Important notice
Please remember that people from all over the world read and post on this forum, and that every country has its own rules, regulations and standards. This forum is based in the USA and so much of the information posted here is for the benefit of people who operate aircraft in the experimental/exhibition or experimental/racing categories. Advice given on this forum may be region specific. A person from Europe, for example, may make suggestions perfectly appropriate for a U.S reader, although not acceptable in his home country!

Please take this into account and carefully consult the authorities, standards and approved documentation where you fly.
Fournier Forums Upload picture | User Cp  |  Register  |  Members  |  Search  |  Help
    |- Fournier Aircraft > Modifications Post New Topic   Post A Reply
Under cowl heat reduction printer friendly version
next newest post | next oldest post
Author Messages
jb92563
Second Lieutenant

Gender: Male
Location: Lake Elsinore, CA, USA
Registered: Mar 2007
Status: Offline
Posts: 583

Click here to see the profile for jb92563 Visit http://picasaweb.google.com/jb92563 Send email to jb92563 Send private message to jb92563 Find more posts by jb92563 Edit or delete this message Reply w/Quote
Posted Monday, February 27, 2012 @ 12:26 PM  

In preparing for a season of flying after my annual I was tinkering with the 4's engine tuning the mixture for for optimum settings and smooth acceleration.

After 30 minutes of adjustments I decided all was as perfect as can be and put the cowl on so I could go fly.

Not 2 minutes of running with the cowl on while taxing to the runway the engine started running rough and just cut out.

Went back to the hanger pulled off the cowl and looked for problems. I touched the fuel system fittings and they were so hot I could barely
keep my fingers on them. It was the dreaded fuel vaporization issue again.

Then I remembered that I had bought some exhaust tape from Aircraft Spruce last year.

Wraping the exhaust tubes in this tape ought to reduce the radiated heat heat from the hot exhaust gases from over heating my cowl
and fuel system.

I also put some loose fitting aluminum heat shields around the fuel system plumbing. (not in these pictures)

The result was great, as I ran the engine cowled up for 30 minutes on the ground as before and no more bubbles in the fuel.

Using higher octane fuel would also minimize fuel vaporization so I was wondering if I could run the engine on 91 Octane instead of the ussual 87 octane. The manual says to use 80 octane which I believe is about the same as the US 87 Auto fuel octane.

What are other folks using for fuel Octane rating?

The new home for my RF4D, better protected from the elements and birds of prey talons.

[Edit by jb92563 on Monday, February 27, 2012 @ 12:27 PM]

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Jorgen
Captain

Gender: Male
Location: Lund, Sweden
Registered: Apr 2007
Status: Offline
Posts: 833

Click here to see the profile for Jorgen Send email to Jorgen Send private message to Jorgen Find more posts by Jorgen Edit or delete this message Reply w/Quote
Posted Monday, February 27, 2012 @ 12:39 PM  

Good thinking Ray,
might there be a risk that the heat is concentrated at the end of the tapewrapping, were the cracks in the short exhausts are usually formed? Keep us posted, the idea sure is interesting!

May the 4's be with you/ Jörgen

Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 2027

Click here to see the profile for Bob Grimstead Visit http://www.redhawksduo.co.uk Send email to Bob Grimstead Send private message to Bob Grimstead Find more posts by Bob Grimstead Edit or delete this message Reply w/Quote
Posted Monday, February 27, 2012 @ 09:16 PM  

Hi Ray,

Great new hangar!

I'm not sure that vaporisation depends on octane rating. Vaporisation depends upon volatility, which is somewhat different, although motor fuel (Mogas) is generally a bit more volatile than Avgas

Octane rating is all about pre-ignition, and varies with compression ratio.
The original 1200cc Rectimos only had a 7 to 1 compression ratio, so 80 octane fuel was fine.
If you're now running 1400cc cylinders & pistons, your compression ratio will be around 8.2 to 1, so you should be using a higher octane fuel.

I normally use approximately 3 parts of 91 RON auto gas (the lowest octane available on the forecourt here) mixed with one part of Avgas. I am told that 100LL Avgas has around twenty times the amount of lead in it that leaded auto fuel had, so I guess that will be more than enough to delay pre-ignition (knocking, pinking or pinging).

You may remember that, when flying solo, I time my climb for the first couple of minutes after take-off to ensure my enigne is performing adequately. Over the years, I have noticed that if I am using more than my usual amount of Mogas (too little Avgas) the climb rate becomes less. I can't hear any pinging, pinking or knocking, but the performance definitely drops off, so recently I've tended to err on having too much Avgas rather than too little.

I know none of this addresses your fuel vaporisation problem, but it should be of general interest.
Of course your vapour lock problem will go away immediately if you use a standard carburettor.

To be honest, with no fuel pump and no flop-tube tank pick-up, I really don't see the point of having a slide injection/carburettor with no float bowl, particularly when there is such a strong reason for not having it.

Yours, Bob

Yours, Bob

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

jb92563
Second Lieutenant

Gender: Male
Location: Lake Elsinore, CA, USA
Registered: Mar 2007
Status: Offline
Posts: 583

Click here to see the profile for jb92563 Visit http://picasaweb.google.com/jb92563 Send email to jb92563 Send private message to jb92563 Find more posts by jb92563 Edit or delete this message Reply w/Quote
Posted Monday, February 27, 2012 @ 11:48 PM  

Thats exactly the reason that I have kept the zenith carb, just in case I want to switch back.

For now the problem seems to be gone and once airborne there should be plenty of cooling airflow to
not have to worry about it.

It was just the ground situation that was annoying.

I'll use the higher Octane from now on to prevent the ping/knock issues.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Post New Topic   Post A Reply Jump to:
Contact Us | cfiamerica.com | Privacy Policy All times are GMT -4 Hours.
Welcome to The Fournier Forum, Guest!  
Login
Username :
Password :
In order to fully utilize the abilities of this board, you are required to register as a member. Registration is free, and allows you to do lots of things including turning on or off certain features of this board. Register now!
Forum Rules & Description
Who Can Read The Forum? Any registered user or guest
Who Can Post New Topics? Any registered user
Who Can Post Replies? Any registered user
Who Can Edit Posts? Any original author
How can you improve on perfection?
Currently Active Users: 95
There are currently 0 members and 95 guests on the boards. | Most users ever online was 822 on 08-01-2020 10:15 PM
Search This Forum
Search Keywords: Search From:
Powered by CuteCast v2.0 BETA 2
Copyright © 2001-2003 ArtsCore Studios