Timing advance has a huge impact on peak numbers, and whether the current map will take advantage of the extra octane. Thorw as much of this stuff in a car with a conservative timing map and you'll see no benefit..... until heat becomes a factor i.e. after hard driving/track use etc.
This is pretty much the bottom line. For the majority of cars (mapped to 97-99) we won't feel a benefit.
It's that 105 map we want.
Ufortunately it's not quite a simple as piling on advance. Flamefront propagation gets to a point where all the timing in the world makes bugger all difference. It's why tuners tend to add advance until it starts to hurt power, then back it off a few degrees for safety. Running 105 octane specific maps, imo, is a daft idea and probably pointless without altering the combustion characteristics to make it worthwhile.
A proper K thermocouple EGT probe is needed for accurate timing measurements too because too little and too much timing can both increase EGTs.
Naturally there's more to it than just increasing the advance. But look at water-meth. Generally the same principles apply. Given the time for development I wouldn't bet against the top tuners being able to create a map for 105 that bumped the curve.
Indeed, and I didn't mean to come across all black & white and negative about it
I remember from my old tuning days playing around with timing, E85, meth injection, EGT tuning etc etc. It was a very steep and interesting learning curve.
When I had my VR6 turbo, it had terrible combustion chambers. Pocketed pistons that weren't flat and gave a triangle shaped combustion chamber, if that makes sense. With such a rubbish squish area, and CR reduced to 8.5:1, a LOT of timing helps because the burn is so slow. I was running 40 deg BTDC at high speed cruise area of the map and 25 deg in boost, increasing to 28 - 30 approaching red line.
Then I played with tuning an R32 engine, which is a whole different kettle of fish. VW changed the pistons to be flat and the combustion chamber was in the head, rather than the piston bowl. This MASSIVELY improved the squish area and therefore the burn speed, not to mention 11.3:1 compression. I could only run about 18 degrees timing at WOT around 2500rpm where the intake tuning kicks in. Even the factory R32 map runs super close to knock all the time, even with 99ron.
It's a similar story with the TFSi. You don't need a lot of timing to make good numbers and they also run into det as standard if you pull up the logs a hot summer's day. TFSi pistons are also notched for valve clearance. Get a load of carbon build up on the edges of these notches and it can create a 'hot spot' that pre-ignites the fuel, so that's something to be wary of when tuning with timing. This is why companies like Toyota are investigating alternative ways to detect knock with modern high compression, small turbo engines because old fashioned knock 'microphones' can't react quick enough, such is the fast rate of torque delivery.
Meth/Water and E85 reduce the combustion temps, but burns slower than petrol, hence the need for more timing, but the two combined does indeed make good power!
Anyway, a bit of boring waffle waffle there, but yeah, timing is great if the engine wants it but some tuners go too far with it and leave no room for safety. I always tune to the lowest quality fuel available and live with the comparatively small reduction in power, but I keep the timing high at cruise speeds to keep EGTs down. I like a simple life, so I don't bother with fuel specific switchable maps. Get in, turn key, drive
