The difference between VTEC systems
Joined: Oct 2006
Posts: 1,920
From: British Columbia
The difference between VTEC systems
Here's some info for anyone that’s like me and want to learn more about how VTEC work.
Traditional VTEC system (B18’s with VTEC), each cylinder has 3 intake valves and 3 cam lobes: two (normal/small cam lobes) that are for normal driving (0-4500 RPM) and one (power/large cam lobe) for more aggressive driving (4500-redline) When the engine reaches above 4500 RPM, a pin is hydraulically pushed to lock ALL cam lobes together. Therefore, only the LARGE cam lobe is used, which means more power.
Here’s a video that explains everything PERFECTLY:
http://www.honda-marine.com/video/VTEC.wmv
In the L15A VTEC system, it uses 2 valves for exhaust at all times and it alternates between one and two valves for the intake side. For the L15A VTEC engine, at normal driving, the engine uses one intake valve. When more power is needed, the second valve operates to increase the amount of airflow into each cylinder since valve opening times are shorted with RPM increases. (That sounds really confusing even to me )
Here’s a link where you can learn about the different models of the “1.2l, 1.3l and 1.5l, all SOHC i-DSI designs and finally a 1.5l SOHC VTEC version which is not i-DSI.”
The Truly Amazing Honda Fit/Jazz
Hopefully this helps!!
PS: if I’m wrong, by all means, correct me. I want to make sure that everyone gets the right info including me.
Traditional VTEC system (B18’s with VTEC), each cylinder has 3 intake valves and 3 cam lobes: two (normal/small cam lobes) that are for normal driving (0-4500 RPM) and one (power/large cam lobe) for more aggressive driving (4500-redline) When the engine reaches above 4500 RPM, a pin is hydraulically pushed to lock ALL cam lobes together. Therefore, only the LARGE cam lobe is used, which means more power.
Here’s a video that explains everything PERFECTLY:
http://www.honda-marine.com/video/VTEC.wmv
In the L15A VTEC system, it uses 2 valves for exhaust at all times and it alternates between one and two valves for the intake side. For the L15A VTEC engine, at normal driving, the engine uses one intake valve. When more power is needed, the second valve operates to increase the amount of airflow into each cylinder since valve opening times are shorted with RPM increases. (That sounds really confusing even to me )
Here’s a link where you can learn about the different models of the “1.2l, 1.3l and 1.5l, all SOHC i-DSI designs and finally a 1.5l SOHC VTEC version which is not i-DSI.”
The Truly Amazing Honda Fit/Jazz
Hopefully this helps!!
PS: if I’m wrong, by all means, correct me. I want to make sure that everyone gets the right info including me.
Member
Joined: Dec 2006
Posts: 289
From: Northern, VA
wow,, i never knew my fit has such a complicated engine...
Great Engine... then it must be tranny with much friction causing bad mpg in auto model..
great info..
thanks..
Moderator.. this should be a "sticky"..
Great Engine... then it must be tranny with much friction causing bad mpg in auto model..
great info..
thanks..
Moderator.. this should be a "sticky"..
Last edited by bestfit; Mar 1, 2007 at 12:58 AM.
Joined: Oct 2006
Posts: 1,920
From: British Columbia
Member
Joined: Apr 2006
Posts: 1,202
From: New YOrk
To "Toy Yota"
Quote : "valve opening times are shorted with RPM increases"
That is what engine builders would call the "natural flaw" of an engine. As the engine increases revolutions speed, the amount of intake is shortened kind of like choking.
How VTEC aids this situation is by adding an additional Valve per cylinder to make the engine breathe better and thus perform better than as apposed to choking and not performing as well.
SO it can be seen as no matter how some people may dispute it, our VTEC systems were built for overall engine performance.
(It just so happens that it also was a good way to save on fuel effiency with one valve in the lower RPM's and a lower fuel trim!) **for those who understand**
Quote : "valve opening times are shorted with RPM increases"
That is what engine builders would call the "natural flaw" of an engine. As the engine increases revolutions speed, the amount of intake is shortened kind of like choking.
How VTEC aids this situation is by adding an additional Valve per cylinder to make the engine breathe better and thus perform better than as apposed to choking and not performing as well.
SO it can be seen as no matter how some people may dispute it, our VTEC systems were built for overall engine performance.
(It just so happens that it also was a good way to save on fuel effiency with one valve in the lower RPM's and a lower fuel trim!) **for those who understand**
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