Noobie With a Logger

[DSM_PWR]

I just got a pc logger the other day and ive been playin around with the features a bit. i tried searching but couldn't find any info on what my sensors SHOULD be reading to make sure nothings reading bad

like my o2's, fuel trims, maf, intake, etc...

any help would be appreciated. Thanks

 

[kenamond]

Do a 3rd gear pull from 2k rpm to redline logging rpm, timing, front O2v, and airflow. Post the text from your log in the log advice subforum under the tuning forum. The numbers will depend on what boost you're running, what setup you have, etc.

O2v won't tell you AFR, but it'll tell you if you're leaning out badly or running pig rich. You can calculate knock count from the rpm, airflow, and timing data. It's a bit involved, but it's possible.

Others will be able to help once they have some data in front of them.

Be careful doing the pull. Redline in 3rd gear is beyond any speed limit. If you do a 2nd gear pull, you go to redline too fast, and you can't sample enough data in that shorter time. An alternative is to use the brakes to slow your acceleration and draw out the pull.

 

[DSM_PWR]

K cool thanx bro. also how do you calculate knock?

 

[kenamond]

Well, let's see...

Given airflow from your logger in lb/min and rpm, you can use the following formula to compute "load" which is the mass of air in the cylinder (in units of grams per revolution):

GREV=LBMIN * 454 / RPM

So to get that, you need to log airflow and rpm.

If you have the 2g timing map data, then you can look up what the timing should be. The table is 3D. It stores timing advance (in ° BTDC) for various rpm and load. So when you also log timing, you have everything you need to calculate what the ECU wants the timing to be if you have no knock.

So given an RPM and calculated load value (from the equation above) and a timing advance - all from one row of your log - you can see what the table says and what your logger says and see if the logged timing advance is less than what the timing map says it should be. The difference is due to knock. There is a formula the ECU uses to convert knock count to timing retard. You can look that one up...I'm too lazy .

Also, if your intake air temperature (IAT) is too high, or your coolant temperature is too low, the ECU automatically retards (pulls) timing. So make sure your car is fully warmed up before you do a pull, and check your IAT in a separate test just to make sure it's not way high (I think it's gotta be over 100°F IAT to pull timing). Once you're sure your coolant and intake air temps are good, then you can reliably deduce knock count from the logged rpm, timing advance, and airflow numbers.

There are other "rules" the ECU uses when it looks up timing advance numbers off of the table, and you need to know what those rules are to do the correct timing comparison, but I forget what the rules are. But they are things like if the measured load is between two values on the table, use the timing advance for the lower load value on the table...things like that.

There's a good thread that has a lot of this information here:
http://www.dsmtuners.com/forums/tun...239-how-ecu-determines-air-mass-flowrate.html

It's kinda long, but zippyshoe links in a good PDF describing the "rules" of the ECU. He also links the 2g timing and fuel map data, but it's in Excel format, so you'd need that to read the file.

Like I said, it's a bit involved to compute knock count from a log, but it's possible.

Hope that helps.

 

[95CarbonEclipse]

Damn.. just when I think I'm starting to figure out this whole tuning thing, I read a post like that... and now I'm even more lost then before.

Good info though. I just need to digest it and then take a dump.