Reading your timing on a logger?

[chanley talon]

Ok the timing reads from a range of 0-50 degrees wich way is advance and wich way is retard ? is anything above 15 advancing or retarding? thanks for your help!

 

[donmagicjuan]

Positive numbers for timing values correspond to timing advance, or number of degrees before top dead center. Negative numbers correspond to ignition that occurs after top dead center (usually a bad thing). In tuning, advancing the timing refers to a larger number than the stock map calls for, while retarding it refers to a smaller value. Hope that helps.

 

[chanley talon]

Ok so if i see my timing is at 8 degress on my logger then it steadily rises to 15 and climbs to 18 is the timing advancing or retarding? Wich is better advancing or retarding under boost?

 

[donmagicjuan]

Your timing sounds like it's behaving (advancing) normally. The more boost you run, or the more air you cram in the cylinder (the higher the torque output), the less timing advance you need. However, as engine speed increases, timing must be advanced for a constant boost level. This is why timing will initially drop as boost builds, but rises steadily after hitting full boost until a peak value is reached sometime before redline.

The goal behind obtaining the optimum amount of timing advance is to get the peak combustion chamber pressure to occur at a specified point in the crankshaft's rotation, or about 14-18 degrees after TDC. If you approximate a constant torque output of the engine from say 4000-6000 RPM, the flame front speed will be the same during this period. Therefore, as the crankshaft rotational speed (RPM) increases, the spark must be initiated at an earlier point in time in order for the peak cylinder pressure to occur at the same spot in the rotation. This is why timing advance should steadily increase as RPM increases once you've reached full boost. Let me know if that does or doesn't make sense.

 

[chanley talon]

I understand what your saying but it really didnt answer the question. When im looking at my logger at idle it says 8 degrees if it was to go down to 5 then the timing is starting to retard correct . If the timing goes to 40 degress then it has advanced itself right?

retard base advancing
0 1 2 3 4 5 6 7<8> 9 10 11 12 13 14 15 16 17 18

 

[donmagicjuan]

Yes, it sounds like you've got it.