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Old 11-26-2005, 01:06 AM   #1
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Default Swapping fuels, help please...

I just got an RC10GT off someone on here. Still breaking it in...

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Broke in on the bench for the first 2 tanks.. I ran it up too 200 on the temp gun then shut it off let it cool with the piston down.. After that leaned out 1/8 of a turn on each tank ran in it for 5 tanks made sure the temps where not over 240.. Mostly idled around with 1/4 throttle blurps and so on..I never really got the chance to run it 3/4 or full throttle.. I was still breaking it in.
I'm going to switch it over to Blue Thunder like the rest of my cars. How should I go about doing so? How much more breaking in?
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Old 11-26-2005, 01:22 AM   #2
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Swapping fuel's is a bad idea, but if you really want to make sure you use the same nitro percentage rate as the other guy did. Also might be a good idea to run rich for a couple of tanks.

On breaking in it is really up to you and I really don't know!
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Old 11-26-2005, 01:30 AM   #3
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Switching fuels is not a problem at all. Just richen up the needles a bit and retune.
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Old 11-26-2005, 11:22 AM   #4
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How far should I richen it before starting her up? How should I go about breaking it in from there, going by what he has already done, and then swapping to new fuel on top of that? I'm really precautious this time around since I just blew my new O.S.

Adjust both needles? The high speed needle on top of the carb, and the low-speed on the side where the throttle attaches?

Run it with the body on at all times and watch the temp?
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Old 11-27-2005, 04:13 AM   #5
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Richen it up a turn on top & see how it goes. There is no rule of thumb when it comes to a used engine because how can you know what the tune is like to start with. Just treat it like you are running in a new engine to be safe. I personaly dont do anything to change fuels unless the nitro content is different, just retune if nececery.
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Old 11-27-2005, 06:10 AM   #6
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What exactly harms the engine by swapping the brand/percentage of fuels? A lot of people say this, but they don't back it up with an explanation.
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Old 11-27-2005, 08:13 AM   #7
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I personally dont believe that an engine(composed of metals) can actually tell the difference between 2 fuels. If in fact they do have a small brain inside that heat sink head, then I stand corrected. The only differences really are oil content and nitro content. There are also variations in quality between fuels. I would do the same as everyone else has said. Richen her up a little, finish breaking her in, and tune for all the power she can handle.
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Old 11-27-2005, 09:14 AM   #8
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Quote:
What exactly harms the engine by swapping the brand/percentage of fuels?
This is a myth, with 30 years of building racing engines I can tell you for a fact it makes no difference. you just need to readjust the carburetor and maybe head clerance, if your below 30% don't worry about the head shimming. period end of story
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Old 11-27-2005, 04:59 PM   #9
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He ran Infinity 20%. I'm going to run Blue Thunder 20%. Supposedly has a little more lubricant, recommended by my hobby shop, and what I use on all the other cars, as well as my bro's.

Thanks for the help guys.

Also, how do you guys usually tune?

I'm going to riched it a little more before running it the first time, but how do you know if you've gone too far? I obviously didn't know and blew my O.S.

I was told to just watch for the blue smoke, and keep turning 1/8.
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Old 11-27-2005, 05:08 PM   #10
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fact is no two batch of fuel is ever going to be the same, even from the same company... it may be mixed close but never the same.
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Old 11-27-2005, 11:18 PM   #11
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Quote:
Originally Posted by Team Duratrax
What exactly harms the engine by swapping the brand/percentage of fuels? A lot of people say this, but they don't back it up with an explanation.
Fuel brand, the only difference may be the quality of the Nitro, Methanol & Oil. Also the types of Oils may be different. Not a big deal but richen it & retune is a precaution. Nitro content is a different animal, a retune will definatly be neccecery. Higher Nitro content & the mixture will need to be richer, less Nitro then leaner. It is still safer to start rich & work back. The engine wont care what fuel you put in as long as it is tuned correctly. A change in Nitro content will also require different thickness headshims & usually a diferent temp glow plug. If you race at events with controlled fuel you have to change fuels, so it is definatly not a problem.
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Old 11-27-2005, 11:26 PM   #12
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Quote:
Originally Posted by RiceEatin1995GT
He ran Infinity 20%. I'm going to run Blue Thunder 20%. Supposedly has a little more lubricant, recommended by my hobby shop, and what I use on all the other cars, as well as my bro's.

Thanks for the help guys.

Also, how do you guys usually tune?

I'm going to riched it a little more before running it the first time, but how do you know if you've gone too far? I obviously didn't know and blew my O.S.

I was told to just watch for the blue smoke, and keep turning 1/8.
A lean engine will still blow smoke. Some fuels have a lot of oil & can be almost at melt down & smoke still pours out. The best way is keep an eye on temprature & tune for performance. If you lean it out & power drops of even a little you are too lean. Unless you have deep pockets tune for 95% performance then richen it up a touch. This will still be fast enough to be competitive at most tracks. Untill you can go a 30min final without a crash you dont need 100%.
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Old 11-28-2005, 12:29 PM   #13
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Quote:
Originally Posted by soc123_au
A lean engine will still blow smoke. Some fuels have a lot of oil & can be almost at melt down & smoke still pours out. The best way is keep an eye on temprature & tune for performance. If you lean it out & power drops of even a little you are too lean. Unless you have deep pockets tune for 95% performance then richen it up a touch. This will still be fast enough to be competitive at most tracks. Untill you can go a 30min final without a crash you dont need 100%.
That might have been why I blew my O.S. It was still smoking but Blue Thunder is supposed to have a little extra oil.

What's a good way to test the calibration of a temp gun? I put it up to my skin and it read 92-93. Sounds about right. Where's the best place to aim it? Directly down the head? at the side of the head?

And how do I tune for performance by temp? I never noticed a drop off in performance with the O.S. but it still blew. What temps am I going for to get 95% performance?
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Old 11-28-2005, 12:51 PM   #14
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If you are re-tuning, richen up by 1/4 turn or so if your engine was tuned correctly previously. One full turn is wayyyy to much. You adjust 1/16 or 1/8 of a turn at a time, running the car as close to race conditions as possible for at least 2 minutes between tweaks. Bring the car in and read the temp right at the glow plug immediatly. You can tune for maximum performance while keeping the temp from going too high by doing this. Just keep in mind that running on the ragged edge will require you to make on going adjustments as the weather changes. If you tune a little conservatively you won't need to make as many adjustments at the cost of a bit less power.

There is no magic temperature. Each engine is different and barometric pressure, humidity, fuel mix and air temp will change the temperature the engine will run best at. The temp gage is only a guide. Check out the TZ thread in the engines forum for some good guidelines on temp ranges.

Last edited by Rapid Roy; 11-28-2005 at 04:46 PM.
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Old 11-28-2005, 03:03 PM   #15
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Quote:
Originally Posted by Rapid Roy
If you are retuning, richen up by 1/4 turn or so if your engine was tuned correctly previously. One full turn is wayyyy to much. You adjust 1/16 or 1/8 of a turn at a time, running the car as close to race conditions as possible for at least 2 minutes between tweaks. Bring the car in and read the temp right at the glow plug immediatly. You can tune for maximum performance while keeping the temp from going too high by doing this. Just keep in mind that running on the ragged edge will require you to make on going adjustments as the weather changes. If you tune a little conservatively you won't need to make as many adjustments at the cost of a bit less power.

There is now magic temperature. Each engine is different and barometric pressure, humidity, fuel mix and air temp will change the temperature the engine will run best at. The temp gage is only a guide. Check out the TZ thread in the engines forum for some good guidelines on temp ranges.
Going a full turn richer on the top I meant for a used engine that you dont know its history. 1 turn does seem excessive but it is better to be safe. It is easier to lean a blubbery engine than richen a dead one. I should have clarified this in my original post. Rapid Roy has got it on the money a lot clearer than I could. It is a lot harder to type what to do than show someone. Goodluck with it.
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