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HelicopterCentury Radikal G20-30 N640 Hawk Predator › Toki 40 + Toki Tuned pipe idle issues !!!
03-18-2009 06:33 PM  8 years agoPost 1
BonesMalone

rrNovice

East Midlands

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OK Guys

Had my Hawk pro for about a year now, it was all brand new with a Toki 40 and Toki tunded pipe.
Right since day 1 i`ve had a problem tuning the engine to idle when the tank is running low, i thought it may have been leaning out with the tank being so big so i fitted a header tank.
Engine now runs fine can cut to idle whilst fuel is in the main tank but as soon as its just on header when dropping throttle to idle the engine will cut...........

I am using Coolpower 16% nitro fuel with an OS No8 plug.

I think i recall at somepoint being told that a Toki will only idle reliably if you use 20% minimum nitro content, anybody care to expand on this ?

Any advice will be greatly appreciated.....

Cheers

Tony

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03-18-2009 08:36 PM  8 years agoPost 2
imnxtc

rrVeteran

BC.Canada

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What needle are you adjusting for idle and hover? The main or the dile screw?

All things being equal when your header tank is on the same center line as your main tank, the fuel draw equation will be the same..so a header tank will then not make a difference to the lean/rich settings of your needle valves. Seems you are under the impression they do make such a difference.

The only time they make a difference is when all the fuel is used from the main tank and you then are running from the fuel left in the main tank. Then the fuel draw (head) will revert to that relative to the center line alignment to your carbs needle valve location to that of the center line of your sub (header) tank.

So if the center line of your header is higher then that of your main, then it will go richer and may cause the engine to die because it is now too rich. If the center line is below that of the main tank, then it will go leaner and cause it to quit from being too lean.

That is why it is generally considered better to have the header tank situated with its center slightly above that of the main...then adjust your motor to idle (using the idle adjustment screw, not the main needle) for a reliable, slightly rich idle and a reliable, slightly rich hover. Then when you burn all the fuel in your main tank your engine will go slightly richer but not enough to kill it...at idle or at hover or upstairs.

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03-18-2009 09:23 PM  8 years agoPost 3
Frank Bostwick

rrElite Veteran

Cincinnati Ohio

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Ok so mabey I should keep my mouth shut here, #1 imnxtc is way more experianced than me adn #2 I run an OS37.
But
I run a header tank, it is mounted CL above main tank and carb intake. No question about it, when my main tank is empty, it goes at least a click more like 2 lean. Smoke drops, HS goes up, power is better. So Im sure Im going lean not rich.

RIP ROMAN

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03-18-2009 09:52 PM  8 years agoPost 4
Furious Predator

rrProfessor

Kitchener, Ontario,​Canada

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Im pretty sure its rich, not lean. i have seen some YS engines do this. but i havnt noticed it on any of mine.

think about the fuel lines for a second.

do you notice when you fuel your helicopter, either with a hand pump, or electric, you can hear/feel the difference in pumping when you fill the header and start filling the main tank?

the medium size fuel tubing we use has a lot of resistance to fuel flow. its just too narrow.

you have your engine tuned to run on the main tank. when that is empty, fuel can now flow faster to the motor because of the reduced distance it has to travel. it is no longer going from the main tank, to the header, to the motor. the fuel is going directly from the header to the motor. so you now have that piece of fuel line between the header and main tank that is empty and not producing nearly as much fluid resistance.

Shawn
Team Leisure-Tech
Team HelixRC

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03-18-2009 09:56 PM  8 years agoPost 5
BonesMalone

rrNovice

East Midlands

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Thanks for the replies so far guys, just a couple of points to add so far,

1) My header tank fuel outlet is at the same height as the main tank, so when the fuel is empty in the main tank then the fuel delivery ratio should be the same i think ???

2) I always tune an idle using the idle needle, i was always told that the main needle is`nt effective until 1/3 throttle anyway, thats the way i`ve always tuned my planes

The bit i cant understand is that the engine will idle ok until its gets low on fuel, I dont have this issue on any of my planes !!!!

I`ve been fiddling for a year so i though it was about time i asked for advice ....

Perhaps i should just fill the header and tune an idle in that config, but will that then upset the mixture when tanks are full ???

Cheers

Tony

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03-18-2009 10:05 PM  8 years agoPost 6
Furious Predator

rrProfessor

Kitchener, Ontario,​Canada

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A lot of people argue about the header tank position, in my opinion, it wont make a significant or even noticable difference.

your right about the idle needle. but it isn't only controlling your idle, it is also a mid-range needle, your larger needle controls the high end. so even at half throttle in a hover, your idle needle still has some influence. atleast this is how it works on my engines, i dont have any experience on a Toki.

what exactly happens when your engine quits?

how does it sound? is it a low slow throaty groan? or does your motor rev at a higher rpm for a little bit and have a higher pitch sound before it quits?

Shawn
Team Leisure-Tech
Team HelixRC

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03-18-2009 10:18 PM  8 years agoPost 7
BonesMalone

rrNovice

East Midlands

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Furious Predator, you may just have a valid point there.

When the main tank is empty and its drawing fuel from the header only, when reducing the throttle to idle the engine just grumbles and dies, there is no increase in revs as if leaning out, so perhaps it does run rich ....

So do i now tune the idle with just the header tank full of fuel ???? or have a play with different sized fuel pipes ???

Tony

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03-18-2009 10:39 PM  8 years agoPost 8
Furious Predator

rrProfessor

Kitchener, Ontario,​Canada

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pipes are only really effective at higher rpm's, you can idle an engine no problem without a pipe or even a pressure line hooked up (ask how i know )

if its going into a slow grumble and sputters out, then your rich. adjust only your idle needle, an just a LITTLE at a time. when i mean a little, i mean just enough so you can see it move, thats about it, 1/20th of a turn at a time.

Shawn
Team Leisure-Tech
Team HelixRC

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HelicopterCentury Radikal G20-30 N640 Hawk Predator › Toki 40 + Toki Tuned pipe idle issues !!!
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