First, comparing DOHC to SOHC timing maps isn't necessarily apples to apples - SOHC combustion chambers by design will require more ignition advance than DOHCs to achieve the same flame propagation completion relative to crank movement.
Second, the way your tuner has established your load axis, means that for ANY of the boost pressures you mentioned as being run, only the very top row is being accessed at 18 psi or 21 psi. 204 kpa is equivalent to (204kpa-101.3kpa)*14.7PSI/101.3 kpa = 14.9 PSI boost at sea level.
13 psi boost = 190.9 kpa (ok, so this one mainly uses the 185 kpa load row)
18 psi boost = 225.34 kpa
21 psi boost = 246.01 kpa
There is basically no change in commanded timing from 120kpa to 160 kpa. This means that at best case, your tuner is not using the load axis efficiently (two or three of your 12 load axis rows are not doing anything differently - your map could be run off of 10 rows basically).
At worst case (and what is happening here), is that there is no differentiation in ignition timing once you surpass 204 kpa or 14.9 psi of boost. The ignition timing you command at 15 psi, will be the same ignition advance for 18, 21, 30 etc.
In the attached screenshot, and concentrating on peak torque (4300 or so), the tuner has removed 9.5 degrees of timing for 12 PSI (185 kpa) and 10 degrees of timing for 15 psi (204kpa). UNFORTUNATELY, as you increase boost, no further timing is reduced.
As you increase boost from 15 psi in this map, your ignition timing gets increasingly more aggressive related to boost pressure.
I can't say whether or not this ignition map is the cause of spun bearings. However, I'm glad to read you are seeking to do your ignition map yourself, because IMO the tuners have not spent your money very well so far. I will admit, I do think your 2nd/3rd guy did a bit better and incorporated some finer details (increase after peak torque to chase the piston), but that's about all I like about that map.
Post up your msq if you'd like me to look at the rest of the tune and give you a second opinion.
I posted my ignition table to show you what I mean about load axis distribution. I run 8 psi which is 156 kpa. I have reduced more than 1 degree per psi of boost, and have not incorporated any additional advance after peak torque. I have been running a similar map for the last 3 years at least, and my engine has been beat relentlessly. Still on a stock block, 200k+ mile engine that was pulled from a backyard with no cover. I intend to build some knock muffs and make this a bit more efficient this summer, but it's hard to mess with something that has worked so far.
As you're running more boost, you would use more than two rows in your boost region, but I would be very surprised if you needed more than four total to get enough resolution in the boost region.
eta: just seeing my ignition map for the first time in a year or so, I've realized that I have some goofy **** going on in the 80-100kpa and 2000-3700 region. My map is far from perfect, but it was free
Boosted single slammer
npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.