boost pressure

[stevenb]

its good to have this forum back.
I have a 1996 t5 with standard motor except pipercross induction kit and bailey dump valve.
Fitted boost gauge and found car boosts to 8 psi then drops to a steady 6 psi and i was wondering what is the highest boost recommended without risking engine damage.

[Alan M]

The standard boost pressure is meant to be just over 9 psi but don't worry to much if yours isn't quite there, it could be just a minor thing like the actuator adjustment is out or a weak BCS. I have all new parts on mine and I still only hit similar figures to yours when running on the standard ECU through the BCS (all my parts are new and uprated with no air leaks). I now have mine set up slightly different with white injectors, an adjustable fuel regulator and an MBC and I run a constant 13psi. I was getting a spike that kept setting off the fuel cut but that was before I carried out the machineing work to the MBC internals and spring change. 15psi is the limit when the fuel cut kicks in on a standard T5 ecu. Its got something to do with the amount of air flow across the MAF which sends to high a voltage to the ECU (because of the more demand for higher boost) thus in turn cutting fuel hence the sudden loss of power ( feels like a kick in the gut if your not expecting it). Mapped ECU's are not limited by this 15psi mark so thats the best and safe way to go but the cheaper alternative is an MBC or slightly more is the EBC. I can't complain about the MBC route, its a little aggresive though and if i really put my foot down I can hit full boost by 2900rpm (this isn't advised so you have be gentle with your foot). Its effective and fun but make sure all your other components are set up properly before any increases in power.