My first RC Car... - RC Groups
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Oct 04, 2004, 12:30 PM
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CooHead's Avatar

My first RC Car...

Hey guys,
After thousands of dollars of Electric RC Planes, I have just bought my first Nitro RC Truck. Got an HPI MT2 4x4 stadium truck. Broke it in acording to instructions and it really runs great. Nice and fast and sounds cool and jumps great.

What are the common hop ups for these RC Cars? Not that I need any more speed or anything, just wondering what you buy for them. I don't really care about more annodized parts to make em look cooler...but what about performance?

For snowmobiles, we put picks in the track. For Electric RC planes we switch over to brushless motors. For road cars, we increase air into and out of the motor. What about these Nitro RC trucks? New pipe? ANything I should know about my new MT2?

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Oct 04, 2004, 08:54 PM
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CooHead's Avatar

A bit frustrated.

It would often die after WOT and sut off. So I started messing with the three screws. Big one on top is for main mixing I take it. Ran good and fast and good response as was so did not mess with that one.
Little screw under air cleaner is for idle. Flush one on side is for slow speed. Messed with those two and now the thing is all screwed up. SOmetimes it starts and goes to WOT...even higher RPM than WOT...I mean screaming. Tweak the throttle a bit and it settles down. Seems to be getting to kuch air or something.
Then I can run it around, but when the throttle is in nuetral position, the car still races. Turn back the Tx trim and it'll die.

So, a couple questions. Is "Idle" considerd with brake depressed and "slow speed" is considered when no finger is on the throttle trigger?

I went thru the first quart of RC "break in gas". That is one of the other diffrences...I now swipped some gas from my neighbors TMaxx. Would a diffrent gas make a big diffrence?

Kinda seems like it's sucking air from somewhere and running way to lean and screaming.

Never had these frustrations with electric planes.

Is there a thread that gives some advice and ideas on tuning the three little screws?

Thanks for any help.

Oct 04, 2004, 09:25 PM
Registered User
Kyle G.'s Avatar
welcome to the world of gas motors!! sounds like your running it too lean. with the main dial on top (high speed needle) turn it about 1/4 turn counter clockwise. performance will go down but see if it helps first. the one by the air intake is the Idle screw like you said and the is how high the engine idels without any imput from the gas/brake. You want it so that the car doesnt move at all without any imput from the sticks. turn it clockwise i THINK to lower the idle RPM which will make is idle without moving. Don't do it too much or it won't start very easily. the last needle (low speed needle) which should be on the little thing that pulls in and out when throttle is applied is for acceleration. for my car I do a pinch test. basicly pinch the tube going into the carb from the gas tank. If it dies all a sudden (less then 3 seconds) its too lean (adjust needle counter clockwise) if it goes for longer then 3 seconds before dying then its too rich (adjust needle clockwise). When properly tuned most cars should have pretty good top speed and acceleration. Make sure you arent overheating your engine. (steam/smoke coming up from the glow plug) like remember when i was driving my car off your jump? there was a little steam coming from the top of the cooling head. Hope this helps a little. anymore questions just ask
Oct 05, 2004, 08:58 AM
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CooHead's Avatar
Thanks KDog....I'll keep messing with it.

How about that glow plug ignighter? DO you leave that plugged into the wall to charger for 10-20 minutes?...2-3 hours?...or overnight? Seems like it only holds a charge for 10-15 starts at best. Then again I've only charged it for an hour so far...often ten minutes at a time. I have it on the charger for hours now...two hours last night and I'm going to do another two hours today.

Would TMaxx gas make a diffrnce over the original "break in gas"?

Oct 05, 2004, 04:22 PM
Registered User
Kyle G.'s Avatar
well gas depends on 2 things
(1) nitro %
(2) oil %

if the TMaxx gas has a high nitro % and a lower or equal oil% I wouldn't use it. i mean 5% difference in nitro is OK but if it has less oil then nope. Is it traxxas top fuel?? If it is it should be safe to use no matter what the %'s are. Mine doesnt have a glow plug lighter. Mine has an easystart which I have a seperate "remote" with a little button and I press it into the plug on the side of my car (the "remote" has a 6 cell ni-mh in it) and when i press the button when its in the plug it will send some of the juice to the glow plug and some to the little Electric starter motor that turns over the engine. REALLY easy and convienient. But Im not sure how long to keep it on the charger. what kind of battery is in it? maybe 2-3 hours?? hard to say. keep at it
Oct 13, 2004, 10:37 PM
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CooHead's Avatar
Wow Kyle,

Not as many people, information, threads, posts, input here as in the electric plane world eh?


Did you see where I got LedKitty all sad?
Oct 13, 2004, 10:46 PM
Registered User
Kyle G.'s Avatar
Well IMO this forum has a lot more plane users still, im sure there are people here that are really informative. Also venture hobbies has a lot of experienced guys in the RC car field. You should see the RC car department! huge 15 pound monster trucks on the counter. T-maxx's, Revo's... etc! pretty impressive. and I see this guy who has a $1000 T-maxx and drops it from 6 feet straight down and nothing breaks. pretty impressive what can be done. and yea, I did read about the LK incident darnit Coo anyways, things are better now so, how has your car been doing? I haven't driven mine since well, your house... which I wish I had more time because your house has all the jumps! I'm not driving mine as much as i used too
Oct 14, 2004, 10:32 AM
Maxx Basher/Savage Hunter
Davcruz's Avatar
Coo Head, it sounds like you bought your HPI new, if so then you should have the manual for it. I have never had an HPI, but I do have a T-Maxx and another truck and both the manuals for these give you the default settings for the HSN, the LSN and they describe how to set the idle screw as well. So I would suggest you look for those settings and put it back to stock, then tune from there.

If you set it back to stock and still have the idle problems you can check to be sure your carb is not loose and sucking air. I actually had that problem and I removed the carb, put the tiniest amount of hi-temp silicon around the throat and reinstalled it.

Also, you want to try to stick with one type of fuel, it makes tuning much easier because different fuels require different needle settings. Also keep in mind that the ambient temp and humidity can affect your setting also, so you may have to tweak your HSN sometimes to get it running perfect. However, once you get the LSN right you can usually leave it alone.

One other note, the idle screw is usually turned CCW to lower the idle speed and CW to raise it. You need to set the idle so that the truck does not try to move forward while it is idling, but does not cut off when you hit the brakes or come to a stop.

I hope this helps. I am no expert by any means, but I have learned through my own and others trial and error. These little engines can be finicky at times and you just have to tweak them until you learn where to stop.
Last edited by Davcruz; Oct 14, 2004 at 10:34 AM.
Oct 14, 2004, 02:40 PM
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CooHead's Avatar
Hey Dav.

I didn't post, but now will let you know what I found. The little arm that opens and closes the carb was loose...or more specifically the linkage that bolts to th arm that opens and closes carb was loose. So it would go to WOT, but sometimes not return...hence hi RPM! Tightened it up and everythig is good. I go about tightening all the little screws and bolts now. That was loose, one shock tower bolt was loose. One steering knuckle bolt. Even had a wheel come off. I understand these little motors vibrate like crazy...real hi frequency too. No wonder so many nuts and bolts and screw back themselves out. Not to mention how much the whole thing shakes whilst blasting across my acorn and walnut riddled yard.

Thanks for your help. It idles great now and hardly ever dies. If it flips and I don't get to it uick to put it back onto it's wheels, it'll die and be hard to start...but that's to be expected I would guess with air in the lines and all.

Picking up two diffrencial gears tomorrow...heavey duty styel. Stipped one out in the rear, so after replacement, I'll have a spare for the front when that goes.

I could probably tune it to run a bit leaner, hence faster. But it's plenty powerfull as is. Rather have it run rich and miss a little top speed than run lean and burn up.


ANy other advice?...other than clean the air filter foam often.

Oct 14, 2004, 08:11 PM
Will race for parts!
Kiiski's Avatar
While you are on the topic of air filters. Get a Motor Saver air filter, a lot more filter area. I have one on EVERY one of my cars and trucks, and you look at what the top drivers use and you will see a Motor Saver on theirs as well. And don't just clean your filter, but make absolutely certain to use air filter oil as well.
Oct 25, 2004, 03:38 AM
Always right
Hovertime's Avatar
Coohead-on the glow plug igniter - have a look at the mA charger is rated for(should be written on it) and also check igniter's battery.
Lets say you got 1300mAh cell, and 130mA charger, then it should be charged in 10 hours, well as per charging data from cell manufacturer it usually takes 16 hours to charge at 1/10 of cell capacity current rate.
If charger were to output twice the current it would charge it twice faster, but my best guess its overnight charger.

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