up, taxi, takeoff and climb I keep the mixture fully forward at Full Rich. I only move it back to Auto Rich once I’m in the climb. Auto Lean I may or may not use after I’ve leveled off.

With regards to the backfiring on taxi, are you using your boost lever at all on the ground?

And are you moving the throttle slowly when applying and decreasing power?

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Thanks for your reply. I have been going to auto rich after starting and I usually keep it there until I get leveled off then go to auto lean. I don't use the turbo on the ground. I may be moving the throttle too fast, because that's when it back fires the most, decreasing and increasing throttle. I tried slowing it down on a flight I just finished. I didn't get much back firing but I still got a bad engine report after landing. On landing approach I did notice some smoke coming from the engine. I had been flying at about 2500 ft with auto lean and switched to auto rich to land. No turbo boost.
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Jacques
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Re: Engine back firing

Post by Jacques »

I’m sorry, I’m a habitual editor of my own posts, so maybe go back up and see what I edited!

One more thing, engine damage could easily occur because your exceeding the Manifold Pressure or RPM limits, or both. Be sure to have the recommended figures at hand for each phase of flight so you don’t over stress the engine.


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Jacques
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Engine back firing

Post by Jacques »

Yeah, even moving the throttle slowly will generate some puffs from the exhaust! Even while flying in cruise settings, occasionally there’s a little puff of exhaust.

Detonation damage will definitely show up if you push the throttle past the recommended max of 52” and (I think 2550 RPM)

Remember also the small water injection (ADI) switch on the front, lower part of the throttle quadrant. If you use TrackIR it’s easy to see, if you only use default cockpit view it looks like another switch on the left side panel so you might need to mouse over it to identify it!


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BigT-65
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Re: Engine back firing

Post by BigT-65 »

I do keep a close eye on manifold pressure and prop rpm. I do use Track IR a lot. I have not used the water injection yet. I don't think it said anything about it in the P-47 manual. I am not sure what it's for or when I need to use it.
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Jacques
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Engine back firing

Post by Jacques »

Water injection I think is discussed on page 37 of the manual, or somewhere nearby. In the real aircraft it was used when War Emergency Power was applied (up to 64” MP).

I think I remember that A2A has this metered (which you can test) to operate when the MP climbs above the 52” limit for normal power application, as long as that switch is activated. So, it doesn’t run all the time, but is triggered by some MP above what would be the normal maximum. It isn’t something you really want to use all the time, but it will delay damage when you really need to push the power. And it can also save you while you are trying to perfect your throttle management during takeoff, etc!

TrackIR is great for quick looks inside as you make your final power adjustments during the takeoff roll.




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BigT-65
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Re: Engine back firing

Post by BigT-65 »

The manifold pressure was my engine problem. I was frequently getting past 52" during flight especially on take off. A couple of flights closely monitoring MP resulted in excellent engine reports. I even tried out the WEP to see how it worked. Thanks for your suggestions. Now that I can make really nice landings and know how to keep the engine in top shape I am good to go.
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Jacques
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Re: Engine back firing

Post by Jacques »

:D



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Jacques
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Re: Engine back firing

Post by Jacques »

:D



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Jacques
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Engine back firing

Post by Jacques »

That is really nice to hear! Thank you for checking back in with the good results.
(apologies for the doubled post above....Tapatalk......)

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DHenriques_
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Re: Engine back firing

Post by DHenriques_ »

BigT-65 wrote:The manifold pressure was my engine problem. I was frequently getting past 52" during flight especially on take off. A couple of flights closely monitoring MP resulted in excellent engine reports. I even tried out the WEP to see how it worked. Thanks for your suggestions. Now that I can make really nice landings and know how to keep the engine in top shape I am good to go.
A little "trick" I always passed on to pilots I checked out in prop fighters.

On take off, in the Jug for example, if you will be looking for 52 inches during the run, don't try and find it with the throttle right away. The spread on the gauge between idle where you begin and 52 inches keeps your eyes on the gauge too long. Instead, advance to a number short of the 52 inches by sound while your eyes are station keeping the nose dead center.........THEN glance at the MP gauge and visually make that "final adjustment" fine tuning your MP at the required 52 inches then go immediately back to the nose.
Works like a charm!
Dudley Henriques

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