Leak proof your MBC

[91-gsx]

I have been trying to find a MBC or any type of boost controller that does not have a leaking system. If you have a high pressure wastegate or actuator and do not require another form of boost control, more power to you. But, for those of us that use a MBC to dial in our boost, this could help save some valuable pressurized air. Now I know that the majority of boost controllers do not leak a lot of air, but they all leak air, and no leak is better then a leak.

There is a hole on any MBC that relieves pressure after the MBC closes. This pressure is relieved after the MBC so that the wastegate does not stay open when you shift, this causes slow spool as you guys already know. So first thing you want to do is seal that hole shut because the leak free system at the bottom will take over its job, without leaking ofcourse.

This is the way I am going to run my MBC because I want to push my setup to its full potential. When I just blow into the MBC, that hole leaks a lot of air, and that is amplified greatly when you add real pressure.

I hope this helps people get rid of a leak that we have all learned to live with for a long time. Feel free to ask any questions that you may have. Later.

 

[Imback]

What are your results after doing this ?

 

[91-gsx]

I am still putting together a few things for my setup before I fire the car up and test everything. This leak free system works on paper. I also tested it outside of the car. The whole thing works on a pressure differential system. This includes the MBC and the new valve.

You all know how the MBC works. The new valve works close to the same way. The lower half of the valve should always see more pressure then the top or you would be running wastegate pressure. So the bottom part of the valve sees high pressure and so does the bottom part of the MBC. This keeps the valve closed. While the valve is closed the pressure pushes up on the ball in the bottom port of the MBC. This forces the spring up until the pressure overcomes the spring pressure enough(Depends on MBC settings) to relieve some of that pressure into the wastegate or actuator. Once you release the gas pedal and the BOV opens, the area under the valve becomes an area of lower pressure then the area above the valve. This makes the valve open and release all the pressure that was built up between the MBC and the wastegate/actuator.

I will update this thread as soon as I test the car with this system.

 

[Rob10_99]

The only thing that system will change is crack pressure(what an MBC does). Yet when you let off the throttle, instead of the line no longer seeing boost and closing it will keep the WG open until the pressure is bleed back through that recirc tube you have going. I understand the concept, but what's wrong with a leaking mbc?
Oh I was reading into the hole being closed by the ball or something, that one way should work, how much pressure is it good for?

 

[RipperXX]

You know, there really isn't that much air being lost by your typical MBC.... the bleed hole in my seriously old school Joe P, is just to let air from the MBC to WG bleed off, after you let off the throttle and boost is no longer being made. And the hole is really small.


Without doing a electrically controlled setup similar to OEM I don't see how you can accomplish your goal.

 

[91-gsx]

The only thing that system will change is crack pressure(what an MBC does). Yet when you let off the throttle, instead of the line no longer seeing boost and closing it will keep the WG open until the pressure is bleed back through that recirc tube you have going. I understand the concept, but what's wrong with a leaking mbc?
Oh I was reading into the hole being closed by the ball or something, that one way should work, how much pressure is it good for?

It should work for people running low pressure as well as high pressure. The reason why it can is because of the pressure differential that is taking place. The hose that goes into MBC will always see more pressure then the hose that comes out of the MBC and to the wastegate/actuator.

Nothing wrong with a MBC that leaks. I just wanted to come up with something that does not leak, in a simple way. If this gets too much more complicated then the drawing above, then it really is not worth putting the time into. But as you can see, the concept is simple, and it does not take much time to put together.

Like I said, I will test this out as soon as I can. If it does not work, so be it.. I'll just unhook my system and use it like a normal MBC. The only things I can see going wrong is trying it out and not getting past the wastegate/actuator pressure. This is not catastrophic situation, so its worth a try.

You know, there really isn't that much air being lost by your typical MBC.... the bleed hole in my seriously old school Joe P, is just to let air from the MBC to WG bleed off, after you let off the throttle and boost is no longer being made. And the hole is really small.


Without doing a electrically controlled setup similar to OEM I don't see how you can accomplish your goal.

The whole time air is going into the MBC and some pressure is getting to the wastegate, the bleed hole will be leaking. This leak is not that bad, but it is similar or worse then something like a leaking BISS screw, or throttle body seals.

Yes, your right that hole does relieve the pressure between the MBC and the wastegate/actuator, but this hole leaks pressure out the entire time your wastegate is opening even a little bit.

If this system just does not work, then I will go back to using the MBC the regular way. It was just an idea and I had the spare parts hanging around. If it works, cool. If it does not work, oh well. There really is not a chance of this going so wrong that I over-boost or anything.

 

[RipperXX]

Oh, don't get me wrong. I am not by any means trying to shoot down your idea. I love it when DSM guys try to do something new or come up with a better way. We should never become content with the way things are, we should always try to do a better job of everything we do.


Just at the same time I thought it looked like a lot of work to fix a small boost leak. But I do hope it does work...theres absolutely nothing wrong with being methodical, thats how records are broken.

 

[tkelly27]

If it doesn't work that way, you can put the line that's going to the check valve to the intake tube for a recirculated MBC. This looks like it should work though.. Boy, I do not miss the mass air sensor one bit.