Ignition beyond MBT- Low load

Iv watched all ignition tuning videos 10 times over,

Im not sure what im missing.

Tuning in steady state using a mainline prohub dyno which has great steady state feedback.

The problem iv been having is in the low load areas I get to a ignition degree where I can absolutely see no gain in torque.

Even base map and other peoples map will have 10 plus degrees in the same cell.

Example 2JZ, 5000rpm -5.8psi I see no change at all past 25-27 degrees , all other maps iv seen including base maps are 34-38deg in the same cell.

What is the gain in going over the MBT value in these cells? Is the MBT gain so small its impossible to pick it up on dyno that im not actually at MBT.

therefore should I bring some common sense into it knowing its low load and can run some more timing? If so what is the gain?

In the boosted areas it's much easier and can definitely see the gains to MBT where my numbers line up with others.

Any tips would be appreciated

I see this particularly tuning steady state at lower RPMs (1500-3000) -- the torque stays flat for a wide range or ignition timings. I am not sure that I understand why the engine is "insensitive" to ignition timing, but I usually try to choose the lowest angle that has the same max torque value. BTW - I monitor the knock level, and stop advancing timing if the knock signals starts to spike.

I have wondered if the spark plug is too hot, and I'm getting auto-ignition or something. But I've never been in a place to swap in a colder plug to try -- it's on my "one day, give this a try" list.

Now, if you were measuring exhaust gas temps (EGT), you might find that using different ignition timing (in the same torque range) changes the exhaust temps.

As for your specific example, I bet there aren't many base maps created using steady-state at higher RPMs (I typically on go to 3500 or 4000), above that I just follow the shape.

Sam, you didn't mention what has been done to the engine - if it's still stock or has been modified. Ignition timing isn't something that stays constant all the time but should correspond to the cylinder filling efficiency, thermal efficiency, octane ratio - all this good little things, so when talking about comparing ignition timing figures we need to compare apples to apples as there are no two identical engines). For instance, head porting, turbo size and engine load, camshafts profile, compression ratio, octane ratio - all of that should be taking to consideration when setting ignition timing.

It's weird that there seems to be a plateau under light throttle - might be some sort of affect of the flame front speeds, the changes in the charge density as it's compressed, and heat rejection to the head, bore and pistons affecting the pressure balances before and after TDC and how that in turn affects effective cylinder pressures?

I don't think it would be auto-ignition from a spark plug, as they'd be expected to be running cooler than under load, or a 'hot spot' that can cause running on on some older engines - but I've certainly been wrong before.

Personally, I'd do the same thing David suggests, running at late as one can while still maintaining the net torque - that way the "waste" thermal energy will be passing out the exhaust, potentially making a slight reduction in spool as the manifold(s) and turbine housing will be slightly hotter, rather than into the cooling system and oil via the piston crown.

As Shota says, don't make direct comparisons to other vehicles as, even with "identical" configurations, there can be stacked tolerances that can add up to be significant.