Vtec
05-19-2004, 04:12 PM
#4
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Originally Posted by KilroyR1
Try as I might, I still can't detect the switchover.
Don
Don
05-19-2004, 05:47 PM
#5
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Ha, talking about Prelude... yes, you will feel the sensational change-over... I always remember the first time I hit Vtec point in my friend's Prelude...
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05-19-2004, 08:49 PM
#8
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From Acura of Canada's site:
Acura VTEC™ (Variable Timing and Lift Electronic Control) gives the TL engine strong low-speed torque and response coupled with class-leading high RPM horsepower. The TL VTEC system has two distinct modes of operation for the engine’s 12 intake valves. At low speeds, the intake valves have low lift and are open a comparatively short period of time during cylinder filling. At high RPM where breathing is critical, the valves switch to high-lift, long duration mode to deliver the best volumetric efficiency possible. The VTEC changeover point occurs at 4700 RPM, takes just 0.1 second and is undetectable to the driver.
In the new TL, the VTEC system continues to be the 3-rocker type, which allows each of a given cylinder’s intake valves to be controlled by its own low-speed cam lobe. (By comparison, with 2-rocker VTEC, both intake valves in a given cylinder are controlled by a single low-speed cam lobe). With different low-speed cam profiles for each intake valve, 3-rocker VTEC allows for staggered valve opening and lift. This promotes swirl in the combustion chambers, which improves efficiency. With better mixing in the cylinders, burn speed and combustion stability are improved. When engine RPM reaches 4700 RPM, the Powertrain Control Module (PCM) triggers the opening of an electric spool valve that routes pressurized oil to small pistons in the intake valve rocker arms. These pistons slide into position to lock together the three intake rockers in a given cylinder, which then follow a single high-lift, long-duration cam lobe. With the engine’s intake valve lift and opening duration continuously adjusted to suit the operating engine speed, the TL benefits with a broad torque curve and superior peak power.
Acura VTEC™ (Variable Timing and Lift Electronic Control) gives the TL engine strong low-speed torque and response coupled with class-leading high RPM horsepower. The TL VTEC system has two distinct modes of operation for the engine’s 12 intake valves. At low speeds, the intake valves have low lift and are open a comparatively short period of time during cylinder filling. At high RPM where breathing is critical, the valves switch to high-lift, long duration mode to deliver the best volumetric efficiency possible. The VTEC changeover point occurs at 4700 RPM, takes just 0.1 second and is undetectable to the driver.
In the new TL, the VTEC system continues to be the 3-rocker type, which allows each of a given cylinder’s intake valves to be controlled by its own low-speed cam lobe. (By comparison, with 2-rocker VTEC, both intake valves in a given cylinder are controlled by a single low-speed cam lobe). With different low-speed cam profiles for each intake valve, 3-rocker VTEC allows for staggered valve opening and lift. This promotes swirl in the combustion chambers, which improves efficiency. With better mixing in the cylinders, burn speed and combustion stability are improved. When engine RPM reaches 4700 RPM, the Powertrain Control Module (PCM) triggers the opening of an electric spool valve that routes pressurized oil to small pistons in the intake valve rocker arms. These pistons slide into position to lock together the three intake rockers in a given cylinder, which then follow a single high-lift, long-duration cam lobe. With the engine’s intake valve lift and opening duration continuously adjusted to suit the operating engine speed, the TL benefits with a broad torque curve and superior peak power.
05-20-2004, 10:51 AM
#9
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Originally Posted by Aegir
From Acura of Canada's site:
Acura VTEC™ (Variable Timing and Lift Electronic Control) gives the TL engine strong low-speed torque and response coupled with class-leading high RPM horsepower. The TL VTEC system has two distinct modes of operation for the engine’s 12 intake valves. At low speeds, the intake valves have low lift and are open a comparatively short period of time during cylinder filling. At high RPM where breathing is critical, the valves switch to high-lift, long duration mode to deliver the best volumetric efficiency possible. The VTEC changeover point occurs at 4700 RPM, takes just 0.1 second and is undetectable to the driver.
In the new TL, the VTEC system continues to be the 3-rocker type, which allows each of a given cylinder’s intake valves to be controlled by its own low-speed cam lobe. (By comparison, with 2-rocker VTEC, both intake valves in a given cylinder are controlled by a single low-speed cam lobe). With different low-speed cam profiles for each intake valve, 3-rocker VTEC allows for staggered valve opening and lift. This promotes swirl in the combustion chambers, which improves efficiency. With better mixing in the cylinders, burn speed and combustion stability are improved. When engine RPM reaches 4700 RPM, the Powertrain Control Module (PCM) triggers the opening of an electric spool valve that routes pressurized oil to small pistons in the intake valve rocker arms. These pistons slide into position to lock together the three intake rockers in a given cylinder, which then follow a single high-lift, long-duration cam lobe. With the engine’s intake valve lift and opening duration continuously adjusted to suit the operating engine speed, the TL benefits with a broad torque curve and superior peak power.
Acura VTEC™ (Variable Timing and Lift Electronic Control) gives the TL engine strong low-speed torque and response coupled with class-leading high RPM horsepower. The TL VTEC system has two distinct modes of operation for the engine’s 12 intake valves. At low speeds, the intake valves have low lift and are open a comparatively short period of time during cylinder filling. At high RPM where breathing is critical, the valves switch to high-lift, long duration mode to deliver the best volumetric efficiency possible. The VTEC changeover point occurs at 4700 RPM, takes just 0.1 second and is undetectable to the driver.
In the new TL, the VTEC system continues to be the 3-rocker type, which allows each of a given cylinder’s intake valves to be controlled by its own low-speed cam lobe. (By comparison, with 2-rocker VTEC, both intake valves in a given cylinder are controlled by a single low-speed cam lobe). With different low-speed cam profiles for each intake valve, 3-rocker VTEC allows for staggered valve opening and lift. This promotes swirl in the combustion chambers, which improves efficiency. With better mixing in the cylinders, burn speed and combustion stability are improved. When engine RPM reaches 4700 RPM, the Powertrain Control Module (PCM) triggers the opening of an electric spool valve that routes pressurized oil to small pistons in the intake valve rocker arms. These pistons slide into position to lock together the three intake rockers in a given cylinder, which then follow a single high-lift, long-duration cam lobe. With the engine’s intake valve lift and opening duration continuously adjusted to suit the operating engine speed, the TL benefits with a broad torque curve and superior peak power.
Is it really undetectable to the driver?
05-20-2004, 11:19 AM
#10
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I can feel and hear when the VTEC switches over. Its subtle but engine note changes slightly and there's a little bit more "giddy up"
in my prelude SH it was almost like a freakin' turbo when the VTEC switched. But then again I really missed having torque, hence I have a TL now.
in my prelude SH it was almost like a freakin' turbo when the VTEC switched. But then again I really missed having torque, hence I have a TL now.
05-20-2004, 01:03 PM
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Originally Posted by 92NSX
Awesome post. Thank you very much for that. I guess my original post came across like I didn't believe what was being said. I apologize for that. It just seemed strange that the switchover point would be lowered that much for the new car. Obviously I was wrong. Glad to hear it though.
Is it really undetectable to the driver?
Is it really undetectable to the driver?
http://www.honda.ca/AcuraEng/Models/...CTION%20SYSTEM
05-20-2004, 03:06 PM
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Originally Posted by Aegir
Awesome link! Thanks.
05-20-2004, 03:17 PM
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ok maybe this is just me but how come people treat vtec like it was some kind of turbo. its valve timing control to adjust the timing of how long the valves open and close. what i notice is people saying that "vtec kicked in and the car took off". if this is true then why wouldn't the car turn on vtec much earlier. i was under the impression that this system allowed the engine to run more efficiently and perform better under high and low rpms and not some extra boost. if you take a look at the dynos there isn't a spike in hp or torque at 4700rpm, just a consistent smooth climb.
05-20-2004, 03:24 PM
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I think on some of the 4 cylinder such as the old Civic Si, Prelude, it did almost feel like a turbo spooled up. Reason being, when the "VTEC kicked in", the valves would stay open longer and the engine would "breathe" better at the higher rpms. On those cars, it was such a marked difference, that you really could feel the engine almost pull right to redline, like it wanted to be thrashed...I've never driven the Prelude, just been a passenger in one.
With the TL, I do notice a slight difference in sound, but not as much in the pull because the engine is so strong anyway...
With the TL, I do notice a slight difference in sound, but not as much in the pull because the engine is so strong anyway...
05-20-2004, 03:27 PM
#15
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Besides Prelude, I don't feel Vtec would kick in like Turbo... but what ppl upstairs said may just mean how excited they are after 4700 RPM...
Any car driving in high RPM will make drivers thrilled, and this 270 HP 04TL would make ppl feel even better...
Any car driving in high RPM will make drivers thrilled, and this 270 HP 04TL would make ppl feel even better...
05-20-2004, 03:37 PM
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Originally Posted by rets
Besides Prelude, I don't feel Vtec would kick in like Turbo... but what ppl upstairs said may just mean how excited they are after 4700 RPM...
Any car driving in high RPM will make drivers thrilled, and this 270 HP 04TL would make ppl feel even better...
Any car driving in high RPM will make drivers thrilled, and this 270 HP 04TL would make ppl feel even better...
05-20-2004, 09:11 PM
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Originally Posted by mobilezen
With a APEX-i VAFC...VTEC can kick in whenever you feel like. 
05-21-2004, 01:40 AM
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I had a buddy with a 1999 Prelude. We thought the VTEC was awesome in that car...until I got an S2000. When the VTEC kicks in on an S2000 it is VERY noticable. It feels like another bank of cylinders just got turned on and the sound is the best thing this side of a Ferrari. Everyone should experience it.
05-21-2004, 04:52 PM
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Originally Posted by texas_acura
I had a buddy with a 1999 Prelude. We thought the VTEC was awesome in that car...until I got an S2000. When the VTEC kicks in on an S2000 it is VERY noticable. It feels like another bank of cylinders just got turned on and the sound is the best thing this side of a Ferrari. Everyone should experience it.
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