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Ignition Timing Math

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Hello all,

Is there any equation calculating ignition timing? (difficult or not) i would like to know please

The short answer is, no.

The more detailed answer is: there are complicated formulas used in commercial modeling software, such as the Livengood-Wu integral, that can be used. However it requires a lot of information, and it needs to be compared to experimental results to work.

The easiest way to "calculate" ignition timing is to start with a base timing map from an engine that is somewhat like your own. So, if the stock map is available, use that. If you have to use a spark map from a different engine (surrogate engine) pick one that's closest to your specification. If you have a 2.0 liter port injected naturally aspirated engine with dual overhead cam, find a spark map from a similar such engine and work from there. Then make some adjustments for differences in fuel or hardware.

Thank you , also finding the MBT with the a dyno at 2500rpm and 60kpa is the same as at 7000 rpm at 104kpa load?

Can you give more background information? What is the car and engine, what modifications have been done to it, is 7000rpm/104 kPa WOT on a naturally aspirated engine?

Okay so lets say for my car N/A Integra type r 1.8L stock block with brian crower stage II cams .Wot is 9200 rpm and lets say 115Kpa since it can draw more air into the cylinder . I just wanted to know if the MBT is the same on every point of the map or it depends on rpm and load .

If you're asking if there's a single best timing value for the entire map, the answer is no. Depending on Load and RPM, MBT will change. Take for example a turbo charged engine that ingests 200kpa from 4000 RPM - it's 7000 RPM redline.

Assuming the engine isn't knock limited, you'll find that you'll need to advance ignition timing as RPM goes up even though load remains constant. Because the rate at which the combustion charge burns remains relatively constant, you have to ignite the mixture sooner so that peak torque continues to happen at ~12 -16 degrees after TDC.

Load and RPM will influence what MBT is for a given engine. Again, whether you'll actually be able to run the engine at MBT is largely depending on if it is knock limited at the load levels that you're running.

Yeap that's what i was asking, thanks both of you for you time explaining .

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