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Engines Plugs Mufflers Fuel > Problems with changing fuels
 
 
baccas66
Heliman
Location: east anglia, united kingdom

I have just changed my fuel from 20% Nitro to 30% Nitro. Bigger gains! Yes, sounds lovely too when flying at high speed.
Just one problem, My YS61st2 used to start first time and idle beautifully. Now i have a problem getting it to idle smoothly and more importantly, consistantly.
The Fuel is Model Technics, a UK fuel. I have changed from Formula Irvine to Yamada 30. The difference being, apart from the Nitro, is 5% difference in oil. From 18% (synthetic and 2% castor) to 23% (fully synthetic)
I have found that by mixing 50-50 that this has eased the problem. I plan to gradually change over to the 30% fuel.
I have reset all needle valves to factory values.
Am i right in thinking that the engine just needs to adjust to the change in proportion of oil?
My main reason for changing the fuel was more power and for the protection that the oil would give me from using a higher rating of nitro.
The fuel is recommended and endorsed by Yamada.
Any input would be gratefully received.
Thanks in advance.
Jeff
09-14-2008 04:44 PM
 
 
Busher
Veteran
Location: Manchester, England

You are bang on, you will have to wait a bit while the engine beds into the new fuel. I thought this was actually BS, until I had exactly the same problems changing from century 15% to wildcat 20%. The engine kept cutting. I was advised by Jerry at wildcat fuels to run a few tanks rich and slowly tune in the needle over 5 tanks or so, until you could find the sweet spot again. I was a total non believer but I gave it a go and it worked like a charm

Good luck
Busher
09-14-2008 07:03 PM
 
 
baccas66
Heliman
Location: east anglia, united kingdom

Thanks Busher for your reply. Has put my mind at rest! Out of curiousity, did you only adjust the idle needle, or did you have to adjust mid and high end also?
Think I better spool the old girl up in the garden and run some fuel through her.
Cheers
Jeff
09-14-2008 07:42 PM
 
 
Busher
Veteran
Location: Manchester, England

I only had the 2 needles, and had to adjust both in order to get a good top end power and a small adjustment to the idle to get a smooth take up.
With a ys I believe the mid range needle affects most of the range, I would concentrate on this area and fine tune the top and bottom needles when you have a satisfactory needle setting.
I would start rich on the mid and top end and adjust the mid needle to get the running you like, and adjust the top end for max power when you have the mid range right. Then adjust the idle setting to give a good smooth transition from spool up.

Good luck
Busher
09-14-2008 11:32 PM
 
 
HeliPhil
Senior Heliman
Location: UK

Yes open up the needles and treat it as new to get the settings correct - don't assume that the old setting will be close.

http://www.olsonracing.co.uk
09-15-2008 11:06 AM
HOMEPAGE  
 
 
Jlerch
Senior Heliman
Location: Parrish, Florida

Think about why this happened (it makes sense)

Oil doesn't burn, it runs thru the motor like diarrhea, cooling and lubing the moving bits before getting chucked overboard.

IF your running 18% oil and your needles are set for a 'perfect' air fuel ratio and then you go put 23% oil in the tank, the needles will no longer be 'perfect'.

The carb dispenses a volume of liquid for a volume of air. When the %oil goes up, the available fuel per volume goes down. The Carb has no idea that this happened, and the result is your going to run substantially lean.

Also, adding insult to injury, the extra oil (a liquid) doesn't compress, this means (as far as I can tell) that you have essentially increased the compression ratio. Higher compression ratio needs to run richer to avoid detonation.

Going from Wildcat 23% oil 30% nitro to CoolPower 22% oil 30% Nitro took about 4 clicks leaner to make the same head speed on my YS-80-ST swinging 620mm blades in my 50class Pantera. (Yea, I scratched my head for a few minutes trying to figure out "What's wrong now?" )

James Lerch - ManateeRC Member - Blade 400 - Raptor 60 - Lots of sim time
09-15-2008 04:19 PM
HOMEPAGE  
 
 
baccas66
Heliman
Location: east anglia, united kingdom

Thanks for the input guys. I gave the needle 1/4 turn richer from factory settings and she starts and idles fine now. After running a couple of tanks through today, the set up is now a lot sweeter.
Consistant power throughout the throttle range. Engine sounds smoother and yes it goes faster too
Cheers
Jeff
09-15-2008 05:41 PM
 
 
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