REFLECTOR: Engine backfiring

[Dave Philipsen]

Ok, I tried the suggestion today of running the aux. fuel pump while 
taxiing with the engine hot.  It did not completely eliminate the 
backfiring but I think it was reduced by maybe 50% or more.  Definitely 
appeared to make an improvement.  It looks like you might have me on the 
right track here.  I'm also going to check the "wiffle" valve and the 
insulation under the spider.


Scott Derrick wrote:
> This is usually a common problem caused by overheating the injection 
> lines and spider, its especially prevalent in updraft engines.  Heating 
> the injection system can help when running at cruise but can be a 
> problem at idle if its too hot.
>
> If  the problem is just a hot injection system you can sometimes 
> alleviate it by doing a couple things. 
>
> 1.)  Run your aux fuel pump while taxing if the engine is hot. The 
> higher pressure can prevent some of the fuel from vaporizing.
>
> 2.) Put an insulated baffle under the spider so it doesn't absorb as 
> much ambient heat from the engine case.
>
> 3.) some folks run a 1/2 inch cooling  duct  to the spider and build a 
> shroud around the spider to direct the air. This can help with the over 
> heating problem but it also cools the fuel when running which may lower 
> fuel efficiency, probably by not much though.
>
> My  TSIO520 has a  heated spider that  is heated with an oil line. This 
> keeps the spider at oil temp which is good for fuel burn but also helps 
> prevent it from getting so hot the fuel vaporizes.
>  
> Scott
>