I'm not sure if anyone else is aware of this issue or not....

I've test at least 5 ECUs and all showed same issue.

I've always noticed the ignition numbers being off by ~2 degrees under boost from log vs actual #'s in map.
So I decided to set all the Leading cells to 10 degrees advanced all around and the Trailing to 0 giving it a 10 degree split.

By revving the engine past idle you'll notice timing jumps to 10-Leading and 0 for Trailing which is correct.....
BUT exactly @ 4krpm it jumps to 11-Leading, 1-Trailing and again @ 5krpm it jumps to 12-Leading and 2-Trailing. It maintained the 12 degrees advance all across to 8.5krpm.
Split timing was always 10 degrees.

I re-tested while driving the car and under boost the problem was identical....@4krpm and 5krpm timing was advanced.

Again, I disconnected the Datalogit and watched the timing issue on the Commander.

For those with the datalogit is an easy test...save current map...change ign #'s and trailing as above and test it for yourselves. Then re-load original map.

Just letting everyone on my findings.

 

Ooops...duplicate....someone delete this one...
thanks

 

I have found this as well( up to three degrees advance on some cars), mine seem to start coming back inline at the top end of the rev range.
I have always wondered if it was the torque effect on the engine?

Jason

 

i checked my map w a recent log and find my log is in synch w the map thru most of the vacuum until n10 4000 where i get an additional 2 degrees.

as i develop boost the advance rises to 3 degrees.

trail follows exactly so my split is unchanged vs my map.

i am not aware of anything on the settings four page that would add advance vs the map.

this is definitely an item to explore. thanks for your post.

howard coleman

 

I have found the same thing I tune using the map watch which shows 2 or 3 degrees more advanced than my actual settings in igl map just to be safe.
Otherwise I could endup running 16 degrees advance instead of 13 by accident and the consequences could be expensive.

rgds

 

Noticed the same years ago but thought it was P row interpretation.

So is it a PFC problem or DATALOGIT problem? If someone had a degreed timing wheel, they could test it with a timing light. This would verify if it is real timing or displayed timing that is wrong.

You need to post this to the DATALOGIT forum for investigation.

 

So this isn't due to any of the settings on the Settings 4 tab? There sure are a lot of correction factors on there that would seem to cause the actual igntion timing to vary from the maps.

 

sometimes i think the PFC has too many variables or too many adjustments..interesting...this could be a reason for my continuing donations to mazdacomp
Greg

 

The problem is with the ECU itself....not the datalogit.

and its always consistent ....1 degree increase @ exactly 4000rpm and again one more degree @ 5000rpm....no matter what load.
Split is always maintained.

So by 5000rpm- higher you're exactly 2 degrees higher then actual numbers on the your 20x20 map.

Tested 5 PowerFCs and another one today and same exact results....

I also did some quick changes on Tab #4 settings and results were the same.

JD

 

Yeah ive noticed this since i started tuning my car bout 2 years now. mine acts exactly as your stating JD. I just set the timing 1-3 lower than i want depending on rpm and it adds it back?????

 

Maybe its a built-in to overcome possible delay in signal reaching coils or coils reaction itself.

Maybe at 1000-4000rpm the coil would have enough time to recharge, and fire accurately, but at 4000-5000rpm, it may have delay, thus PFC is programmed to send the signal 1 degree earlier, and at 5000rpm 2 degree earlier.

Perhaps if someone could calculate the time between coils recharge and the time available between firing in miliseconds, we can see some explanation...

Just a thought.

 

If that's the case, then why does it go back to normal as soon as it reaches 6k when the coils have even less time to recharge?

 

I don't know. I am just suggesting. Maybe that is why by 6000rpm, the torque curve always drop on stock engine.

 

I think there's some confusion....

Timing is advanced 1 degree @ exactly 4000rpm and again one degree @ 5000rpm and it maintains that 2 degree increase all across. It does not go back to normal until revs drops below 4krpm.

 

So, is it recommended to decrease desired timing on the 20x20 map by 1 degree from 4k to 5k and decrease desired timing by 2 degrees from 5k to redline on the 20x20 map to offset this issue?

 

I think as Chuck has mention above, we should check the actual timing as seen on timing wheel.

All we see now is the difference between what datalogit and commander says. All this are still on the ECU side of the whole equation. We need to confirm it with what happen on the engine side too.

 

If someone was getting ready to tune and this issue hasn't been fully investigated yet, what would be recommended...adjust the timing until a conclusion is made or don't change anything?

 

Has anybody put a call into Apexi about this? Their tech guys (as opposed to the people that answer the phone) have been very helpful in the past. If I have some time later this week I'll try to get in touch with them. Regardless, this info is pretty disturbing.

 

It's disturbing if you don't do anything about it, all you have to do is lower the timing as much as the PFC advances it, like that you're back where you wanna be.

 

I'd rather know exactly what we're dealing with before making any changes. Considering how easy this 'problem' is to observe I seriously doubt it is simply a software or hardware glitch, and for this reason I would like to get Apexi's input.

 

For some it might be OK since their #'s might be conservative but for others running on the edge with timing or pump gas such as myself I rather back off those 2 degrees. Rather lose ~10hp rather then rebuild a motor. Mainly if timing is being advanced in your peak torque curve.

I've always noticed this ign difference for a long time and simply guided myself with the numbers showing on the Datalogit or Commander.

JD

 

Suggest someone get a hold of a Power Excel dealer to determine if their software has the same results as Datalogit’s. Perhaps that would isolate whether the issue is with the PFC or Datalogit’s s/w.

 

On the 20x20 IGL map, would that be decreasing present timing by 1 degree in columns N09-N11 in the boost range and decreasing timing by 2 degrees from N12-N20 in the boost range?

 

Just look @ settings#3 under map reference to confirm rpm vs N#s....
If still using default settings it should be N10-N20 less one degree and gain N12 or N13-N20 less one degree again.

JD

 

whats the max timing you guys push at 15-20 psi area??