Nitro HP/Torque Questions

[Robb]

I am a complete nitro/2-cycle idiot, so I am lost on all of this.

I am looking into building a 1:6 Nascar project, and want to run it off gas/nitro, but as I stated, I know NOTHING about micro piston engines.

My first question is about HP numbers that I am reading about. I read about these glow-plug nitros in the ballpark of 2HP (TRX 2.5R, 3.3), but these things are only 2.5-3cc. Now, I have an old 25cc Powerstroke 2-cycle sitting around, that as far as I can find, only produces about 1HP.

Is the difference between normal fuel and nitro fuel that great? Is that the reason for the large difference in numbers here?

With that, even if I can get HP numbers close to each other, how about torque? Just thinking to myself, bigger piston/jug = bigger torque. Sound about right? So, I am thinking that even if I can get a nitro engine to produce the overall HP I would like, I think the work of moving the weight I want to move may be too much for such a tiny piston. The rig is going to end up at somewhere around 20lbs (hopefully), so this is a little different than the 10lb rigs these nitros were built for. Is such a mass/weight beyond the capabilities of a such an engine?


At the end of the day, for a 3' and 20lb car, is a larger 2-stroke my best bet? I would love to run cheap fuel all day long, but I may run into a size issue trying to fit this bastard, so I may have to look into smaller alternatives.............like little nitros.

Thanks!

[JasonInAugusta]

http://www.northwestmotorfest.com/20...ALE_RACING.htm

http://www.quarterscalemtrsports.com/

[slobin3d]

its an issue of rpm vs torque. a gasoline motor will produce 2hp at 2 ftlbs of torque at 3000 rpm where a nitro willl produce 3 hp and 1/4 or less ftlbs of torque at 30,000 rpm its the gear reduction that makes up for the lack of umph..


for a car the size you want I would look into a fuelie motor. like used in a baja 5b or look into other 1/5 producer for a ready made nascar type car there out there

[Norcal crawler]

Depending on how big the 25cc engine you have is and if you have enough money maybe try using two nitro engines? 1 might not be enough but i havent seen any tests to see how much a single engine can push. But there are some massive nitro engines out there. If you go with a nitro, go with a big block no matter what, they make more torque. here is a pretty big and powerful motor.

https://www.ssl-stormerhobbies.com/c...rc=ns&pn=AX042

[slobin3d]

if you want to go nitro, spend some time researching you're motors. There are great ones on big steaming piles and you can't really tell just by looking at it.


I guess that's true of any motor you would buy nitro or not. but nitros are spendy to maintain and rebuild, and don't last nearly as long as a fuelie will

[slobin3d]

Originally Posted by usmc8541

Hey Robb, check this page out it wil shed some light on the characteristics of nitro versus gas, and why it has more power in a smaller package. http://auto.howstuffworks.com/question642.htm

I have run many weed eaters (30cc)on 60% nitro when I was younger, and they screamed. All you need to do is tune the needles. I think you could get away with a Baja 5B fuelie engine on 30% nitro, maybe 9-11 HP. You can get nearly 8 times the power with a nitro engine than a gas engine.
I hope that link helps with your quest for power, I will be watching for a build thread.

nitro requires more compression and more heat to function properly, and wear the motor much faster but thats the price you pay for that kind of Hp just look at top fuel dragsters, 3000hp for 3 seconds then a complete rebuild

[constantmotion]

QuarterScale Motorsports' cars are four feet long, power by 22.5cc two stroke engines and weigh 30 pounds.....pushing 65+ mph

[BigBoy]

If you decide to go with nitro there are engines that will mover your 20 pound rc with ease. My nitro MT weighs in at 14 pounds, it's powered by an LRP .28...It has enough power to lift the front end at will and still push the 50 mph mark on the top end, gearing is everything! You are right about torque, bigger jug/piston will bring more torque.

[Robb]

Thanks for the great advice guys!!!!

Another newbie question as I am learning here. Since a 2-cycle doesn't rely on any type of sump, does it care if it is set sideways, or even upside down?

Just using what I know, the piston/jug shouldn't care what orientation it is sitting in.................but I question the carb. Looking over my freebie engine, the carb doesn't have a traditional bowl under it, but in it's place, is the primer bulb, which in turn, is kinda sorta directly associated with the tank. On these engines, does the primer bulb area also function as a fuel bowl? I would think that these function as traditional engine carbs, and out of level situations for any time would lead to a dry bowl, and therefore a dead engine. Sound about right? Or do these act in a way that placement doesn't matter?

At the end of the day, the overall height of my freebie won't work in my body sitting upright, so I am just thinking of ways to possibly lay it sideways. Creating an intake tube between the carb and engine shouldn't be a big deal if the carb needs to be "upright" and the engine has to be on it's side.

Thanks for the advice, and keep it coming please!!!!

[Usmc8541]

Nah, it doesnt have to run any particular way, as long as it has fuel, a two stroke will run in any configuration. I hope this helps you, Robb. And I would recommend a "clunker" type fuel tank. It has a peice of fuel line in the tank with a filter rock attached to it. The function of this is, that if you roll the vehical, the fuel line with the rock will fall to the top of the tank in an upside-down situation. Thus, preventing it from shutting down. Most airplane tanks have this feature. Heres an eight ounce one for $3.89. Click

Do you mind uploading a picture of the engine?

[BigBoy]

I have never done it but the engine should run fine on it's side. When my truck rolls over it will run until it burns the fuel in the lines (the longer the fuel line the longer it runs) but because the tank is also upside down it dies. Just being curios I ran an engine upside down for over a minute holding the tank right side up and it never even hesitated.