Well, it has been 15 years since DOHC VTEC hit the US shores in the form of the 1991 Acura NSX...
It has been 5 years since i-VTEC hit the US shores.
VTEC was absolutely a ground breaking technology when it debuted worldwide, as it blurred the traditional compromise between low RPM performance and high RPM horsepower. By incorporating a system that allowed multiple cam profiles on one cylinder, they were able to build engines that had leading edge emmissions and MPG performance, while putting out power numbers and revving to heights that had not been seen from those displacements before.
This allowed Honda to develop a line of engines that had the highest specific outputs ever seen in production engines. The original S2000 still holds that record for NA engines...
Most are used to DOHC VTEC with its distinctive kick in the pants at changeover.
Over time, technologies developed that equalled or exceeded the abilities of VTEC.
Some companies chose to incorporate what is known as "variable cam phasing" to improve their engines power band.
Variable cam phasing has no effect on the lift or duration of the camshaft, rather it is like an electronically adjustable cam gear. Changing the position of the cam gear results in the shifting of the powerband up or down the RPM range. This has become the most common method of "variable valve timing."
Variable cam phasing is the technology that Honda adopted to put the "i" in i-VTEC. They have incorporated it on the intake cam only. The majority of new Honda i-VTEC engines feature VTEC on the intake cam only, with an unadjustable standard camshaft running the exhaust valves. This is true of most K series, the R series, and the J series.
On certain high performance engines, there is VTEC on both intake and exhaust cams. Even on these engines, variable cam phasing is only incorporated on the intake cam.
Eventually, BMW came up with a system called "Valvetronic" that basically uses a series of adjustable rocker arms to vary the amount of lift produced by the intake camshaft. This not only allowed further blurring of the high vs low RPM compromise, it also allowed BMW to eliminate the throttle body on cars equipped with this technology because Valvetronic allows 0" lift and 0" duration. By varying the amount of valve lift, it is possible to throttle the engine using only the intake valves.
Pretty neat stuff.
This brought several advantages with it, not the least of which is improved fuel economy. This occurs because when the throttle plate on a traditional engine is closed, we get what is called a "pumping loss". Basically the valve lift stays the same, and the engine is trying to suck just as much air through an intake system that is closed by the throttle.
This results in a tremendous usage of energy because the engine has to suck really really hard to get air. It also has to suck really really hard on a very large volume (head, ports, IM etc).
Valvetronic virtually eliminates this problem, because now the engine only needs to suck air past the partly open intake valves, so the overall amount of energy used is reduced significantly.
Any time we can get the same job done, while using less energy or harnessing more of it, we are going to burn less fuel.
BMW had previously developed VANOS which is basically variable cam phasing, just like the "i" in i-VTEC. BMW eventually developed it for both the intake and the exhaust cam. I do believe they were the company that introduced this technology to the market.
When coupled with VANOS, Valvetronic allows virtually no compromise in powerband, because we can use Valvetronic to get the best lift and duration for a given RPM, and we can use VANOS to change the cam position in relation to RPM, putting our lobes at the most beneficial point for that particular RPM.
VOILA! High RPM power AND Low RPM torque, while improving gas mileage and improving emmisions. This system also improves throttle response because there is less delay in the cylinder getting what it needs.
The next evolution in variable cam phasing has been the development of electric cam gears. Originally, the gears were controlled by changing the amount of oil passing into the gears.
Electrically operated gears are more precise, and aren't dependent on oil pressure to move (i.e. potentially better at low RPM).
http://www.vtec.net/news/news-item?news_item_id=615777
Here is a link to a new press release from Honda today, about the new technology VTEC system.
It is very similar to BMW's Valvetronic system, and still retains intake cam phasing.
They don't mention whether the exhaust will retain no variable lift, or if it will be equipped with a system similar to DOHC VTEC, where there is a low lift profile and a high lift profile.
The reason for all the focus on the intake side, is that the benefits from adjusting this side of the equation are much larger than adjusting the exhaust side. I suppose as we continue to approach the limit of the reciprocating piston engine, they will eventually incorporate exhaust technology, but that is just speculation.
What we do know, is that this will result in significantly more bottom end torque, while allowing the engine to continue pulling all the way to redline.
It will also reduce fuel consumption by 13%, while allowing an increase in emmissions performance, allowing the engines to meet the toughest standards in the world.
This engine is slated for production within "3 years," but will most likely seen in the next gen Accord.
I hope they incorporate this technology into their V6s soon. It will probably also be featured in their V8 which is currently under development as well.
Just think, perhaps it was VTEC that allowed the great increases in power we have now. It created such a power disparity, that it forced other companies to find ways to meet and leapfrog Honda's technology. The result? More average horsepower per car than we have seen EVER.
We have V6's putting down more than 427's and 428 of years past. Keep in mind too, that HP measurement has gotten lower and lower over the years, so 300HP today is far more than it was in 1969.
Who knows, maybe without VTEC, we would all still be impressed with 120 HP out of 2.2 liters.
It is speculatory, but feasible.
It is a GREAT time to be an enthusiast.
It has been 5 years since i-VTEC hit the US shores.
VTEC was absolutely a ground breaking technology when it debuted worldwide, as it blurred the traditional compromise between low RPM performance and high RPM horsepower. By incorporating a system that allowed multiple cam profiles on one cylinder, they were able to build engines that had leading edge emmissions and MPG performance, while putting out power numbers and revving to heights that had not been seen from those displacements before.
This allowed Honda to develop a line of engines that had the highest specific outputs ever seen in production engines. The original S2000 still holds that record for NA engines...
Most are used to DOHC VTEC with its distinctive kick in the pants at changeover.
Over time, technologies developed that equalled or exceeded the abilities of VTEC.
Some companies chose to incorporate what is known as "variable cam phasing" to improve their engines power band.
Variable cam phasing has no effect on the lift or duration of the camshaft, rather it is like an electronically adjustable cam gear. Changing the position of the cam gear results in the shifting of the powerband up or down the RPM range. This has become the most common method of "variable valve timing."
Variable cam phasing is the technology that Honda adopted to put the "i" in i-VTEC. They have incorporated it on the intake cam only. The majority of new Honda i-VTEC engines feature VTEC on the intake cam only, with an unadjustable standard camshaft running the exhaust valves. This is true of most K series, the R series, and the J series.
On certain high performance engines, there is VTEC on both intake and exhaust cams. Even on these engines, variable cam phasing is only incorporated on the intake cam.
Eventually, BMW came up with a system called "Valvetronic" that basically uses a series of adjustable rocker arms to vary the amount of lift produced by the intake camshaft. This not only allowed further blurring of the high vs low RPM compromise, it also allowed BMW to eliminate the throttle body on cars equipped with this technology because Valvetronic allows 0" lift and 0" duration. By varying the amount of valve lift, it is possible to throttle the engine using only the intake valves.
Pretty neat stuff.
This brought several advantages with it, not the least of which is improved fuel economy. This occurs because when the throttle plate on a traditional engine is closed, we get what is called a "pumping loss". Basically the valve lift stays the same, and the engine is trying to suck just as much air through an intake system that is closed by the throttle.
This results in a tremendous usage of energy because the engine has to suck really really hard to get air. It also has to suck really really hard on a very large volume (head, ports, IM etc).
Valvetronic virtually eliminates this problem, because now the engine only needs to suck air past the partly open intake valves, so the overall amount of energy used is reduced significantly.
Any time we can get the same job done, while using less energy or harnessing more of it, we are going to burn less fuel.
BMW had previously developed VANOS which is basically variable cam phasing, just like the "i" in i-VTEC. BMW eventually developed it for both the intake and the exhaust cam. I do believe they were the company that introduced this technology to the market.
When coupled with VANOS, Valvetronic allows virtually no compromise in powerband, because we can use Valvetronic to get the best lift and duration for a given RPM, and we can use VANOS to change the cam position in relation to RPM, putting our lobes at the most beneficial point for that particular RPM.
VOILA! High RPM power AND Low RPM torque, while improving gas mileage and improving emmisions. This system also improves throttle response because there is less delay in the cylinder getting what it needs.
The next evolution in variable cam phasing has been the development of electric cam gears. Originally, the gears were controlled by changing the amount of oil passing into the gears.
Electrically operated gears are more precise, and aren't dependent on oil pressure to move (i.e. potentially better at low RPM).
http://www.vtec.net/news/news-item?news_item_id=615777
Here is a link to a new press release from Honda today, about the new technology VTEC system.
It is very similar to BMW's Valvetronic system, and still retains intake cam phasing.
They don't mention whether the exhaust will retain no variable lift, or if it will be equipped with a system similar to DOHC VTEC, where there is a low lift profile and a high lift profile.
The reason for all the focus on the intake side, is that the benefits from adjusting this side of the equation are much larger than adjusting the exhaust side. I suppose as we continue to approach the limit of the reciprocating piston engine, they will eventually incorporate exhaust technology, but that is just speculation.
What we do know, is that this will result in significantly more bottom end torque, while allowing the engine to continue pulling all the way to redline.
It will also reduce fuel consumption by 13%, while allowing an increase in emmissions performance, allowing the engines to meet the toughest standards in the world.
This engine is slated for production within "3 years," but will most likely seen in the next gen Accord.
I hope they incorporate this technology into their V6s soon. It will probably also be featured in their V8 which is currently under development as well.
Just think, perhaps it was VTEC that allowed the great increases in power we have now. It created such a power disparity, that it forced other companies to find ways to meet and leapfrog Honda's technology. The result? More average horsepower per car than we have seen EVER.
We have V6's putting down more than 427's and 428 of years past. Keep in mind too, that HP measurement has gotten lower and lower over the years, so 300HP today is far more than it was in 1969.
Who knows, maybe without VTEC, we would all still be impressed with 120 HP out of 2.2 liters.
It is speculatory, but feasible.
It is a GREAT time to be an enthusiast.
R.I.P. 
What field do you work in? I remember something about you wanting to become a pilot...
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