Under spark

[twinki025]

Newbie here under spark im adjusting the timing values what does gram per cylinder mean. Please explain...thanks guys

[joecar]

Twinki, welcome to the forum... :cheers:

The PCM calculates how much airmass fills each cylinder under the current operating conditions (MAP, MAF, ECT, RPM, VE, others...)... grams/cylinder.

The PCM uses this value to lookup spark advance, and to calculate the fuelmass required to achieve the commanded AFR (which is looked up in tables (or, for closed loop, is stoichiometric (which is also looked up))).

The spark tables B5913, B5914 show the scantool->tunetool "linking" PID being GM.DYNCYLAIR_DMA.

Edit: I added to this post.:beer:

[twinki025]

Thank you, so i would think the higher the rpm the more air mass is in the cylinder?? Is that correct????

[joecar]

Thank you, so i would think the higher the rpm the more air mass is in the cylinder?? Is that correct????Depends on the cam.

As rpm increases, cylinder has less time to fill using a stock cam...
a cam with greater duration and overlap allows more time to allow greater fill.

[twinki025]

I have a lot of learning to do. I programmed ny first tune into the car today. Any other pointers you can give me. Thank you once again.

[joecar]

The Auto VE tutorial has information that ties various tables together, good to read while following along in the tunetool.

[twinki025]

auto ve i was reading about is that a speed density tune. Thats what it looked like to me??? Ill look at it again