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Practical Diesel Tuning: 4. Optimise Tune

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4. Optimise Tune


00:00 - The next step of our process is where we get to put into practice everything we've learned through this course so far.
00:05 This becomes an iterative process for optimising our boost pressure to increase airflow and optimising our fuel pressure, fuel quantity and injection timing to deliver a powerful yet safe tune for our particular engine and our particular application.
00:18 As we've discussed throughout the body of this course there are no absolutes here, we need to consider the way the engine is going to be used as well as any known reliability issues with the stock engine, fuel system or turbocharger.
00:29 What I mean here is that if you have an engine that is known for having a weak turbocharger that's prone to failure, we probably aren't going to want to push the boost much above the stock level.
00:38 Ultimately, this won't limit how much power we can produce unless we're prepared to switch to a different turbo.
00:44 Likewise, if you're tuning a truck engine that's going to be hauling heavy loads then we aren't going to want to have exhaust gas temperatures pegging 750 to 800°C during a short ramp run on the dyno.
00:55 In this sort of situation, being conservative might be frustrating when you know there's more power on tap.
01:01 However, doesn't matter how much power the engine produces if it falls to pieces the first time it's used tow a heavy load.
01:07 As far as our fuel delivery goes, we want to watch our EGT obviously, however we also want to be mindful of the air/fuel ratio as well as exhaust smoke output.
01:15 As we've learned in this course, this is particularly critical on engines fitted with DPFs as smokey tunes will quickly fill up a DPF but won't be readily apparent on the dyno.
01:25 In this case, unless you have the luxury of a smoke meter, that you can fit in the exhaust system pre DPF, watching the air/fuel ratio and keeping it leaner than 1.1 lambda is a sensible approach.
01:35 With the injection timing, we can now make some iterative tests to see the effect of changing the timing.
01:40 I break this up into two regions, first we can test the wide open throttle operation for the effect on power and torque and then we can test the cruise areas for economy.
01:48 I'd suggest starting by making two degree changes and assess the effects.
01:52 Just like tuning a gasoline engine, if we see no change in power and torque when we make the timing change, we're best to reverse the change we just made.
02:00 When we're making timing changes, we always want to be mindful of maintaining a smooth shape to the completed table.
02:06 By going through this process, you should now be at a point where you have a well tuned engine that's producing a healthy increase in power and torque while keeping control of our exhaust gas temperatures and not producing exhaust smoke.