Gadd

Ok I’m looking for some feedback on this idea. I’ve been trying to control my boost spike for some time now with limited success. I currently have a mbc on both the pre-spool and wastegate and I can reduce the spike to almost nothing by increasing the restriction in the pre-spool valve, but then I have 12lbs on the primary turbo. If I turn it down to 10lbs then I’ll spike to 12+ at the transition. So if the problem is the wastegate not responding quickly enough at the transition, wouldn’t in make sense to put the mbc in the line between the wastegate and the turbo control solenoid and an unrestricted line from the turbo to the wastegate actuator? Has anyone tryed this? Anyone see any pitfalls?

adam c

iTrader: (2)

I suggest that you remove the prespool controller and install the factory hose with the restrictor pill in it. This should give you a solid transition at 8 psi. Adjusting the wastegate line with a MBC will be easy after putting back the stock prespool line.

Gadd

Thanks for the reply adam.. but the stock pre- spool pill gives me the same spike as the pre-spool mbc set to 10lbs.

adam c

iTrader: (2)

I don't have a good answer for that. Perhaps you have another problem. What are your mods?

DaveW

Ccomments and questions:

When most people talk about a MBC, they do not mention whether it is a needle valve, or a ball/spring type. These two types function totally differently.

The needle valve types are just adjustable orifices (pills), and, as such, are subject to all the lag and control troubles related to the duty-cycle solenoid-controlled stock boost-control system. These systems attempt to balance two orifices (the pill vs. the solenoid duty-cycle) against each other, using very long (causing response lag) pneumatic circuits.

A properly made and installed ball/spring type with the WG and PC actuator exits plugged should do a much better job of controlling both the boost level and the spike.

Therefore, are those of you who have had trouble controlling the spike with a MBC using a needle-valve, or a ball/spring type? I'd guess the needle-valve type.

Damian dela Huerta related his success using two ball/spring types.

Comments?

Gadd

My mods:

K&N, dp, Racing Beat catback

Gadd

I'm using Joe P MBC's (spring type w/the bleed port plugged) And I have read Damian Dela Huerta's very well done writeup. ( along with every thing else I could find ) The only difference with my set-up is I didn't bypass the stock solenoids like he did. I guess I'll give that a try.

DaveW

Gadd,

If I understand correctly how this all works, one has to plug the exits from the actuators to divorce the boost-controllers' actions from the stock solenoids, and to speed response by eliminating excess volume after the actuators. In this case, the (0.02" or so diameter) bleed at the controller(s) would be left open to allow the pressure at the actuator to be controlled by the ball and spring. If the controller bleed is blocked, then pressure would remain in the line to the actuator even after the actual boost has diminished.

alberto_mg

Or you could just get a used Profec for ~200 and not have to worry about it anymore....

Gadd

Dave..

My stock solenoids are still hooked up to the actuators and therefor bleed the pressure like the stock system, the valves Damian Dela Huerta used are not bleed valves, but he did bypass the solenoids. So do you have the lines to the solenoid blocked off? and air bleed at your mbcs?

DaveW

Gadd,

With a ball/spring controller, the stock solenoids, if still hooked up, are trying to balance a controlled inlet pressure against a simulated orifice - the duty controlled solenoid. This, theoretically, will not work. The stock system is designed to balance two orifices, not a controlled pressure and an orifice.

Therefore, to get a ball/spring controller to work, you have to block the actuator exits to eliminate the effects of the stock solenoids, and allow the pressure that the actuator sees to be controlled by the boost controller. Along with this, the CONTROLLER bleeds must be left open so that excess pressure can bleed off when the pressure in the actuator exceeds what the controller is allowing through. Otherwise, the controller acts like a check valve, and prevents any reverse flow.

Gadd

Thank you for your replys Dave, I'll give that a go..

DaveW

Good luck. Please post your results.

Dave