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Practical Diesel Tuning: Fuel Delivery and the DPF - Practical Demo

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Fuel Delivery and the DPF - Practical Demo


00:00 - Nick here with HP Academy, today we have a 2018 GM Duramax L5P on the dyno and what we're going to be using this truck for is to show you the correlation between lambda and opacity.
00:10 So we have an opacity meter in the exhaust just before the DPF and we also have a wideband O2 sensor in the tailpipe.
00:18 So we have a stock tune file in the truck and we're going to go ahead and make a ramp run here and show you what we have for opacity and lambda on the stock file.
00:33 Beautiful, now let's have a look at those results.
00:35 We have our dyno run complete here on the stock file, I'm going to draw your attention to the screen which is going to show you the horsepower number, 446 horsepower at peak but we're also going to be able to see our lambda values and our opacity.
00:47 So starting at the beginning of the run, at 1900 RPM, making 290 horsepower, 1.17 lambda, that's the lowest lambda we'll see during the test and we opacity at 1.04.
00:57 We really see lambda and opacity track right around that 1.2 and over 1.2 with opacity just over one up to about 2500 RPM.
01:09 Now at 2500 RPM we start to see opacity climb a little bit, and this is interesting because lambda stays the same as the test runs out to 2900 RPM when the truck makes peak power.
01:20 But opacity climbs and the units of opacity are K, not terribly important you know what K is, really it's just a relative value that we're going to use to compare against the modified tune.
01:31 So we see K climb from 2.0 at 2560 RPM all the way up to 6.9 and 9.6 at 3000 RPM.
01:45 Just a note at 3000 RPM where we're making peak power, 448 horsepower, we see a lambda of 1.2, 1.264, that's 18.5 AFR.
01:57 So if you're keeping track of units, lambda versus air/fuel, 1.26, 18.5.
02:04 OK now let's go ahead and load up that modified file and see how that compares to this test.
02:10 OK so we have our modified tune file flashed in, let's make a run.
02:26 OK so we finished the run with the modified tune file and we're going to have a look at these results here, interesting worth noting that this modified tune is 555 wheel horsepower.
02:35 So at the start of the test, we're at 1900 RPM and the stock file made 290 horsepower here, our modified file's making 430 horsepower here, a significant gain.
02:46 The lambda numbers are fairly close, 1.17 compared to 1.15 on the modified file and our opacity numbers, one compared to two.
02:57 So still tracking fairly close.
03:02 As we move along, 2370 RPM, you can see our factory lambda number, 1.24, modified, 1.17, now we're making 500 horsepower compared to 390 horsepower so more than 110 horsepower increase.
03:17 We can see our opacity really starting to come up here.
03:20 One on the stock file compared to 6.7 on the mod file.
03:24 And that opacity's going to continue to climb as we go later and later into the rev range where the turbocharger's going to lose the ability to control our lambda.
03:32 So you can see, 2560 RPM, is probably about the last RPM break point where we had good control over lambda and we're making 536 wheel horsepower compared to 416, so 120 horsepower more than stock.
03:49 1.13 lambda compared to 1.21.
03:53 8.4 on opacity compared to 2.0 and you can see after than, we get a divergence and lambda starts to trend towards 1.1 and even goes below 1.1 to 1.05.
04:08 End of the run, 555 horsepower, 1.05, 1.06 on lambda compared to 1.26.
04:15 So you're off by quite a bit on lambda compared to stock.
04:18 Clearly this tune is designed for one thing and that's making a lot of power.
04:22 We're at the limit of the turbocharger and as such, we see the loss of the ability to keep that lambda number in the 1.2 range and we're trending to 1.1, even below 1.1 where we lose control of opacity as well and that climbs towards 10.
04:38 Hopefully this test was a useful tool to see the relationship between lambda and opacity.
04:42 Of course they're not directly related but you can see as you trend below that 1.2, 1.25 lambda, towards the 1.1 and deeper towards 1.0 lambda at the end of our modified tune test you can really see opacity come up.
04:56 Very useful when you're tuning a DPF equipped truck.