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purge line recommendation?

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Erich_Weaver(at)URSCorp.c
Guest

Posted: Thu Aug 03, 2006 1:18 pm Post subject: purge line recommendation?

Howdy



I need to install a fuel purge line for my fuel injection system.  What

kind of hose do folks recommend for the portion that will be in front of

the firewall? Since its only a purge line, does it really need any special

protection (i.e, steel braid and/or firesleeve)?



thanks



Erich Weaver

Terry Watson

Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA

Posted: Thu Aug 03, 2006 2:16 pm Post subject: purge line recommendation?

I bought a fire-sleeved line 41 or 42" long directly from Airflow

Performance for mine. It was quite expensive -- I think about $60, maybe

more. It was what they recommended.



Terry

--

garrys(at)tampabay.rr.com
Guest

Posted: Thu Aug 03, 2006 3:18 pm Post subject: purge line recommendation?

Erich,



What's a "fuel purge line"?  I'll be receiving my Aero Sport IO360 engine 

next week and no one ever mentioned anything about a "purge line".



Garry Stout

Odessa, FL

---

Erich_Weaver(at)URSCorp.c
Guest

Posted: Thu Aug 03, 2006 8:26 pm Post subject: purge line recommendation?

Garry:

 

Made me smile when I read your question, as thats exactly what I said when I got my engine from Aerosport Power (IO-360B1B).

 

Check the archives for further info, but the purge line is in common use for fuel injected engines to make starting easier when the engine is already hot.  The thought is that the fuel sitting stagnant in the hose within the hot engine compartment can vaporize, making subsequent starting difficult.  How big of a problem this really is depends on who you talk to.  I know plenty of pilots with fuel injection on their certified planes that have never heard of a purge valve either.  Regardless, the "solution" to the problem is a purge valve at the fuel divider, where the fuel is distributed to the individual cylinders.  The purge valve is manually opened the using a bowden cable, and returns the hot fuel into one of the lines leading to your tanks.

 

You should also know that the purge valve is also used to kill the engine.  Apparently, mixture control cannot completely stop all fuel from reaching the engine and it may be able to keep running- not the case when using the  purge valve.

 

Somebody else chime in if Ive missed anything.



Erich Weaver

URS Corporation

130 Robin Hill Rd

Santa Barbara CA 93117

805-964-6010

FAX 805-9640259

This e-mail and any attachments are confidential. If you receive this message in error or are not the intended recipient, you should not retain, distribute, disclose or use any of this information and you should destroy the e-mail and any attachments or copies.

khorton01(at)rogers.com
Guest

Posted: Fri Aug 04, 2006 1:36 am Post subject: purge line recommendation?

On 4 Aug 2006, at 24:22, Erich_Weaver(at)URSCorp.com (Erich_Weaver(at)URSCorp.com) wrote:

 	  Quote: 	
		  --> RV-List message posted by: Erich_Weaver(at)URSCorp.com (Erich_Weaver(at)URSCorp.com) Garry:

 

Made me smile when I read your question, as thats exactly what I said when I got my engine from Aerosport Power (IO-360B1B).

 

Check the archives for further info, but the purge line is in common use for fuel injected engines to make starting easier when the engine is already hot.  The thought is that the fuel sitting stagnant in the hose within the hot engine compartment can vaporize, making subsequent starting difficult.  How big of a problem this really is depends on who you talk to.  I know plenty of pilots with fuel injection on their certified planes that have never heard of a purge valve either.  Regardless, the "solution" to the problem is a purge valve at the fuel divider, where the fuel is distributed to the individual cylinders.  The purge valve is manually opened the using a bowden cable, and returns the hot fuel into one of the lines leading to your tanks.

 

You should also know that the purge valve is also used to kill the engine.  Apparently, mixture control cannot completely stop all fuel from reaching the engine and it may be able to keep running- not the case when using the  purge valve.

 

Somebody else chime in if Ive missed anything.



	




We need to distinguish between two different fuel injection systems:



Airflow Performance (AFP) - AFP fuel injection systems are commonly used to modify carbuereted engines to fuel injection.  They are also commonly used on new built or overhauled engines for experimental use.  AFP recommends a purge line for their system, to facilitate hot starts, and because in many installations the engine cannot be stopped with the mixture control.



Precision (originally made by Bendix) - this is the fuel injection system that comes on fuel-injected engines as delivered by Lycoming.  This system, as installed on type certificated aircraft, does not have, or need a purge valve.  The vast majority of installations on experimental aircraft are without a purge valve.



Find out what type of fuel injection your engine will have, then you can figure out whether a fuel return line will be needed.



 Kevin Horton

Ottawa, Canada

rv9jim(at)juno.com
Guest

Posted: Fri Aug 04, 2006 12:49 pm Post subject: purge line recommendation?

Garry,

        Its a Air Flow Performance thing.  Its necessary to be sure that

the fuel stops going to the spider and on to the injectors.  The purge

valve lets off any pressure that may be there after the engine trys to

stop.  (not quite).    It also lets you run cooler fuel up to the

distribution spider when doing a "hot  start".  This stops any unwanted

burps when starting after a hot start.  I don't want to be on take off

and have a air bubble in the line suddenly cause the engine to quit.  

The vaporization is caused by hot fuel vaporizing in the system.  I'm

told some systems do fine with out the purge system.  Me?  I'll use it.

Jim

charlieray(at)optonline.n
Guest

Posted: Fri Aug 04, 2006 2:28 pm Post subject: purge line recommendation?

Unless you take off within about a minute I do not forsee this happening. 

Many pilots claim to suffer from vapor hot starts but it just turns out that 

they do not know how to start their own airplane.



When you pull the mixture to idle cut off it should fully make the stop and 

thus close off the mixture valve or slide in varying carbs, throttle bodies, 

etc. Fuel flow dividers have a spring loaded poppet valve to stop fuel flow 

to the cylinders below 3psi.



FYI



Charlie



---

Terry Watson

Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA

Posted: Fri Aug 04, 2006 3:05 pm Post subject: purge line recommendation?

We have been through all this before, more than once. Check the archives.



Airflow Performance's owner's manual states that idle cut-off with the

mixture will NOT reliably shut off the engine. Some fuel still leaks by. So

they recommend installing the purge valve to be used to recirculate the fuel

to cool it down when it the engine gets head soak, AND to shut down the

engine.



Terry

RV-8A, Aerosport Power/Superior IO-360B1B (180hp) with Airflow Performance

fuel injection



--

ceengland(at)bellsouth.ne
Guest

Posted: Fri Aug 04, 2006 5:37 pm Post subject: purge line recommendation?

Terry Watson wrote:



 	  Quote: 	
		  



We have been through all this before, more than once. Check the archives.



Airflow Performance's owner's manual states that idle cut-off with the

mixture will NOT reliably shut off the engine. Some fuel still leaks by. So

they recommend installing the purge valve to be used to recirculate the fuel

to cool it down when it the engine gets head soak, AND to shut down the

engine.



Terry

RV-8A, Aerosport Power/Superior IO-360B1B (180hp) with Airflow Performance

fuel injection




	


You know, every time that I've just about convinced myself to forget 

about auto conversions because they are just too much trouble to adapt & 

install, I get a little reminder about 'aircraft quality'. (And this 

thing is supposed to be an *improvement* over the Bendix !)

shempdowling2(at)earthlin
Guest

Posted: Sat Aug 05, 2006 9:30 am Post subject: purge line recommendation?

Do you even need a purge line?  I have a bendix system without a purge line 

and mine works fine.



Shemp/Jeff Dowling

RV-6A, N915JD

295 hours

Chicago/Louisville

---

sarg314(at)comcast.net
Guest

Posted: Sat Aug 05, 2006 10:59 am Post subject: purge line recommendation?

Erich:

    I treated it like any other fuel line.  I used steel braided teflon 

throughout.



 	  Quote: 	
		  > 

> Howdy

>

> I need to install a fuel purge line for my fuel injection system.  What

> kind of hose do folks recommend for the portion that will be in front of

> the firewall? Since its only a purge line, does it really need any 

> special

> protection (i.e, steel braid and/or firesleeve)?

>

> thanks

>

> Erich Weaver

>

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