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Practical Diesel Tuning: Boost Tuning - Practical Demo

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Boost Tuning - Practical Demo

07.58

00:00 - We're in a 2005 LLY Duramax, stock truck, tune only and our goal with this episode's to show you what making changes in boost can do to the power, air/fuel ratio and kind of how those dynamics play with the vane position.
00:13 So we want to watch how the truck makes adjustments to reach the desired boost levels that we put down.
00:17 So what I'm going to do is walk you through the tune file and show you how I make those changes in the tune file and how we're going to switch between them and then we're going to jump into the dyno test.
00:26 So here we go.
00:27 So in the tune file I'm going to pull up the desired boost table, so this is desired boost with EGR off at sea level, Charlie is sea level and we're going to be down here near the 100 mm³ area, so during the dyno test we're expecting the truck to run down here.
00:42 This boost number, less ambient which is up in the left hand corner, is going to be our target boost so we're targeting just over, just about 20 pounds of boost.
00:52 34 - 14.5 so just under 20 pounds of boost.
00:55 What my hope is, is that this will bottom out the turbo vane position so the desired vane position should jump down near zero and we should run the turbocharger at full open to establish that low boost baseline.
01:08 Now all of our tune files are the same fuelling.
01:12 So I go to DSP one which is going to be our first switch and I'm going to do to the target boost in that tune which is right here and you can see that where we used to have 33.8 or so, I've added about three pounds of boost and we're up around 37 so minus ambient, we're just in the low 20s.
01:31 We jump into DSP two, again we're going to go to desired boost and now we're commanding 40 total.
01:42 So those are our changes, that's the only changes I had between all three of these tune files, we're going to get this thing running on the dyno and then we're going to go over the data.
02:03 Here's the run for tune two.
02:08 Should be able to hear a little more sing in the turbo.
02:25 And here's the third and final run.
02:50 OK so we have the first dyno run up on the screen right now in front of me, what we're going to do is compare that dyno run as far as the desired boost goes, to the log file and see what the vane position and boost are doing.
03:01 So if you remember in the tune file, you had commanded about 33 or 34 pounds of boost or of total MAP during the run depending on RPM and you can see down lower here we go from 33 up to 34, looks like she overshoots just a little bit.
03:18 But if you watch on the screen here, this green line is the vane position and you can see those micro adjustments and some macro adjustments to get our vane position in line to meet the desired boost number and that's really a nice line, I mean that thing is tracking our desired boost very closely.
03:34 And very smooth and controlled run.
03:37 So we'll pull up tune two, if you recall we had about three pounds of boost, three pounds of total MAP on tune two so we're going to be looking at the boost trace and we're going to also be looking at the vane position trace to see if those micro adjustments and those adjustments look like they track about like we'd expect, compared to tune one with three pounds of boost less.
03:53 So I'm going to look on the screen here, looking at my green line you see the vane position is higher than the first run.
03:59 In the first run we were in the mid 20s.
04:01 Then I'm going to look at the pink line, the pink line is MAP and that MAP is tracking higher as well.
04:06 We're seeing about three pounds higher on the MAP which is exactly what we asked for so we're right in the meat of the control range of this turbocharger on tunes one and two.
04:14 OK now we have the third and final tune and that file has another three pounds on top of it so remember we're targeting just about 40 pounds MAP and it'll be interesting to see what the vane position does in that scenario.
04:24 So I'm going to peak down at the log file here, we've got the green line and we can see our vane position is up slightly over the previous one, we're in the mid 40s now.
04:32 And we're tracking down, down, down and we're still mid to low 40s all the way through the run.
04:40 Interestingly we look at the MAP line and that MAP, that pink line is right at 40 pounds.
04:44 Beautiful, that's exactly what we asked for.
04:46 So really we're in the meat of the control range of this turbocharger.
04:49 I don't usually like to run these much past 45% vane position.
04:54 Once you start getting past that, your drive pressure to boost numbers start to go kind of upside down.
05:00 We have the dyno graphs pulled up, we've already looked at the log file, the scanned data and we've seen that the engine and the turbocharger are fouling our command so we have a consistent fuel rate across three tunes, we've changed those tunes and we've seen that the vanes and the target boost and the actual boost are adjusting per our request.
05:18 So it doesn't make a difference, let's look at the dyno graphs.
05:20 Let's start with the most interesting data first.
05:23 Most interesting data that I see is in the air/fuel ratio.
05:25 On the tune that has the lowest boost we see a lot of variation in the air/fuel ratio.
05:29 Starting at the beginning of the test, we start at 17.5 or 17.6 air/fuel ratio and come up around 19 and then we fall back off as the turbocharger, boost command comes down and you can see that reflected in the air/fuel ratio.
05:46 Similarly in tune two you can see that same slope at the end of the test.
05:51 You can see the air/fuel ratio drop, you can see things come down off of 19.5 which is the limit of the sensor.
05:58 Right around 2890 RPM you see that air/fuel ratio start to drop off towards the end of the test.
06:06 Now on the full boost test, that is the 40 MAP test, you can see that the air/fuel ratio maintains solid maxed out 19.5 air/fuel ratio all the way towards the end of the test.
06:17 And then we finally drop off that slow curve right towards the end of the test.
06:22 So what does that tell us? Far and away tune three is going to be the cleanest.
06:29 You're going to have the least particulate matter output on tune three, I can guarantee you that.
06:33 Now what didn't change? What did we expect to change, we probably expected to make a lot more horsepower by changing the boost three pounds, three pounds three pounds, I mean more boost is more power right? Well not necessarily, when we're already at an air/fuel ratio that's fairly high, you're seeing 19, 18 air/fuel ratio, we're already using a lot of air to make that power so yes while we are moving more air through the motor, we're just not seeing a big change in power and that's reflected in our dyno graphs.
07:04 You see less than a 10 horsepower change through the dyno.
07:10 It's called mid range here, 2700 RPM, 387, 377, 366, 370, you're just not going to feel that difference in the truck.
07:26 It's very interesting how close the torque and horsepower numbers are for how different the air/fuel ratio is across that board.
07:33 So let that be a lesson to you, if we were another three pounds lower, or maybe we scaled this while test down further into that 14:1, 15:1 range, we'd probably see a bigger difference in the horsepower number.