Peak cylinder pressure (1 Viewer)

flapjack

Staff member
Nitro Member
I was talking to a friend of mine who informed me that tuners look for peak cylinder pressure at around 12 to 15 degrees ATDC. Previously, I thought TF engines peaked at 18K PSI at ignition time, but it is definitely ATDC. RacePaks don't have a sensor for that, tuners use a different logging system:

http://www.tfxengine.com/

which uses a pressure sensor spark plug. Pretty cool.
 
Obviously the BTDC ignition event has a direct impact on when the peak event occurs. I recall somewhere where 14 degrees ATDC was thought to be the ideal point for a roughly 800 cu in nitrous motor (Nitrous produces a very high peak, and a fairly short duration). When the lever (the crank) is at the ideal point you want to crank on it as hard as possible, so when you retard timing to let the crank turn further (say to get down a marginal track at a certain point) you really turn down the effective horsepower output at the crank. I have some math that I use for our set up to manage power coming out the crank.
 
Obviously the BTDC ignition event has a direct impact on when the peak event occurs. I recall somewhere where 14 degrees ATDC was thought to be the ideal point for a roughly 800 cu in nitrous motor (Nitrous produces a very high peak, and a fairly short duration). When the lever (the crank) is at the ideal point you want to crank on it as hard as possible, so when you retard timing to let the crank turn further (say to get down a marginal track at a certain point) you really turn down the effective horsepower output at the crank. I have some math that I use for our set up to manage power coming out the crank.

Hey thanks Jeff for chiming in. I majored in math and am getting ready to be a mentor for a student, so any real world applications of math that I can pass on are cool by me. I think most people have a problem with math because it gets all so esoteric and people are left wondering "when am I going to use this in real life?"
 
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