VCM Scanner and Timing

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16 mustang gt 2650 Edelbrock SC


When i am looking at the VCM scan log and i have spark listed in my chart and i am seeing say 15 deg and the my borderline table commands 15 at that rpm i am seeing that the computer is adding 2deg is that the 15 plus 2 more or is it just 15. If it is just 15 and thats whats commanded why would it show its adding.

Hope this makes sense. Here is the log

[engineermike]

Normally, the "timing advance" is the final advance after all the adders, modifiers, and corrections. At 6500 rpm your timing advance in the log is showing as 17.3, which appears to be 15.2 deg borderline timing plus about 2 deg knock advance.

Couple other comments:
- Speed up your borderline knock timing data rate.
- Cam timing looks very typical for a SC coyote.
- The air flow and max load seem to indicate only about 9-10 psi boost. Is that right?
- Air load noses over past 6500 rpm, but the throttle is staying open. It acts like the throttle body, MAF, or filter is restricting flow.
- Looks like it's staying in individual-cylinder knock retard.
- I have a pretty accurate "rolling dyno" calculator and you happened to log everything needed to make it work. 636 rwhp and 575 ftlb sound right to you? The torque is very strong but the power seems to correlate with the air load dropping at high rpm.

gen2 eb dyno.JPG

[Bill88stang]

Hey mike would you care to share that rolling Dyno calculator?

[engineermike]

Here’s where I learned about it and added development:

https://www.f150forum.com/f123/nerd-...canner-504014/

You have to choose one gear and stick with it. Also, it really is best if you have a street pull in that gear and a dyno pull in the same conditions to calibrate it to. I log in 4th and wound up having to use a 1.2 multiplier to get it to agree with a 6th gear dynojet pull.

[engineermike]

One last thing, the math I use takes the average speed over the future 1/2 second so it doesn’t accurately report within a 1/2 second of the initial hit or 1/2 second of max rpm.

[[email protected]]

Thanks for you insights. I purposely have it set for per cylinder since i am having trouble with the car pulling timing only on cylinder 3 even with meth and even with straight C12 and only in 3rd gear. No signs of detonation on the plugs what so ever. It is an edelbrock 2650 and either i am having belt slip which i see no signs of or i suspect the filter is just too small but havent got around to doing a pull without it yet . I do live at elevation of 2500 ft which accounts for some loss of boost it also lost a bit when i put on headers . As for HP that is pretty typical for this blower with the stock pulley. I am suspecting false knock but trying to find info on desensitizing the knock sensor is like looking for hens teeth.
Not sure how to speed up the data rate perhaps you could enlighten.

[engineermike]

The elevation does help explain the low peak load.

In VCM Scanner, right click the PID and click "Polling Interval". Speaking of, it looks like your data rate on Cylinders 1 and 3 knock are much faster than the rest. You should speed up the rest if you want to address this issue.

In the log you posted, it looks like in the first hit, 5 and 8 got some knock retard and in the second hit, none of them did. Be careful because of cylinder numbering vs firing cylinder can be confusing.

See graph: eddy cyl kr.JPG

[[email protected]]

The elevation does help explain the low peak load.

In VCM Scanner, right click the PID and click "Polling Interval". Speaking of, it looks like your data rate on Cylinders 1 and 3 knock are much faster than the rest. You should speed up the rest if you want to address this issue.

In the log you posted, it looks like in the first hit, 5 and 8 got some knock retard and in the second hit, none of them did. Be careful because of cylinder numbering vs firing cylinder can be confusing.

See graph: eddy cyl kr.JPG

I appreciate you schooling me here What do you mean cylinder numbering vs firing cylinder. Is the 3rd cylinder in the channel list not cylinder #3 ? You have a good eye ,i did not realize the polling speed was different and not sure why it would change,possibly something i inherited off another channel list.

Just checked and the polling speed is the same for all cylinders, why do you think it is different .


So far i have determined that if i drive for a few minutes then make a run from 3200 to7k it pulls timing. If i do a hit right after that it does not pull any timing. Consecutive hits all add tiiming across the board. Very weird situation.

[engineermike]

Open vcmeditor and look under timing->general bottom right and you see cylinder number vs firing cylinder. I was just cautioning you to keep that in mind while looking at cylinder numbers.

I have been told that the pcm does some level of knock baseline engine noise level learning and never to use the first hit to determine knock limits. I can’t personally verify this, though.

[[email protected]]

Open vcmeditor and look under timing->general bottom right and you see cylinder number vs firing cylinder. I was just cautioning you to keep that in mind while looking at cylinder numbers.

I have been told that the pcm does some level of knock baseline engine noise level learning and never to use the first hit to determine knock limits. I can’t personally verify this, though.

FFS it shows cyl 3 is actually 4 wtf why would they do that now its more confusing,thanks again for the heads up .When this started it was pulling timing globally and it would really kill the power so i went to per cylinder and eventually i found a pattern where it would pull timing above 3200 but not if you i started the hit below 3g. The weather is cooling so im worried it will skew any further testing but i will persevere .