How Does Honda VTEC Work?

today i'm going to show you how vtec works on your honda now vtec stands for variable valve timing and electronic lift control and it's found on many common honda engines today including this 3.2 liter v6 engine out of a third generation acura tl it's a j32a3 model now we don't really know why this engine was scrapped although half of it's already taken apart so we're going to continue tearing this engine down to figure out what's going on inside of the vtec portion at the bottom here and what happens in the head when vtec engages now this engine the vtec solenoid is located down at the bottom here near the oil filter and when it engages it's going to engage vtec in both heads to vary the valve timing and lift and duration just taking a broad look at this engine at the top here we have the air intake platinum we have the two heads where the valves are and their ignition coils respectively at the front of the engine here we have the timing side which uses a timing belt you have the water pump over here the crankshaft at the bottom here and the oil control portion down over here first start by removing this air intake plenum at the top here just a bunch of 12 millimeter bolts and i'm going to lift off that air intake at the back here i'm going to remove this water inlet assembly that houses the thermostat and this egr valve here next up i'm going to remove the valve covers from the top of the engine here and i'll just pop that cover right off i forgot to remove the ignition coils but we don't need those and i'll remove the valve cover for the other side here i've disassembled about four different j-series engines in the last couple of months and i've always noticed that this side of the head here is always much cleaner than this side of the engine head here where you can see it's much more tarnished so i wonder if there's some kind of design flaw in the oil flow or something i'll just remove this timing belt taking a look under this valve cover you could see where the magic happens now if honda's still using a single overhead camshaft on each head which means that there's one camshaft that runs in the middle and it's shared between the exhaust side and the intake side of the top here now the exhaust side is fairly straightforward you just have two exhaust valves per cylinder they each have their own individual rocker that correlates to a spot on the cam shaft over here now looking on the intake side is where things get interesting with vtec you now have three rocker arms and two valves for the intake side of this cylinder that means that these two outside valves here are going to do normal daily driving duties and follow a typical profile on this cam shaft over here to open and close the valve at a preset height that's good for economy and pollution however when you step on it and you want more power the vtec is going to kick on and that's going to enable these middle rockers here which follow a taller profile on this camshaft here and that will allow these valves to open up taller which will give you more air into the engine and with the addition of more fuel from the computer it'll give you more power now because this is only a single overhead cam engine you've only got vtec on the intake side if you were to put it on the exhaust side then things would become a lot more complicated now honda has done that in the newer accurate rls and that's going to give you about 18 rocker arms under one valve cover now as i rotate this camshaft you can see as these rockers move up and down the two outside rockers are moving the same pace as each other same height and same distance here and that's based on these two profiles you'll also notice that this inside rocker here is not locked to the outside rockers now when vtec engages a locking pin is going to lock these together and they're all going to become one piece here and are forced to follow the taller cam profile of the vtec camshaft let's take apart the rest of this engine then we'll have a closer look at that camshaft action now the bottom of the engine here we have the vtec solenoid which is what is responsible for enabling the oil flow to enable those vtec at the top there it's held on by three bolts here and it's also part of this oil filter housing and there's the vtec solenoid and oil housing assembly i'm just going to remove some of these idler pulleys here and unbolt the water pump listen to the knock when i move the crankshaft back and forth next up i'm going to remove the head bolts just break them feet with a breaker bar now with those bolts broken for you i'm going to wind off these head bolts fuel line in the way here and remove that engine head and i'll remove this engine head now as i rotate the engine i don't notice anything else except that this cylinder is super rusty inside just use my wife's little toothbrush here and brush this off see how rusty this piston was it probably had a lot of water built up sitting here now the bottom of the head did not look damaged at all with the exception of these valves here that were on that rusty cylinder showed a little bit of signs of rust so water must have crept into this cylinder and stayed there for a while now it's time to turn this engine over literally oh shoot just use my brother's old shirt here to wipe up that cord next i'm going to remove all the bolts for the oil pan and lift off that oil pad looks pretty clean inside actually i'm going to remove a bunch more 10 millimeter bolts holding the splash guard on and remove the plastic oil pickup tube and this baffle now spinning this engine over i don't notice anything loose or broken so far just go ahead and loosen off the cap bolts here for the connecting rods and then i'll just remove the caps and this cap looks okay bearing looks fine and removing the piston from below this is itself and its bearing looks pretty good although there's a lot of carbon buildup so you can definitely tell that it's either skipped its oil changes or the person driving this engine kicked in vtec a little too much i'm happy to report as honda's engines are pretty strong all the connecting rod bearings look pretty good when removing the piston next i'm going to remove all the main bearing bolts for this crankshaft i'm going to remove a bunch of 10 millimeter bolts and i'm just going to remove that oil pump housing in order to get this crankshaft out i got to remove the rear main seal which is blocked up behind here i'm just going to tilt this down here all right with the engine on the ground here i can remove this rear main seal and then i can remove the main bearings this one looks good i remove that last bearing now all the bearings didn't look good until the crankshaft itself also looks good there's no scoring on any of these bearing surfaces so overall this engine was pretty good mechanically on the bottom end now with the entire engine torn apart here we're gonna take a close look inside this engine head here as to how that vtec works now i'm going to remove all these 12-millimeter bolts that hold these rockers onto the head i'm just going to use the pry bar to remove this up here they are spring-loaded and remove the exhaust rocker arm here just pry up on the intake side here and remove this rocker arm here i'll just pop off the cap from over here this is my brother's little t-shirt again to wipe this up and then with that cap out of the way i can remove this cam shaft now one other thing you notice inside of here is that we have the two springs for the two valves but for that third rocker in the middle here we have its own spring and this is just a return spring to bring it back up to follow that cam profile now taking a look at this rocker arm assembly here you can see we have the two twin rocker arms on the outside here as this one here and this one here and if i remove this bolt here i can slide them out so we can have a closer look now if you look at just the rocker shaft assembly on the bottom of it we have this extra hole here which correlates to an extra hole on the block head now that's going to bring oil that's activated by the vtec solenoid into this rocker arm assembly which is hollow now not only is that going to allow it to lubricate these rocker arms as they move back and forth through these holes here but it's also going to enable the vtec to work by pumping oil through this hole now that oil pressure is going to flow into this first rocker arm through this hole over here and activate this little piston which is going to pop out now that piston is then going to inject over to the second rocker arm which happens to be the one that follows the large cam profile in the middle and that's going to push on this pin over here and it's going to lock these two together because this one's halfway pushed out and this one's halfway pushed in so these two are going to be locked together like that now the third rocker arm here we have this little spring loaded receiver now that pin is going to push from the secondary one into this receiver here and lock these together so now all of these form is sandwiched and they move at the same speed now that return spring is going to help to push this piston back once the oil pressure reduces and v-tech disengages once v-tec disengages the pin from inside of here is going to stay at its steady state in the middle here and not bother the other two rocker arms that work around it therefore these two rocker arms can follow their lower profile again so essentially vtec works in the principle of the two outside rockers following their own individual cam profiles or all these rockers locked together when vtech's engaged so they all move together taking a look at the camshaft assembly these three here the one that control the intake and this rocker arm has this little roller on it that's going to always follow the profile of this cam shaft now the two outer profiles here you can see are exactly the same height and width but the middle profile which is the vtec profile is a little bit taller than this other one here you can see there's a bit of a step that's going to allow that valve to open up just this much more and it's also wider which means that during the rotation of this camshaft it's going to be open for a longer duration of time now technically speaking you can have multiple profiles in like three or four vtec switchover points for higher higher and highest power but then things just get really complicated under this rocker cover now if we take a look at how vtec works on this cheesy drawing that i drew we've got this green cam profile here which is your normal cam profile the rocker arm is going to follow that to move the valve in normal operation it's a little bit lower and it opens the valve a certain amount to allow better fuel mixing and just enough air to get in especially at lower rpms to give you better fuel economy now when vtec kicks in yo at higher rpm it's going to follow this red camshaft profile which is going to angle the rocker a little bit steeper and therefore push the valve down into the cylinder a little bit more now this is on the exhaust side it's going to allow air to escape faster and if this is on the intake side it's going to allow more air to enter for more top end power now if we graph the motion of the valve lifting across the rotation of the camshaft you can see a normal lift it's going to follow this green profile here and it's got a set duration a set timing as well as a set lift now when vtec kicks in it's going to follow this red line and you can see right away it's got a much higher lift which means that that valve is going to be pushed more into the cylinder to allow more air to enter but it also can vary the duration of it by making it a little bit wider here which means that the valve is open for a longer period of time from 0 to 360. we can also shift the peak of when the valve opens so they can open a little bit later to change your engine characteristics now if we take a look at the oil circuit for this engine it's going to start at the bottom here where oil is going to flow into the oil pump through the pickup tube it's then going to flow over to this port over here which is going to correlate to this oil filter housing now the oil filter housing has these two ports over here one that takes oil in and the other one that brings filter oil back out now also part of the oil filter housing is this vtec solenoid now this solenoid is going to direct oil from this port over to this port over here now that's going to correlate to this port on the oil pump housing and that's then going to flow over here to the back over here and then into the engine block now if we take a listen to the solid note as it engages you can hear it click but i don't see the valve moving around inside of here if i move this solenoid out of here you can see that it uses ground and a 12 volt connection to activate and you can see this here is the mechanism inside that has to move the oil from one side here to the other i definitely hear it clicking but i don't see anything moving inside so if your vtec doesn't engage it could be a bad solenoid or a sticking valve that vtec circuit is then going to continue through this oil galley that runs down the middle of the v of this engine is then going to feed oil to the head through these two ports over here the oil from that port is then going to flow through this head bolt hole down into the head to the other side now that oil is then going to come from the bolt hole through a channel over to this little port over here which is going to feed the bottom of the rocker over here and that's what's going to engage the vtec on this rocker arm so the question really is what does vtec do to your engine and if we take a look at this plot here you can see the blue line is your horsepower and the red line is the torque on the engines don't really have much torque anyways right around 5700 rpm is where the vtec changeover point is and you can see right away there's a bump in power so not only does engaging vtec give you a really nice sound when it changes over but it also gives you a sensation that you're getting a little bit more power in a very limited range of rpms so that you can think that your little honda civic is actually fast now there are economy versions of vtec that instead do the opposite instead of giving you a larger cam profile for more power it actually reduces the cam profile to save fuel economy that's called vtec-e now honda was a late bloomer when it came to adopting variable valve timing to their v6 engines now when they do have variable valve timing it's going to have a cam phaser here i've got a video on variable valvetime if you want to see that but when you combine that with vtec honda calls it the i-v-tech system or intelligent vtec now anyone who's owned a honda knows that these vtec gaskets always leak that's because it has to hold so much pressure some of them even have a screen built in that gets clogged up that you have to clean out periodically so the next time vtec kicks in yo you can think of all these components that have to go into making it work now make sure you keep your oil topped up and clean regularly because this system is highly dependent on oil quality and pressure make sure you follow me on instagram for more behind the scenes footage and subscribe for more videos just like this one check out my vtech engine table with this gold and silver theme i've also got my type s engine table here as well as a good old corolla engine table make sure you subscribe if you want to see more tables just like these

Channel: speedkar99

Views: 126,817

Keywords: honda, acura, TL, accord, J-series, J30, J32, J35, J37, RDX, MDX, pilot, odyssey, passport, RL, TLX, RLX, CR-V, civic, VTEC, kicked, in, yo, NOS, boost, modify, ricer, variable, valve, timing, control, phase, camshaft, engine, car, motor, overhead, cam, actuator, oil, pressure, 5w20, strong, power, turbo, rocker, arm, adjustment, gasket, fix, repair, free, efficient, maintenance, toyota, piston, head, cylinder, block, crankshaft, belt, replacement, K20, K24, drive by wire, NSX, lift, duration, filter, mazda, nissan, economy, supercharger, horsepower, torque, racing

Id: hgiwUJKyk3U

Length: 12min 55sec (775 seconds)

Published: Mon Nov 23 2020