okay I am sure this has been covered somewhere else but I am new to the site, and to nitro cars. What is this difference between engines for r/c planes and the ones for cars? I know there are many sizes but what are the big differences? can you use airplane motors in cars? thanks. point me to an earlier thread if need be.

if you look at some pictures of car and airplane engines side by side, i think you will probably see one of the biggest differences. the car motors have HUGE heatsinks because there is no prop blowing cool air over it, they arent traveling nearly as fast most of the time and they are usually mostly enclosed in a body and not sticking right out at the front in the open.

i think most airplane engines can have the head replaced with a buggy head, if the engine you have comes in buggy/airplane models. i don't think i would stick an airplane engine in a buggy, but i don't have either, just marine glow engines

airplane engine most effective RPM range 10,000 - 13,000 *
car engine most effective RPM range 20,000 - 30,000 **

airplane engines cant rev with the car engines and the car engines cant swing the props that the planes need so there is alot more diffrence then the head. there has been people dropping airplane 4 strokes into trucks but they have to gear it way up and usually use the OS .40 as its got a high RPM compaired to other 4s.

* : just an example YMMV
** : see *

The RPMs of a model airplane engine are usually given with a prop installed (it's under load). The prop diameter and pitch determine the RPM (look at any airplane engine test). The RPMs of a car engine are given without a load. Also, the larger an engine is (displacement) the less RPMs it can achieve. As an example, a Cox .049 (about one third the size of a .15 engine) airplane engine can turn around 40,000 RPM. A .60 size engine (four times larger than a .15) would be hard pressed to turn over 25,000 RPM.

Krusty, that isn't always the case though. Many .12's don't rev as high as .21's there are many more factors involved than just displacement for how high it can rev.

That can be true. I gave a general example. The stroke of the engine tends to be a limiting factor. A short stroke engine typically can rev higher than a long stroke engine. Larger engines typically have (due to displacement) a longer stroke for a given displacement. Basically the ultimate limiting factor is the connecting rod. An unloaded engine will continue to rev until the rod (or its bearing) explodes.

I think the true limiting factor in RPM is the carb bore. It is possible to get a .21 with a 10mm carb whereas a .40 airplane engine is only at 7-8mm. The 10mm carb can let a lot more air through it than a smaller one allowing the engine to rev higher. If you ran a large carb with a high load the air speed through the venturi would be too slow to properly atomize the fuel. Equip a 40 engine with a large enough carb (14mm) and you now can have an engine that is happiest in the 25k range. Also the porting of the engine has a large factor in the equation.

Before, the fighting starts let me just say that the cooling issue has been the only problem. We have successfully installed and ran a supertiger 40. heli engine in a traxxs sportmax! It has produced a heck of alot more rpms, and speed then the 2.5 that comes in the sport maxx.

Krusty is absolutly right about props and under load rpm! This is not the factor..The problem is even with the heli head cooling fins the engine is getting way to hot...Now we have compsated by installing a small cpu cooling fan from radio shack to below across the motor with the body on!

Even though this combo will exceed the traxxs 2.5 and whoop it's but all over I don't reccommend it for the performance issues and mods that we have encountered....

But YES it can and has been done....And yes it is faster, No it hasn't been Fun!

Hope this helps and stops the fires about to brew!

Tom (fuelguy)

car engines also have more ports then airplane engines

Here's an idea: Strip out the engine on your car and bolt on a rig with a mount at the top above the car. Bolt on your plane engine and prop and fire it up. Woohoo, a propeller powered car! Somehow I don't think this will catch on but roll-overs would be spectacular with prop pieces flying everywhere.

so I guess the consensus here is that for the most part you cant put an airplane motor in a car........is an old super tigre 25 worth anything?

how old? Im not sure if the nitro car forum is the best place to ask. I own a avistar with a .42 tigre but im not sure of the .25

it could be as old as from the late 70's early 80's but i dont really know. it says "serie x" on the side. It's in good shape where should I ask about this? thanks

worth about 45 dollars with good compression....Plane engines are realitivley inexpensive compared to cars

Tom

I am running an OS .46 fx airplane motor in one of my T-Maxxes and it absolutely rips and doesn't get too hot with a heli head on it.

My other T has an OS .40 four stroke in it.

Here is a vid of the .46T.


http://www.rcgrabbag.com/rccars/videos/contemporary.htm

Scott