patriot fuel delivery problems
02-03-2005, 11:38 AM
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patriot fuel delivery problems
I maiden my patriot yesterday with a jett 50, spring air. All I can say is awesome!!! However anytime I make a high speed turn or roll or even a basic loop the engine throttles back momentarily as if it is starving for fuel. I needed to raise the front retract mount up 1/2" in order for the nose retract to be concealed thus not enough room for a 4oz header tank. SO I went with a jett bladder tank hoping this would resolve the issue.
At this point I only see a couple of fix's
1). install a perry or kline pump - heard a lot of negatives there
2) Install a2oz header tank, but that means cutting an access hatch in the top of the fuse for installation
I'm open to any suggestions!!!
Mike
At this point I only see a couple of fix's
1). install a perry or kline pump - heard a lot of negatives there
2) Install a2oz header tank, but that means cutting an access hatch in the top of the fuse for installation
I'm open to any suggestions!!!
Mike
02-03-2005, 01:45 PM
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RE: patriot fuel delivery problems
Theres no way you need a pump or regulator or header tank. The first thing that comes to mind are the adjustments of of both needles. Also check the routing of the fuel line from the tank to the carb. If there is any type of 90 degree turn, the line can be pinched enough to go lean in the air but not noticable on a a ground check. I had this happen.
02-03-2005, 03:01 PM
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RE: patriot fuel delivery problems
Glad to hear you got the new bird in the air!
With the jett tank, you do not need or want to add a header tank. Just another place for air to get stuck.
A normal roll or vertical manuver should not cause the engine to sag off. (sometimes a high-g turn can, but a patriot can not turn "that" tight).
Where did you end up locating the fuel tank ?? Which size bubble-jett fuel tank ?
What prop are you running? Fuel?
You want the engine set 600-800 rpm down from peak RPM prior to launch. When it gets on the pipe (muffler) in the air as it unloads, it will need the fuel.
As noted, check the fuel lines and such. Ensure you are evacuating all of the air from the bubble-jett tank...that is critical. Its sometimes tricky with the larger tanks.
With the jett tank, you do not need or want to add a header tank. Just another place for air to get stuck.
A normal roll or vertical manuver should not cause the engine to sag off. (sometimes a high-g turn can, but a patriot can not turn "that" tight).
Where did you end up locating the fuel tank ?? Which size bubble-jett fuel tank ?
What prop are you running? Fuel?
You want the engine set 600-800 rpm down from peak RPM prior to launch. When it gets on the pipe (muffler) in the air as it unloads, it will need the fuel.
As noted, check the fuel lines and such. Ensure you are evacuating all of the air from the bubble-jett tank...that is critical. Its sometimes tricky with the larger tanks.
02-04-2005, 11:50 AM
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RE: patriot fuel delivery problems
Wow, thanks for all the replies
The tank is mounted just behind the wing dowel former. It is an 8oz tank. the lines continue straight to the firewall, but I do have a 90 degree bend be cause I couldn't figure out an alternate spot for the needle valve except on the outside of the fuselage. I'm turnning a 9x9 apc but at 3500" altitude maybe thats the wrong prop? ALso, i'm using cool power by morgan fuels.
I did richen the high speed to 3 1/2 turns out did cure about 65% of the problem. not sure if I should richen the bottom end, try a 10x8 prop?
mike
The tank is mounted just behind the wing dowel former. It is an 8oz tank. the lines continue straight to the firewall, but I do have a 90 degree bend be cause I couldn't figure out an alternate spot for the needle valve except on the outside of the fuselage. I'm turnning a 9x9 apc but at 3500" altitude maybe thats the wrong prop? ALso, i'm using cool power by morgan fuels.
I did richen the high speed to 3 1/2 turns out did cure about 65% of the problem. not sure if I should richen the bottom end, try a 10x8 prop?
mike
02-04-2005, 12:34 PM
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RE: patriot fuel delivery problems
Any pics? 
I always ran the Jett-50 on a 9x9 when it was fully broken in (As Bob stated) If you really wan to try another prop. a 10x7 would be interesting- or a 9x8 APC I used Powermaster-15% and a K&B1L/ OS-8 (or OS-F plug 
) I am @ 1,500 ASL
Mine had a 2 oz. header tank up in there.... Never missed a beat---
I always ran the Jett-50 on a 9x9 when it was fully broken in (As Bob stated) If you really wan to try another prop. a 10x7 would be interesting- or a 9x8 APC I used Powermaster-15% and a K&B1L/ OS-8 (or OS-F plug ) I am @ 1,500 ASLMine had a 2 oz. header tank up in there.... Never missed a beat---
02-04-2005, 01:33 PM
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RE: patriot fuel delivery problems
If the engine is still a bit new, make sure it turns up. Worse thing you can do is overload it. Keep it running over 17K rpm. RPM is your friend with the SJ-50.
Id suggest going with the 9x8 for a while. No 10x8 prop. Too much. 10x7 after some run time is possible. Try the 9x9 later on after you have a gallon or so in flight time. Setting the needle for a 9x9 is a bit tricky... if you do not set it correctly, you will get a false peak, and the engine will tend to go lean in the air. This is because the muffler will not properly stage on the ground (false max load due to static rpm).
If you want to try something different, utilize an APC 8.75x9W prop. I have not tried one on an F-20 yet. Probably will work ok.
Don't change the low end mixture from where Dub had it set. It does not function exactly the same as the low speed mixture on some other carbs. Any changes should be no more than 1/4 turn either way from where it was set. The low end mixture will not affect the top end/quitting issue.
If you are going to run heavier props... definately run a castor/synth blend fuel. Omega is good. Or add an ounce or so of castor oil to the cool power. Will guard against a missed needle setting trying to push the big props.
Bob
Id suggest going with the 9x8 for a while. No 10x8 prop. Too much. 10x7 after some run time is possible. Try the 9x9 later on after you have a gallon or so in flight time. Setting the needle for a 9x9 is a bit tricky... if you do not set it correctly, you will get a false peak, and the engine will tend to go lean in the air. This is because the muffler will not properly stage on the ground (false max load due to static rpm).
If you want to try something different, utilize an APC 8.75x9W prop. I have not tried one on an F-20 yet. Probably will work ok.
Don't change the low end mixture from where Dub had it set. It does not function exactly the same as the low speed mixture on some other carbs. Any changes should be no more than 1/4 turn either way from where it was set. The low end mixture will not affect the top end/quitting issue.
If you are going to run heavier props... definately run a castor/synth blend fuel. Omega is good. Or add an ounce or so of castor oil to the cool power. Will guard against a missed needle setting trying to push the big props.
Bob
