V70 2.5t boost pressure

[Daz86]

Hi all I’ve got a v70 2.5t with the b254t2 engine . Sorry if this question has been asked a million times but I can’t find a definitive answer. I’ve fitted a boost gauge and looking to squeeze more powere from the lpt unit . It hits .9 bar on hard acceleration and then drops to .5 of a bar once revs get higher . So my question is could I up the boost anymore to a more constant 1bar at higher revs

[clarkey1984]

There are flow charts and things around to work out the CFM (amount of air the turbo can flow) but generally speaking, the more boost you run the narrower the powerband will be, when I got my t4 and fitted a boost gauge I found that a previous owner had mis adjusted the wastegate actuator rod so it was set too low at about 0.8 bar, it however maintained that boost up until nearly 6000rpm where it started to tail off as you'd expect.

Then I set it to 1 bar which is standard for the t4, the car was more punchy, but the boost tailed off a bit earlier, more like 5000rpm.

Then, then I got silly and set it to 1.25 bar, when it came on boost it was an animal, chuck you back in your seat stuff with a big dollop of power, but by 3500 to 4000rpm is was falling and falling to barely a third of that by just over 4k, approaching redline it was pretty much non existent, then the engine shat a piston ring, big boost isn't big or clever, although it was fun.

So in basic terms boost dropping off at higher rpms is pretty normal, as the turbo reaches a point where it can't flow any more air so therefore can't maintain the pressure at higher engine speeds.