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How to Break-In & Tune an Engine.

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Nitroaddict

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I have titled this thread in order to come up on searches. Please do not post any unrelated comments here. Feel free however, to add any other important steps I may have left out:
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How To Break-In & Tune an Engine
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To start - make sure your needle settings are at factory break-in settings. Please refer to your specific manual for proper settings. As a starting point for those who have no manual, an general rule of thumb is:

Bottom End (Low End)- Flush with carb

High End (Top End)- 3 Turns out

Idle- Set the gap inside the carb at 0.7mm to 1.0mm


DO NOT OVERTIGHTEN NEEDLES, AS YOU WILL RIP THE O-RINGS!

Factory Settings are not the fix-all answer to engine tuning problems. These settings will likely set your engine rich, and may not work under the conditions you are in. There are many variables which we can not control. Variables include type and percentage of fuel, type of glow plug, length of fuel and pressure lines, ambient temperature, barometric pressure, humidity, and even your level of experience and knowledge level. .

Here are some tips to help tune your engine, read on even if you are an experienced racer.

1- The break in process is the most crucial time in the life of an engine. Take care not to over rev and over heat an engine during this time. Conversely, do not take too long to break in an engine, as running an engine too rich for too long can cause damage to the conrod. When breaking in an engine, you may need to leave the glow igniter attached to keep the engine running.

2- Always make adjustments after allowing the engine to warm up fully. I strongly suggest setting the optimum tune with 1/4 tank or less of fuel in the car. Most engines will run slightly rich with a full tank and slightly lean with a low tank.

3- Don't assume that a properly tuned engine on a street surface will run the same on a loose dirt surface. Keep an eye on changing conditions including weather, track conditions, tire size, etc.

4- The type of glow plug used has a huge effect on engine tune and performance. Sometimes changing the type of plug makes all the difference.

5- If you are unsure of the settings, it is safer to tune rich. It you are unsure of what you are doing, stop and seek help from someone with experience.

When Tuning an engine - Always Tune in the Following Order:
  • HSN - High speed needle
  • LSN - Low speed needle
  • ISS - Idle set screw

Tune one needle at a time. Never at the same time. Once the engine is properly tuned, it may run to fast at idle, due to the now leaner LSN. Adjust your ISS accordingly.

When tuning an engine, tune needles only 1/8th of a turn or less, and allow at least 60 seconds of running between adjustments.

When final tuning, or tuning for power, tune at increments of 1/16th or less.
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Please add any relevant comments as you see fit. This is not a question/answer thread - do not post questions in this thread. Thank you.

Please feel free to print this out and use at your leisure
 
I'd tune it at a half or less, since most setups tend to lean out at about that point. You wouldn't want to tune it for max power at a full tank and have it cook at half a tank.
 
I also heard that. Because after it gets to about half way or so, it slowly starts to lean itself out. I suppose that if you tuned with around 3/4 to 1/2 is probly pretty good. i am not 100% sure on that so dont quote me.
 
Hey NA this is an awesome guide! I know you know my the problems I had until you pointed me in the right direction. I hope this helps a lot of people out. I am about to run my new MT12 and this is definitely the guide I will use. I am also getting an OS.12
Thanks NA
Jon:w00t:
 
tuning.gif


edit re: SkyMaxx's comments below. This IS Traxxas documentation...
 
Last edited:
That is a nice chart.

The only one I disagree with it the Nitro% rows. A higher nitro percentage means more fuel by volume. Thus a leaner setting would be better (all things being equal in the air department)...and vice versa.

Just food for thought.
 
But wouldnt that advance the timing too much if you leaned it with, lets say, 40% nitro? Thus creating higher rpm's and heat?
 
I'm just thinking fuel to air mixture by volume. The timing thing is beyond me.:D
 
My thought would be that if the nitro % is higher and you didnt richen/or lean, it would combust earlier than on the lesser % of nitro. Thus, causing the piston to not rise as high as usual and run at a hotter temp and higher rpm that 'normal'. I think I explained it right.

Hell I dont know. I'm beginning to think that 25% of this is theories vs. theories!

Does it run? Is the temp ok? Does it PERFORM? Then stick with!

lol

And no, the piston still makes the full uprise cycle, just the point of combustion would be earlier.
 
Jeeze, you guys are gonna argue about this. Here's a thought that doesn't involve rocket science. Get the temp gun out, if the plug is below 240, lean it a bit, higher than 270, richen it. Damn.
 
Originally posted by wdavidhicks

edit re: SkyMaxx's comments below. This IS Traxxas documentation...

Figures.

Error, who's arguing? We are trading thoughts on the complexities around changing fuel percentages. If you have anything productive to say, then do so...otherwise...BITE ME!
 
ADDENDUM

Here is a flowchart that you can print out - should also help with diagnosing engine problems.

595flowchart.gif
 
that chart came with my duratrash. LOL

Originally posted by SkyMaxx

The only one I disagree with it the Nitro% rows. A higher nitro percentage means more fuel by volume. Thus a leaner setting would be better (all things being equal in the air department)...and vice versa.

interesting you bring that up. a guy at our track (the engine pro guy) run sidewider 30%. his buddy, a good racer that runs a Roddy-modified RB WS7, also runs the same 30%. his HSN is 4+ turns out!

i also noticed the change in my carb setting going from 10% to 20%. in general all of the RC's i own tended to like a richer setting on the 20%.

i don't unstand it, but i agree with the generalizeation that the higher the nitro percent, the richer the setting.

i'm not trying to piss people off. i'm just trying to share what i've seen.

-Rob
 
OK, I'll just stfu and let ya'll pick gnat poop out of pepper and I'll just go play with my temp gun......

Just don't over think it guys, ya'll might hurt yourselves.
 
ok I got hold of a temp gun which should make my tuning better along with the great info on this thread!!!!!:banana:
 
Re: How to Break-In & Tune an Engine.

Originally posted by Nitroaddict
Please do not post any unrelated comments here. .....
......This is not a question/answer thread - do not post questions in this thread. Thank you.




Damn you motherf'ers can't any of you read? LOL.
 
Na is right about overtightening the LSN or HSN I stripped the o-ring on my carb and trying to tune it was useless. It always overheated. Be careful!!!
 
Putting a heardryer or heatgun before starting a new engine helps a lot.Allso try to get your engine to running temp (200- 220) as quik as you can to prevent the piston and sleeve of pinching,less strain on your conrod.
 
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