quote:

ORIGINAL: JohnP2

I was the one who suggested he fatten his gap, merely to rule out having too small of a gap (and we ALL see that too often). However. this has been a FASCINATING thread concerning idle gap I'm spendin my Saturday night talking idle gap on an Internet forum. I am proudly hooked! ;-) We always hear .5mm can be too small and 1.0mm too big, so I agree that sounds ideal. .7mm sounds about right (at worst the best starting point). In thinking about it, most of my best tunes had ~.7mm gap.

Anthoop (and I LOVE your avatar by the way!) you posed some great questions. If i'm to deduce this thread, it's that you work your mixture around the idle-stop gap. i.e., that is what you start with and go from there. Only assume this is the first entry way of air, and you stabilize that and work in the fule mixture.

quote:

ORIGINAL: Anthoop

quote:

ORIGINAL: JohnP2

I was the one who suggested he fatten his gap, merely to rule out having too small of a gap (and we ALL see that too often). However. this has been a FASCINATING thread concerning idle gap I'm spendin my Saturday night talking idle gap on an Internet forum. I am proudly hooked! ;-) We always hear .5mm can be too small and 1.0mm too big, so I agree that sounds ideal. .7mm sounds about right (at worst the best starting point). In thinking about it, most of my best tunes had ~.7mm gap.

Anthoop (and I LOVE your avatar by the way!) you posed some great questions. If i'm to deduce this thread, it's that you work your mixture around the idle-stop gap. i.e., that is what you start with and go from there. Only assume this is the first entry way of air, and you stabilize that and work in the fule mixture.

It is nice to have a natter about a hobby you love with like minded poeple.

For me it is not a case of adjust the gap to X and that is where it stays, most important is to get the amount of fuel correct for the amount of air, then adjust the gap for the correct idle speed to prevent the clutch engaging. In the video (OP) the engine has an uneven idle, pointing to an incorrect mixture, this can be fixed by altering the amount of fuel or air....whether we adjust air or fuel does not matter...if (when we have the correct mixture) the idle speed is too high/low it can be adjusted with the idle screw.
I think Neal and I are reading from the same page...just using different methods to get the same end result.

quote:

ORIGINAL: Anthoop

I could point you to far more cringe-worthy answers to various questions on other forums I frequent.
Most of the people asking tuning advice here are not racing and are running RTR engines, my advice to those people is start from the manufacturers settings and work from there....although we know how dubious those settings can be sometimes:-

Slide gap= 0.25-0.5 ... http://www.racing-cars.com/images/Technical_Info/Schumacher/Old%20Cars/Fusion%2021/Instruction%20Manual/fp10.jpg
Slide gap 1.0 ... http://www.cmldistribution.co.uk/diagrams/HoBao/Engines/HB_Engine_settings_Hyper_21%20_3-Port.pdf
Both pretty similar engines but very different base settings....they both work with those settings.

At the end of the day (after adjustment) the hope is that the needle will be in the correct position pertaining to the slide gap....but those settings will at least get it running.

quote:

ORIGINAL: supertib
tuning around a large idle gap causes all sorts of of issues............

quote:

ORIGINAL: Anthoop

quote:

ORIGINAL: supertib
tuning around a large idle gap causes all sorts of of issues............

The only reason I can see for that is people using the LSN to adjust the idle speed.

quote:

ORIGINAL: JohnP2
Is there ever a reason to tune LSN for idle? Not talking about the ability to idle.....but idle performance....if that makes sense.

Thanks!

quote:

ORIGINAL: JohnP2

I spent an hour yesterday jacking with the tune on my OS .25xz.. I think I'm happy with it, and will post a video of it on the track so you guys can tell me where to improve.  I'm definitely learning there is a difference between a ''tune'', and a ''race-tune.''

One of the items I'm working on is RPM decrease after mid+ throttle. What is the rule of thumb for this? I've heard/read a breadth of suggestions, but the majority seem to state it should decrease to idle 1-2 seconds after letting off WOT.

I don't know the answer so am trying to learn what I can on the subject. Thanks!

quote:

ORIGINAL: JohnP2

Still running the P3 (I have the P4 but did not put it in). Losi Nitrotane 30%

I have read thru most of this discusion and there is an old school way to adjust the LSN needle and I also discuss some glow plugs.

http://www.xenonproject.com/tuning-your-nitro-gas-vehicles-engine-a-10.html

The old school way of adusting an LSN is called a pinch test.   The engine should only run for  a few  seconds after pinching the fuel line. 

 

• Step 2. Low-Speed Fuel Mixture Adjustment
  
• The low speed mixture adjustment is performed only after the high speed needle has been correctly adjusted. The easiest way to adjust the low speed mixture is by doing the "pinch" test. The valve is located where the throttle arm pivots.

  “Pinch” Test
  Having set the high speed needle correctly, take the RC vehicle and pinch the fuel line going into the carburetor. The engine should run for about 2-3 seconds, speed up, and die.
  If the engine runs longer than 3 seconds, give the low speed needle a 1/16 turn clockwise. Run the vehicle again and retest. Repeat as necessary.
  If the test results in the engine dying immediately, without speeding up, richen the low speed needle by giving it 1/8 turn counter clockwise. Run the vehicle again and retest. Repeat as necessary.
  
  Once the low speed needle is correctly adjusted, the engine throttle should respond very quickly. It is now time to adjust the idle speed.   
  
  Now we can get into Glow plugs while there is no perfect solution for these in the winter time HOT plugs will keep an engine running longer because in the cold air temps you require richer fuel mixtures,   In the summer time Meduim Heat Glow plugs will last longer in most fuels between 10 to 30 % nitro.  Why because the Filiment is thicker.   For racing engines some suggest cold plugs when running 30% or over nitro content.  Problem with Cold plugs they will flame out if the idle screw is not set right on the edge of clutch engagement..
  
  

  This chart indicates the direction in which you should adjust the fuel mixture when faced with changing conditions. It assumes the engine is currently well tuned. You could face any combination of conditions listed in this chart. Knowing how to adjust the fuel mixture is a crucial part of operating and maintaining your RC vehicle. Higher Air Pressure Lean Lower Air Pressure Rich Higher Humidity Lean Lower Humidity Rich Higher Barometric Pressure Rich Lower Barometric Pressure Lean Higher Altitude Lean Lower Altitude Rich Higher Nitro Content Rich Lower Nitro Content Lean Higher Oil Content Lean Lower Oil Content Rich Hotter Glow Plug Rich Cooler Glow Plug Lean

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