TT350

Has anyone confirmed that the timing they are seeing in there tuning software is actually what they are getting?

The plan for my new motor is to use a keyed balancer hub and make a timing tab and putting timing marks on the balancer.
After the short block is built I will find TDC and make the pointer point to TDC on the balancer so I can confirm that the timing in the tuning software is accurate.

I plan on using Tunercat, if the timing is off is there a way to adjust the software to make the needed corrections ?

shoebox

As long as the opti and the cam and crank gears are lined up correctly, whatever the scanner says is what you are getting. The scanner readings are infinitlely more accurate than looking at a timing mark and pointer. I think you will just end up chasing your tail.

Yes, Tunercat will let you make most any kind of timing adjustment. It does not stop you from making any choices that might do harm to your engine.

TT350

What I'm trying to say is if the software is showing let's say 20 degrees BTDC and the timing light is showing say 25 degrees can this be corrected?

If a cam is degreed is will change the timing because the OPTI is not adjustable.

bobdec

TT350, The PCM gets it cam reference off the OPTI pulses driven by the cam dowel pin. If TDC on the dowel pin position is NOT actual cam TDC then the PCM displayed timing data and the actual engine timing will be off. You can alter the PCM timing settings in the main and extended timing tables to have the PCM add or remove timing across the board, but it gets tricky as the PCM also has other timing tables (cold temp, closed TPS, idle overspeed, idle underspeed, DFCO, EGR active, etc). There are also constant settings such as max timing that must be adjusted. You will then have to convert the data logs to actual timing going forward and insure real timing is what you expect.

TT350

To sum it up there's no way to synchronize the software
with the actual timing that one would see with there timing light if it where off by a few degrees.

Injuneer

If you put a scanner on the PCM, it will tell you what advance the PCM is setting. If the Opti is indexed correctly, that is the timing you will get. You can't find a single "advance" number in the software. As noted, the timing the PCM is calling for is a mathematical addition and subtraction from the main timing table, based on the offset tables for the items listed above by bobdec.

I run an aftermarket ECU. I run it off the Opti cam position sensor, which tracks the cam position to a resolution of 1/2-degree. I have an ATI damper, with 360-deg markings. I have a pointer that was installed when the enigne was being assembled. What you see is what you get.

How would it get "off by a couple degrees"?

shoebox

bobdec already pointed out some of the tables that can be modified.

There are also few constants that can be modified (ex. spark advance table bias, spark reference angle, spark coolant temp correction bias) that might cause global effect, but I don't know how many people even have messed with them (or know what real effect they have). I am still skeptical that it can even be proved that it is needed unless a cam degreeing variance were part of the equation.

IMHO, if you are looking at it with a timing light and see something that seems out of whack, you won't know how normal that is without some sort of baseline data that others have gathered. Provided that most people don't do this, there will likely be little or no data to compare to. Like bobdec said, there are so many inputs that influence timing, it is going to be hard to tell what to adjust. It's not like the old days with just a distributor to move around.

TT350

I understand what you guys are saying, The PCM looks a variety of tables and outputs a timing number
for a given condition.

All I’m saying what if this timing number is “mechanically” inaccurate.

In the aftermarket EFI systems I’ve messed with there are places in the software
to make adjustments.

If your software is saying you are idling at 20 degrees and you timing light is showing 25
you can adjust the software until the two match.

As soon as I get my car swapped over to OBD1 and get a good look at TunerCat
I will confirm that the timing I’m putting in the tune is what I’m getting.

I can see a adjustable OPTI in the makings for my motor.

There are too many variables that can add up to inaccurate timing.

Any way thank all of you guys for taking the time to post,
you input is much appreciated.

WS6T3RROR

Maybe my background in oem engine development skews my view, but i'm going to go ahead and throw this out there anyways (I assure you I am not trying to be an *** so don't take it that way please). If I were you, I would not be worried one bit with how accurate the timing is vs what you command. It will be reasonably close no matter what the situation is with a good quality timing chain set and cam. The actual number for ignition timing does not mean jack crap. It is merely a basis for comparison. You in no way have the resources/data required to develop the entire spark map for your now modified engine like we do in a lab. Also being quite honest with you, you don't need to. The factory one will need some massaging here and there, but if your primary objective is performance theres only two rows you need to mess with and it will work comparatively. Advance timing... did the car knock? did the engine make more power, less, or the same? Then based on that choose what the next move is.

In other words, its really just a crap shoot anyways and timing is all comparative with the usual tools an individual has available to them. Spend your time/money/hard work on something else its not worth it I assure you. Use the classic hotrod approach to timing for max performance and get on with your life.

TT350

No affiance taken.
You are absolutely correct.
Timing is just a number, either the motor likes it or it doesn’t.