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Injection timing and ignition delay

Practical Diesel Tuning

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When I was looking into the timing maps of my EcoDiesel and doing the calculations by hand with the guideline of delivering 40-60% of the fuel quantity in before TDC I found that my OEM timing map is much more advanced than the calculations around 2-5 degrees more, with it up to 24 degrees at max load 4000RPM, injection pressures are quite high so the pulse width is quite low. Is there something I'm missing when tuning Injection timing? Could OEM be compensating for low Cetane value with their advance or compensating for injector dead time? If so is it really possible to tune without a dyno and or a cylinder pressure transducer?

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It's important to remember the factory doesn't use this guideline while setting their timing curves. They balancing best torque, noise and NOx production. You can see in the in the factory curves that timing is quite low below 2500RPM where NOx output is a concern for emissions tests. As RPM comes up you'll timing jump dramatically from 2500 to 3000 RPM where the vehicle is mostly running high loads or otherwise outside the emission test cycle. I would only concern yourself to with timing at high load if you're newer to tuning. Of course it's very handy to have a dyno for this type of testing to so you can verify power gains, but you can also work from the factory theory. Take note of how much extra timing they're adding when they add fuel and use a similar rule to stay safe when you add fuel.

Hope this is helpful,


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