|
|
|
09-24-2005, 03:04 PM | #1 |
RCC Apprentice
|
why 5% nito in ducted fan fuel?
Hi, guys I just finished registering to this site and it's my first post.
Why do you ducted fan guys use only 5% nitro fuel? Is there a reason? I too am just re-finishing a tga f-15 and an old a-4 the f-15 has an os91 and the a-4 has a k&b 45. My buddy Greg Simpson sold me the a-4 and said only to use 15% or I'll be going through glow plugs like no tomarrow, is he right? I have a full jug of COOL POWER 15% that he gave me for the .45 will it work or am I going to have problems? |
. |
09-24-2005, 04:06 PM | #3 |
RCC Senior Contributor
I am: Peter Harasiewicz
Join Date: Nov 2002
Location: Bolton,ontario, Canada
Radio of choice:
JR12X Feedback: 2 / 100%
Posts: 600
Total Props: 0
|
Fuel
HI, OS 91 are high compression engines and that is why only 5% nitro works fine, any higher and you"ll overheat the engine. If you hear eggs cooking in the engine, then it"s running to hot.
OS engines have nickle plated cylinders which are very subsesable to hot and lean runs, you can loose the taper in the cylinder in just one run. If you are getting less than 6 runs on a glow plug, start to add head shims to reduce the heat. BVM engines have chrome plated cylinders and lower compression, thats why they love 10 to 15% nitro And lastly , only use Wildcat ducted fan fuel. Rcpete |
. |
09-24-2005, 04:28 PM | #4 |
RCC Senior Contributor
I am: Peter Harasiewicz
Join Date: Nov 2002
Location: Bolton,ontario, Canada
Radio of choice:
JR12X Feedback: 2 / 100%
Posts: 600
Total Props: 0
|
Fuel
HI again, back in the days when we flew ducted fan jets and their was no wildcat fuel, so we had make our own mixes of caster and fuel and it was always a crap shot.
Another important note is to always have a good smoke trail, by having a onbaord fuel mixture control, you can adjust the mixture as the tanks get low. When you are flying and started with a good smoke trail and loose it, you know you have lost pressure in the fuel tanks, check for broken pipe seals or loose carb or your disconnected pressure line. If you have a older OS 91 or one thats been sitting for a while, replace the o rings in the carb, especaly the low end mixture, the mixture screws will back out from the vibration. Rcpete |
. |
09-24-2005, 04:55 PM | #5 |
RCC Apprentice
|
Thanks rcpete, can you tell me why on k&b's web site they recomend 12 and a half % for there .45? Is it because it is a low compression engine also?
Lastly, can I use any kind of 5% with the right lube in it or I am I going to have to get some df fuel from the other side of the country ,cause if I do I'm just going to sell both of these jets and go back to props. thanks Mike |
. |
09-24-2005, 05:35 PM | #6 |
RCC Senior Contributor
I am: Peter Harasiewicz
Join Date: Nov 2002
Location: Bolton,ontario, Canada
Radio of choice:
JR12X Feedback: 2 / 100%
Posts: 600
Total Props: 0
|
Fuel
HI, it"s a lot cheaper getting the right fuel , then loosing a plane after all that hard work and money.
K& B"s where the original BVM motors and yes they are lower compression In Europe they run a lot of engines on no nitro. Another expert in ducted fan and who still flies ducted fan is Jim Browm, he might want to chime in hear with a few more tips. Rcpete |
. |
09-24-2005, 07:39 PM | #7 |
RCC Apprentice
|
yeah thats true, but can I get some df fuel in B.C ? I haven't even fired either one of them up yet and I guess can't until I've got the right stuff .
NO NITRO? whats that about? Yeah, the F-15 was $450and the A-4 was $500 which to me is a pretty good deal considering they were both full of servoes ,had engines with good compression and good retracts. I'm just doing some painting and filling dings and scratches. |
. |
09-25-2005, 12:24 PM | #8 |
RCC Supreme Contributor
I am: John Davidson
Join Date: Feb 2003
Location: Vulcan,Alberta
Radio of choice:
EVO(12), Futaba # of RCs: ?
Feedback: 0 / 0%
Posts: 2,927
Total Props: 0
|
Jetace11,
I am not sure but maybe out to lunch on this one. Nitro is very scarce on the other side of the pond so most engines are set up for no nitro and we usually up the compression and add nitro. Engines built here like KB's are set to use nitro to start. You adjust for blowing plugs by adding or taking out shims. I usually start at 15 thou. head clearance and go from there. It gives a baseline to start with and usually you then add shims till you get a reasonable life on the plug. With low nitro fuel you will require more clearance and with high nitro less clearance but blow plugs all the time. Running 65% was 1 plug, 10 oz. fuel, 1 run. For FAI when set right you did not need a lot of extra plugs as the plug element did not take that much of a beating and would last quite awhile. I also believe that the Tetras tank would give you a more consistant run especially when near the end of your run where you can get air in the line. Some people think they are a pain to fill but if your engine gets leaned out in flight you are wrecking the sleeve and piston. Lots of money invested in the engine and piston/sleeve sets are not cheap. Tuned pipes are great but have to be set properly. The fuel question for brand is mostly what you like. Some are reccomending Wildcat but also what is wrong with Powermaster, Red Max and a lot of others. They are not in business to sell junk especially with the internet now a days. If you check you will find they all have fuel that is reccomended for different applications. I use mainly 15% in all my engines and some of them are quite old compared to what is on here. I like the little better idle and also cold weather running. If I rambled on I am sorry but i'm not much in favour of reccomending brands especially when you have to sit and wait for an order especially when a good LHS probably has what you need in stock. John, (ex FAI and Formula 1 driver) ps: Ed feel free to jump in.
__________________
John Davidson Keep the shiny side up and the wheels down |
. |
09-25-2005, 01:19 PM | #9 |
RCC Apprentice
|
Thanks John, whats a tetras tank? any pics?
I'm not a brand guy either, I just need stuff that works. Everyone says 5% is the best and any higher for the os91 will over heat it. Why can't I just run it richer or leaner to componsate for the 5% increase in nitro content? Love the info. keep it coming!! Thanks Mike |
. |
09-26-2005, 10:48 AM | #10 |
RCC Supreme Contributor
I am: John Davidson
Join Date: Feb 2003
Location: Vulcan,Alberta
Radio of choice:
EVO(12), Futaba # of RCs: ?
Feedback: 0 / 0%
Posts: 2,927
Total Props: 0
|
Mike,
The Tetras tank is the clear plastic type with the bag in it. Check your Lhs to see if they have them. Not usually stocked like the others because of the price but for higher rpm applications it is the best way to go. To fill it you suck all the air out and then fill with fuel, consequently no air bubbles in the system. I made one years ago from a balloon inside to try and then used for racing. Changed the balloon after a day of racing but it worked. Not conveniant for you to change all the time and advise to go with good ones. What fuel do you use for normal flying? A low nitro fuel 15% or lower should work. If you blow plugs every run or 2 add a shim till it doesn't. For the overheating part most of it is from being compressed to much and running to lean. For a normal ac some of it is from the cowl. When setting up and flying keep a book on your flights. Leaving a trail in the air is good. Most people back off a couple of 100 rpm and go fly which is okay for sport but the higher rpm you run you will find you have to go back a bit further. The other part I would add is when flying and you notice you are going lean or lose the trail, chopp the throttle and land. Staying up just burns it up and there goes the sleeve and piston. Your spotter can also help on this as well. John
__________________
John Davidson Keep the shiny side up and the wheels down |
. |
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
Thread Tools | |
Display Modes | |
|