-Like it or not, emissions devices are a fact of life if you're in the diesel tuning world
and in particular one of the common devices we'll see on most diesel equipped
vehicles is a DPF or diesel particulate filter.
One of the common ways that we've got available to us in the diesel tuning world
to improve performance is to increase the fuel delivery into the engine.
When we do this though, we do risk increasing the particulate output in the exhaust system
and this can easily block our DPF meaning that when we are tuning a DPF equipped
engine, we are walking a little bit of a tightrope.
In this lesson, we're going to have a look at how the fuel quantity that we are introducing
to the diesel engine affects the opacity of the exhaust and in turn the life expentancy
and reliability of the DPF.
- 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.
So we have an opacity meter in the exhaust just before the DPF and we also have a wideband
O2 sensor in the tailpipe.
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.
Beautiful, now let's have a look at those results.
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.
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.
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.
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.
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.
So we see K climb from 2.0 at 2560 RPM all the way up to 6.9 and 9.6 at 3000 RPM.
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.
So if you're keeping track of units, lambda versus air/fuel, 1.26, 18.5.
OK now let's go ahead and load up that modified file and see how that compares
to this test.
OK so we have our modified tune file flashed in, let's make a run.
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.
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.
The lambda numbers are fairly close, 1.17 compared to 1.15 on the modified file
and our opacity numbers, one compared to two.
So still tracking fairly close.
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.
We can see our opacity really starting to come up here.
One on the stock file compared to 6.7 on the mod file.
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.
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.
1.13 lambda compared to 1.21.
8.4 on opacity compared to 2.0 and you can see after that, we get a divergence and lambda
starts to trend towards 1.1 and even goes below 1.1 to 1.05.
End of the run, 555 horsepower, 1.05, 1.06 on lambda compared to 1.26.
So you're off by quite a bit on lambda compared to stock.
Clearly this tune is designed for one thing and that's making a lot of power.
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.
Hopefully this test was a useful tool to see the relationship between lambda and
opacity.
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.
Very useful when you're tuning a DPF equipped truck.
We know you may not have access to an opacity meter but hopefully this test has
given you a nice window into the relationship between lambda, opacity and the power level.
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