🛠 Tuning with Volumetric Efficiency and other VE fun facts | TECHNICALLY SPEAKING

[Music] greetings earthlings matt from healthtech here today's topic is volumetric efficiency or ve for short we've got lots to cover so let's get into it [Music] volumetric efficiency or ve is a measure of the actual amount of air that is moved through an engine versus the engine's cubic capacity so you may have heard the saying that an engine is just an air pump what that's saying means is if we just forget for a moment about the process of combustion that happens when the valves are closed for every engine cycle all we're really doing is taking air from the intake manifold sucking it into the combustion chamber and then pumping it out into the exhaust manifold or simply pumping air from intake to exhaust thus the engine is just an air pump if we think now of our engine as just an air pump we know that for every engine cycle our pump should suck in and pump out again a fixed volume of air that fixed volume of air that our engine should pump is equal to the engine's cubic capacity so a 350 cubic inch engine should move 350 cubic inches of air or 5.7 liters or whatever the capacity of your engine is but if we're to put a flow meter in front of our air pump and we actually measure the amount of air that is being pumped in and out what we find is that it doesn't always equal the engine's capacity it's normally a little bit lower and that's because the engine is not 100 efficient at moving air from the intake to the exhaust if it was we'd say the engine has a 100 percent volumetric efficiency and much of the work in engine design and engine building is focused on improving this volumetric efficiency things like intake runners exhaust headers valves camshafts they all play a big part in how efficient our air pump is at moving air from the intake to the exhaust so that's volumetric efficiency it's a measure of the actual amount of air that moves through an engine versus that engine's cubic capacity but why is it important to us as engine tuners or calibrators the answer to that is simple volumetric efficiency tells us how much air is going into the engine knowing how much air is going to the engine is really important to figuring out how much fuel to deliver to the engine the right mix of air and fuel or air-to-fuel ratio is critically important to not just making good horsepower but also ensuring that an engine runs reliably and predictably for many many miles now i said previously engine design considerations like intake runners exhaust headers valves and camshafts all affect ve but once the engine is together they're all pretty well locked in and fixed when the engine is actually up and running the biggest factors that affect how efficiently our engine can pump air are engine load and engine speed so now we're starting to put all the pieces together volumetric efficiency is important because it allows us to know how much air is going into the engine that information is used to determine how much fuel to deliver to the engine volumetric efficiency varies with rpm and engine load which is why the fuel map in your haltech tuning software has rpm and engine load as the two axes on map now if you're happy with that overview explanation press pause now head back to the main healthtech youtube channel and watch some more of scotty the tuning fork making big power on the dyno [Music] alright so you're still here which means you want to be a rocket surgeon nothing i'm about to say invalidates that previous definition of volumetric efficiency it's just that technically it's a really poor definition because we don't actually measure the volume of air or anything else for that matter that goes through an engine volume is a measure of three-dimensional space it's cubic centimeters or cubic inches air on the other hand is gas or at least a mixture of gases you can't measure air as a volume it's a bit like me saying that i'm going to measure the weight of my arm in dollars like it makes no sense they're different things one is a weight now there is currency now on the other hand if we said arms are worth a dollar a pound and my arm is 20 pounds then i've got a 20 arm that works that's a lot more like what we actually do with volumetric efficiency we have a known volume of the engine and we want to calculate the mass or weight of air that passes through the engine in one engine cycle and we compare that to the mass of air that would reside in that engine as its total volume so possibly more correctly volumetric efficiency would be better described as the actual mass of air that passes through our engine in one engine cycle versus the mass of air that would be found in the cubic capacity of that engine but that that's all a little bit wordy and possibly confusing so we'll just stick with the previous definition from earlier but be aware it's the mass of air that we're interested in that's really important to know because mass is affected by temperature and pressure this isn't really a problem though we can control for it because we measure both air temperature with the intake air temp sensor and air pressure with the map or manifold pressure sensor so if you're running 15 or 30 or 60 psi of boost that doesn't double triple or quadruple our engine efficiency i mean how could it our air pump didn't get more efficient at pumping air from intake to exhaust just because you added air into the intake at a higher pressure no our air pump is equally efficient under boost we make more power because of the higher air mass in the same air volume but we're no more efficient at moving that air from one point to another but hang on didn't i say earlier that ve varies with rpm and engine load and the fuel map axes are based on these two variables precisely because they change the ve you don't need to rewind i did say that and now i'm saying that boost does not change ve isn't this a direct contradiction i'm contradicting myself here well yes and no yes on the service that sounds contradictory but no boost alone does not change ve let's zoom in a bit and take a look at where this boost comes from so most of the time we're getting boost from a turbocharger and what is a turbocharger well it's another air pump and this air pump has its own set of efficiencies one on the intake side or one on the exhaust side and this turbo air pump directly affects the engine air pump efficiency because it's actually a restriction on both the intake side and the exhaust side of the engine air pump so this is not the case for superchargers on the other hand while they too are an air pump and they have their own efficiency they don't affect the engine air pump efficiency because they're not a restriction on either side of the intake or exhaust so therefore they have no effects on engine ve so while we're down here in the weeds it's worth mentioning another big restriction the one that we intentionally put in place and whose sole purpose is to actually reduce engine efficiency the throttle yeah that's a pretty big restriction to the air intake and it plays a really big part in engine ve as well alright so let's just back it out again and try and make sense of all this information we use ve to determine how much air is going into the engine so we can calculate how much fuel to deliver to that engine once the engine is bolted together ve will vary with rpm and engine load but engine load is controlled by the throttle so we certainly could and often do use the throttle position as one of the axes in the ve table instead of manifold pressure although with that said most people are familiar with using manifold pressure as the load axis of the ve table which is actually fine too because the only way to get vacuum into the intake manifold is to close the throttle so manifold pressure correlates pretty consistently with throttle position anyway in the vacuum areas of the map now on the positive pressure side of things because the turbo sits as a restriction on both the intake and the exhaust side of the engine pump and both the compressor and the turbine wheels have their own separate efficiency curves it's not uncommon to see changes in engine ve with a change in boost due to the turbocharger's efficiency affecting engine efficiency so as you can see it's perfectly acceptable to be using either manifold pressure or throttle position as the load axes along with rpm when you're tuning an engine in ve mode now then of course there's things like variable cam timing or the cooling effect of methanol on the incoming air charge or wastegate opening exhaust back pressure intake bleed valves nitrous injection the list goes on but i don't have time to cover all of these topics today the underlying principles of tuning all ve based systems are the same the ecu needs to know a few basic parameters and with that it can do some real magic the basic parameters that the ecu needs to know are engine volume manifold pressure intake air temperature and because the ecu is going to use this information about the mass of air going into the engine to calculate how long to open the fuel injectors you also need to tell the ecu some information about the fuel system so equally important as the ve map is accurate data on your injector flow rate and injected dead time so now that the ecu is reading the actual intake air temperature from the air temp sensor and the actual intake air pressure from the manifold pressure sensor it can calculate the mass of air that should be entering the engine based on the engine's capacity the ecu then looks over to the base fuel map or the ve map to find out how efficiently the engine pumps air from intake to exhaust to any given rpm and load with this information an accurate calculation of the actual mass passing through the engine at any point in time can be made now of course knowing the mass of air going through the engine isn't the end goal here delivering fuel to the engineers so knowing the mass of the air going through the engine ecu looks over the target air fuel ratio map to determine the mass of fuel that needs to be delivered so let's stop there for a second we've all heard the term air fuel ratio but did you know that when we say we want an airfue ratio of say 14 to 1 we're actually talking about the relative mass of air going through the engine to the relative mass of fuel we want to go through the engine so 14 1 means for every 14 kilograms of air that passes through we need to deliver one kilogram of fuel 14 to 1. now of course different fuels have different densities and different stoichiometric air to few ratios so all ve based systems will have a setting to let these you know what the density of fuel you're using are and somewhere to set the stoichiometric air to your ratio of the fuel you're using now the ecu has enough information to both determine the mass of air entering the engine and calculate the mass of fuel it needs to deliver out to the fuel injections to give you the fu ratio that you're targeting in your target fu ratio map but what happens now well we measure it we measure to see if all of that math worked we grab a wideband o2 sensor we put it in the exhaust this sensor tells us what the actual mass of burned fuel is to the actual mass of burned air we take this reading of actual combusted air and fuel and we compare it to the target air fuel ratio map and if the actual fu ratio does not match up to our target then one of our settings is wrong it could actually be any of our settings that i mentioned earlier it could be that you've entered the incorrect flow rate for your injectors it could be you've told the ecu an incorrect engine capacity it could be that your map sensor or air temp sensor are reading incorrectly but they're actually all fairly easily checked the most likely thing is that the ve number that is entered into your base fuel map is not actually correct for the volumetric efficiency of your particular engine at that particular point in time so we're at a point now where we move on to the actual process of tuning or calibrating the fuel map which when you boil it all down is just the process of adjusting each of the cells in the ve map until the actual airfue ratio that we read on the o2 sensor matches the target air fuel ratio that we have in the target fue ratio map now traditionally we do this on a dyno but that is a video for another day so let's do a quick recap volumetric efficiency or ve is the measure of the actual amount of air that is moved through an engine versus the engine's cubic capacity the engine's volumetric efficiency map is used in an engine control system to calibrate how much fuel to deliver to the engine it's important to ensure that you enter the correct engine capacity inject the flow rate and target air fuel ratio if you want the system to respond how you expect it to alright i know this has been a long video so thank you for sticking with me until the end i'm matt from haltech i'm heading back now to my spaceship with my mask don't forget like us on the socials follow us on youtube ring that bell for updates i'll see you next time [Music] you

Channel: Haltech

Views: 116,593

Keywords: haltech, ecu, engine management, tuning, engine tuning, technically speaking, volumetric efficiency, ve, tuning using ve, ve tuning, tuning tech, tuning tech tips, internal combustion engine, four stroke engine, tuning basics, programmable engine management, tuning a car, ignition tuning basics, how to tune a car, how to tune, efi tuning

Id: E96rBIzZ_sE

Length: 13min 50sec (830 seconds)

Published: Mon Jul 12 2021