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The Autonerdz Community Forums
https://www.autonerdz.com/cgi/yabb2/YaBB.pl General Public Area >> PicoScope >> ZOOM ZOOM https://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1116365302 Message started by Tom Roberts on May 17^th, 2005 at 2:28pm

Title: ZOOM ZOOM
Post by Tom Roberts on May 17^th, 2005 at 2:28pm

Trying to keep up with Kevin :P

Right click the movie for the controls.

http://www.autonerdz.com/flash/snaps.swf

1988 Saleen Modified 351

A is PIP
B is SPOUT
C is Secondary
D is Primary Current

Start with no trigger, then select trigger to capture snaps and save to hard drive followed by a zoom in examination of the last frame.

Title: Re: ZOOM ZOOM
Post by romain on Jun 30^th, 2005 at 7:10pm

Hi Tom,

I've been looking at this screen a few times, and my question is: there appears to be an issue with sudden dwell changes , what in your estimation causes this? I think I've seen this before when there is a secondary issue like in a misfire. will e-mail a print screen shot of the event.

Title: Re: ZOOM ZOOM
Post by Tom Roberts on Jun 30^th, 2005 at 8:25pm

Hi Romain,

Yes, I saw that too. It only happens on a snap accel. There are no associated performance issues. In this Push Start TFI4 ignition system, dwell is a function of the ICM.

Notice that the sudden dwell change is a result of the sudden timing change when the throttle is snapped open. Timing is, of course, a function of the computer ECA through the SPOUT command. At that point where the dwell changes, the timing suddenly retarded to about 10 deg BTDC. This created the excessive dwell event. Then the ICM has to play catch up to recover the dwell time. It's not a very smart ICM ::)

I'm thinking that this is normal for the system. Another good reason for creating Computer Controlled Dwell ;)

At least that's my theory at this point :P Thoughts?

Here is your shot:

Title: Re: ZOOM ZOOM
Post by Doug_Montgomery on Jun 30^th, 2005 at 9:35pm

Awesome Tom ;D

Title: Re: ZOOM ZOOM
Post by Tom Roberts on Jul 1^st, 2005 at 7:12am

Hi Doug! Good to see you visiting.

I wasn't happy with the sound on that little movie. Lot's of noise. It was a good attention getter at the NAIT show though. 8)

I just used the PC sound card and a long standard extension cable. The extension cable caused a lot of noise. I'm getting that worked out now with a balanced mic and a Tascam digitizer. Trying different mics. I got rid of all the noise now but need a mic with a little more gain.

Have a movie from the same car with an injection misfire that sounds much better but not enough volume with the vocal mic I used.