Originally Posted by themyst
The whole point here is, the stock ignition curve is too aggressive for increased boost. Ask BMW why they dropped the targeted curve 4 degrees across the board on the 335is in "overboost" mode.
It is nice that the stock ignition curve is set so aggressively from the factory though in that there are gains to be realized with meth and/or race gas on increased boost without altering the ignition tables directly (JB, for example).
Actually, I'm really curious to see the timing table for the 335is as I'm not so convinced that it would be much (if any) different than a normal N54 335i timing table. I say that because with a device like the JB, you're altering the MAP signal, so the DME can't see full load. If the DME sees you're hitting a load value of around 115 (throwing a random number out there), when you're really seeing load levels that should be around 145 at XXXX rpm, the DME is first going to attempt to base timing off of the value it can see (i.e. 115 in this fictional scenario). Whereas, if you weren't manipulating the MAP signal in order to get the DME to increase boost, if you were using something like a cheap MBC (for arguments sake, assuming no fuel cut, CEL's ect) or a flash program that only modified boost settings and the ECU could actually see the fictional load of 145, it would react accordingly, which would be to decrease timing by X degrees based solely on the higher load, not that it necessarily has timing values that are different, it just wouldn't be blind to the increase in load.
The point in making a full timing table is to get the ECU to react accordingly under damn near any circumstances. If BMW did this correctly, on the 335is in "normal" mode, logging values should be similar to just about any 335i, but in overboost mode, the tables could be identical, but we would never know because the 335i never hits those load calculations, whereas if it did (via MBC or flash tune that only altered boost), it could actually pull the same ~4 degrees of timing, based solely on the higher load. That's just a theory, it'll be interesting once Cobb cracks the 335is DME in order to test my theory haha.
Either way, from the factory these timing tables can be fairly aggressive in many conditions, so it makes sense that Cobb would pull a few degrees in various locations throughout the table.
Just my $.02