neubie need engine size explanations
 

is there a chart explaining all this?

neubie need engine size explanations
 

ok lets see

.12 to .26 engines are usually used for nitro cars and trucks

.12 way up to 3 can be used for airplanes

.30 to .90 engines are for helicopters

now as far how much horse power a engine procuce depends on a lot of things first is manufaturer...You can buy an high quality .21 engine that will beat the crap out of a cheap .26 engine....

you would have to be more specific on what information you are looking for...

neubie need engine size explanations
 

OK what is the relationship between engine sizes(.26) and cubic centimeters

what is the cut off between smallblock and bigblock?
like a small block 400 chevy and a 402 bigblock chevy are the same CI but have way different torque #'s and size difference.

A new 2.5 t-rex monster truck is still a small bolck?

are engines with high HP numbers and small displacement a problem to "putt" around with cause of no power at low RPM?

like a .21 is really 3.5CC?
what does the .21 stand for?

neubie need engine size explanations
 

Ok simply put
.12 or .21 or .15 or anything you see in a car or truck in this range is referring to cubic inches.

a .15 ci engine is approximately 2.5 cc
a .21 ci engine is approximately 3.5 cc

a small block is anything that is physically based off of a .12 ci block, typically all of your 1/10 scale stuff. They make them up to about .18 ci, I think.

A big block is anything based off of a .21 ci block, typically any 1/8 scale stuff. I think they are making big blocks up to .27 inches now.

It is similar to Chevy having the small block and big block, but a little different.

If you are going to get into any serious racing and plan to go to any ROAR events, stay with either a .12 or .21 depending on your racing class. If you are just messing around, get the biggest and most powerful your wallet and truck can handle :)


Sean

neubie need engine size explanations
 

Not always. :D

neubie need engine size explanations
 

Ok I understand.
next question;
the glow plug, used to start the engine. Does it serve a function after the engine is running?
it must or these would be called deisels LOL!

btw I bought a CEN mt-2 last night for 260.

neubie need engine size explanations
 

Correct, there is a catalytic reaction between the alcohol in the fuel and the platinum (i think) in the coil that keeps it hot while the engine is running. If you "loose" your plug, your engine stops running.

Sean

neubie need engine size explanations
 

so if .15 is really 2.5 cc and so on. what would the TRX 2.5 be????

Thanks,
Larry

neubie need engine size explanations
 

a .15

traxxas just used that number to make it sound big. dont get it. the engine sucks. it is great for 2 gallons and its downhill from there. in the tmaxx it is way overstressed from the weight and stuff. it is great for the other traxxas cars though, as from what i understand. soon im going to be dropping in a .18 sirio or a big block conversion chassis. i cant decide though. the big block will cost nearly $650 when everything in the drivetrain is bulletproof.... oook straying off topic.

anyways, hp really means nothing in rc. its more of the torque curve yous hould be after. if the engine reaches its peak (1.6 lets say) horsepower at 35,000 rpms, then it will more than likely be horribly weak at moving a big vehicle since it would have no low rpm grunt.

neubie need engine size explanations
 

ok?... but if its the same...how come its so much faster?

also, do you have any proof about the 2 gallons then downhill (as in, did it only happen to you?)

neubie need engine size explanations
 

No, it is called a 2.5, because a .15 is a 2.5cc motor. It was actually called the 2.5, to separate itself from the 1st series TRX 15's that were used in the 1st gen MAXX's, 4-tec's, and Nitro Rusty's....a 2.5 to me doesn't sound bigger than a .15, it sounds the same....because it is :)

neubie need engine size explanations
 

Actually, the metal coil in the glow plug absorbs some of the heat when the combustion takes place in the engine.

In order for our hobby fuel to combust, you need air, fuel, compression, and heat (supplied by the glow plug). When starting the engine, you preheat the glow plug by running current through it. When the engine fires, the heat from combustion also heats the glow plug (and keeps it hot enough for the fuel to burn next cycle).

neubie need engine size explanations
 

the fuel does have a reaction with the platinum plug element as well as retaning heat so you are both right.

neubie need engine size explanations
 

You have to admit, to an uneducated consumer, a 2.5 does sound like a larger engine than a .15. Does Traxxas actually market it because it sounds bigger? Only Traxxas can answer that. My personal opinion, yes, but that’s just my opinion.

And, i8tweety, there is an reaction that occurs, I am sure the metal in the coil holds some heat, but is a reaction too.

Sean

neubie need engine size explanations
 

If heat wasn't key, you wouldn't need a glow igniter. The metal composition has to do with it's ability to absorb and radiate heat (as well as longevity properties in the harsh environment in which it is subjected to).

If you take a new glow plug, while holding it upside down, take a thermal temp on it (I use my raytec temp gun). Measure the temp of some hobby fuel. They will both be at ambient temperature. Put a drop on the glow plug coil and measure the temperature every couple of seconds. You will find the temperature doesn't change. I don't buy into the chemical catylist theory.


With respect to traxxas calling the new engine a 2.5, their previous generation engine (which they still sell) was called the traxxas .15 pro. In my opinion, they used it to differentiate between the two.

neubie need engine size explanations
 

Sorry to burst your bubble....



"Can you explain to me how a glow engine works? Is it just like a diesel truck engine?
Glow engines are a hybrid between diesel and spark-ignition engines in regards to their mode of operation. In a glow engine, the catalytic action of the platinum glow plug coil is what ignites the fuel-air charge rather than a spark or the heat due to compression of the mixture in the chamber. As a consequence, the compression ratio used tends to be higher than in a spark-ignition engine but lower than a diesel engine. "


This is right off of Super Tigers home page, if you do a little reseach you will find out everyone else will tell you the same thing, because its how our engines opperate.


http://www.supertigre.com/faq/product-faq.html#q210

Sean

neubie need engine size explanations
 

it is from more efficient porting and timing i guess. there is an article on it at www.rccaraction.com

that is a great website if you want to find out how a lot of this stuff works.

some people like this engine, but ive heard way more bad than good about it. people are always having problems with it overheating in the tmaxx(not really any of the other traxxas vehicles), it is very picky about tuning, and although traxxas claims it can wheelie, you usually need to run it very lean for it to do this, i broke it in by the book and it never did. i live at sea level so i should have been able to get it.(it has to do with air density and whatnot when tuning). as for the overheating, mine did that very often, i could richen it so far out it is practically blowing a small stream of unburnt fuel out of the exhaust and the engine head was still smoking. i think the 2.5 doesnt have enough power to move a big 10lb truck. it is fine in the n4tec or nitro rustler though. when you first get it, you think it is awesome. as time goes on you hate it witha passion. as soon as i get a new engine i am going to maul that 2.5 witha hammer and send it to traxxas as an appreciation gift :)

neubie need engine size explanations
 

Who's bubble are you bursting?

neubie need engine size explanations
 

I was bursting i8tweety's who "I don't buy into the chemical catylist theory. " even though its how the engine works

Sean

neubie need engine size explanations
 

Just as I stated in my post....the statement above, was "a .15
traxxas just used that number to make it sound big. dont get it."

Whatever their marketing technique is, so be it....but it was called the TRX 2.5, more than likely to differentiate it from being the original TRX .15, which there is a HUGE difference between the 2 motors. I don't think it was a tactic or a ploy, to confuse the consumer....but the fact is, it is a VERY POWERFUL .15 motor anyway, much more than the majority of .15's out there.

neubie need engine size explanations
 

glow plugs
I'm glad to see you did your research with respect to glow plugs.

As an engineer with a chemistry background, here's my explanation.

Here's the quote you provided. I agree with everything it says.

Glow engines are a hybrid between diesel and spark-ignition engines in regards to their mode of operation. In a glow engine, the catalytic action of the platinum glow plug coil is what ignites the fuel-air charge rather than a spark or the heat due to compression of the mixture in the chamber. As a consequence, the compression ratio used tends to be higher than in a spark-ignition engine but lower than a diesel engine.

It does not refer to the platinum coil as a catalyst, but rather states the platinum coil provides a catalytic action. The catalytic action is the absorption and radiation of heat energy.

Glow engines do not use spark ignition and do not use "heat due to compression", but use heat radiated from the glow plug's coil.

neubie need engine size explanations
 

the 2.5 may be a fast engine, but so many people have problems with it. i dont know a whole lot of people who have had their 2.5 for lets say 4 gallons and like it. as for the naming thing, maybe they didnt intend for that to happen, but it did. i remember reading a ton of posts a while ago. tons of new people to the sport had thought that it had 2.5hp and stuff along the lines of that.

neubie need engine size explanations
 

I too am an engine FYI.

And if you read what I wrote, I never said the planinum coil was a catylist, I said

"Correct, there is a catalytic reaction between the alcohol in the fuel and the platinum (i think) in the coil that keeps it hot while the engine is running. If you "loose" your plug, your engine stops running.

Sean"



it is a reaction between the methanol and the platinum, you can not run ethanol with a platinum glow plug and get the engine to run, you will need a spark ignition if ethanol is run. So yes I am saying the heat comes from the reaction between the methanol the platinum.

Sean

neubie need engine size explanations
 

Well, I have had now, 5 of the 2.5 motors, all BRAND NEW, and never have had a problem with any of them. I think, that Traxxas made this high performance motor, to center around a very young age group, who no offense, has no experience on a 3-needle motor. The 2.5 is known as a high-performance motor, because of it's BHP and high RPM's, more than the average .15, more in the class of a Nova Rossi or CMB (not a comparisson, but the same level of power ratings)....and you have 12 year olds trying to tune it.

It's a simple motor (to me), to tune, and I have never had any personal issues. There have been many "kids" at the track, who were fed up with thei 2.5's, telling me how much crap they were, and how they heard such bad things....they gave me 3 minutes with their motors, and they haven't had a complaint since!

I wish I could have everybody on here send me their 2.5's, and for me to adjust them correctly, and send them back. I am noot preaching Traxxas, but preaching more the fact of the inexperienced level of knowledge, that are tuning these motors. I think to single out the 2.5 as a disaster, does not do the motor justice at all....I think it is an inaccurate assumption, which has lots of bandwagoners, who look to that excuse, as an excuse for their motors not running, than rather looking at themselves, for not knowing how to get it running....

I Agree
 

I agree with you RCFREAKINFL, I have been in RC for 10 years, and have had no problems with any of the 2.5's. They are a little harder to tune than the regular motors but it can easiley be done if you have the exp. with engines.