So on the left axis here we have our combustion pressure. So here we have a graph of the pressure inside the cylinder as we move through the combustion cycle. So now we understand a little bit about the terms, let's have a look at a diagram that explains exactly what's going on inside the cylinder. So we actually normally start the spark event as the piston is still coming up towards the top of the stroke during that compression stroke, as it's compressing that new charge of fuel and air. So generally when we're talking about ignition advance, the ignition advance angle will be in degrees of crankshaft rotation before top dead centre. So our ignition timing or ignition angle is referenced relative to that point in the engine cycle where the piston has reached top dead centre. So we consider this point to be the zero point when we're referencing our ignition angle. When it is at the very top of the stroke, on that compression stroke, that point is called TDC which stands for top dead centre. So it's already inhaled a new charge of fuel and air, the valves have closed and the piston's moved up to the top of the bore. So that's the principal behind which most internal combustion piston engines operate on.Īnd the point that we're going to reference is where the piston is at the top of its stroke on the compression stroke. Now we need a way of referencing that or talking about what that ignition angle actually means.Īnd to do that we need to discuss briefly the four stroke process.
So obviously we need something to begin the combustion event and the aspect that does that is obviously the spark jumping the gap in the spark plug.Īnd the point during the engine cycle where that spark occurs is really critical to both the performance of the engine as well as its reliability.Īnd the point that that spark occurs in the engine cycle is the ignition advance angle. So in this lesson we're going to look at that second part which is the ignition timing.īefore we get into that though, we need to discuss a little bit about what we mean when we say ignition timIng or ignition angle. When we take away all of the advanced features that these new ECUs have and new engines have, one of those things is we're tuning the fuel delivery through the fuel injectors and the other part of our job is tuning the ignition advance or ignition timing. Now in our last lesson we looked at the fuel delivery and air fuel ratio on a Nissan 350z running an AEM Infinity ECU.Īnd at the time I said to you that there's really only two things we as tuners are trying to do.
Ignition timing series#
I'm Andre from the High Performance Academy and I want to welcome you back to the second in our series of free tuning lessons.
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