Tuning question XRD GT

Old 04-20-2018, 02:20 PM
  #1  
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Default Tuning question XRD GT

Hello gents,

My XRD GT 0.21 (15 litres old) running in an 1/8 GT is running reasonable but.....Today it was quite hot (27 Celsius) so I leaned the HSN 1 hour or so. When I start my run the idle is pretty good but after I've run for about 10 laps the idle is like very high and stays high. After let say 10 seconds I blip full throttle and then it goes down to normal. Its not a stuck slide barrel. My thought was the idle screw is to high and after I blip full throttle the crankcase fills up and due to the "richness" the idle goes down. More or less the same behaviour as a rich LSN.
If I lower the idle screw and the engine has cooled of a bit it wont stay idle.

Do I have to lean the LSN a bit? Any advice here?

regards
In addition: If i lower the idle screw I lower the LSN also if I'm not mistaking. The air gap gets smaller but the needle is also closer to the jet.........right?
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Old 04-21-2018, 08:45 AM
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I would try richening the LSN slightly. Sounds like the idle is too lean, causing the high idle. Which goes away with the full throttle blip (extra fuel into mixture) as you mentioned.

But im no pro, i apologise if its the wrong advice. Do let me know if it works.
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Old 05-05-2018, 06:33 PM
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Originally Posted by wkloppen View Post
Hello gents,

My XRD GT 0.21 (15 litres old) running in an 1/8 GT is running reasonable but.....Today it was quite hot (27 Celsius) so I leaned the HSN 1 hour or so. When I start my run the idle is pretty good but after I've run for about 10 laps the idle is like very high and stays high. After let say 10 seconds I blip full throttle and then it goes down to normal. Its not a stuck slide barrel. My thought was the idle screw is to high and after I blip full throttle the crankcase fills up and due to the "richness" the idle goes down. More or less the same behaviour as a rich LSN.
If I lower the idle screw and the engine has cooled of a bit it wont stay idle.

Do I have to lean the LSN a bit? Any advice here?

regards
In addition: If i lower the idle screw I lower the LSN also if I'm not mistaking. The air gap gets smaller but the needle is also closer to the jet.........right?
Consider if the bottom end is rich, then a large air gap is required to keep it idling. The rich mixture pulls down your idle speed, but once you clear the crank of fuel at wide open throttle and brake, The mixture at IDLE has a LOT of Air, until the engine richens up the crank.

Called a Faux Idle.

NOTEL It can be too lean and resemble similar OverRun symptoms as well.
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