REFLECTOR: Engine backfiring

[Scott Derrick]

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

Dave Philipsen wrote:
> Here's a question perhaps for some of the engine experts:  I've got a 
> STD FG with IO360-A1A engine.
> It has one standard magneto and one Jeff Rose electronic ignition.  The 
> engine and oil cooling are not a
> problem even with OATs in the low 90s. But, I have a problem (it's not a 
> huge problem) with backfiring
> during taxi *after* I land.  Taxiing before takeoff seems to be ok.  The 
> backfiring happens maybe once
> every 30 seconds or so.  The engine also seems to run a little rough at 
> this time.  I've tried running lean,
> running rich, running on just the magneto, running on just the 
> electronic ignition.  None of these seems to
> prevent the backfiring during taxi.  The engine never seems to have 
> problems before or during takeoff or
> during cruise or descent...just taxiing back after landing.
>
> I'm starting to think it's a vapor lock problem or something since the 
> fuel flow is way down and the fuel is
> sitting in the lines longer and heating up.  I had the cowling off the 
> other day and was checking the routing
> of the fuel injector lines and they don't appear to be routed near the 
> exhaust manifolds or anything like that.
> I was thinking of maybe experimenting with some insulating material 
> around the individual injector lines as
> well as the main fuel line.  Any ideas?
>
>   

-- 

-
    The most effectual engines for [pacifying a nation] are the public papers... [A despotic] government always [keeps] a kind of standing army of newswriters who, without any regard to truth or to what should be like truth, [invent] and put into the papers whatever might serve the ministers.

    Thomas Jefferson to G. K. van Hogendorp
    Oct. 13, 1785. (*) ME 5:181, Papers 8:632