before top dead center, nitro engines. (1 Viewer)

[flapjack]

I remember reading years ago they light up the plugs in a TF engine BTDC because nitro is hard to light by spark, or something like that. Is that still the case? If so, by how many degrees? And I can't remember if they advance or regard the ignition over the course of a run.

 

[flapjack]

Found this article:

http://www.hotrod.com/how-to/engine/ccrp-1009-8000hp-top-fuel-engine/

It has a lots of good information. Turns out the plugs are fired at about 55 degrees BTDC. I assume that the ignition is retadrd during the run, I can't see them advancing beyond 55 degrees BTDC.

 

[Jeff]

There is a nice NFC tuning article in a recent issue of Drag Racing Online (I think what they call an "innerview") where Del Worsham speaks about timing changes they make mid run to avoid shake. We use the same type of methodology in our 2000 hp program .... haha, but we don't pull 25 degrees. In our nitrous car the flame front is so quick, that when all of the stages are on we are single digit before TDC.

 

[flapjack]

Jeff, they have to spark it so soon since the the incoming air/fuel is more fuel than air. THe early spark gets it hot enough that eventually you have more vapor for ignition. And even then, the combustion is not finished by the end of the power stroke, it is still going during the exhaust stroke, which is why nitro motors are so loud.

 

[Crew Chief Pro]

The teams I have worked with run 52 - 58 degrees depending on weather. Nitro is very slow to burn, once it lights you can't stop it though.

 

[flapjack]

Don, do you happen to know the duration of the spark?

 

[flapjack]

Don, do you happen to know the duration of the spark?

I found something that says up to 26 degrees of spark duration. Wow.