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Tuning issues for newbie

Tuning issues for newbie

Old 10-25-2008, 05:16 PM
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Default Tuning issues for newbie

I have a new T-Maxx 3.3 and it runs pretty decent most of the time.I've run about 12 tanks thru it including 5 tank Traxxas breakin procedure.It runs good ,but, gets too hot.I've adjusted the needles til it was really rich and it will get to the point it won't hardly run and I have to lean it back out to get it to run and make power.I usually get to a point where I think I have it and then it suddenly is too lean again.I couldn't get a infrared temp gun as they were out of stock.I do have a Venom onboard temp meter and that's what I'm using.I'm not necessarily tuning for a specifis temp I'd just like to find a way to keep it below 270 consistently and then work from there.

Last edited by SCXTREME; 10-26-2008 at 06:52 AM.
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Old 10-25-2008, 06:57 PM
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Check the placement of teh temp element on teh onboard gauge. I use one on one of my TMaxxes and had to move it a few times to get it to agree with my raytech ir gun's temp from shooting the glowplug.

The temp sensor can't be too close to the exhaust and needs to be in a fin height wise so its close to the same height as the shoulder of the glow plug. I had to move my sensor so it was as close in to the plug as possible - up against the innner wall of the cylinder head. Can you borrow a good IR temp gun to double check the onboard?

Ideally, the onboard temp should agree with what a good IR gun sees, or you may be making wrong clnclusions about temps you're reading. TRX engines tend to run hot, here at 90F ambient, mine run 270-280F with good smoke and good punch. That's about as good as it gets. If yours is running 270 and its 50F ambient - that is too hot.

After tweaking the location of sensor on mine, it agrees real well with my raytec. I don't use raytec for it anymore - I'm confident it reads right temp. Now if the batt would just last a little longer longer!!
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Old 10-26-2008, 06:51 AM
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That's good info.I'll check on sensor placement because that makes alot of sense.I need to get an IR gun to check it with.Thanks for the input.
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Old 10-26-2008, 05:11 PM
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newbies tune too much and get married to temperature. get to tuning the motor running it at least 1-2min, not a couple up and backs full blast, and seeing how the engine punches. if she runs best at 250 or 195, so be it. people are futz with their 2spd on that type of truck too much when it fact its the engine thats the prob

R
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Old 10-26-2008, 06:11 PM
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Originally Posted by ultegrasti View Post
newbies tune too much and get married to temperature. get to tuning the motor running it at least 1-2min, not a couple up and backs full blast, and seeing how the engine punches. if she runs best at 250 or 195, so be it. people are futz with their 2spd on that type of truck too much when it fact its the engine thats the prob

R
I'm not trying to tune to a specific temp.I'm just concerned that I wasn't able to keep it below 270 consistently which I thought would damage the engine from what I'd read.
I did have the temp probe too close to the exhaust port like the previous post from Duster_360 mentioned.I'm going to try it again tomorrow and see if that is the answer.Just don't want to cook the motor is all.I also haven't touched the trans adjustment yet since I figured it would make more sense to stabilize the tune and then try adjusting shift points.
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Old 10-26-2008, 07:39 PM
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Talking kick it

have you tried kicking it... yea kick it..kick it...lol maybe a leak.. carp, header, gas tank,, if nothing works.. kick it....lol
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Old 10-26-2008, 07:42 PM
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Default oops

i mean carb... and o yea kick it,,,,
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Old 10-27-2008, 09:22 AM
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Mine didn't start shifting until I had it leaned out and running pretty good. Your plan is a good one - don't touch trans til you've got it running right.
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Old 10-30-2008, 05:48 AM
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went over the truck again and found that the fuel tank may not have had a good seal around the cover.I adjusted the oring and it's a much more positive seal.not sure yet if it was the problem with tuning consistency.I haven't had the oppurtunity to run it again as the weather has been terrible.I staightened around the temp probe and really don't pay much attention to temps unless they approach 260+.I'll hopefully get a chance to run it again today.
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Old 10-30-2008, 06:13 AM
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The TRX motors some can be touchy when it comes to a good tune. sometimes you have to just bearly move the needle on way or another to get it good. There was a couple people on here that are correct when it comes to the trans. Do not adjust the trans until you get an established tune, because when that tune is good the trans will shift when its suppose to. I have had 3 tmaxxes so far and delt with all kinds of mishaps. I currently have a Picco P-3 on my maxx. But for a 50F you should be close to about 200F. if your tipping over 240F then you need to richin her up abit. you will know when you have it right when you hit the throttle and there is and instant burst of acceleration and no lag. when you have that thats when you tune to performance with the high speed needle. Get that little stream of blue smoke coming out and your golden.

Good Luck

Anymore questions feel free to ask.
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Old 11-09-2008, 07:22 PM
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Have you cut any vent holes in the body?
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Old 11-17-2008, 07:31 PM
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Boy do I remember those days. I started in RC with the TRX engines. They make great power when they run right, but that perfect tune is a bit elusive. I'll let you in on a few things that I found to work with them. First off, they leak air. EVERYWHERE. I never had one that didn't. Seal it off well with RTV before you try anything else. Carb, backplate and bearings are the problem areas. The needles get loose and won't hold a tune after a while. A bit of teflon tape around the threads works pretty well to tighten them up again. I changed to OS A3 plugs. They just seemed to work better, longer. If you are still using the electric start, you can file off the post a little so the starter wire still fits. Tune the HSN with the smallest increments that you can make. It seems like the TRX is more sensitive to tuning than any other engine that I ever used. Keep the fins clean. Drill vent holes in the body. Different fuel brands and mixtures can make a huge difference in tuning and heat. I found out the hard way that they don't really like the low oil racing fuels.

If none of these fixes work, throw it away and get an OS! That's actually what I ended up doing. I don't run any TRX engines anymore, but I keep one to remember the good old days!
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Old 11-17-2008, 08:08 PM
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One area that gave me fits leaking air was the carb body. I used a little bit tooo much screwdriver thinking I'd make sure carb pinch bolt was tight and cracked that composite carb body. Thing was - it wouldn't leak until throttle was opened either suddenly or near WOT - then crack in the carb body would open and it would leak air and run poorly. Ran fine otherwise.

It took looking for it with a manifying glass to find it, and someone tipped me that symptoms I was having sounded like a cracked carb body. Be careful and don't tighten the carb pinch bolt too tight!

The other tip trick I learned was to remove needles and coat o'rings with some white grease and reassemble. This prevents them from drying out/cracking under the heat or aging. I seal everything - brand new, right out of the box. Too easy to just eliminate air leaks from the start.
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