SOI?

[907DAVE]

Originally Posted by cleatus12r

Some program Bill has with a much faster sample rate than AE has....come to think of it, it's way faster than the Genisys too.

Pretty neat to be able to datalog like that....... any ideas on what program that is?

[cleatus12r]

No sir.

I know AE will datalog as with most scan tools. However, I am still skeptical as to the accuracy of any data coming off of the OBD port.

[907DAVE]

Originally Posted by cleatus12r

No sir.

I know AE will datalog as with most scan tools. However, I am still skeptical as to the accuracy of any data coming off of the OBD port.

Agreed! I too am skeptical of most data that the scan tool shows. Great for getting an idea but 100% accurate, no way! I am curious what you find when using a scope to check thinks out.

[Power Hungry]

I am curious as to why you would be skeptical of anything coming from the data bus? I mean, with the exception of SOI which depends a LOT on the mechanical relationship between the crankshaft and the CPS, why would you assume that any of the data form the bus is invalid? You're seeing exactly what the PCM is seeing. The PCM doesn't fudge the numbers it sends you.

As for the SOI, I don't think there are ANY scantools that offer that parameter because it's not a PID.

The hardware and software that I use for datalogging are available for about $1200.00. Not practical for most folks.

[cleatus12r]

Originally Posted by Power Hungry

I am curious as to why you would be skeptical of anything coming from the data bus? I mean, with the exception of SOI which depends a LOT on the mechanical relationship between the crankshaft and the CPS, why would you assume that any of the data form the bus is invalid? You're seeing exactly what the PCM is seeing. The PCM doesn't fudge the numbers it sends you.

As for the SOI, I don't think there are ANY scantools that offer that parameter because it's not a PID.

I guess I really don't have a valid reason for not trusting the data. I think it stems from a few different sources dating back almost a decade. I haven't datalogged or scanned a 7.3L for almost 6 months. I may have confused the scan tool timing data on a Duramax.

I apologize for causing a stink and possibly throwing out some bad information.

[907DAVE]

Originally Posted by Power Hungry

You're seeing exactly what the PCM is seeing.

That is why I dont trust scan tool data 100%. There are alot of things that will affect what the PCM "sees" (volt drop, resistance, etc)and corrupt your PID's.

[Power Hungry]

Cody... don't worry about your post. It's not bad information as such, just a difference of opinion on how reliable you find the data bus to be. I certainly don't disagree with the theory of "garbage in, garbage out" but I would ask you to consider for a second that if the PCM can't produce consistently reliable data pertaining to the vehicle's operation, then what's the point of it in the first place. Granted there are mechanical aspects that the PCM might not be able to compensate for:

• Timing gear/chain wear affecting the CPS output
• Bad CPS
• Worn injectors/weak solenoids
• Weak IDM

However, the only thing that's going to tell you if those (or other) items are causing problems is a scope, a breakout box, and time.

Because I expect the PCM to generally work from reliable data, I tend to trust the data being provided via the OBDII port. After all, this is the same data that the PCM is using to generate all its outputs. Is it the end-all, be-all of tuning? Of course not. But it does provide valuable data in relation to changes on a specific vehicle and I can use it to determine just how much more or less aggressive certain files are in comparison to each other. In the grand scheme of things, is 2 or 3 degrees of SOI or .3 ms PW going to make all that much difference when there are tunes out there that more than DOUBLE the SOI or Injection PW? Probably not.

Like anything else, it's a tool that provides information. As I see it, the more info, the better.