Interesting read on GM's VVT and Honda's VTEC
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Joined: Mar 2005
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Interesting read on GM's VVT and Honda's VTEC
I don't know if any of you guys follow domestic engine's, but GM's ecotech is kind of the lastest craze in the domestic compacts. Recently they incorporated VVT into the ecotech engine. Drastic differances between the two techs:
I think there are alot of people that might be confussed as far as people thinking that the 2.4 ECOTECs have V-TEC or plainly just don't know what Variable Valve Timing is or does and what the difference is between Variable Valve Timing & V-TEC.
I know what it is but here is a better explination...
Variable Valve Timing itself
Now V-TEC
Now the 2.4 ECOTEC Variable Valve Timing technology is mainly from Toyota, just like how the Toyota Celica GT-S, Toyota Matrix and Pontiac Vibe uses them. I want to say that the 2.4 VVT is more so like the Toyota VVT-i technology.
Toyota VVT-i
Now some of you might think to yourselves "How come the 2.4 has more torque than a V-TEC motor and they both have Variable Valve Timing?". That's simple....displacement, powerband & compression play a huge part of that. Example: The GSR Motor runs a 1.8L and 10:1 compression...a good amount of compression but small amount of displacement. Alot of the Honda motors also can Rev higher than the ECOTEC in stock form. They rely on high revs, short stroke and variable valve timing to make power. If you ever hear people say "Hondas make more horsepower to comphensate for torque"...that's kind of a BS thing to say.
So with that said, torque is needed in most cases. Also, the CFM of a V-TEC cylinder head is bigger than a stock ECOTEC cylinder head for the purpose of supplying more airflow at higher RPMs. Honda motors rev higher, need more air....ECOTECs don't relatively rev that high so they use smaller ported cylinder heads. The use of smaller cylinder ports also helps with a more torquey powerband.
Also, examples of Honda Motors with V-TEC and compare it to the 2.4 VVT ECOTEC:
Acura RSX Type-S (uses i-VTEC btw) - 16 valve, DOHC, 2.0 liter, 200 HP @ 7400 RPM / 142 lbs/ft torque @ 6000 RPMs
Chevrolet Cobalt SS - 16 valve, DOHC, 2.4 liter, 171 HP, 163 lbs/ft torque @ 5000 RPMs
With everything I have explained, you will see why Honda motors have such different outcomes of power compared to the 2.4 VVT ECOTEC even though they share the same thing of Variable Valve Timing. In the end, it's not the comparison of VVT, but the Engines themselves and internal characteristics.
Hopefully you guys under a bit better between the 2 and understand why Hondas and the 2.4 VVT share the same kind of technology but are still different.
I know what it is but here is a better explination...
Variable Valve Timing itself
Variable valve timing, or VVT, is a generic term for an automobile piston engine technology. VVT allows the lift or duration or timing (some or all) of the intake or exhaust valves (or both) to be changed while the engine is in operation. Two stroke engines use a Power valve system to get similar results to VVT.
VTEC (standing for Variable valve Timing and lift Electronic Control) is a system developed by Honda Motor Co., Ltd. to improve the combustion efficiency of its internal combustion engines throughout the RPM range. This was the first system of its kind and eventually lead to different types of variable valve timing and lift control systems that were later designed by other manufacturers (ie. VVT-i from Toyota or VANOS from BMW).
Toyota VVT-i
VVT-i, or Variable Valve Timing with Intelligence, is an automobile variable valve timing technology developed by Toyota. The latest version of VVT-i varies the timing of the intake valves by adjusting the timing chain connecting the intake and exhaust camshafts. A pump applies hydraulic pressure to adjust the gear driving the timing chain.
Toyota recently started offering a new technology, VVTL-i, which can alter valve lift (and duration) as well as valve timing. This is accomplished differently than Honda's VTEC. Instead of switching between two different cam shafts, there are spacers that are slid between a single cam shaft and the valves. At higher RPM, controlled by the ECU, oil pressure is directed to push the spacers between the camshaft lobes and valves, effectively simulating a much "hotter cam" and creating increased valve lift. When the engine falls in RPM the spacers are pulled out of action and the engine operates more economically. This system is used in the Yamaha designed 1.8 liter 4 cylinder 2ZZ-GE which is used in the Toyota Celica GT-S, Toyota Matrix Toyota Corolla XRS, Pontiac Vibe GT and Lotus Elise 111R. This variable lift technology allows the engine to be quite fuel efficient at lower RPMs and, when called upon, able to produce much more power at the expense of fuel economy.
Toyota recently started offering a new technology, VVTL-i, which can alter valve lift (and duration) as well as valve timing. This is accomplished differently than Honda's VTEC. Instead of switching between two different cam shafts, there are spacers that are slid between a single cam shaft and the valves. At higher RPM, controlled by the ECU, oil pressure is directed to push the spacers between the camshaft lobes and valves, effectively simulating a much "hotter cam" and creating increased valve lift. When the engine falls in RPM the spacers are pulled out of action and the engine operates more economically. This system is used in the Yamaha designed 1.8 liter 4 cylinder 2ZZ-GE which is used in the Toyota Celica GT-S, Toyota Matrix Toyota Corolla XRS, Pontiac Vibe GT and Lotus Elise 111R. This variable lift technology allows the engine to be quite fuel efficient at lower RPMs and, when called upon, able to produce much more power at the expense of fuel economy.
If torque is in lbf·ft and rotational speed in revolutions per minute, the above equation gives power in ft·lbf/min. The horsepower form of the equation is then derived by applying the conversion factor 33,000 ft·lbf/min per horsepower:
Also, examples of Honda Motors with V-TEC and compare it to the 2.4 VVT ECOTEC:
Acura RSX Type-S (uses i-VTEC btw) - 16 valve, DOHC, 2.0 liter, 200 HP @ 7400 RPM / 142 lbs/ft torque @ 6000 RPMs
Chevrolet Cobalt SS - 16 valve, DOHC, 2.4 liter, 171 HP, 163 lbs/ft torque @ 5000 RPMs
With everything I have explained, you will see why Honda motors have such different outcomes of power compared to the 2.4 VVT ECOTEC even though they share the same thing of Variable Valve Timing. In the end, it's not the comparison of VVT, but the Engines themselves and internal characteristics.
Hopefully you guys under a bit better between the 2 and understand why Hondas and the 2.4 VVT share the same kind of technology but are still different.
Thread Starter
Joined: Mar 2005
Posts: 767
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RE: Interesting read on GM's VVT and Honda's VTEC
Did I say the ecotech was better? I didn't think so....I'v heard alot of talk amongst my car buddies around town that GM is "just trying to rip off honda's design and slap a new name on it" Which I didn't know the differance, I came across this article, figured some of you might be interested, so I shared. Don't like it, don't read it
Nail Bunny:
It does, in that article under the Vtec explaination it states that.
Nail Bunny:
It does, in that article under the Vtec explaination it states that.
