Break-in for higher nitro levels
03-13-2014, 06:08 AM
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Break-in for higher nitro levels
Hi All,
Here's a technical question. If after breaking in a glow engine with 0% or 5% nitro and using it for a while, if you move up to 10%, should you "break in" the engine again for a tank or two due to the higher temperature obtained from using the higher nitro content?
Thanks in advance.
Antares100
Here's a technical question. If after breaking in a glow engine with 0% or 5% nitro and using it for a while, if you move up to 10%, should you "break in" the engine again for a tank or two due to the higher temperature obtained from using the higher nitro content?
Thanks in advance.
Antares100
03-13-2014, 06:30 AM
#2
No, the break-in is only there to mate the machined surfaces in a new engine.
Increasing the nitro level can actually give a cooler running engine, depending what nitro levels was is set up for to begin with. Higher nitro requires less compression ratio, an easy fix with an extra head shim or two.
Increasing the nitro level can actually give a cooler running engine, depending what nitro levels was is set up for to begin with. Higher nitro requires less compression ratio, an easy fix with an extra head shim or two.
03-13-2014, 06:45 AM
#4
Depending on the engine, not likely. It wouldn't be wise to run a SuperTigre for example on 10-15% fuel without adding a shim. A Thunder Tiger on the other hand, a shim isn't needed most likely.
03-13-2014, 12:42 PM
#5
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Mr Cox explain how and engine will run cooler with more nitro?
More nitro means more power. Power is heat so how will it run cooler? I would say that if you change the tempature that the engine is running at when its broken in then you might have different wear patters with more or less heat.
An example is that when an engine is col its very tight and may not even turn over till you heat it some.
I can take this even father to get your head working some. You all know that meatl expands and contracts with temp change. Some most cylinders and pistons are round. Now look at the cooling air flow on a model engine from the propeller around the cylinder. The front of the engine slightly to one side will have the most cooling air while the back of the cylinder will have a pocket of stagnant air(no air movement). The front will be cooler than the back and will have different expansion rates. So if you were able to cool the cylinder evenly then we will have a more round cylinder that will/could make more power. Some could argue that the piston and cylinder will fit to each other which it sorta does.
Anyway back to the higher nitro. I only try to change it 10-20 % difference. So if i plane to run 50% in an engine once broke in then I will break it in on 30-35%.
More nitro means more power. Power is heat so how will it run cooler? I would say that if you change the tempature that the engine is running at when its broken in then you might have different wear patters with more or less heat.
An example is that when an engine is col its very tight and may not even turn over till you heat it some.
I can take this even father to get your head working some. You all know that meatl expands and contracts with temp change. Some most cylinders and pistons are round. Now look at the cooling air flow on a model engine from the propeller around the cylinder. The front of the engine slightly to one side will have the most cooling air while the back of the cylinder will have a pocket of stagnant air(no air movement). The front will be cooler than the back and will have different expansion rates. So if you were able to cool the cylinder evenly then we will have a more round cylinder that will/could make more power. Some could argue that the piston and cylinder will fit to each other which it sorta does.
Anyway back to the higher nitro. I only try to change it 10-20 % difference. So if i plane to run 50% in an engine once broke in then I will break it in on 30-35%.
03-13-2014, 01:02 PM
#6
Antares, what engine are you talking about? A lot of engines go from 5% to 30% just fine. Sometimes you may need to go to a cooler plug. For example, I have a .46 that uses 2 shims and always burns 15%. I'm thinking of using 30% just for grins and taking out those two shims too. Every model of engine has its own character and way of running.
03-13-2014, 05:03 PM
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BLW, I am breaking in 3 engines. A K&B .40 and .65 Sportster and an OS FP .61. Had planned on using SIG 5% and run them that way. I didn't think a 5% difference to 10% would be a problem, but wanted to throw it out there. Not really into speed, more of a sport flyer (after a long break). I was just thinking with the added heat the extra 5% would produce, perhaps I should run it blubbery rich the first few tanks with the 10% (again, should I decide to go 10%).
03-13-2014, 05:52 PM
#8
BLW, I am breaking in 3 engines. A K&B .40 and .65 Sportster and an OS FP .61. Had planned on using SIG 5% and run them that way. I didn't think a 5% difference to 10% would be a problem, but wanted to throw it out there. Not really into speed, more of a sport flyer (after a long break). I was just thinking with the added heat the extra 5% would produce, perhaps I should run it blubbery rich the first few tanks with the 10% (again, should I decide to go 10%).
The OS and other K&B should take the extra nitro without much guff but the FP being ABN and bushed will greatly benefit from a good castor diet as well.
I hadnt noted a big difference in engine temps using 5% nitro versus 10% nitro. If the needle is adjusted properly, they should run close to the same temp (5% versus 10%. 5% versus 25% on the other hand would be a different story)
Last edited by 1QwkSport2.5r; 03-13-2014 at 05:55 PM.
03-13-2014, 11:58 PM
#11
This is engine dependant and may not sound at all logical at first, but I have seen this from experience. In an engine which is properly set up for the higher nitro level, then running a lower nitro level means that one will try to compensate by running the engine leaner, hence the higher temperature in practice.
Back to the original question, going from 5% to 10% nitro is not a problem, the oil level and prop size is far more important.
Back to the original question, going from 5% to 10% nitro is not a problem, the oil level and prop size is far more important.
Last edited by Mr Cox; 03-14-2014 at 12:00 AM.
03-14-2014, 12:38 PM
#14
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The nitro versus temp relationship has been discussed ad nauseam on this forum. If you search you will find a ton of discussion. If I remember correctly, more nitro = more fuel through engine = more hot oil blown out the exhaust = better cooling. The extra heat transfer from the higher waste oil volume exceeds the additional heat input from more power... or something like that.
This is relavant to the original question because the OP was asking if he should re-break in his engine because of the change in temperature caused by a change in nitro.
By the way, I often change from 5% to 10% and have never worried about a second break in. In fact I can't tell the difference other than having to readjust the carb.
This is relavant to the original question because the OP was asking if he should re-break in his engine because of the change in temperature caused by a change in nitro.
By the way, I often change from 5% to 10% and have never worried about a second break in. In fact I can't tell the difference other than having to readjust the carb.
03-15-2014, 12:37 PM
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Hi!
The answer is really simple!
Increasing nitro content from 0% to lets say 10-15% will make the high speed needle setting much broader ,thus you can run the engine at a richer setting and still have the same power but not risking running tjhe engine lean at certain manuvers.
The answer is really simple!
Increasing nitro content from 0% to lets say 10-15% will make the high speed needle setting much broader ,thus you can run the engine at a richer setting and still have the same power but not risking running tjhe engine lean at certain manuvers.
