Vtec / I-vtec / Vtec-e ???
- Thread starter Superfly
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yellowturbo
Guest
VTEC = 1 GEN....
I-VTEC = intelligent vtec
VTEC-E = ecological vtec
je suis pas mal sur si je me trompe corriger moi....
I-VTEC = intelligent vtec
VTEC-E = ecological vtec
je suis pas mal sur si je me trompe corriger moi....
Mothercanucker
Legacy Member
I would like to know as well
voila mon cher
VTEC-E is a twist on the regular VTEC mechanism. Whereas VTEC's purpose can be more or less summarized as: extracting high RPM performance while maintaining smooth low RPM operation, VTEC-E can be summarized as: allow extremely lean fuel-air mixture at low RPMs in order to increase fuel economy. In other words, VTEC technology is used to optimize different ends of the RPM range in the two different implementations
First, some background information. Fuel is mixed with air and then combusted in cylinders to make torque. How much torque is generated is affected directly by how much and how well the fuel and air are mixed together. Less fuel and more air is called a "lean" mixture, the opposite is called a "rich" mixture. For low RPMs, a normal engine's intake charge velocity is low enough that the fuel and air are not mixed together very well. To make up for the sub-optimal mixing effect, a slightly rich fuel/air mixture (more fuel) is needed to maintain smooth operation. VTEC-E artificially increases the intake charge velocity, which creates a swirling effect inside the cylinder. This promotes a very good mixture of the fuel and air, thus allowing a lean fuel/air mixture to be used. The result of this is great fuel economy when running at low RPMs. Indeed, the current Civic HX, a 2400lb coupe, is capable of 37cty/44hwy fuel economy from a 115hp 1.6L VTEC-E engine. Now lets see how VTEC-E works in detail.
Unlike regular VTEC mechanisms, there aren't any extra cam lobes in a VTEC-E engine. So each pair of valves works off of exactly two cam lobes. Since VTEC-E merely increases the low RPM intake charge velocity, it is a mechanism that only affects the operation of the intake valves. VTEC-E is found only in SOHC engines due to its economical intentions. All this means that we only have to look at the two intake cam lobes and the associated rocker arms and valves in order to gain a full understanding of VTEC-E.
A non-VTEC-E engine normally has one single cam profile for the intake valves. A VTEC-E engine has two different intake cam profiles. At low RPMs, each intake valve works from its own intake cam profile. One of the intake cam profiles is very normal looking. The other one, however, is almost perfectly round, with just enough profile to it so that it pushes the valve open just enough to avoid pooling of fuel above the valve lip. Therefore at low RPM, only one intake valve is opening and closing. Most of the intake fuel and air are squeezed through this one valve, resulting in a good swirling effect in the cylinder. The swirling effect optimizes the fuel/air mixture, thus allowing a very lean mixture to be used.
As the RPMs increase, the demand for more fuel/air rises as well. Once a certain RPM is reached (approximately 2500RPM for the Civic HX), the one-intake-valve configuration starts to become a significant intake restriction. At this time, a solid pin is pushed through the two intake valve rocker arms, thus binding the two rocker arms into a single unit. This causes both intake valves to open and close according to the normal cam profile, while the almost-round cam profile is no longer used.
VTEC-E is some times confused to be just another high-RPM optimizing mechanism like other VTEC variants. And there is some truth to this: since only one intake valve is used at low RPMs, the one normal cam lobe is made to open that one valve slightly taller and for longer duration than if both intake valves are used. At higher RPMs, both valves follow this same cam lobe so they are both opened slightly taller and for longer duration. This results in a slight improvement in high RPM breathing compared to non-VTEC-E engines and thus slightly more power. This is evident by comparing the Civic DX and Civic HX engine. The two engines are essentially the same except for the VTEC-E in the Civic HX. But the Civic HX's VTEC-E mechanism results in 115hp, versus 106hp from the Civic DX. So the Civic HX has more power in addition to better fuel economy. But make no mistake, VTEC-E is designed with economy as the primary goal, not power output.
VTEC-E is a twist on the regular VTEC mechanism. Whereas VTEC's purpose can be more or less summarized as: extracting high RPM performance while maintaining smooth low RPM operation, VTEC-E can be summarized as: allow extremely lean fuel-air mixture at low RPMs in order to increase fuel economy. In other words, VTEC technology is used to optimize different ends of the RPM range in the two different implementations
First, some background information. Fuel is mixed with air and then combusted in cylinders to make torque. How much torque is generated is affected directly by how much and how well the fuel and air are mixed together. Less fuel and more air is called a "lean" mixture, the opposite is called a "rich" mixture. For low RPMs, a normal engine's intake charge velocity is low enough that the fuel and air are not mixed together very well. To make up for the sub-optimal mixing effect, a slightly rich fuel/air mixture (more fuel) is needed to maintain smooth operation. VTEC-E artificially increases the intake charge velocity, which creates a swirling effect inside the cylinder. This promotes a very good mixture of the fuel and air, thus allowing a lean fuel/air mixture to be used. The result of this is great fuel economy when running at low RPMs. Indeed, the current Civic HX, a 2400lb coupe, is capable of 37cty/44hwy fuel economy from a 115hp 1.6L VTEC-E engine. Now lets see how VTEC-E works in detail.
Unlike regular VTEC mechanisms, there aren't any extra cam lobes in a VTEC-E engine. So each pair of valves works off of exactly two cam lobes. Since VTEC-E merely increases the low RPM intake charge velocity, it is a mechanism that only affects the operation of the intake valves. VTEC-E is found only in SOHC engines due to its economical intentions. All this means that we only have to look at the two intake cam lobes and the associated rocker arms and valves in order to gain a full understanding of VTEC-E.
A non-VTEC-E engine normally has one single cam profile for the intake valves. A VTEC-E engine has two different intake cam profiles. At low RPMs, each intake valve works from its own intake cam profile. One of the intake cam profiles is very normal looking. The other one, however, is almost perfectly round, with just enough profile to it so that it pushes the valve open just enough to avoid pooling of fuel above the valve lip. Therefore at low RPM, only one intake valve is opening and closing. Most of the intake fuel and air are squeezed through this one valve, resulting in a good swirling effect in the cylinder. The swirling effect optimizes the fuel/air mixture, thus allowing a very lean mixture to be used.
As the RPMs increase, the demand for more fuel/air rises as well. Once a certain RPM is reached (approximately 2500RPM for the Civic HX), the one-intake-valve configuration starts to become a significant intake restriction. At this time, a solid pin is pushed through the two intake valve rocker arms, thus binding the two rocker arms into a single unit. This causes both intake valves to open and close according to the normal cam profile, while the almost-round cam profile is no longer used.
VTEC-E is some times confused to be just another high-RPM optimizing mechanism like other VTEC variants. And there is some truth to this: since only one intake valve is used at low RPMs, the one normal cam lobe is made to open that one valve slightly taller and for longer duration than if both intake valves are used. At higher RPMs, both valves follow this same cam lobe so they are both opened slightly taller and for longer duration. This results in a slight improvement in high RPM breathing compared to non-VTEC-E engines and thus slightly more power. This is evident by comparing the Civic DX and Civic HX engine. The two engines are essentially the same except for the VTEC-E in the Civic HX. But the Civic HX's VTEC-E mechanism results in 115hp, versus 106hp from the Civic DX. So the Civic HX has more power in addition to better fuel economy. But make no mistake, VTEC-E is designed with economy as the primary goal, not power output.
Future_Dubber
New member
so you're the one who stole my name (superfly), pas vraiment
chu plus nouveau que toi... j'ai essaye de prendre ce nom la et
i got screwed..
chu plus nouveau que toi... j'ai essaye de prendre ce nom la et
i got screwed..
i-vtec
Varying the camshaft in relation to the crankshaft is done with engine oil pressure acting on an actuator located on the end of the intake camshaft. The computer varies the oil pressure to change the rotation of the camshaft on its drive sprocket. This changes the valve overlap. Valve overlap is the amount of time both the intake and exhaust valves are open at the same time. Retarding the camshaft decreases the amount of overlap, while advancing the camshaft increases overlap.
Valve overlap plays an important part in engine operating characteristics. Very little overlap gives the engine a smooth idle and good slow speed torque, but it hinders high rpm engine performance. A large amount of overlap allows excellent engine breathing at high rpm but causes a rough idle and poor performance at low rpm. By varying the camshaft rotation and amount of overlap, the engine can have excellent performance at both low and high speeds.
Variable valve lift is accomplished by opening the valves with two different rocker arms and camshaft lobes. In the past, Honda operated VTEC engines with three rocker arms: two to open the two intake valves and a third that could be locked to the other two causing them to follow a different camshaft profile. With the new "two rocker" design, only one valve is opened at lower engine speeds. This causes the intake air fuel mixture to swirl, optimizing combustion at lower engine speeds. At a rpm programmed into the engine computer, oil pressure is used to lock the two rocker arms together. Now both valves open together but follow the higher camshaft profile the second rocker arm follows.
On the Honda CRV and 160 hp Acura RSX, only the intake valves are operated using this system. On the 200 hp Acura RSX Type S, both the intake and exhaust valves use this technology. Like the VTEC system first introduced on the NSX, this operation of both intake and exhaust valves provide maximum horsepower and torque.
Increased performance is one advantage of the i-VTEC system. The torque curve is "flatter" and does not exhibit any dips in torque that previous VTEC engines had without variable camshaft timing. Horsepower output is up, but so is fuel economy. Optimizing combustion with high swirl induction makes these engines even more efficient.
Finally, one unnoticed but major advantage of i-VTEC is the reduction in engine emissions. High swirl intake and better combustion allows more precise air-fuel ratio control. This results in substantially reduced emissions, particularly NOx. Variable control of camshaft timing has allowed Honda to eliminate the EGR system. Exhaust gases are now retained in the cylinder when necessary by changing camshaft timing. This also reduces emissions without hindering performance.
Currently, the Honda CRV and Acura RSX models are the only 2002 models on sale in Canada that meet Tier 2 emission standards which come into effect in 2004. Honda's i-VTEC technology gives us the best in vehicle performance. Fuel economy is increased, emissions are reduced, driveability is enhanced, and power is improved. It is a good possibility to win AJAC's "Best New Technology".
Varying the camshaft in relation to the crankshaft is done with engine oil pressure acting on an actuator located on the end of the intake camshaft. The computer varies the oil pressure to change the rotation of the camshaft on its drive sprocket. This changes the valve overlap. Valve overlap is the amount of time both the intake and exhaust valves are open at the same time. Retarding the camshaft decreases the amount of overlap, while advancing the camshaft increases overlap.
Valve overlap plays an important part in engine operating characteristics. Very little overlap gives the engine a smooth idle and good slow speed torque, but it hinders high rpm engine performance. A large amount of overlap allows excellent engine breathing at high rpm but causes a rough idle and poor performance at low rpm. By varying the camshaft rotation and amount of overlap, the engine can have excellent performance at both low and high speeds.
Variable valve lift is accomplished by opening the valves with two different rocker arms and camshaft lobes. In the past, Honda operated VTEC engines with three rocker arms: two to open the two intake valves and a third that could be locked to the other two causing them to follow a different camshaft profile. With the new "two rocker" design, only one valve is opened at lower engine speeds. This causes the intake air fuel mixture to swirl, optimizing combustion at lower engine speeds. At a rpm programmed into the engine computer, oil pressure is used to lock the two rocker arms together. Now both valves open together but follow the higher camshaft profile the second rocker arm follows.
On the Honda CRV and 160 hp Acura RSX, only the intake valves are operated using this system. On the 200 hp Acura RSX Type S, both the intake and exhaust valves use this technology. Like the VTEC system first introduced on the NSX, this operation of both intake and exhaust valves provide maximum horsepower and torque.
Increased performance is one advantage of the i-VTEC system. The torque curve is "flatter" and does not exhibit any dips in torque that previous VTEC engines had without variable camshaft timing. Horsepower output is up, but so is fuel economy. Optimizing combustion with high swirl induction makes these engines even more efficient.
Finally, one unnoticed but major advantage of i-VTEC is the reduction in engine emissions. High swirl intake and better combustion allows more precise air-fuel ratio control. This results in substantially reduced emissions, particularly NOx. Variable control of camshaft timing has allowed Honda to eliminate the EGR system. Exhaust gases are now retained in the cylinder when necessary by changing camshaft timing. This also reduces emissions without hindering performance.
Currently, the Honda CRV and Acura RSX models are the only 2002 models on sale in Canada that meet Tier 2 emission standards which come into effect in 2004. Honda's i-VTEC technology gives us the best in vehicle performance. Fuel economy is increased, emissions are reduced, driveability is enhanced, and power is improved. It is a good possibility to win AJAC's "Best New Technology".
Last edited:
anthony90si
New member
http://world.honda.com/HDTV/news/2003-4031127a/
this might not be exactely what you are looking for but it give you a great idea on how i-vtec works.
this might not be exactely what you are looking for but it give you a great idea on how i-vtec works.
anthony90si
New member
oops i didn't see the video was already posted!!
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