Wednesday, April 23, 2008 - 10:32 pm, by: Fran Valdivia(Silvasoarer)
There are no stupid questions.....only stupid people. Was wanting to ask all you out there in Soarerlia if it is possible to increase boost on the stock ct12a turbos by inserting a small diameter restrictor pipe in the hose between the actuators and pressure outlet on compressor housing. I am led to believe that the restriction (reduction of internal diameter) will decrease the amount of boost passing thru the hose to the actuator thus increasing overall boost, because more boost would be required to open the actuator valve. Now is this true, and if so, what is the smallest internal diameter that would give a safe boost increase, or is that just someone pissing in my pocket???
Thursday, April 24, 2008 - 07:48 am, by: Jeff Bedsor(Jeff_bedsor)
Wrx's have that kind of setup, I think it has more to do with keeping an constant even pressure instead of sharp jerky response. I'm not sure I explained that correctly but no it will not allow you to run higher boost levels.
Thursday, April 24, 2008 - 10:41 am, by: Cihan Aday(Cihan)
I'd imagine a restrictor would act to increase gain, causing boost spikes! If you think about it, it takes longer to fill the void between the restrictor and the actuator. Eventually the space would be filled and the gate would open causing boost to drop off at high revs. If you're going to cause a restriction and bleed the excess, might at well go a for a cheap bleed valve.
Use the bleed valve with the boost reference coming form the intake manifold. Block off the pressure sources coming from each of the turbos and use large internal diameter hosing to the bleed valve and actuators themselves. Works great like this.
Thursday, April 24, 2008 - 03:42 pm, by: Brad Knudsen(Knuddo)
Correct me if I’m wrong, but I don’t think it is recommended to reference the actuator to the intake manifold (After the throttle). This is due to actuators not being designed to take vacuum. This recommendation is also on the Garrett web site. http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html
However it seems to be a common practice. I understand this is done to account for the pressure drop between the turbo to intake and is suppose to help response. Doing this on an externally wastegated setup is fine though. Cheers
Thursday, April 24, 2008 - 10:52 pm, by: Cihan Aday(Cihan)
Brad, The humble CT12a factory actuators have no problem with vacuum. Neither have any of the actuators i've used with this method.
I can see where the problem may occur under full vacuum though, the actuator internals may collapse (if they're soft enough) and not sit right under boost causing leaks etc. I never really thought about it before, thanks for bringing that up
Friday, April 25, 2008 - 08:29 am, by: Brad Knudsen(Knuddo)
Cool, it was just a thought.
Apart from the vacuum incurred, I do think it’s a better set-up as the actuator gates a true indication of what's going into the engine at the time – rather than what’s coming out of the compressor. I’ve always been concerned about the vacuum damaging the actuators, but from what I gather, it’s probably not much of an issue.