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Old 07-03-2006, 06:38 AM   #1
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Default newbie .21 nitro question

i am experiencing some difficulties with my .21 nitro engine which is in my x-ray xb8 4wd off-road buggy and is what it is the car gets to a certain temperature or time period in running which is about 1/2 tank of fuel then it makes that bogging sound and doesnt have any power like it did before 1/2 tank so would this be due to the low speed needle not being rich enough??
because it seems to do it when i first start accelerating again after ive slowed down at around the 1/2 tank mark and does it until i get a bit of speed out of it for it to progress to the high speed needle at higher speed obviously but like i said the once its slowed down when i press the throttle on all the way it makes the bogging sound and it struggles to go anywhere unless i muck around trying to clear it and slowly get it up to speed.


any analagies to fix this problem would be much appreciated oh and also why does my temp guage say it gets to over 300 degrees celcius thats way to hot how could my engine get that hot even if the guage is out a bit its still in the 350 degree celcius mark.

also would taking one of the head shims/gaskets out increase its compression if not what would this do if i removed one?
thanks regards Aaron.
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Old 07-03-2006, 08:41 AM   #2
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First of all I have never seen an engine run past 425*F, I have seen them hotter but they arn't running. 355*C is almost 650*F. I think the temp gun you are using is a little off.

Having said that you are probably still running way too hot & lean form your discription. Normally if you are a little too lean on the LSN you will have the symtoms you discribe, loosing power after a few min of running. My guess is you are running too lean top & bottom. I would recomend you start over with your tune. Richen up both needles a full turn and start from there or reset to factory settings what ever they may be. If you must use a temp gun, get one that you know at least works right.
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Old 07-04-2006, 12:23 PM   #3
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Quote:
Originally Posted by downunder23
i am experiencing some difficulties with my .21 nitro engine which is in my x-ray xb8 4wd off-road buggy and is what it is the car gets to a certain temperature or time period in running which is about 1/2 tank of fuel then it makes that bogging sound and doesnt have any power like it did before 1/2 tank so would this be due to the low speed needle not being rich enough??
because it seems to do it when i first start accelerating again after ive slowed down at around the 1/2 tank mark and does it until i get a bit of speed out of it for it to progress to the high speed needle at higher speed obviously but like i said the once its slowed down when i press the throttle on all the way it makes the bogging sound and it struggles to go anywhere unless i muck around trying to clear it and slowly get it up to speed.


any analagies to fix this problem would be much appreciated oh and also why does my temp guage say it gets to over 300 degrees celcius thats way to hot how could my engine get that hot even if the guage is out a bit its still in the 350 degree celcius mark.

also would taking one of the head shims/gaskets out increase its compression if not what would this do if i removed one?
thanks regards Aaron.
you have probably shot that motor already, that's way to hot to be running these engines. i would suggest getting another motor, unless it has descent compression and if it does you better richen the fire out of it
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Old 07-04-2006, 11:23 PM   #4
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ok thanks guys for your help ill richen it right up and take it from there.
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Old 07-04-2006, 11:27 PM   #5
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Default getting more compression.

is there anyway of modifying the engine to get more compression?
because i havnt had it all that long and it had massive compression when i first got it (secondhand) and sinse ive been mucking around with the tune its lost compression so it cant be all that bad i just want to know how to gain a lil more compression out of it any suggestions?
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Old 07-04-2006, 11:51 PM   #6
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Quote:
Originally Posted by downunder23
ok thanks guys for your help ill richen it right up and take it from there.

300C???? most rc temp guns dont even got hat far!!!

i think you need to richen it out ALOT pronto!!!

temps should be 100C to 120. maybe 150MAX
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Old 07-05-2006, 11:01 AM   #7
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Hey downunder23

Are you SURE your motor has Good Compression or just a tight motor??? How did you measure Compression??? Nova motors are tight, and some others also. What motor do you have??? What Nitro Ratio are you using??? That will help in figuring out what maybe up???

Alum turns to Plastic at 425 F(and, YEA I don't care what type of Alum it is... Look it up in a Materials Book)... So your Temp Gauge is Off... Always tune by hear and then Temp it, look for smoke out of the tail pipe.


Have a Good One!!!

Brad
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Old 07-05-2006, 11:08 AM   #8
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UMMMMMMM....

aluminum does NOT melt at 425 degrees fehrenheit. A simple search wouldve found that out buddy.

Thermal Properties


Heat of Fusion 390 J/g 168 BTU/lb
CTE, linear 20C 23.6 m/m-C 13.1 in/in-F 20-100C
CTE, linear 250C 25.5 m/m-C 14.2 in/in-F Average over the range 20-300C
Specific Heat Capacity 0.9 J/g-C 0.215 BTU/lb-F
Thermal Conductivity 240 W/m-K 1670 BTU-in/hr-ft-F
Melting Point 660 - 660 C 1220 - 1220 F
Solidus 660 C 1220 F
Liquidus 660 C 1220 F
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Old 07-06-2006, 11:15 AM   #9
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Quote:
Originally Posted by downunder23
is there anyway of modifying the engine to get more compression?
because i havnt had it all that long and it had massive compression when i first got it (secondhand) and sinse ive been mucking around with the tune its lost compression so it cant be all that bad i just want to know how to gain a lil more compression out of it any suggestions?
the only way to do that is pinch the sleeve and that dont always work, it will last a little while after that, but if you have little or no compression your motor is probably shot
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