REFLECTOR: Engine backfiring

Dave Philipsen velocity at davebiz.com
Wed Aug 16 12:19:36 CDT 2006


Mine *is* an updraft engine.  The spider is up on top somewhere so it 
makes sense that it could overheat.  I will do some experimenting with 
insulation and perhaps even a cooling duct when I get a chance.

The oil line sounds like a neat idea.  Can't imagine that the oil would 
ever get warm enough that you'd have vaporization.  In effect, it would 
keep the fuel in a fairly tight temp. range.


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
>
> 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?
>>
>>   
>>     
>
>   

-- 
Dave Philipsen
STDFG
N171SP




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