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Why does my engine back-fire ?

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gerf(at)gerf.com
Guest

Posted: Wed Feb 14, 2007 1:47 pm Post subject: Why does my engine back-fire ?

(Not just my engine - just about every RV I've ever come across.)



It does it when I pull the throttle to idle, even if I do it fairly slowly ... and if I lean too far in flight ...



I was thinking that idle throttle, or lean mixture means less fuel - so what's to burn in the exhaust ?



g

     [quote][b]

dwhite17(at)columbus.rr.c
Guest

Posted: Wed Feb 14, 2007 3:14 pm Post subject: Why does my engine back-fire ?

We had same problem.  Potential cause is too  lean mixture, which could indicate an air leak in carb.  In our case, there  were some burrs in the throttle body of the carb.  We had to send away to  get corrected.    It is much, much better now and only cracks or  pops only occasionally.

  

 RV-6, Lycoming O-360-A1A.

 [quote]   ---

ronlee(at)pcisys.net
Guest

Posted: Wed Feb 14, 2007 3:29 pm Post subject: Why does my engine back-fire ?

At 02:46 PM 2/14/2007, you wrote:

 	  Quote: 	
		  (Not just my engine - just about every RV I've ever come across.)



It does it when I pull the throttle to idle, even if I do it fairly slowly 

... and if I lean too far in flight ...



I was thinking that idle throttle, or lean mixture means less fuel - so 

what's to burn in the exhaust ?



g


	


Mine does not



Ron Lee



Do not archive

andygold(at)rkymtnhi.com
Guest

Posted: Wed Feb 14, 2007 3:56 pm Post subject: Why does my engine back-fire ?

Mine did too, until I started using TCP in the fuel.



Andy



---

lifeofreiley2003(at)yahoo
Guest

Posted: Wed Feb 14, 2007 3:56 pm Post subject: Why does my engine back-fire ?

If I'm not mistaken, an intake tube sucking air will

also cause this problem.



Darrell



--- dwhite17(at)columbus.rr.com wrote:



[quote] We had same problem.  Potential cause is too lean

 mixture, which could indicate an air leak in carb. 

 In our case, there were some burrs in the throttle

 body of the carb.  We had to send away to get

 corrected.    It is much, much better now and only

 cracks or pops only occasionally.

 

 RV-6, Lycoming O-360-A1A.

   ---

truflite(at)yahoo.com
Guest

Posted: Wed Feb 14, 2007 4:05 pm Post subject: Why does my engine back-fire ?

Check this link out and see if it helps.



Dave



http://en.wikipedia.org/wiki/Back-fire



--- dwhite17(at)columbus.rr.com wrote:



[quote] We had same problem.  Potential cause is too lean

 mixture, which could indicate an air leak in carb. 

 In our case, there were some burrs in the throttle

 body of the carb.  We had to send away to get

 corrected.    It is much, much better now and only

 cracks or pops only occasionally.

 

 RV-6, Lycoming O-360-A1A.

   ---

T.gummo(at)verizon.net
Guest

Posted: Wed Feb 14, 2007 4:24 pm Post subject: Why does my engine back-fire ?

I had a leak in the induction system of my FI  system.  Extra air means extra lean.

 Leak fixed, backfires stopped.

  

 Tom Gummo

Apple Valley, CA

Harmon  Rocket-II

  

 do not archive

  

 http://mysite.verizon.net/t.gummo/index.html



 [quote]   ---

sportav8r(at)gmail.com
Guest

Posted: Wed Feb 14, 2007 6:51 pm Post subject: Why does my engine back-fire ?

Backfire?  Or afterfire?  Two different problems, if I understand

correctly.  Is the fire coming out the exhaust, or the air intake?



When I close the throttle quickly, I get some popping, but always

assumed it was after-firing, from mixture going rich.  Never seen any

evidence that the air filter was being hit with a flame front, but I'm

out of my expertise here.



Anyone?



-Stormy



On 2/14/07, Tom Gummo <T.gummo(at)verizon.net> wrote:

[quote]



 I had a leak in the induction system of my FI system.  Extra air means extra

 lean.

 Leak fixed, backfires stopped.



 Tom Gummo

 Apple Valley, CA

 Harmon Rocket-II



 do not archive



 http://mysite.verizon.net/t.gummo/index.html

 ---

gerf(at)gerf.com
Guest

Posted: Wed Feb 14, 2007 9:52 pm Post subject: Why does my engine back-fire ?

Hard to say where its happening - I'm usually in the cockpit 



You description of "close the throttle quickly" and "popping" sounds like what I'm experiencing.  The same thing happened when I was flying the factory 7 with Mike Seager.  Dan C's did it as he swooped down into the pattern at HAF when he came to seem my project.  I'm not worried about it, seems to be common - just curious why it does it.



g

 

 >--

phil(at)petrasoft.net
Guest

Posted: Thu Feb 15, 2007 5:26 am Post subject: Why does my engine back-fire ?

Gerry,

Mine does the same thing.  Don at AFP told me that it had something to do with the Vetterman exhaust.  I don't really know the explanation but I've asked a few people and none thought it was a big deal.  It does kinda freak out the passengers though so I started trying to tell them as I was turning final that it was normal for it pop when I pull the throttle back.



I wish somebody would 'splain it to me, so if you get a good explanation, be sure to let the rest of us know.



Godspeed,



Phil



On Feb 14, 2007, at 11:51 PM, Gerry Filby wrote:

[quote]Hard to say where its happening - I'm usually in the cockpit 



You description of "close the throttle quickly" and "popping" sounds like what I'm experiencing.  The same thing happened when I was flying the factory 7 with Mike Seager.  Dan C's did it as he swooped down into the pattern at HAF when he came to seem my project.  I'm not worried about it, seems to be common - just curious why it does it.



g

 

 >--

lifeofreiley2003(at)yahoo
Guest

Posted: Thu Feb 15, 2007 6:01 am Post subject: Why does my engine back-fire ?

Maybe the sound you're hearing is just that... the

sound of straight pipes used on RV's?



Darrell

--- Gerry Filby <gerf(at)gerf.com> wrote:



[quote] Hard to say where its happening - I'm usually in the

 cockpit 

 

 You description of "close the throttle quickly" and

 "popping" sounds like what I'm experiencing. The

 same thing happened when I was flying the factory 7

 with Mike Seager. Dan C's did it as he swooped down

 into the pattern at HAF when he came to seem my

 project. I'm not worried about it, seems to be

 common - just curious why it does it.

 

 g

 

 >--

Dale Ensing

Joined: 11 Jan 2006
Posts: 571
Location: Aero Plantation Weddington NC

Posted: Thu Feb 15, 2007 8:10 am Post subject: Why does my engine back-fire ?

With highly tuned race engines the situation  described is usually a result of unburned fuel in the exhaust . When the  throttle is closed quickly the engine (the pump) is being driven externally. In  our case is by the windmilling prop. The pump is packing more fuel into  the cylinders than is being burned in the cylinders and the excess is  suddenly dumped into the hot exhaust causing the small explosion in the  exhaust.

  

 Could this be the cause?

  

 I have not had it happen. Just putting forth a  theory. 

 Dale Ensing  

  

 

 

 [quote]Gerry,   

   Mine does the same thing.  Don at AFP told me that it had something    to do with the Vetterman exhaust.  I don't really know the explanation    but I've asked a few people and none thought it was a big deal.  It does    kinda freak out the passengers though so I started trying to tell them as I    was turning final that it was normal for it pop when I pull the throttle    back.

   

   I wish somebody would 'splain it to me, so if you get a good explanation,    be sure to let the rest of us know.

   

   Godspeed,

   

   Phil

   

      On Feb 14, 2007, at 11:51 PM, Gerry Filby wrote:

    	  Quote: 	
		  You description of "close the throttle quickly" and      "popping" sounds like what I'm experiencing.  The same thing happened      when I was flying the factory 7 with Mike Seager.  Dan C's did it as he      swooped down into the pattern at HAF when he came to seem my project.       I'm not worried about it, seems to be common - just curious why it does      it.



	




[b]

_________________
Dale Ensing
RV-6A
Aero Plantation
Weddington NC

phil(at)petrasoft.net
Guest

Posted: Thu Feb 15, 2007 2:23 pm Post subject: Why does my engine back-fire ?

This seems feasible.  Come to think of it, I can't remember hearing any pops while I was practicing power off stalls, so that would support your theory.  Would an exhaust system with higher efficiency contribute?  That is what I understood Don to be saying.  If there was more back pressure then the fuel would be burned up before it exited and wouldn't make as much noise?  Just guessing.

Phil



On Feb 15, 2007, at 10:09 AM, Dale Ensing wrote:

[quote]With highly tuned race engines the situation described is usually a result of unburned fuel in the exhaust . When the throttle is closed quickly the engine (the pump) is being driven externally. In our case is by the windmilling prop. The pump is packing more fuel into the cylinders than is being burned in the cylinders and the excess is  suddenly dumped into the hot exhaust causing the small explosion in the exhaust.

 

Could this be the cause?

 

I have not had it happen. Just putting forth a theory.

Dale Ensing  

 



 

 	  Quote: 	
		  Gerry,

Mine does the same thing.  Don at AFP told me that it had something to do with the Vetterman exhaust.  I don't really know the explanation but I've asked a few people and none thought it was a big deal.  It does kinda freak out the passengers though so I started trying to tell them as I was turning final that it was normal for it pop when I pull the throttle back.



I wish somebody would 'splain it to me, so if you get a good explanation, be sure to let the rest of us know.



Godspeed,



Phil



On Feb 14, 2007, at 11:51 PM, Gerry Filby wrote:

 	  Quote: 	
		  You description of "close the throttle quickly" and "popping" sounds like what I'm experiencing.  The same thing happened when I was flying the factory 7 with Mike Seager.  Dan C's did it as he swooped down into the pattern at HAF when he came to seem my project.  I'm not worried about it, seems to be common - just curious why it does it. 	




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[b]

kcflyrv(at)comcast.net
Guest

Posted: Thu Feb 15, 2007 8:17 pm Post subject: Why does my engine back-fire ?

I notice it more when I'm entering the pattern as usual I'm traveling a

little faster than I should be. I always figured it was poppin' because the

prop was in flat pitch and the excess speed was pushing the prop to a higher

rpm than it would otherwise be. At idle the unburned fuel would end up

burning or "popping" in the exhaust stack. A sure way to stop it if you're

too high and hot is to pull the mixture to cut off and that really slows you

down in a hurry if you have a CS prop. Then when you get it slowed down to

80, put the mixture back to rich and you're where you want to be.  ...and no

more poppin'

No one has ever accused me of being any kind of authority on these things

but it's just my .02 worth.



Ken Cantrell

RV-6 O-360 A1A

580 hrs.



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