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Practical Diesel Tuning: Fuel Delivery and the DPF

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Fuel Delivery and the DPF

03.00

00:00 - One of the issues that you need to concern yourself with on newer trucks, those fitted with DPFs, is that that DPF is there for the purpose of collecting and filtering out soot from the exhaust gases.
00:09 As the DPF does its job, it will over time fill up with soot and then we'll need to go through a regen cycle to burn off the soot so that it's cleaned and ready to collect more.
00:19 The issue is that by its very nature, when the DPF is doing its job, we should have no visible exhaust smoke coming from the tailpipe.
00:26 This is obviously fine in a stock calibration however as we add more fuel to improve engine performance, it's very easy to end up generating additional soot in the DPF and that needs to be dealt with.
00:37 If we create a tune that's producing excessive exhaust soot then the DPF may have a hard time dealing with this.
00:42 We can end up with a DPF needing to go through regen cycles more frequently or we may even get to the point where the regen cycle is ineffective and the DPF simply becomes blocked which can be expensive if it needs to be replaced.
00:54 This is a tricky situation because the best way to deal with this is to use an opacity meter or smoke meter as it's more commonly called to check the soot output prior to the DPF.
01:04 There's a couple of problems with this technique though and the biggest issue is really the cost of the equipment you'll need.
01:09 An entry level opacity meter is likely to cost in the region of $1000 - $3000 USD and they quickly go up from there.
01:17 Fitting the meter to the exhaust system is no small task and this needs to be done of course pre DPF to get useful data.
01:25 While this is the ideal scenario, we also know that not too many enthusiasts are going to go through this expense just to tune their own vehicle.
01:31 On the other hand if you're a professional tuning workshop then I'd strongly advise you consider this sort of purchase as it will set you apart from other tuners producing smokey tunes that block up DPFs and waste customers' money.
01:43 If you're not going to use a smoke meter then this is where the addition of an air/fuel ratio sensor can at least give you some guidance.
01:49 A good place to start is to log factory air/fuel ratio under sustained high load operation and see how rich the factory calibration is running.
01:57 It's a reasonable assumption that the air/fuel from the factory calibration will be safe for the DPF over the long term and we can use this as a guide for our own tuning, making sure that we remain close to the stock numbers.
02:09 You might be thinking that if we're going to stick to the same air/fuel ratio as the factory tune, then there's not going to be any more potential to make power.
02:16 However, as well see in the next module, we'll also be adding additional airflow thanks to the turbocharger and this in turn will allow us to add more fuel while maintaining a safe air/fuel ratio for the DPF.
02:28 We can also apply what we learned from tuning non emissions equipped engines and while there are very few absolutes, we generally find that once we run richer than about 1.1 lambda, we will start to see a visible haze of smoke from the exhaust on a diesel engine.
02:40 As we move richer still, this exhaust smoke will become more prominent and of course that visible smoke needs to be dealt with by the DPF.