What about fire sleeve/insulation for the spider fuel lines?

[logansc]

Like a lot of fuel injected engines, mine is a bit of a challenge to start hot (IO 540K). The other day I had occasion to take the top cowl off while the engine was quite hot and even with a purge valve and a considerable period on the electric fuel pump, 3 or 4 of the spider lines were very hot.

Got me to wondering if sleeving them with a suitable insulator would be a good idea. Since the famed TS of TSF is building his RV-7 in my hanger (helped him with his flap enclosure and floor boards this weekend), I asked him if he had a solution. He said he'd look into it and already has a sample or two coming for us to examine.

I can't do much on it until November because I'm leaving the country for a month to do some motorcycle riding in Italy this weekend, but I thought I'd best ask if anyone has ever done anything like this and what the results were. Since I've never seen an engine with fire sleeved spider lines, I'm guessing there may be reasons not to do it, but honestly I don't know.

Any ideas?


Lee...

[RVDan]

I don't think insulating the lines to the injector nozzles will help with starting. The lines will heat soak during shutdown, as the insulation only reduces the thermal conductivity and with no fuel flowing to cool the lines they will end up a short time after shutdown at the same temp as the compartment. If you flow enough fuel in those lines during starting you will likely have a flooded engine. Note the hot start procedure is mixture lean until the engine is running.

[Mike H]

I don't know if it would make any difference but be aware that covering these fuel tubes will make it difficult, or impossible to inspect them for cracks. They are supposed to be inspected every 50 hours for correct attachment (Adel clamps per SB 342G), chafing and cracking. These lines usually crack at the juction where the tube is silver soldered to the machined flare fitting. The most common failure is actually not a failure of the tubing itself, it is cracking of the solder, or weld which allows the tubing to leak or even seperate from the flair fitting. Cracking of the solder/weld usually propagares fairly slowly and can be caught during inspection before a problem occurs.

I have never seen flex lines installed in this location, but Tom may be able to make you some nice firesleeved flex lines. After all this is EXPERIMENTAL aviation.

[MikeyDale]

I thought about wrapping mine with fiberfax and covering the fiberfax with heavy aluminum tape to reduce the rumbling and ocaisonal backfiring during hot taxi after landing. Running the boost pump usually cures that though.

[aerhed]

About a minute after shutdown you will hear a skoosh noise. That's the fuel boiling in the injector lines. If you really insulate the heck out of them that will happen in two minutes. Same difference. Don't do it.

[Mike H]

Lee, it sounds like the Rocket would be a good candidate for EFII. Stop by LHW some day and check out the EFII installation on Scotty's -7.

[pierre smith]

Lee, I have a Lightspeed ignition and one mag...hot starts no problem.

Best,

[RVbySDI]

Originally Posted by pierre smith

Lee, I have a Lightspeed ignition and one mag...hot starts no problem.

Best,

Same here. I also have return fuel lines that help purge hot fuel back to the fuel tanks. Hot starts are really not an issue with this setup.

[TS Flightlines]

Lee's Rocket does have a purge valve, but has 2 mags. Anxiously waiting on the PMags. I know he's been on the list to get them.
Tom

[Mike H]

Originally Posted by TS Flightlines

Lee's Rocket does have a purge valve, but has 2 mags. Anxiously waiting on the PMags. I know he's been on the list to get them.
Tom

Maybe Lee should stop waiting and go ahead and install the EFII ignition.