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Old 06-13-2007, 01:31 PM   #1
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It seems everybody is going WOT

The trend from the major car makers seems to be a variable valve timing and volume, with no more need for a throttle butterfly:

Toyota Announces New Intake Valve Lift and Timing System.



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Toyota Motor has announced its new variable valve lift mechanism, which it calls Valvematic. Valvematic combines the existing VVT-i (Variable Valve Timing-intelligent), which continuously controls intake valve opening/closing timing, with a new mechanism that continuously controls the intake valve lift volume.

In the case of a new 2.0-liter engine developed by Toyota, Valvematic improves fuel efficiency by 5% to 10% (depending on driving conditions), reduces CO2 emissions, boosts output by at least 10% and enhances acceleration responsiveness, according to the company.

TMC plans to introduce Valvematic shortly, starting with a new vehicle model featuring a 2.0-liter engine.

Valvematic adjusts the volume of air taken in by continuously controlling the intake valve lift volume as well as the timing of valve opening and closing. This boots performance based on the engine?s operational condition, helping vehicles achieve better fuel efficiency and dynamic performance.
The comments have some interesting discussions.
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Old 06-13-2007, 06:00 PM   #2
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It certainly makes sense, having variable intake lift and timing would allow the engine to be alot more efficient across a large rpm range. BMW has a similar system. I analyze product failures for a living and systems like this always make me wonder what happens when the system fails. Could you end up with a virtual wide open throttle, or is there a fail safe system that at least shuts down the engine?

It reminds me of something I really wouldn't want in a car, the Mercedes 500 SEL has a drive by wire brake system. Yikes. I don't know about you, but I like the idea that when I push my foot on the pedal that I'm actually increasing hydraulic pressure directly and not relying on a CAN based computer system directing a pump.
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Old 06-13-2007, 06:14 PM   #3
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This is equivalent to what is in the r18, innit?
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Old 06-13-2007, 06:19 PM   #4
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Think so, just like BMW too.
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Old 06-13-2007, 06:48 PM   #5
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Originally Posted by mrmad View Post
It certainly makes sense, having variable intake lift and timing would allow the engine to be alot more efficient across a large rpm range. BMW has a similar system. I analyze product failures for a living and systems like this always make me wonder what happens when the system fails. Could you end up with a virtual wide open throttle, or is there a fail safe system that at least shuts down the engine?
Interesting point. I haven't heard of a failure or a fail-safe mode, but I imagine I'd put in the clutch and turn off the key. After all butterflies and throttle linkages to get stuck too.
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Old 06-13-2007, 07:01 PM   #6
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The r18 has a throttle body butter fly. Its integrated into the control system with there tricky dicky ivtec. With attention paid to pumping loss, coupled with a variable length intake manifold.

Heres a Honda vid.
http://world.honda.com/HDTV/news/2005-4050705a/

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Old 06-14-2007, 07:42 AM   #7
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Ya, I have NO love for drive-by-wire braking.
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Old 06-15-2007, 04:41 AM   #8
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I like the theory, but the mechanics would seem prohibitively complicated (apparently I'm wrong if they are pursuing the technology)
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Old 06-15-2007, 04:44 AM   #9
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It's complicated because the problems (FE and emisisons) are complicated problems to solve. This is an attempt to address the requirements for a consumer product.
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Old 06-18-2007, 01:26 PM   #10
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Chevy did something else: Displacement on Demand, or Active Fuel Management™. Probably ain't too many of these on the board. Problem is, they're putting the technology in the huge V8s and some V6s. I wonder if they'll be applying the technology to a 4-banger.
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Displacement-On-Demand V8
With DOD technology, the 5.3-liter V8 runs on four-cylinders when not under load. All eight cylinders come on line within milliseconds once the accelerator is depressed.
http://www.jdpower.com/autos/reviews/review.aspx?ID=143

I didn't really have the time to research if there were any problems or what happens if the system fails.

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