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Rookie troubles with new Savage 25.

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M

mwritter

RC Newbie
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First off, I just bought my first R/C nitro truck: a Savage 25. I think I may have jumped in a little over my head, but I really like it and I am learning as I go. I have about 5 tanks of fuel through the truck, and I was very careful to break it in properly (though it took a lot of time). I am now doing my best to tune the truck for proper operation now that the engine is broken in. I bought a handheld infrared temp gauge to help me. I get about a tank through it each weekend, but it is running so poorly that it has become quite frustrating. So I am turning here for help.

I am having a lot of trouble getting the low and high-speed settings adjusted so that it runs well at idle all the way through WOT. Also, there is a bad sputter that has developed, that seems to appear all of a sudden after the truck is warmed up. If it were a car I would call it a misfire. I thought it was a worn out glowplug (from break-in), but it does the same thing with a brand new one.

Can anyone help me get a nice baseline on my low and high-speed settings that I can start from, now that the truck is broken in? Should I try to take it to a professional?

Also, can anyone suggest a cause/solution to the “sputtering” problem?

Thanks for the help, and I look forward to learning a lot from this great forum.
 
first off...we would need a more detailed explanation of what is going on from idle to wot throttle...how it acts idling and how it acts during accelration/full speed. you say you have a temp gauge...what are your temps after the engine has warmed up? to me it sounds like you are running to lean on either the low speed needle or the high end needle...or maybe both.
 
Where do you have your needles in relation to the break in setting? I would put the lsn back to the stock setting and work on getting the hsn tweaked before attempting to work on the lsn.
 
Good points...sorry about that. I doubt I am running lean, because I don't think I have turned either needle more than 1/2 turn towards lean from the factory settings. I think the manual says I could be running as much as 2-2.5 turns leaner. I am also a little scared of screwing up my new toy, so I have been quite hesitant to lean it out too much, but that may be what it needs.

I have never seen a temp higher than 250-60. But therein lies another problem...exactly where should I point the temp gauge, at the header, heatsink or the block itself? I was going by the highest temp I could find. Am I correct that I am safe at temps up to about 290?

I can't really give a good explanation as to what is happening from idle through WOT because it seems different all the time. For a while, it would stall if I gave it more that a little throttle off-idle. Sometimes it seems to bog down at higher speeds, but I am not sure if I could tell the difference between too much and too little fuel at high speed just from sound... That's why I was trying to get some sort of "broken-in" baseline that I could try to adjust from.

Hope that helps a little, but I doubt it.
 
to me, too much fuel sounds like "vlug-vlug-vlug" at high rpm, and too lean at high rpm sounds like "vreeeehh-blah-blah". i know that is really silly..but thats the best way to describe how an engine sounds to me at least when there is to little/much fuel.

BTW i always point my temp gun right at the glow plug. i would go back to stock needle settings.....and work only the high speed needle. the low speed you can try after you feel comfortable in knowing what is going on with the engine. i still feel like one of your needles are to lean. the temps and symptoms you describe.
 
Try to keep your temps below 270 ... as a general rule. Point your temp gun at the glowplug or just to the side of the glowplug. Bring your needle settings back to factory settings and start tuning from there, turn the needles a little at a time ... starting with the HSN.

As I said, the temp is only a general rule. Too high and you'll fry the engine, too low and there will be early wear and tar on the piston. Tune your engine for performance and keep your temps in check. The higher the temp, the faster it will be but also heat probs will come into play. Try to find the sweet spot where there is a good compromise in performance and temp. generally over 220 and less than 270. I'd shoot for 245-250.
 
Thanks everyone for the input. I am going to read the article carefully and try to get back to a nice baseline.

In the meantime, can anyone give me a good guess as to what is causing my engine sputter? I don’t really think it is a tuning problem, but I don’t really know.
 
To make sure your needles are where you think they are, turn them all the way closed (don't over-tighten them!) and then open to the factory settings in the manual.

A lot of those engines shipped with the factory settings way off.
 
Well I tried to work on my tune a little this weekend after reviewing the very good article posted above. I am still having the idle problem I described, but it is a little different. Before it seemed like a slight miss, but now I would characterize it as a surge.

When I run the truck around for a few minutes, and after it warms up, it seems to start surging, to the point where i have to hold the brake to keep the truck still. It is like someone is blipping the throttle while the truck is sitting still. Any ideas what this could be?
 
Cheeck to make sure the throttle linkage, and servo aren't jumping.

If it is not physical, as in hardware related.

Then look for an air leak. Is it possible one of your fuel lines, or air pressure lines from the exhaust is chaffed or has a pin hole in it?

Just to let you know, it wasn't that long ago I was new at tunning. Trust me, tuning can cuase all kinds of missing, and cutting out.

It's really hard to diagnose with out a very accurate description of what it does from the very start.

Are you gettting a belch of smoke when you hit the throttle?

Do you have a puddle under your exhaust pipe when it sits still for a while?

When going full throttle what does it do? Slowly bog down to a halt? Or wind up really good, then loose power?

When you nail it from a stand still what does it do? lurch forward? Or slowly gain speed while spewing smoke?

The LSV is very finicky. If it would run and idle at break in, seriously leave the LSV alone until you can get the HSV tuned as good as possible for temp, and power.
1/16th on the LSV can be the difference from flooding on accel to just flat dying.

trust me it;s frusterating. Especially only to find out that you have an air leak. BTW what fuel are you running?
 

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