Emissions Tuning Fundamentals: Common Aftermarket Parts

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Common Aftermarket Parts

11.31

00:00	Now, it's time to dive into aftermarket part selection and design.
00:04	With the right component design, selection and calibration, if needed, increased performance and emissions compliance can go hand in hand.
00:12	Everything in the airflow path through the engine from the air filter to the last emissions control in the exhaust, plus everything in the fuel and emissions systems and hoses tends to be emissions regulated.
00:23	First I'll touch on items impacting air mass measurement and calculation.
00:28	Larger than stock MAF housings increase maximum flow and mass measurement but they can also decrease the resolution and accuracy of that measurement.
00:37	A modest increase in diameter, along with design improvements such as a velocity stack and air straighteners can combine to create an improved product that works great all around.
00:47	Be mindful because as you increase the MAF housing diameter, eventually you reduce the resolution of the stock MAF sensor's measurement to the point that significant loss in accuracy can occur.
00:57	Without accurate air mass determination, engine control becomes less precise which is detrimental to emissions control.
01:05	Essentially the ECU loses the ability to measure the air mass entering the engine with the accuracy required to deliver the correct amount of fuel and hence we can end up with the engine running richer or leaner than expected.
01:17	In a speed density setting, you can think of extended MAP sensors in the exact same way.
01:23	Within a given family of MAP sensors, the error band specification is typically the same and percentage based, often 1-2%.
01:31	Before installing a 7 bar MAP sensor on a vehicle that will never run more than 2 bar of boost, consider that a 3.5 bar MAP sensor's effective error range would be half as big as the 7 bar.
01:43	So, to be clear, that means 2% of 7 bar is twice as much as 2% of 3.5 bar so the expected inaccuracy of the 7 bar would be twice as large.
01:54	The resolution of the analogue to digital converter within the ECU may further compound that loss of accuracy.
02:00	What I mean by this is that the ECU will convert the analogue voltage from the MAP sensor into a digital signal that the ECU can understand and use.
02:09	For the sake of simplicity, let's say that the converter uses 100 steps.
02:13	That means that for a 0 to 5 volt sensor, each step is 0.05 volts.
02:18	We're simply dividing 5 by 100.
02:21	For our 3.5 bar example, assuming again for simplicity the sensor range is the full 5 volts, we can work out the pressure change per volt by dividing 3.5 by 5 which gives us 0.7.
02:34	Now, if we multiply that by our voltage step of 0 .05, we find that each step in the digital converter is 0.035 bar and if we run the same calculation for the 7 bar sensor, the result of course doubles to 0.07 bar.
02:51	Some loss of accuracy may not cause failing emissions results and it's possible to have certification success with both larger MAP housings and higher range MAP sensors.
03:01	Just be aware, there's a limit to how far you can go before the loss of precision becomes an issue.
03:07	MAP housings and MAP sensors also require tuning so be sure that the calibration on the vehicle matches the parts fitted.
03:13	When it comes to inlet hoses, charge pipes and intercoolers, these are generally emissions controlled but creating aftermarket solutions is usually relatively straightforward.
03:23	Make sure that new components are durable, don't leak or significantly impact engine operation.
03:29	Verify fuel trims remain acceptable and lambda targets are being hit.
03:34	Ensure that all factory sensors and vacuum or breather hoses are retained.
03:39	Avoiding leaks comes down to material selection as well as fitting and clamp selection.
03:45	Sticking with hoses and fittings that have an SAE or similar rating that's acceptable in your area can streamline design and compliance efforts.
03:53	Next, if your area allows for aftermarket catalysts, providing they pass emissions testing, not all cats are created equal.
04:01	Don't worry too much for now though as we'll help you make that determination when we get into more detail on what makes a cat perform better or worse in the next module.
04:10	If you're going to create or use an oil catch can or air oil separator, these devices tend to be highly scrutinised.
04:17	While they don't vent gases to the atmosphere which would be prohibited, they do intercept the flow of gases.
04:23	Great separator systems can have emissions and reliability benefits but they are investigated for their potential impact on the evaporative emission system and how the engine runs.
04:33	Avoiding disrupting EVAP system operation, retaining the factory PCV valve and alerting the driver if a can is becoming full are requirements these systems may have to meet for compliance.
04:44	Atmospheric venting blow off valves and any exhaust dump prior to catalysts are some other examples of items that are not emissions legal.
04:52	Turbochargers can often be upgraded without disrupting emissions though most applications will require an accompanying tune for proper engine operation which can of course have negative implications on emissions.
05:03	In the diesel world, I'll add a caveat that if your vehicle came stock with a VGT or VNT turbo, it may be challenging or impossible to pass emissions with a non VGT turbo.
05:15	The VGT or VNT system is a critical part of not only throttling engine output but also varying exhaust pressure which impacts exhaust gas recirculation.
05:25	Next, while OEM injectors are optimised to an engine, that's not the only way to run clean.
05:31	We've seen great success with Injector Dynamics 1050cc units due to a combination of quality design and function along with accurate characterisation data.
05:42	ID's data allows the ECU to determine appropriate on time to deliver the correct fuel mass for the desired air fuel ratio, hence providing optimal combustion.
05:52	Fire flowing injectors can deliver fuel accurately but choose wisely and don't go overboard with the flow rate on port or direct injectors.
06:00	For example, 2000 plus cc per minute port injectors are simply not the right tool for precise fuelling at start up, idle and light throttle cruise on gasoline in many instances.
06:12	That being said, the ID1050 injector may still be a 400% flow increase over a stock injector and still pass emissions testing which is pretty impressive.
06:23	On a direct injected engine however, a 400% increase in flow simply isn't reasonable or achievable.
06:30	Experience has shown that about a 30% flow increase over stock is as far as you'll want to go on emissions controlled vehicles.
06:37	Even then, a 30% larger DI injector will need proper tuning, good injector data and have an appropriate spray pattern for the application.
06:46	Going 40-45% over stock flow makes it more challenging to run clean and anything beyond that is certainly an off road modification for something like a drag car or a pulling truck.
06:57	Diesel injector characterisation hasn't progressed quite as far as gas injectors but companies like S&S Fuel Systems and Exige Performance do provide useful characterisation data with their injectors that can save you time.
07:11	By request, they may even provide you with data matching the axis breakpoints for fuel pressure and volume in specific engine management systems that you're working with.
07:20	That's not to say that you can't have success with another brand, just be aware that it may require more effort on your part so it's worth doing your homework prior to parting with your hard earned cash.
07:31	Upgrading pumps on the other hand generally isn't going to harm emissions.
07:35	It's important to make sure injector seals, hoses, fittings and pressure regulators prevent fuel vapour permeation.
07:43	Aside from emissions compliance, using the wrong type of fuel hose can end up with your cabin permanently smelling of fuel if these lines run through the cabin.
07:51	When it comes to intake and exhaust manifolds, some aftermarket units have passed emissions testing but careful design and testing is required.
08:00	Functional catalysts must also be present in similar locations.
08:04	When it comes to the engine itself, modern factory engines are built with relatively small ring end gaps, piston to wall clearances and have modestly sized cams, head ports and valves.
08:15	This suits efficiency, excellent air fuel mixing and clean, complete combustion rather than maximum airflow and horsepower.
08:23	Oversized valves, significant porting and other cylinder head modifications suited to supporting high airflow at peak RPM tend to slow air velocity and reduce swirl and mixing at low airflow.
08:36	This trade off generally degrades combustion quality and emissions during idle and gentle driving so these modifications are best kept to competition vehicles only.
08:45	I mentioned the issues an insufficient battery voltage can cause earlier but it's also important to mention that some modern lithium batteries offer excellent cranking performance in very small and light packages.
08:57	Smaller than stock lead acid or gel cells that can't maintain normal cranking speed and voltage should however be avoided.
09:04	Next, there are a few groups of common aftermarket parts that lots of people have and may not think of when they think of emissions.
09:10	The first being wheels and tyres.
09:13	If you've installed much larger wheels on a truck, car or other vehicle and felt their weight, it can be substantial.
09:20	You likely also noticed it took more engine effort to get the vehicle up to speed once the heavier wheels were installed.
09:26	On a roller dyno, this will show up as a loss in power and the extra load needed to get up to and maintain vehicle speed can be an emissions concern.
09:34	Don't forget about tyres either.
09:36	Bigger tyres tend to weigh more too and sticky high performance tyres often have greater rolling resistance.
09:42	The next group of common aftermarket parts that increases engine load and potentially emissions are exterior modifications.
09:49	If you have a big wing, a roof box, a bike rack or perhaps you've spaced your wheels out, these increases in aero drag can have a significant impact.
09:58	Increased ride height and replacing body panels with units that cause more drag may also contribute to emissions increases though this doesn't show up in stationary tests on a chassis dyno.
10:09	Again, items that make the engine work harder due to increased aero drag, rotating inertia, weight or rolling resistance may increase emissions but certainly negatively impact fuel economy.
10:21	We ran through a lot of parts in this module so let's take a moment to review some of the key points.
10:26	Precision engine operations start with precision air mass measurement so choose your MAF housing, MAF and MAP sensors wisely.
10:34	Making a replacement inlet, charge pipe or intercooler out of another material or resizing it generally won't increase emissions but be sure it doesn't leak and retain all factory hose connections.
10:46	Catch cans and air oil separators are highly scrutinised parts introduced into the evaporative emissions system so achieving compliance presents additional challenges with these items.
10:57	Avoid venting any gas or liquid to atmosphere unless it was vented in stock form.
11:02	Big cams, oversized ports and valves can be great in racecars but they'll most likely prevent you from passing emissions testing on the road.
11:09	Consider whether the parts you're choosing are too wild to have a chance at clean engine operation or not.
11:15	Modest head packages with near stock compression short blocks can maintain proper air velocity, swirl and combustion chamber mixing, retaining more complete combustion and limited emissions.