Getting rid of the gascolator....plumbing question

[MacCool]

My RV-9A with IO320-D1A has a gascolator. My under-cowl temps run a bit hot, which manifests primarily as hard hot-restarts (not impossible, just a bit complicated). I have rigid un-insulated tubing coming out of the fuel selector to the gascolator then across the firewall to the red cube then Weldon boost pump. This all involves some right angle fittings which I gather are less than useful. I'd like to clean up this up a bit, at least getting rid of the gascolator, perhaps re-locating the boost pump and maybe the red cube to a more conventional location and eliminating the right angle fittings..but my main thrust at this point is the gascolator and associated plumbing.

My question...(I haven't run this by my A&P yet) is..do I :

1. pull the gascolator an interpose some rigid fuel line
2. pull the gascolator and interpose some rigid fuel line wrapped in firesleeve
3. pull the gascolator and interpose flexible fuel line with fire sleeve

 

[lr172]

Generally two heat related issues. The hot start issue generally comes from fuel boiling in the 1/8” ss lines to the injectors. Your remediation plan won’t prevent that. Not much can. The second is rough running post start due to hot fuel creating vapor. For that, i would put firesleeve on every fuel line FF. For things like the pump, you can put reflective material, like that stuff that has shiny metal on one side and adhesive backed fiberglass on the other, to eliminate some of the heat, but definitely not all. The problem with something like a 20 minute fuel stop is that the entire under cowl area goes up to around 180*. Insulation helps for a bit, but eventually the heat soaks through that.

 

[JonJay]

I would consider reworking the system to get the fuel pump inside the cabin and the flow transducer in its recommended location between the servo and the spider.
If you can, get the fuel bulkhead fitting in the firewall closer to mechanical fuel pump and reduce the fuel line length.

All of that “stuff” and plumbing on the firewall is just absorbing heat.

Normal plumbing is:

Inside cabin-
Selector
Fuel Filter
Boost Pump
Firewall Bulkhead fitting

FWF -
Mechanical Pump
Servo
Fuel Flow Transducer
Divider

Hot starts should be a non event.

 

[MacCool]

Thanks guys, but for right now, my only concern is best options for removing the gascolator and re-plumbing. If easy enough, I'd move the red cube to it's preferred location as a matter of best practice, but not really having any red-cube issues ATM and it's not a priority.

 

[JonJay]

Thanks guys, but for right now, my only concern is best options for removing the gascolator and re-plumbing. If easy enough, I'd move the red cube to it's preferred location as a matter of best practice, but not really having any red-cube issues ATM and it's not a priority.

Understood. Some have reported good fuel flow readings when put ahead of the servo, but it’s still a heat sink in that location as is the fuel pump and the non insulated lines.
Perhaps removing the gascolater and adding some heat shielding will get you were you want to go.

 

[DanH]

That's a rather strange boost pump location. It should be someplace cool, aft of the firewall, not sucking warmed fuel through the red cube restriction.



If you're insistent on leaving the pump where it is now, the least risk from all factors is a firesleeved flex line.

 

[Snowflake]

Slightly more work but maybe not that much, would be to remove the gascolator and move the fuel pump to it's location. Then a straight hose with a longer bend radius from the output of the red cube to the next location. That solves the gascolator, removes a bunch of 90-deg fittings, and puts the pump before the cube.