Open Tuning/Turbo Theory Discussion

[Enki]

Just looked over the last few logs I took before my engine went down and I don't have torque spikes. Both my timing tables are identical and sloped, and even with a boost spike early on (from heavily forcing spool) it's mostly flat. Also my OL/CL transition is 20, and my closed loop max load tables all match my load limits; I use load by gear to actually control target loads and dial that in appropriately.

 

[mazdaspeeder]

I don't have torque spikes

Torque spikes may not be the best way to say it. Maybe instant WOT torque?

I use load by gear to actually control target loads and dial that in appropriately.

This is a good way to control load ramp and keep max torque down from early WOT (< 3K), but what if you are cruising along and then mashing it at 4k? Shit's gonna be hot and you are asking for instant max power.
I mean if you got meth and forged internals, it probably isn't an issue.

 

[Enki]

I was running an EFR turbo so you'd think the issues would be worse, but they aren't.

 

[Redline]

I just found this forum so I'm going to revive this to share my knowledge on prevention of this from self tuning over the years.
My technique to combat this torque spike on spool up but keep that turbo spooling as fast as possible is to stop the ignition advance from hitting like a sledge hammer on WOT. This also helps with spool up KR.
Here's how:

1) Set your Closed Loop - Exit Delay B to 40
I have found this controls the time it takes after hitting the Max Load D value
until the transition starts from CL -> OL IGN Table
This allows a decent time to ramp up of about a second after Max Load D has been hit.
View attachment 5370

2) Set your Closed Loop - Max Load D table up to attainable but close to max on a hot day.
I have found that this table is used to determine when to transition from CL -> OL IGN Table
View attachment 5371

3) Set your Ign Table - Low Throttle/CL tables from 1.63 down to about 3-5 degrees less
than your Ign Table - High Throttle/OL table values
CL IgnTable
View attachment 5372
OL IgnTable
View attachment 5373

See my attached log how at 4k it hits Load of 2 and then after about 3 rows it starts the transition up to OL timing.
You may want to adjust the time it takes after or the starting CL Ign based on your mods to allow maybe some heat soak in your inter-cooler/manifold to be brought down after slow cruising or idling.
My logic could also be completely flawed, I'd like to hear your thoughts.

Appreciate the knowledge drop. From my years of self-tuning, I took a different route to completely eliminate spiking: boost control, particularly the WGDC tables and dynamics tables, in conjunction with the load targets/gear (I used a hybrid tuning strategy). I never had any spiking at all, even in the coldest of weather. I didn't find C/L to O/L transitions to have any affect on spiking either. In that regard, I just went with a that many of the top pro-tuners use in all their tunes, using a very popular, middle-of-the road C/L to O/L exit delay value, or adjustment of timing. Honestly, I didn't really touch C/L timing at all. I focused exclusively on O/L and had all of my tables matching. The tune was still setup to pull timing with knock events, obviously, and I ran (and still run) ethanol, so I wasn't worried about pre-detonation or uncontrolled flamefront. Knock events were very rare, besides the characteristic tip-in knock, and end-of-log pulling into neutral knock after hitting redline.

Just goes to show that some cars respond differently. Tuning is as much of an art as it is an exercise in knowledge expertise, IMHO. It's pretty much like wearing a toolbelt and having lots of options/strategies to get to the same goal; or, to put it more shortly, the old adage: "there's more than one way to skin a cat."