Emissions Tuning Fundamentals: Emissions Tuning Foundation

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Emissions Tuning Foundation

10.19

00:00	So far, we've learned about the various tailpipe emissions we're interested in, how they're produced and how we can measure them but in this module we'll dive into the specifics of tuning to aid in minimising and controlling your emissions.
00:12	Assuming for a moment you're dealing with reflashing a stock engine control module, generally speaking, emissions tuning efforts start with a factory calibration.
00:20	Since the stock tuner's already demonstrated compliance, it's a great guide and a known good set of values.
00:26	I'm likely stating the obvious but this is so often overlooked.
00:30	During the tuning process, each time you're going to make a change, think about whether that change is actually needed or not.
00:36	One of the best ways to avoid failing emissions testing for a silly reason is not making changes to tables or parameters that could have been left alone.
00:45	If you're working with a system you aren't familiar with and isn't fully documented, some trial and error will be inevitable.
00:51	Specifically, you'll have to test various changes and review their effects to confirm how the systems operate.
00:58	Once you've figured out the best way to manage torque, boost and other systems though, it's a good idea to start over.
01:04	Revert all unnecessary changes and only retain those that you're sure are both required for proper operation and prudent, then complete your fine tuning.
01:13	This method avoids retaining extraneous or less than ideal changes that you made before you knew the best way to modify the stock calibration.
01:21	If you're working on a vehicle with a transmission that shifts automatically, whether it be a DCT, CVT or conventional automatic, consider the impact shift scheduling changes will have on a fuel economy and your emissions.
01:34	The OEM generally sets shift schedules up to keep engine speed relatively low.
01:39	This reduces frictional losses, improves fuel economy and it may also reduce emissions.
01:45	Making modest increases to the engine and vehicle speed where automated shifts occur during part throttle driving may be possible without exceeding emissions limits.
01:54	More aggressive increases in shift points run a higher risk of having a negative emissions impact so don't go too far here.
02:01	As with all changes, how far is too far depends on the vehicle and the conditions so this is where testing is key.
02:08	If your changes cause unfavourable emissions results, consider shifting them back towards the stock values.
02:14	In our automatic transmission tuning course we dive much deeper into this subject but for now I'll just add that keeping shift schedules efficient and enjoyable is a very in depth process.
02:24	If your goal is to certify or test engine operation after changing the tune or changing a physical part, leaving transmission operation stock avoids a significant variable.
02:35	If transmission recalibration is important to your project, we'd suggest testing transmission calibration changes on a stock engine calibration first.
02:43	Changing engine and transmission tuning at the same time makes it much harder to determine what went wrong or where you went too far if the changes do cause poor emissions results.
02:54	Next, let's cover drive by wire tuning.
02:57	If you drive the same route twice, the first time smoothly and the second time you're more aggressive in how you press and release the accelerator pedal, emissions and fuel economy will suffer during the more aggressive driving style.
03:09	With that in mind, if you're altering the drive by wire translation to make the throttle more responsive to a given input, consider that this can make it more challenging to drive the vehicle smoothly.
03:20	It doesn't necessarily mean that you can't drive the vehicle smoothly or that you can't pass an emissions test but it is going to be much harder and in a certification setting, you wouldn't be the one driving.
03:31	Next, when it comes to the calibration of the evaporative system control, air pump and EGR, you simply want to let these systems operate as the OE intended.
03:41	Let's clarify though, there may be an opportunity to adjust ignition timing during EGR operation to reduce detonation but we don't suggest altering the operation of the actual EGR system itself.
03:53	Next, we always want to keep the engine and drivetrain in one piece so that's likely already on your mind but in your emissions tuning efforts, make sure that you aren't damaging emissions components either.
04:05	Unless you're more creative than us, it's unlikely you're going to damage the evap or air pump systems with your fuel, timing and boost tuning but as you're making performance enhancing changes, it's critical to avoid harming some other components.
04:17	We've talked about avoiding clogging particulate filters in a prior module but now let's talk about protecting the catalysts.
04:24	Overheating a catalytic converter can result in irreparable damage, sometimes called moon rocking a cat.
04:31	The failed cats literally look like rocks from the moon after they melt and deform.
04:35	Clearly there's no coming back from that and the component would need to be replaced.
04:40	It's up to your calibration to avoid this.
04:42	To do so, you need to monitor exhaust gas temperature with a probe, either in the cat core or you can install probes before and after it.
04:50	Always get baseline readings in stock form so that you know what the OE deem to be acceptable.
04:57	Manufacturers have the opportunity to select a catalyst tailored to each application with the appropriate margin of safety.
05:04	Well before overheating causes total meltdown, you can overheat a cat to the point that the coatings are damaged and this can impact its ability to scrub emissions.
05:13	Since these limits vary per unit, and that information generally isn't published, keeping maximum cat temp at, below or close to stock is suggested to save you from this particular issue.
05:25	To offer a ballpark, damage may occur somewhere in the 850 to 1000°C range.
05:31	One of the factors regulators consider when scrutinising parts and calibrations is their impact on the durability of the emission systems.
05:39	If your tune disables catalyst protection, that's going to be a red flag and isn't recommended.
05:45	Catalyst protection strategies are designed to step in when cat temperatures may be increasing to dangerous levels and can come in the form of fuelling changes, airflow reductions and more.
05:56	It may be possible to adjust the cat protection thresholds a bit without causing damage, but this is not a place to get greedy so be careful.
06:04	Some key factors related to cat temp are lambda target, ignition timing, cam timing, compression, air mass and temperature.
06:13	If all other settings left stock and you throw more fuel in a diesel or run less enrichment than stock on a gas engine at full power, you'll generally be increasing exhaust gas temperatures.
06:24	If you retard the ignition timing on a gas engine, you can decrease the combustion chamber temperature but actually increase the exhaust gas temperature.
06:31	Variable cam timing and aftermarket cams can have a large impact and increasing compression typically increases exhaust temperature so this is an area where you'll want to test various combinations and determine which nets the best combination of performance, emissions and maintaining acceptable conditions for emissions components.
06:50	Whether your engine is gas or diesel, NOx generation occurs when excessive combustion temperature is present and keep in mind, combustion temperature and exhaust temperature are not the same thing.
07:01	If you're monitoring EGT and it appears acceptable, that doesn't mean combustion temperature is also acceptable.
07:07	Various factors like injection timing, ignition timing and cylinder head temperature are variables that dynamically impact on how much heat transfers to the cylinder head and how much makes its way into the exhaust.
07:19	Factors like exhaust path, size and length and exhaust manifold pressure and probe placement also impact the difference between your EGT reading and the combustion temperature.
07:30	NOx increase at light load may be improved by increased EGR, either via cam phasing or the EGR system itself.
07:38	If you're running aftermarket high flow DI injectors, retarding the start of injection to bring end of injection closer to stock often brings NOx back to reasonable levels at light load.
07:49	On a diesel engine with higher flow injectors, you may also have the option of pilot control.
07:54	With pilot injection, you can both lengthen the pilot injection and retard start of injection to bring the main end of injection closer to stock.
08:03	At mid to high load, if you have excess NOx, gas engines most often require additional enrichment or this indicates you're operating lean of the lambda target that you're trying to hit.
08:14	On a diesel, high NOx under load generally means your combustion pressure is too high, perhaps over 200 bar and you'll need to make the tune a little less aggressive.
08:23	Remember that with extreme pressure, always comes extreme heat since they're mathematically linked together.
08:28	If you've advanced the start of injection point on your diesel to reduce EGT and make that more conservative, you've actually increased cylinder temperatures and pressures which makes engine operation more aggressive and may be causing the excessive NOx.
08:43	As always, all things in moderation and you may need to find a different combination of injection timing, fuel mass and boost to satisfy both your turbo protection needs and your engine protection and emissions needs.
08:55	Since reducing fuel delivery reduces combustion pressure on a diesel, you can avoid extreme pressure and reduce hydrocarbon and particulate matter emissions by simply injecting less fuel.
09:05	This of course will come with the compromise of reducing torque and power, all other things remaining equal so it is a careful balance.
09:12	During overrun and the transition to overrun, gas engines can show NOx spikes if ignition timing isn't optimal so watch out for this if you're attempting changes to reduce rev hang which is often part of an emissions reduction strategy.
09:27	We'll dive deeper on some of these aspects like air fuel ratio, target selection in the next few modules but let's first recap these foundational suggestions.
09:35	Battery calibrations are a roadmap to emissions success.
09:39	If you haven't tuned a vehicle before and need to perform trial and error to come up with the best way to do some things, go for it.
09:45	Just remember to revert unnecessary changes to stock after your investigation and only make changes required to meet your goals.
09:53	Within reason, you can make automatic shift schedules or drive by wire translation more aggressive without failing emissions.
09:59	But going too far can increase emissions so this must be done with caution.
10:04	Overhead and catalytic converters must be avoided at all costs.
10:08	Damaging this component requires expensive repairs and is not an acceptable outcome for any calibration or component upgrade.