Emissions Tuning Fundamentals: Opacity Meter
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Opacity Meter
05.42
| 00:00 | The next piece of equipment we're going to cover is the opacity meter which is a relatively simple device that projects light into the exhaust and observes the obstruction of that light which comes largely from soot and other particulate matter. |
| 00:12 | Because this doesn't require lots of fancy sensors or any warm up, it's cheaper and easier to use than a 5 gas analyser. |
| 00:20 | Like most things, you can find a really fancy version but $500-2000 USD currently gets you a unit that can provide you with data helpful in cleaning up tunes. |
| 00:30 | Opacity meters can be used at the tailpipe but with the addition of catalysts and particulate filters, it's helpful to take readings before those aftertreatment systems. |
| 00:40 | Taking measurements after a DPF for example can give a misleading idea of how clean a tune is since the DPF's job of course is to remove the particulate matter. |
| 00:50 | What we really want to understand is how much particulate matter is being produced prior to the aftertreatment devices as this is critical to their reliability and function. |
| 01:00 | If a particulate filter is being clogged up quickly by a dirty tune, regeneration cycles won't be able to clear it back out quickly enough. |
| 01:08 | If you can measure opacity pre DPF and get it dialled in there, great but getting access to that part of the exhaust can also be a challenge. |
| 01:16 | If you're monitoring opacity at the tailpipe, remember that modern diesels with DPFs can handle so much soot that you shouldn't be running into opacity issues at the tailpipe unless your fuelling is way beyond optimal for emissions. |
| 01:29 | Once you get down to reasonable opacity readings at the tailpipe, you generally want to take a bit more fuel out rather than staying near the edge of unacceptable results. |
| 01:39 | Then when you think you have the tune pretty dialled in, do a bunch of driving and see how your regen intervals compare to stock under similar driving conditions. |
| 01:47 | If the DPF has to regen after 30% less miles than it did on the stock tune, even though you're not producing more soot than stock at the tailpipe, you're asking a lot of the DPF. |
| 01:59 | Regen cycles can also be an annoyance for some vehicle owners. |
| 02:03 | Depending on the driver's habits, they may not spend much time cruising at constant speed where the regen can occur. |
| 02:10 | If they have to take a specific drive just to perform extra regens after a tune, customers may be less satisfied. |
| 02:16 | Any significant shortening of the distance between regens is also a sign that opacity is significantly higher than stock pre DPF. |
| 02:25 | This is your window into what's happening pre DPF if you haven't been able to take an opacity reading there. |
| 02:31 | If you tune gas engines, gas particulate filters are present on some DI turbo vehicles at the time of recording and perhaps more will have them in the future so keep this in mind. |
| 02:41 | Used properly, relative improvements observed on an opacity meter will generally improve particulate matter test results. |
| 02:49 | If you go from 50% opacity to 5%, you've made an enormous improvement. |
| 02:54 | Just keep in mind that opacity meters do not correlate directly to laboratory PM readings due to the shortcomings of this measurement method. |
| 03:02 | Particles under a certain size tend to be missed by an opacity meter. |
| 03:06 | Certain gases like nitrogen dioxide can also cause false positive readings due to absorbing the light spectrum that the meter is monitoring. |
| 03:14 | Much like most 5 gas analysers don't have the resolution and range to verify super low NOx emissions, opacity meters generally aren't sensitive enough to tell whether a diesel engine meets 2024 emission standards or not. |
| 03:28 | The allowed particulate matter is so minuscule that the meter simply can't detect at that lower level. |
| 03:34 | Some opacity meters will display inferred particulate matter. |
| 03:37 | Despite the value not accurately correlating to true particulate matter measurements, again if you massively decrease the number, you've still made a great improvement. |
| 03:46 | All this is to say that you can make great progress without perfect conditions or millions of dollars in equipment. |
| 03:53 | In terms of maintaining an opacity meter, it meters light so if the lens or other components get dirty, they need to be cleaned. |
| 04:00 | While you're at it, it's also worth cleaning the sample hose. |
| 04:03 | A moment ago I mentioned opacity meters don't require warm up time but there is a warm up related concern. |
| 04:09 | Water condensation also disrupts light. |
| 04:12 | So while the opacity meter doesn't need a warm up as such, as the exhaust systems cool, they tend to collect condensation. |
| 04:19 | By warming up the vehicle exhaust, you can clear that moisture out first and then attach the opacity meter to help avoid skewed readings. |
| 04:27 | Opacity meters work well when exhaust is flowing past so if you're sampling pre particulate filter, setting up inline monitoring is preferred. |
| 04:35 | Specifically some exhaust gets diverted, often through copper pipe to cool it, then through the meter and plumbing and then back into the exhaust so it's continuously flowing past the meter. |
| 04:45 | As with 5 gas units, opacity meters aren't meant to accept extremely high exhaust gas temperatures. |
| 04:51 | Copper pipe is often wound into a tight coil shape to increase surface area for heat exchanging without taking up lots of space. |
| 04:59 | Copper pipe certainly isn't the only option and some kits again come with their own solutions. |
| 05:04 | Before we move into talking about high end emissions analysers, let's review the key points around this more wallet friendly option. |
| 05:11 | Opacity meters observe obstruction and absorption of light. |
| 05:15 | This is caused not only by particles but also by certain gases and water can skew results as well. |
| 05:21 | While this isn't the perfect way to monitor particulate matter, relative improvements are still valuable. |
| 05:27 | Opacity meters work best when the exhaust has already been warmed up so that it's free of condensation. |
| 05:33 | With mid level measurement tools covered, now it's time to step up the price tag and the accuracy level. |
