Scanmaster 2 - Injector Pulse Width

[Mile Hi GN]

My new Extender chip has the fast update patch. As such, SM2 is now picking up spark advance and injector pulse width. Spark advance is a no-brainer, but I'm not sure what PL is telling me. It appears to be on a 0-50.0 Millisecond scale.

I'm seeing 2.4 at idle.

12.9 to maybe 16.~ at WOT.

What is this telling me, and how can I use this new information going forward?

I should have more than enough injector with my MSD 50's.

Thanks in advance,

 

[U1ARUNIT]

heh heh.. I thought the same thing.

It's telling you that they should have used injector duty cycle in percent instead so that we can understand it.

That reminds me again why I like my Direct Scan so much.

 

[bruce]

Re: heh heh.. I thought the same thing.

Originally posted by U1ARUNIT
It's telling you that they should have used injector duty cycle in percent instead so that we can understand it.

That reminds me again why I like my Direct Scan so much.

If you want DC, or %, just hook up a dwell meter on one of the injector leads to the ecm.

I'd much rather have PW.

At idle your at like 2-3 msec or 1-2% duty cycle, and you have to make a large change to see any difference using DC.

If your real curious, About the only place you actually need to see DC is at WOT, and DC works great for recording that and displaying available PW time available.

 

[Mile Hi GN]

Thanks Guys...

I've come up with an answer, big thanks to Sleeper and his "Injector pw max?" thread. Check me here if I've missed something.

Scanmaster 2 is reporting commaned injector "On Time" in milliseconds, nothing more.

To convert this information to "Injector Duty Cycle", a percentage, we need to divide injector "On Time" by the total available time. Total available time is defined as the time from intake valve open to intake valve open, and is represented by this formula:

60,000 X 2/RPM = Total Available Time

The total available time becomes less and less as RPM's get higher. I used the formula and developed the following table representing total available time at different RPM's:

RPM's....................Total Available Time
800.......................................150 Ms
1000......................................120 Ms
2000.......................................60 Ms
3000.......................................40 Ms
4000.......................................30 Ms
5000.......................................24 Ms
6000.......................................20 Ms

Divide the injector "On Time" as reported by Scanmaster by the total available time above and bang theres your injector Duty Cycle - stated as a percentage.

So.....back to the original question:

What is this telling me?

Duh....see above.

and how can I use this new information going forward?

If your injector duty cycle reaches 90-95% at WOT, you are on the edge, and you should think about moving up.

Or, as Mark suggested, start using Direct Scan and have it do the math, and retain the data on the hard drive for later review

 

[Turbojorge]

2 year old thread but...

I'm having trouble understanding this. If I'm at 19.9 (PL) at full boogie at around 5,300 in 2nd gear, what does that equal to.

I am ASSuing the PL will be the same in every gear at the same RPMs right?

Ex: PL 19.9 at 5,300 RPMs in 2nd will be 19.9 at 5,300 in 3rd?

 

[Eric Stage I]

120000/5300rpm = 22.64 ms available time

19.9/22.64 = 88% duty cycle

Whether the pulsewidth is the same in the different gears depends on the chip configuration. But it will be relatively close.

Regards,
Eric

 

[TurboDave]

ya, what Eric said.

Forget about what gear you're in. It's purely a matter of rpm vs. injector PW.