Vtec/hp??
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Instructor
Joined: Jan 2008
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Vtec/hp??
I was thinking about this and im kinda confused. What exactly does vtec do for HP related reasons? I know that when in vtec additional valves open up allowing for more air but what exactly does this do? Create more HP? Would the TL have less hp with the same motor without vtec? Any help appreciated.
Intermediate
Joined: Feb 2009
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From: Escondido California
well first of all no additional valves are opened they ( the valves) are just opened longer, allowing more air and fuel to enter the combustion chamber, and yes the same motor without Vtec will not have the same amount of horsepower as one with vtec
Burning Brakes
Joined: Feb 2008
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From: QUEENS NYC
http://www.youtube.com/watch?v=AcT_ZyY3F0k this will explain evverything
Team Owner
Joined: Sep 2006
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more air means more fuel means more combustion means more torque
VTEC also delays the opening of the 2nd intake valve causing a tornado like swirl of air into the cylinders--
people scoff at the tornado device,,,--we have one built into the engine operation!!!
VTEC also delays the opening of the 2nd intake valve causing a tornado like swirl of air into the cylinders--
people scoff at the tornado device,,,--we have one built into the engine operation!!!
Safety Car
Joined: Jan 2006
Posts: 4,442
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From: Houston, Texas
When VTEC activates, the engine switches to a much more radical (aggresive) cam profile. Just like Superman.. mild mannered Kent (mild cam profile) for normal driving. But when provoked, it switches into Superman (racing cam profile).
Team Owner
Joined: Sep 2006
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iirc the actual happening is a longer open duration of the intake valves and possibly more lift via the 2nd valve cam profile, plus the delayed open of 2nd valve for the tornado action
I call it going from v6 mileage to v8 mileage
I call it going from v6 mileage to v8 mileage
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2008 tl-s sleeping in
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From: AC.NJ
Thread Starter
Instructor
Joined: Jan 2008
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I guess my question is - lets say the tl has 260 hp vs another car with 260 hp, will vtec do anything special to let the tl win the race? Does the TL always have 260 hp or only when vtec engages? Do you guys get what im saying?
10th Gear
Joined: Aug 2009
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vtec in a 3.2 TL is mild at best. Yeah it's there but not anything like the old honda motors. I had and old 97 civic ex 1.6 and that was "vtec just kick in YO"
My 05 TL is "where's vtec YO". Another great motor was the old integras GSR
My 05 TL is "where's vtec YO". Another great motor was the old integras GSR
Three Wheelin'
Joined: Nov 2001
Posts: 1,649
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From: Millersville, Md.
Here is the answer you are looking for. At low rpm's, engines need a mild cam for smooth idle, decent torque upon initial acceleration and low emissions. Hopefully you know that the cam lobes control how long the valves are held open AND how deep. As rpm's increase, power eventually falls off as the engine begins to sufficate with that mild cam. If only we could change cams enroute.......voila VTEC. Up to 4000 rpms (whatever) the intake valve runs off the mild cam lobe but above that, it switches to the bigger lobe. The engine can now breath and the computer adds fuel to keep the air/fuel ratio correct and hence, more power. There in a nutshell I hope is your answer. BTW here is a question: Why not just put in a big cam for all the time? You could, but you would fail emissions, driveability would suffer and your idle would be rough as if it were misfiring.
Team Owner
Joined: Mar 2006
Posts: 20,172
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From: Bakersfield
Here is the answer you are looking for. At low rpm's, engines need a mild cam for smooth idle, decent torque upon initial acceleration and low emissions. Hopefully you know that the cam lobes control how long the valves are held open AND how deep. As rpm's increase, power eventually falls off as the engine begins to sufficate with that mild cam. If only we could change cams enroute.......voila VTEC. Up to 4000 rpms (whatever) the intake valve runs off the mild cam lobe but above that, it switches to the bigger lobe. The engine can now breath and the computer adds fuel to keep the air/fuel ratio correct and hence, more power. There in a nutshell I hope is your answer. BTW here is a question: Why not just put in a big cam for all the time? You could, but you would fail emissions, driveability would suffer and your idle would be rough as if it were misfiring.
To add to that, vtec keeps the torque curve very flat instead of falling off as rpms increase. Since hp is a function of torque and rpm, torque remains flat and hp rises all the way to redline.
If you have ever heard a muscle car with a large cam and lopey idle you know the disadvantages of a large cam. This is the best of both worlds. A mild profile for idle, emissions, and normal driving and a wild profile as rpms get up there.
To some of the other posters, hp is hp. Vtec is nothing special, it can't help you to win a race in any other way than to provide additional hp.
If you were to use the "big" vtec cam profile all the time the car would make the same peak hp numbers but it would lose low end power and would not pass emissions.
Also, you can't feel it as much on the TL as it only acts on the intake valves. What I noticed right away the first time I floored the car was it idles smooth, has ok low end yet pulls all the way to the revlimiter without running out of breath. While it's not real noticable, if you're used to a normal car like my GN, it pulls like crazy down low and then starts falling off around 4,900rpm instead of pulling strong to the redline.
Three Wheelin'
Joined: Jul 2007
Posts: 1,557
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From: GSO, NC
Very good explanation.
To add to that, vtec keeps the torque curve very flat instead of falling off as rpms increase. Since hp is a function of torque and rpm, torque remains flat and hp rises all the way to redline.
If you have ever heard a muscle car with a large cam and lopey idle you know the disadvantages of a large cam. This is the best of both worlds. A mild profile for idle, emissions, and normal driving and a wild profile as rpms get up there.
To some of the other posters, hp is hp. Vtec is nothing special, it can't help you to win a race in any other way than to provide additional hp.
If you were to use the "big" vtec cam profile all the time the car would make the same peak hp numbers but it would lose low end power and would not pass emissions.
Also, you can't feel it as much on the TL as it only acts on the intake valves. What I noticed right away the first time I floored the car was it idles smooth, has ok low end yet pulls all the way to the revlimiter without running out of breath. While it's not real noticable, if you're used to a normal car like my GN, it pulls like crazy down low and then starts falling off around 4,900rpm instead of pulling strong to the redline.
To add to that, vtec keeps the torque curve very flat instead of falling off as rpms increase. Since hp is a function of torque and rpm, torque remains flat and hp rises all the way to redline.
If you have ever heard a muscle car with a large cam and lopey idle you know the disadvantages of a large cam. This is the best of both worlds. A mild profile for idle, emissions, and normal driving and a wild profile as rpms get up there.
To some of the other posters, hp is hp. Vtec is nothing special, it can't help you to win a race in any other way than to provide additional hp.
If you were to use the "big" vtec cam profile all the time the car would make the same peak hp numbers but it would lose low end power and would not pass emissions.
Also, you can't feel it as much on the TL as it only acts on the intake valves. What I noticed right away the first time I floored the car was it idles smooth, has ok low end yet pulls all the way to the revlimiter without running out of breath. While it's not real noticable, if you're used to a normal car like my GN, it pulls like crazy down low and then starts falling off around 4,900rpm instead of pulling strong to the redline.
Team Owner
Joined: Mar 2006
Posts: 20,172
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From: Bakersfield
VTEC is probably the most basic of all variable valve timing/lift. iVTEC I believe can vary cam timing and duration, not just on or off like regular VTEC. Nearly every manufacturer has some sort of variable valve timing, duration, and overlap. Same concept, same purpose, nearly the same execution. With some of the newer systems, the EGR valve can be eliminated altogether because the variable cam timing and overlap can be used for a natural EGR effect.
BMW engines have their own version of VTEC as well. More advanced of course.
