If you are limited by the fuel you get, lets say 91 octane. Would you run higher boost 26psi with 3 degrees of timing OR 22psi with 7 degrees of timing? Which one would make power and which one is riskier?


I personally went with higher boost and lower timing to avoid knock with the 91 octane. So im running 25psi with around 4 degrees of timing at peak torque.

I would like to hear from people around here and what they did with their setups?

 

It takes time to find the balance. Some engines like timing, some boost, some lean (probably never all three!). I found that my car liked a bit more timing and less boost. It depends on the turbo. I have a TD05 (9 blade) based turbine and that is going to choke the car a bit on the exhaust side. This essentially causes back pressure / heat and therefore knock if you just wham up the boost. Instead I backed off the boost and slowly added timing while holding a sensible AFR, and made good power. A bigger turbine based turbo would have done better with boost. I am not an expert on this, and know just enough to be dangerous. My turbo could probably hold 30PSI to redline but the engine wouldn't like it.

~Jaraxle

 

See if either make you knock, id say more boost less timing, but as stated above really depends from car to car

 

Yes thats what worked for me, but i wanted to know if im missing anything going go the other route(lower boost and more timing)

 

Like mentioned about every car is different. I've managed to squeeze out 25psi tapering to 22 on a stock evo 8 turbo, other stock turbo evos 8's may like less boost, timing on pump gas is easier to dial in because it will knock once you advance it a degree past MBT, on e85 this becomes tricky because it will not necessarily knock with advancement of timing,

its a balancing act, do a bit more research and log your car, takes time if you dont do it for a living, but you can figure it out, just work in incriments.

one more thing to remember, when you tune, weather makes a big difference, so if you're tuning, and advance ignition timing another degree and it starts pinging, i would pull 2 degrees instead of one, just to give yourself a cushion. Also make sure your transition in the tables are smooth. Hope this helps.

Also, the more efficiently the turbo can compress the air, the more boost you can run without detonation. This would mean an efficient/bigger intercooler, bigger turbo, etc. thats why you can run 27-28 psi on bigger turbos even on pump gas, but get limited on smaller turbos.