question about VVEL, throttlebody, and drive by wire...
 

As I understand it, the throttle body is basically wide open all the time, and the engine is controlled completely by the VVEL system - where the intake timing/lift/duration is varied to increase/decrease to increase or decrease RPM and/or power.

So...with that, the VVEL system is powered by a DC motor...one for each bank of cylinders, where it controls the lift/duration/timing part of the whole equation (I there's an eccentric shaft that replaces the camshaft, I know...)

What happens if one (or both) DC Motor(s) fails and locks up, and say you're going 75MPH down the highway?

You know, I have wondered that same question.

John

probably just some engine knock and really cr@py performance.

At best!

At worst who knows maybe you can kiss your head good bye

Kind of wrong but I lol'ed.

I would hope the system is fail safe in some way. Such as any loss in current would immediately shut all the valves to prevent any piston contact.

Nebermind..... Each throttle body has an electronic control actuator that opens/shuts the throttle body plate based on needs the drive by wire system. You cannot finely control engine speed with camshaft rotation alone. You must be able to control the Air at some point. I see now that the cam lift (VVEL) does the majority of the work there..

You are right that you can't finely control engine speed with camshaft rotation but this engine doesn't have an intake camshaft. The intake side is electronically controlled. The video shown here dmonstrates that even at partial throttle conditions the throttle plates remain wide open allowing the valves to control air flow into the cylinder. The orange blocks refer to throttle pressure.

I stand corrected! Though the throttle body is used for some control as mentioned. While there is No "Cam" in the classic sense, there is an eccentric shaft which is, in a sense, a cam..

After reading more (at 370Zdotcom), I see even more hindrances with this system to improving intake performance with classic techniques (Throw that out the window!). Forced induction should prove interesting.

This is a design that makes me curious about proper function of a blow off valve in a turbo setup. Any of the turbo companies have any insight on how you made this happen?

Yeah....BOV's or diverter valves typically need vacuum to trigger as you go off throttle. Potentially this could be handled electrnically I suppose. Some mention of Vacuum for brake boosters is in the article I read and controlled by the throttle plate

I am not sure where this information comes from, or if something is being lost in translation. The VQ37 VVEL most definately has an intake camshaft, and a throttle plate that works like any other car.

Now, like most newer cars, the TB is of the drive by wire type, with no physical cable connecting the accel pedal to the TB. The VVEL mechanism is on a jack screw, that adjustes lift within a defined area of sweep using a small motor.

I think a lot of this is Nissan marketing of the VVEL, and they are confusing the hell out of people.

Here are some pics of the VQ37 VVEL cylinder heads that we took a while back:

http://onfinite.com/libraries/1509046/4aa.jpg

http://onfinite.com/libraries/1509047/06c.jpg

http://onfinite.com/libraries/1509045/247.jpg

The system is so complex, that I can't really explain it in words, but that black looking upper shaft is what determines lift. There is a camshaft spinning just below it. The camshafts are controlled and secured but a ladder structure. It's almost like a double stacked camshaft. :) Definately easier to explain in person, with this cylinder head on a bench.

Nice pics...

Still, the question remains - what happens if the engine is running at 3,000 RPM, and the DC motor is unplugged (simulating a failure)?

I imagine there won't be and destruction of the valves/pistons, etc, since the timing of the cams should still keep everything intact...

Still, it doesn't have a cam in the traditional sense...

There is a vacuum tank somewhere, built into the intake manifold. It uses a one-way valve to maintain a supply of vacuum for the brakes. There typically is vacuum in the manifold only at idle as that's usually the only time the throttles close (unless the VDC system is cutting power to maintain traction). So, vacuum pressure should be maintained at a fairly constant level.

Late,
Trav

I just remember my good ol' B16A1 with cable tranny hittin' that VTEC at 4,500 RPM and pullin' all the way hard to 8,300 in my CRX HF....that was a sleeper beast. It'd give the 370 stock a hard time in the straights.