Marc sierra

iTrader: (1)

Something that my sapph has been doing for as long as I know is that the boost pressure is fluctuating quite fast. It's not visible on the boost gauge, but I have a Dynojet wideband sensor fitted that also reads the boost pressure.

At idle the pressure is constant, but during cruising it's already fluctuating a bit and during full throttle it's fluctuating even more (about 0.1 bar per 0.1 sec). At first I thought it was the readout of the sensor. So I put 1 barg of pressure on just the sensor (while the engine was off) and then the readout of the sensor was perfectly stabile.

So now I wonder what can make the boost pressure fluctuate that much. The car has a bleed valve fitted and has the max boost pressure set to about 1.3 barg. To limit the amount of air to bleed I put a restrictor just before the bleed valve (in between the turbo and bleed valve). I also tried a longer/shorter hose between the bleed valve and actuator to change the time constant of the system and hopefully make the boost more stabile, but this didn't make it stabile.

Am I missing something here? Is the wastegate really opening and closing that fast that my boost pressure is constantly fluctuating because of this? And is there a fixed length of hoses and restrictors to use between the turbo, actuator and bleed valve (or amalvalve if you use that)?

carl/saff

what boost contol are you using ?

What strength actuator are you using ?

Marc sierra

iTrader: (1)

A simple bleedvalve for boost control and a -31 actuator.