E85 timing with boost on Gen III's?
10-12-2012, 07:05 AM
#21
I would think there is no generic answer to this. Every combo will be a little different and the more efficient the turbo and engine the less timing you will need to run to make the power. A good example is the difference between a Subaru motor and an Evo motor. Subarus need more timing due to their less efficient head design and will run up to 26* at redline compared to the Evo motor that may only run 6* at redline!
Consequently I usually add a degree or two towards the top of the rpm band compared to timing at peak torque. I may be running 10* at peak torque and 18* at redline. Also larger, more efficient turbos will need less timing to make the same power at the same boost level as a smaller less efficint turbo.
As has been noted above it is about cylinder pressure and density as well as the fuel. The best advice I can give is make a set of "det cans" (you can do this for about $20 for electronic) and listen to the motor. Start low and work your way up.
Consequently I usually add a degree or two towards the top of the rpm band compared to timing at peak torque. I may be running 10* at peak torque and 18* at redline. Also larger, more efficient turbos will need less timing to make the same power at the same boost level as a smaller less efficint turbo.
As has been noted above it is about cylinder pressure and density as well as the fuel. The best advice I can give is make a set of "det cans" (you can do this for about $20 for electronic) and listen to the motor. Start low and work your way up.
