Engine heat

[anthony_marquart]

I know that running my .21 engines hotter has made them run better. I have read where people say that a hot engine burns fuel better. I agree with the theory of running hot and rich with a short pipe, because it works.

But I do not understand why a hot engine burns fuel better. The fuel mist is warmed in the case,.. OK,. but in the overall temp delta of liquid fuel to combustion, this temp change is just a blip on the needle.

Can anyone help me understand the relationship between hotter engines and better combustion? To me 30-40 hotter is not much change to the fuel..

 

[Glenn Gates]

Anthony, Hard for me to explain so just try to bear with me. If a motor runs too cold you will not get the best piston/sleeve fit so by reducing water flow and getting the eng. temp. up you get a better fit and that results in better speed. Running rich just insures the motor will get the lubrication it needs. It has been MANY years since I've run a .21 but found this theory applies to .45 and .67's as well.

 

[Grimracer]

Its all about the fit!

Grim

 

[Jerry T]

Very simple, Nitro needs more heat to ignite it and keep it burning.

Thus heat makes horsepower.

 

[anthony_marquart]

I know the P/L liner fit part.. But I don't buy the more heat ignites nitro part. The difference in running a cold motor to hot motor to us is maybe 30-60 delta. To us that is a lot. As far as the chemical change in the fuel,. that is nothing. Also, you cannot assume that the delta in motor temp is the same as the delta in fuel temp. It will be less as the fuel is moving through the engine and will not get to the same temp delta as the engine before combustion.. just my thoughts

 

[David Santistevan]

I believe the speed of the sonic wave coming back from the pipe is also a function of temp. There is a good chance you are getting a more dense slug when compressed will give you a better burn rate. The person who could really answer this is Marty.

D

 

[bjacobsen71]

I do believe it has to do with how the nitro dissociates with its oxygen molecules, the hotter it is the better this happens. Fit and pipe depend on temp too. I do know that top fuel teams do not like when drivers get into staging duals because the engines make more hp the hotter they get and the crew chiefs have to set the car up based on predicted parameters, if the car makes more hp than their predictions the setup suffers.

 

[dwilfong]

The only thing you want hot is the combustion chamber. The case should be cold. as far as the fit. you need to keep the top of the liner temp stable. It dose not mater what temp just as longe as it dose not change "after" break in. If the top of the liner heat changes it will change the fit. the temp of the piston also will change the fit. if you run the top end cold then you go to a hot setup you may lose the fit.

Isolating the top of the eng from the case will keep the heat in its place. there is power in top end heat.

Rich will keep it all lubed and keep the fit.

 

[richard jones]

I know that running my .21 engines hotter has made them run better. I have read where people say that a hot engine burns fuel better. I agree with the theory of running hot and rich with a short pipe, because it works.

But I do not understand why a hot engine burns fuel better. The fuel mist is warmed in the case,.. OK,. but in the overall temp delta of liquid fuel to combustion, this temp change is just a blip on the needle.

Can anyone help me understand the relationship between hotter engines and better combustion? To me 30-40 hotter is not much change to the fuel..

AnthonyQuite a lot of different ideas posted here, what would happen if U did not make the engine hotter with the same needle setting,

probably back to where U were running slower, running the engine on the rich side will cool the combustion chamber, adding heat in

whatever way will bring the combustion temp up enough to help burn the rich mixture, which the glow plug can not do by it self, so many add heat in different forms, restricting the water, can be very risky trying to get just the right amount of water, especially in areas of the country that have large swings in both air and water temps from spring time running with cold water and air temps, to hot summer with high air temps while trying to maintain constant engine temps, can be problematic. The easy way to look at small changes in combustion temps is to start out with a rich engine and lean the third channel 1 click at a time. As U lean the engine out it will start

increasing in RPM. By restricting the amount of fuel going into the engine U are increasing the combustion temps little by little until the engine goes from a 4 stroke rich combustion chamber to a 2 stroke hooter combustion chamber. U give temp change of 40 degrees hotter on your engine, I assume this temp is on the outside of the engine, the 40 degrees measured on the outside can be doubled or sometimes tripled in the combustion chamber and just like leaning can improve the combustion chamber burn rate.

The limiting key factor in our nitro engines is the GLOW PLUG!!!!!!!!!!

Hope this helps

JM2CW

dick