Can someone help me?
http://www.picotech.com/support/topic6787.html?sid=7da425ad34c5895dc88c7de1419776f9
thanks
shay

Shay,

Post your question and maybe someone can.  It was not clear to me what you were asking in your link.

If you were asking if you could measure VVT advance with a two channel scope, the answer would be yes.  You would monitor CKP and CMP, then force the VVT to activate.  Then you could measure the degrees of change and the time it took for the cam phaser to move the cam.

Hi
my question was how do I  check VVT with 2 channel scope?

I try to trigger on CMP and force the VVT to activate  it is hard to see the degrees of change  because of the trigger "jump" on the CMP signal.
Do you have some tip for Better trigger?

Thanks
shay

Shay,

You would really not have any need to use trigger at all.  Just increase your capture time so you can see the entire event on one screen.

With a PicoScope, you can do that  8-)

If ever there was an argument for having a four channel scope then I think this discussion makes the point nicely.

Here is a capture taken from a VTECH Honda that we had a look at. Logging fault codes that suggest that the VTECH mechanism is sticking, we needed to see the whole picture.

http://www.londonroadgarage.com/images/honda_frv_vtech.gif

Seeing is believing!

Its a thing of beauty isn't it? (I like it anyway  :P )

Dave,

Being a Honda Tech for ten or so years, it was nice to see that in action.  Was that done with the new Pico software?  Maybe not, cause of the mouse movement?  Either way, Nicely done.

Ed

Dave,

Could you please identify each trace and what is happening with the relationship between them that suggested that there was or was not sticking?

Thanks, Bill

Hi Ed

The capture was made with the latest Pico software at the time, although the animation is created with a different application. Pico's own software does allow you to create a basic animation, however you have very little control over the output. (you won’t get random mouse cursors though in Pico’s own animations :-[ )

Hi Bill

In the capture, we can see the crankshaft position signal in blue & the exhaust cam position is represented in green. The red signal that can be seen to shift, is taken from the intake camshaft sensor.The "stretching" effect that can be seen on the blue & green traces, is caused by the change in engine speed, in response to the inlet cam shift.

The engine control system has a dual method of control over the intake camshaft. The V-Tech system gives control over the intake valve lift & duration, by introducing a more aggressive secondary cam profile at higher engine speeds. The second means of control is by regulating the angle of the intake cam, in a manner that we are familiar with from many other manufacturers. A de-phaser pulley is mounted on the intake camshaft & this allows the control unit to regulate the angle & overlap of the inlet valve.

In the animation, we are activating the de-phaser pulley, by independently energising the oil pressure regulator solenoid, which diverts an increased oil pressure to the de-phaser pulley. The shift in the red (intake cam) signal demonstrates that the command has been acted upon. This is capture does not indicate that the V-Tech mechanism is functioning correctly.

Regards

Dave

Dave Hill wrote on Nov 14^th, 2010 at 8:39am:

The red signal that can be seen to shift, is taken from the intake camshaft sensor.

Dave Hill wrote on Nov 14^th, 2010 at 8:39am:

This is capture does not indicate that the V-Tech mechanism is functioning correctly.

I guess that is where I am a little confused about how this capture indicates that the V-Tech mechanism is not functioning correctly, the intake cam is seen to be shifting when the de-phaser is energized.

Is it shifting too much? Not enough?

I appreciate you clarifying this for me.

I need to spend some play time with the scope on one of these the next time one comes in to the shop.

Bill

Just to clarify Toms point....

Although my capture demonstrates nicely the close up view of the cam & crank relationships, it is possible to see the same effect, by cranking up the the "collection time", so that you capture many seconds of data.

With a two-channel scope, if you were to scope the exhaust cam (which has a fixed relationship with the crankshaft) & also the intake camshaft, you would be able to achieve a similar result, by zooming into the detail at various points in the capture.

If I am totally honest though, I think two channel scopes are too limiting in today's workshops. For a quick look they are fine, but when you need to study things a little deeper, then you will often need four channels (& often wish you had more).

As Tom has said many times before, any scope is better than no scope, but you will soon realise that the extra investment in four channels was worthwhile.

Cheers all

Dave

Hi Billl

To answer your question about "is it shifting too much or not enough" would require a capture from a fault free vehicle I think. I can say though, that this car had a very intermittent fault & 80% of the tine it would not log a fault.

This capture was taken in the workshop & no faults were logged during this time.

HTH

Dave

I was confused myself, Dave... have you said that the animation was inconclusive; that you cant verify that it is a bad phaser from the capture?

Hi Fisher

The capture was taken from a vehicle that would intermittently log a fault code.....

22-03 (P2646) ROCKER ARM ACTUATOR "A" PERFORMANCE PROBLEM OR ACTUATOR STUCK OFF

The fault code refers to the V-Tech fault & not a fault within the de=phaser system.

My thoughts are that the capture represents a "full sweep" of the intake cam angle range. Although, with no known capture to compare against, I can't be 100% sure.

On this vehicle, we found a lot of oil sludge clogging the V-Tech actuator & also the de-phaser control solenoid.

After a thorough cleaning of these components, the fault has not returned. I am not convinced that this is the end of the matter though.

Intermittent faults can make the best technician look like a fool.  :-/

Cheers all

Dave

Dave,
Could you post the psdata file if you still have it?

Bill

mr. bill, here is some more really good vvt stuff too:  http://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1267761185

Dave Hill wrote on Nov 13^th, 2010 at 1:31pm:

If ever there was an argument for having a four channel scope then I think this discussion makes the point nicely. Here is a capture taken from a VTECH Honda that we had a look at. Logging fault codes that suggest that the VTECH mechanism is sticking, we needed to see the whole picture. http://www.londonroadgarage.com/images/honda_frv_vtech.gif Seeing is believing! Its a thing of beauty isn't it? (I like it anyway  :P )

Hi Dave
What is the trigger for Chanel  D?
Thanks
Shay