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Old 09-26-2006, 01:48 PM   #1
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Exclamation nitro tuning question

I am having some issues with a fairly new P5X (about 2 gallons on it). I broke it in on 20% nitro and ran a gallon and a half of 20% nitro through it and then switched to 30% nitro. The whole time I ran 20% in it I always ran it a little rich except towards the last few races I started leaning it out to get more power.

After switching to 30% I am having trouble getting it to run properly. I use the recomended plug for 30%. I can tune it to run pretty good on the bench and on the track during practice it sometimes runs hot and some times it does not. But when I am racing it seems to always run hot, if I try to richen it up to cool it down it runs like crap, if I lean it out to run better it over heats.

I have had it apart and see nothing obviously wrong with it. So that leads me to believe I am tuning it incorrectly. I have had some help from guys at the track but I get conflicting ideas on how to get it to run cooler.

So what is the proper way to take the heat out? richen the low side or the high side needle?

One theory is to richen the low side needle then lean the high side to keep the motor running well through out the power band.

Another person I have seen richen the high side when I complain about the heat and not really touch the low side as long as there is good power on the bottom end.

this is pretty much a new motor and I hate to think it's ruined! I would rather find out that it's tuned wrong and get it fixed! I had some issues with keeping it cool even running it on 20%

thanks
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Old 09-26-2006, 02:01 PM   #2
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Put the temp guns away and tune it until it feels how you want on the track. Don't start tuning it until the engine and chassis are both good and warm. There is no set temp to run at, if it feels good at 280 run it there. If it feels good enough at 210, run it there. What temp are you considering to hot?
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Old 09-26-2006, 02:04 PM   #3
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Quote:
Originally Posted by jbrow1
Put the temp guns away and tune it until it feels how you want on the track. Don't start tuning it until the engine and chassis are both good and warm. There is no set temp to run at, if it feels good at 280 run it there. If it feels good enough at 210, run it there. What temp are you considering to hot?

300 degrees +

it's not that it just running hot, it's over heating!
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Old 09-26-2006, 02:26 PM   #4
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Hehe, I was going to put something about 300* too.

Have you changed the fuel line, checked the filter, tank, and also sealed up the engine? Sounds like an air leak to me. Check the manifold gasket as well.
Reset the needles to stock settings as well and retune after doing all the above.
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Old 09-26-2006, 02:45 PM   #5
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I have checked over alot of those things but it is possible there is a leak or some other problem.

I do not want to rule out it being a tuning issue. So to reiterate my question, which needle should be used to cool the motor down if it's running hot?

thanks
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Old 09-26-2006, 03:15 PM   #6
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Did you add a head shim to run 30%???
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Old 09-26-2006, 03:31 PM   #7
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Quote:
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Did you add a head shim to run 30%???

Nope... Should I? This is the first anyone has mentioned the need for one on a P5X
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Old 09-26-2006, 03:55 PM   #8
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Quote:
Originally Posted by HookaMega
I have checked over alot of those things but it is possible there is a leak or some other problem.

I do not want to rule out it being a tuning issue. So to reiterate my question, which needle should be used to cool the motor down if it's running hot?

thanks
I would think a P5 would be fine with 30% without adding a shim. Guess somebody else have to answer that one if you want a more definate answer than that. I switched between 20 and 30 in a couple of my .21's this summer and never had a problem other than retuning. I've only had 20% through my P5 for now though.

Either needle can cause high temps. If they get way out of balance they will possibly run right for a bit, but then after continous running keep getting hotter and hotter. That's why I suggested going back to the stock needle settings and retune. That would be the first thing I did. Tune the high speed needle first, then the low, then the idle.

You can spend all day trying to diagnose what needle is wrong, or which one is the one you need to tune. But if you just go back to factory settings you know it should be rich and need leaning out from there and it saves alot of time.

A bad oring on the fuel tank lid will cause pretty big problems as well.
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Old 09-27-2006, 02:58 AM   #9
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I would tend to look at where you are in the thottle most of the time when you are racing. Are you full thottle out of every corner or maybe your track is really wide open and requires lots of wide open thottle? Then I would richen the High needle. If you track is tight and you send most of the time at 1/4 to 1/3 throttle then rich up the low needle. That motor has enough power when tuned right to only need 1/4 to 1/2 thottle for most of the track, you should only be hitting full thottle on large jumps and long straights. If you find that you are having to pull full thottle most of time to get it up to speed, than your low needle is problably to rich and you are having to lean the high needle to get it to clear out but it ends up being to lean for wide open thottle and that motor slowly starts to over heat the longer you run. Also check the front bearing, the factory ones are total junk and will cause overheating if going bad. Good Luck.
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Old 09-27-2006, 09:20 AM   #10
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For what it is worth here is my .02.............

There are hundreds of posts like this one all over the net. One of the most important things in the posts that follow is most always left out. This would be the Air gap/idle setting on the carb slide. You canít tune an engine if this is not set right. In order to tune an engine properly this gap should be set to somewhere between 1.0mm to 1.5mm no more or less than that to start. There is a specific ratio to fuel & air mixture that these engines are designed to run at. Once the engine is tuned properly you can fine tune the idle some. Most of the time when this gap is set too small you will be running too lean on the bottom. This is because to get a nice idle with it that small you will have to lean it out or your idle will be to low. Also most of the time when this gap is set too big you will be fat on the bottom. This is because to get a nice idle you will have to richen it up or your idle will be too high. I keep a 1.5mm drill bit in my pit box to set this gap. Once this gap is set correctly fire the engine up and get it running good enough to put it on the track. Then run some hot laps to get some temp in it and bring it in and richen the top end to the point where it is not clearing out on the straights, this way you know it is fat for sure. Once you have done this start leaning the top end out to where it is just clearing out on the straights. After this bring it in to get the low end set close. When you do this pay attention to how the car comes in after being wide open on the straight. If the car went out on the track when you first put it down with a decent idle but is coming back in with a high idle for a while (8+ sec) and then settles back down then chances are you are too fat on the bottom. If this is so then lean the bottom out an hour until when it comes back in it stays high. Once you have done this you can set the idle/air gap to get the idle you are after, it wonít be much. (Once I have found this I will usually fatten the low end about an hour or so just to make sure) If when you are out running you hot laps you start to bog coming out of the corners and donít see a good smoke trail chances are you are too lean on the bottom. Fatten the bottom until it is not lean bogging coming out of the corners, has a nice smoke trail and you have the power you are after on the low end. If this is the case and the idle is now too low bring the idle up using the air gap/idle screw, again it wonít be much. Once you get the low end set go back and re-tune the top end for performance with a good smoke trail.

Oh and Jbrow1 is right, try not to use the temp gun too much. If after tuning for performance and you have a good smoke trail coming out of all the corners and your engine is running 280, let it!

Also the P5X is shimmed for 30% out of the box.

The bumpster!

Last edited by SpeedBump57; 09-29-2006 at 11:41 AM.
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Old 09-28-2006, 01:58 AM   #11
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Anyone know what the factory needle settings should be for a Orion wasp 21 - I need help?
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Old 09-28-2006, 05:55 AM   #12
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speed bump that was an excellent Nitro Tune post.
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Old 09-28-2006, 07:40 AM   #13
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^ Thank you Sir!

Here is a tip that I forgot to add to that post.

Setting your nitro engine up that way is almost fool proof once you get it down. The other thing that is cool is this! Letís say I have found the perfect tune on race day and then go out next week to race and the tune is a little off. What this tells me is my surroundings have changed i.e. temp, humidity and such. Letís say after running my engine for a little bit I notice that the idle is a little high. What this tells me is the engine is now running a little lean due to changes in atmospheric conditions i.e. air temp & humidity. Most people at this point would simply turn the idle screw a bit to bring the idle down some. Buy doing this yes the idle will come down but chances are you are still running lean! The better thing to do would be to fatten up the low end some to bring the idle down. This will maintain the correct air gap on the carb slide and air/fuel mixture and you won't be running lean for the day. If you noticed that your engine is idling a little low at the start of a new day then the opposite would be true i.e. you would be a little fat on the bottom. If this is the case then lean out the bottom a little until the idle comes back to where you want and fine tune from there. Also now that you know that you were either a little lean or fat on the bottom chances are you are a little lean or fat on the top end for that day. So take a look at the top end after setting the bottom. If I have a day like this I will set the top again to where I know its rich i.e. not cleaning out on the straights and re-tune from there.

I hope all this makes sence to those that are reading, I felt is was hard to put all this into words.

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Old 09-28-2006, 04:40 PM   #14
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Thanks for all the advice!

I must say, I have bought a book or two and have read guides on nitro tuning in magazines. I can say I have learned from this thread as those books and magazines really do not tell you what to do when you get into a bind. Yeah they all mention that you can return the needle settings back to factory and start over but they usually only cover one process to tune from break in to race tune.

There are several good ideas here that could help determine if your motor is running properly as well as getting it there if it's not.


Thanks.
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Old 09-28-2006, 07:48 PM   #15
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You are welcome, I hope it helps to shead some light on nitro tunning. I am sure there are different ways, this is just the way I have learned in the last couple of years.
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