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Engine help please

Engine help please

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Old 08-25-2013, 05:05 PM
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Default Engine help please

Hi all
I am running an o.s. 28 xz in my losi 8ight-t 2.0. With 30% nitro fuel. My problem is the I have the tune so rich that the performance of the motor is suffering ( bogging down out of corners and of the line ect. ) yet my motor seams to still get extremely hot + 140 c. I've taken the motor apart and every thing looks fine. There's no pre detonation signs on the pistons or glow plug. Will adding a extra head shim make it run cooler? Anyone got any other ideas why it might be running so hot? I've even cut the windows out on my shell so it's not a air flow issue.
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Old 08-25-2013, 10:28 PM
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do you have any smoke from your pipe? how well does your engine idle? an extremely lean tune will show similar signs to a rich tune, bogging ect.

check your plug and make sure its correct for the ambient conditions your running. let your engine warm up completely before tuning.

i suggest starting over. set idle gap to about 1.5mm, reset your needles to factory (usually flush, but not always). slowly lean out your hsn till you engine opens up with a decent amount of throttle, just a bit of smoke, then slowly lean out your lsn till your idle stays constant, and not too high. if you have a temp gun, monitor your engine temp at idle, if temps are dropping your lsn is rich. if they increase your lsn is lean (assuming your idle speed is correct). if your idle is high, then drops and holds, your idle speed is too high and your lsn too rich.

try that, if it dont work then we can look into other issues
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Old 08-25-2013, 10:47 PM
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There is plenty of smoke right though the rev range. Car idles fine. It's that rich that its still spits unburnt fuel from the exhaust and I only get about 5 minting time from a full tank. I've had other drivers at my club try to tune it and they also so it's running extremely rich. I've tried different fuel's, different plugs, the motors always seamed to run hot since new ( has about 18 litres though it now) and it seams to like it when it's hot but it gets that hot that its killing my clutch bearings almost every race.
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Old 08-25-2013, 11:15 PM
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how tight is your gear mesh and hows your clutch shoes look? you mentioned eating clutch bearings... is it possible something is binding somewhere or too tight?

your gear mesh shouldnt be super snug, your chassis will flex, and when that happens your mesh tolerances change.

have you compared the readings of your temp gun with another?

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Old 08-25-2013, 11:42 PM
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I use the paper trick between the clutch bell and sper gear to set my gear mesh. Na it's not to tight you can normally hear when it's tight just by rolling it. I was getting a temp reading of 150 c of of my controller ( spectrum dx3s ) so I bought a cheap temp gun off eBay for $12 and although the gun reads cooler then the controller it's still high ( gun will read 140 c when controller reads 148 c ) you can tell the clutch bell bearings are failing due to temp because the way the metal discolours. This engine gets to that temp within a few minutes of racing but then just stays that hot hot for the remander of the race. I just think my engine must like to run that hot because it dosent seam to be damaging the engine. Just getting annoyed at having to change bearing almost every race.
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Old 08-25-2013, 11:45 PM
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I can even lean it off to the point that the motor will perform
Like it should and it still runs the same temp
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Old 08-26-2013, 12:20 AM
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throw out your temp guage and your onboard temp.They are both wrong..

Tune for smoke and performance. just make sure its still blowing smoke at full throttle. you will know when you've gone to far it will start to bog and no smoke.

i tempted my engine after 30mins with my guage it said 240F, temped with a friends guage an it said 290F
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Old 08-26-2013, 05:47 PM
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one more thing to consider...

if your idle gap is set too low, and to compromise you also have your lsn set too lean your idle will sound ok... but your engine temps will be noticably higher.

you want to make sure your hsn is set before attempting the following, but sinse u say u got smoke its prolly ok...

you can try just slightly increasing your idle gap, your idle will come up then richen your lsn till your idle comes back down. you can continue that in very small increments as necessary. if above is the case your engine temps will drop drastically, and after doing so, if you have a stable idle then it drops off, you know u went too large with the idle gap.

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Old 08-28-2013, 06:12 PM
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Originally Posted by LosiPRRACER View Post
throw out your temp guage and your onboard temp.They are both wrong..

Tune for smoke and performance. just make sure its still blowing smoke at full throttle. you will know when you've gone to far it will start to bog and no smoke.

i tempted my engine after 30mins with my guage it said 240F, temped with a friends guage an it said 290F
I would agree, BUT, you are burning up bearings each race? Have you ruled out gear mesh, clutch wear, and other things that could be wearing the bearing out? Sure that it's not coincidence? Could it be that this engine simply likes to run at these temperatures and there is, coincidentally, something else ruining you clutch bearing?

The fact that you say it runs consistently at these temps and the fact that it's an O.S., would seem to indicate that you have an engine that likes these temps. Guess I gave more questions than answers.lol Subscribed though, curious to see how this turns out.
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Old 08-31-2013, 08:46 AM
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Stop using a temp gauge. 290 ain't nothing. IR temp gauges aren't the least bit accurate.

Good smoke, good performance. No problem.
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Old 08-31-2013, 09:48 AM
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How much fuel thru engine. I was helping a guy a track with same engine and same problem. He thought engine was broken in. I checked TDC and it was tight as hell.
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