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Insulating Fuel Injection Spider and Injector Lines

Tumper

Well Known Member
Has anyone had luck insulating the fuel injection spider and the lines from the spider to the fuel injectors? If so, what did you use to insulate it and how did you insulate it? Also, could you post some pictures.

I think I have fuel vaporizing in those lines on a hot day after landing.

Thanks,
 
It's been discussed a lot over the years. No reported success that I recall.
 
I tried it using firesleeve and a reflective foil sleeve over that. Didn't improve the idle boiling issues and blocked some airflow to the cylinders raising CHTs. I removed most of it.

Ed Holyoke
 
I tried it. Used some foil covered/fiber heat tape wrapped around the lines. No real change in the low RPM on the ground with hot engine stumbling issues. Took it all off after about 9 months.

IMG_6251-M.jpg


IMG_6250-M.jpg
 
Physics is stacked against you on trying to effectively insulate these.
 
Hi Dean,

As others have indicated, this may not be the root cause of your problems. Because the mechanical fuel pump is mounted directly to the back of the engine, what may be more important is making sure the oil cooling is adequate, because the oil temp will effectively be what this pump body temp is. If the pump is too warm, as the fuel is drawn under suction to it, it may boil and mean that the pump is only drawing vapor. To help this situation, use light colours when painting your tanks to limit solar heating, insulate the fuel lines as they enter the engine compartment, put a titanium belly skin with ceramic insulation beneath the forward floor and ensure you have the best possible airflow through your oil cooler (good baffles, gaps sealed with RTV etc) or increase the cooler size if necessary (many -7 builders raise the cooler by a inch or so to improve airflow).

Tom
RV-7
 
Blast tube on Mechanical fuel pump

I have no evidence to support this but I think an attempt to cool mechanical pump with a blast tube ( with a shroud if possible) makes sense
 
I have no evidence to support this but I think an attempt to cool mechanical pump with a blast tube ( with a shroud if possible) makes sense

I seem to recall that the shroud and blast tube for the mechanical fuel pump is recommended by Vans. I would think it’s standard practice. Not perfect but it can’t hurt.

Bevan
 
I was having problems with my IO-360 engine chugging, while idling on the ground when the engine is hot. I put fire shield on last summer and saw a big improvement with the idling. I also aggressively lean the mixture on the ground, which also helps with the idling.
 
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WE use hose for the SDS injection, but we leave the stainless rigid lines alone for mechanical injection.
WE posted some time ago about using hose to replace the stainless lines, but no real takers. Do make them for primer packages.

Tom
 
I was having problems with my IO-360 engine chugging, while idling on the ground when the engine is hot. I put fire shield on last summer and saw a big improvement with the idling. I also aggressively lean the mixture on the ground, which also helps with the idling.

Can you elaborate on the installation of your fire shield?
 
I seem to recall that the shroud and blast tube for the mechanical fuel pump is recommended by Vans.

All but useless for pump cooling at idle and taxi speeds.

For whatever reason, builders tend to focus on the band-aid, rather than the root problem. Given evidence of fuel heating, why not reduce the original heat sources?

For example, consider the models with many feet of aluminum fuel line in a center tunnel, which is being heated by hot air flowing along the belly. I've seen installations with several feet of line on the firewall, and others with the line from the pump to the carb/servo running within two inches of the exhaust headpipes. Ever considered how much radiant energy beams upward at the bottom of the pump from 4 tailpipes?

A little here, a little there...
 
Vapor

I have tried a number of things to reduce the "chugging" from vapor when the engine is hot--with very little success except for one item. I tried using thick walled silicone tubing with an I.D. the same as the ss fuel lines out of the spider--split and covered the lines. Some improvement while running slow in the pattern but still there after a short "turn around" for fuel or a long taxi in. I took the tubing off after 3 months.

After talking with Don at Airflow (I have one of his injection systems on my IO360/180), he did some calculations to insure sufficient fuel flow and we replaced the stock 028 restrictors with 023--to increase the head pressure and therefore reduce the potential for vaporization. This approach helped some but the issue still persists although at a lower level.

Just my own experience!

Cheers,

db
 
As DanH indicated above - there are ways to completely get rid of vaporlock on our airplanes, but it involves more work than most people are willing to do. Modifying fuel systems carries some risk - most people are not keen on that idea (understandably) and there are a lot of folks that just plain shouldn't handle tools at all. If you don't believe you can do it, you are probably correct.

Having said that...

Eliminate the engine-driven fuel pump and install dual electric pumps either in the wingroot or tunnel area with returns direct to the tanks, and boost the fuel pressure to the 35-40 psig range. Eliminate the gascolator if you have one installed. Insulate the FWF fuel lines with double firesleeve material, this includes the lines to and from the fuel servo. Install heatshields around any exhaust that is in proximity to the fuel lines. Put smaller orifices in the fuel injectors, I had great results with .022 in my 360. Install an AFP purge valve on the spider divider to recirc fuel prior to a hot-start to eliminate the "hot start dance".

Full disclaimer - I'm not advising anybody to do this. Fuel system modifications carry risk. If you're not comfortable with it, then don't do it.
 
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