JohnP2
Posts: 1069
Joined: 12/31/2011
Last Login: 5/18/2013
From: Fort worth,
TX, USA
Status: online
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quote:
ORIGINAL: bikeordie092
the warmer it gets, the worse it gets, it doesnt seem like its bogging down but that its jumping up
Hmmm...perhaps it is too lean. You noted you've "tuned and tuned. Below is a clip I got off the Information Super Highway, from Ed Bridges (sorry Neal, I'm sure you respect him anyway). I subscribe to much of this when I tune my engines.
Performance Tuning Guide
There are many ways to tune a nitro engine but I figure this is the most simple way to do it. This technique is for a fully broken in engine that is ready for a full performance tune. This tuning procedure will set your needles to where they need to be for optimum performance, the engine will tell you all you need to know.For this method to work the engine has to be at running temperature (or as close to it as possible) as well as having the standard 1mm gap for the carburetor opening. High Speed Needle
Pull a full throttle pass a couple of times and listen to what the engine does when you let off the throttle. If the it drops right to idle, the HSN is either good or on the rich side. At this point you can lean the HSN in 1/12 turn increments until the idle seems to hang a little after a full throttle pass. If it starts to idle high after a pass it is just on the lean side of a perfect tune. Back the HSN out 1/12 turn at a time after a wot pass until the engine drops right to idle after a pass. Now your HSN is set. An explanation to what is happening is simple - if your HSN is too lean, after a full throttle pass when you let off the throttle the engine is still lean causing the idle to hang and idle high until the LSN has a chance to take over and meter the right amount of fuel to bring the idle down to normal running speed (given the LSN is set correctly). If the opposite happens, after a full throttle pass when you let off the throttle it drops to a good idle right away and then starts to idle back up too high, this is a sign that the LSN is too lean. If it comes off full throttle with a good tune and will drop RPM nicely then the HSN is metering the fuel properly but once it hits idle the LSN being too lean will quickly take over causing the RPM to go back up. Low Speed Needle
Most of this setting was explained above but there are a few little tricks you can use to make sure the LSN is adjusted perfectly. We all know that you don't tune for temperatures, but a temperature gun is very handy for this part. After some full throttle passes with the engine good and warm, bring it in and let it sit for about 10 seconds. At this point take your temperature gauge and hold it as steady as possible on the head, what you want to see is the temp dropping a degree every 4-5 seconds. You want the temp to drop very slightly at idle because when your off throttle the engine should be cooling, if not, the temps will keep pushing higher during on and off throttle running and will cause temperature issues. This is how I do it and I have tuned a lot of engines for people, whether bashing or racing. I have seen across the board from beginners to veterans that when they hear the high idle after a pull, the first thing they go for is the LSN when in fact it is the HSN causing the issue.
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All Forums >> RC Cars, Buggies, Trucks, Tanks and more >> RC Car Engines >> Car Nitro & Gas Engines >> weird idle, help please? 
weird idle, help please? - 
