|
VTEC, like most things in life, is not for everyone. To decide whether VTEC is for you or not,
here are the pros and cons.
Pros
The main benefit of VTEC is that the resulting engine is very versatile. The torque curve is
very flat: among the flatest of all the engines on the market. Thus where other engines are running out of breath, a VTEC
engine maintains a nice and steady output of torque, making the whole RPM range usable for acceleration. So when you are
just driving around at a reasonable pace, the car is very smooth and fuel consumption is similar to other engines of the
same displacement. When you need more power for passing, all you have to do is down shift and take advantage of the extra
power available at the higher RPMs. So you get the smoothness and fuel efficiency of a small economical engine when you
drive a low RPMs, and the power output of a much larger engine at high RPMs.
Due to the greater range of usable RPMs, shorter gears can be used. Thus for any given
speed or engine RPM, a VTEC engine will allow for a larger ratio multiplier, resulting in more wheel torque. Thus
the benefit of the VTEC technology in terms of acceleration improvement also affects low RPM operation.
Since VTEC creates more power without increasing displacement, the engine is likely to be
smaller and lighter.
Cons
A vehicle achives its greatest acceleration by keeping the engine RPM as close to the HP peak
as possible. And for DOHC VTEC engines, this means keeping the needle at some rather lofty RPMs, and more frequent shifts
to keep the RPMs up. To some people, including yours truely, this is a desirable trait: lots of driver involvement in the
process of extracting excellent performance. To others, especially those accustomed to the Kansas-flat HP curves of muscle
cars, the high RPM and frequent shifts become bothersome.
For a good launch off the line, such as at the start of a drag race, a certain amount of tire
spin is desired. Muscle cars have torque peaks at low RPMs, and then taper off as the RPM builds. This is perfect for drag
racing as the initial torque peak generates the desired tire spin, and then the lower torque at higher RPMs allow the tire to
find and maintain grip. But DOHC VTEC's torque curve is very flat, so the initial tire slip is much harder to generate. And
once the tire looses traction, the flat torque curve makes it hard for the spinning wheels to find traction. So to properly
launch a DOHC VTEC car, the driver must slip the clutch at high RPMs to generate the initial tire spin, and then carefully
modulate the clutch and gas to regain drive wheel traction while maintaining maximum acceleration.
Even though Honda's VTEC engines has lived up to the legendary reliability of Honda products,
the fact remains that having the VTEC mechanism adds complexity and cost.
----------------------------------------------------------------------------------------------------------------------
The info on this page is a copy of the webarchive.org pull of www.leecao.com, which at the time of this posting this (10/31/2007) was no longer a valid site.
| |