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Being a mechanical engineer I really like the simplicity of a ball and spring type MBC. They make the car feel ‘eger’ and smooth to drive and give a solid level of control and a boost curve that matches the best I've been able to get from the stock 2 port solenoid. They are really good for tuning as you can hit a wider range of load & rpm cases much more easily. I’m finding driving with it more than not. However there are 2* immediate problems, for me at least:
*I’m sure they are others also, but these are the biggies for me.
I know there are cabin adjustable solutions from Turbosmart and Hallman, but liking a project I want something a little more elegant, so….. I’ve started this: A motor adjustable MBC with adjustable max. boost warning/indicator (I wanted a min. indicator to but couldn't fit it this time ). It has a steering column mounted adjustment using a car window switch for boost up/down.
I’ll be the first to admit that it’s the definition of contraption, but this is a prototype and I’m running it on my car now and have to say, it does work!
I already have some thoughts and ideas to improve the design and spotted some major bloopers in the design layout, particularly around the adjustable indicator. For one I’m thinking to replace the MBC female hex head adjuster with a normal M10 bolt and driving it with a deep hex socket, then mounting the spur gear directly to the outside of the socket. Or better still, if it can fit, mounting the motor and MBC inline, doing away with the gears altogether.
This is V1.0. For the next ones I want to:
V1.5) Include a vacuum solenoid to act as a diverter to switch between ‘high’ and ‘low’ boost settings. i.e. switch between the wastegate spring and the MBC. ‘Low’ boost can be used for motorway driving where the car mostly suffers the shuddering as mentioned above.
(this is under way already)
V2.0) Include additional MBC for min. boost. I can eek out more than stock boost levels before the shuddering occurs, so this will allow for that.
(timing is TBC!)
V2.5) Improved package and include switchable motor control for both max. and min. MBC.
(way off!)
Boost and AFR gauges fitted, plus knock detection by a permanent knock sensor fitted so I can hear whenever I'm 'tuning' it. I'm running my own tune anyway, so know where it's safe to play.
With a MAF sensor fueling is managed by that in the usual way, just in different load/rpm parts of the map according to where you're hitting - that's why MBC is particularly useful because you can change boost levels quickly to hit different parts of the map and check for knock etc.
The only risk is hitting the boost fuel cut level I've set at around 22.5 PSI which is fine for my engine. That's why I've got the adjustable indicator!
Last edited by Bazil_SW; 08 January 2017 at 11:46 PM.
V1.5 is live. Switchable high/low boost from the steering column:
- low boost provided by the wastegate spring gives ~10.4 psi
- high boost provided by the motor adjustable MBC
- switched using a denso vacuum solenoid
v1.5a: try to add a switch on the throttle pedal as a 'kick down' function so when in low boost it will switch temporarily to high boost when the throttle pedal is mashed (for overtaking etc). I got the idea from this site: http://www.gusmahon.org/html/boostcontrol.htm.
08 January 2017, 11:12 PM
DIY Project: Motor adjustable ball and spring MBC
). It has a steering column mounted adjustment using a car window switch for boost up/down.
