mobythevan Posted February 12, 2006 Share Posted February 12, 2006 OK, after spending several hours today messing with the MBC on the Talon I think I see one shortcoming to some of the MBC designs. Other people have undoubtedly noticed this but I haven't seen it discussed, and I know the poor operation bugs bastaad to death. The type I had on my datsun was the grainger type which had the threads for the adjustable part on the outside of the housing so the threads don't interfer with the springs movement. The type worked good for me, other than one time it got debris on the ball and one time the hose got pinched off. So in other words I was happy with the grainger type. The Talon came with an un-installed cheapo controller that the PO bought for his planned upgrades. So I installed a boost gauge today and installed this cheapo type which is not made like the grainger. It has a bolt that threads into the housing where the spring resides. Undoubtedly the threads will interfer with the spring. The spring is large enough in diamter to get caught and drag on the threads inside. After several hours of adjusting this thing I could not get consistent results. One time it would hold steady at 12psi, no spike. Then I would back it off 1 turn to lower the psi and it would spike to 14psi then settle at 12psi?? I gave up on it for now, but wondered if some of the varied reports on the MBCs out there can be correlated to the design of threads inside the housing vs. threads outside?? I dunno Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted February 12, 2006 Share Posted February 12, 2006 with my Z Brian... I adjust it 1/4 turn at a time.. the best results I get are 8.5psi in 1st gear, 10psi in 2nd, spikes to 12psi in 3rd and settles back down to 10psi, then spikes to 12.5psi in 4th, and settles to 10psi, then 5th gear it holds 11psi. Sooo.. ball and spring setup's suck.. simple as that Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 12, 2006 Share Posted February 12, 2006 mine worked a little better after I put a small... like 1mm, bleed hole inline after the mbc before the wastegate actuator. I obviously had to adjust the grainger a little bit looser, the bleed hole added like 2psi of boost. But I noticed it spiked a little less, held a little more smoothly, and fell off even less. But all there things were really minor improvements, barely noticeable, but still... any noticeable improvement is worth it especially considering the cost of the bleed I had done some of the other tips given to me when I posted a thread a long time ago about how to improve it's performance, the one that really payed off was moving the MBC as close to the wastegate actuator as possible. Initially I had about 1 foot of hose between the MBC and the actuator... so when I moved it closer I did notice it spiked quite a bit less. Never did get around to trying different springs or any of that. Quote Link to comment Share on other sites More sharing options...
Thumper Posted February 12, 2006 Share Posted February 12, 2006 the best results I get are 8.5psi in 1st gear, 10psi in 2nd, spikes to 12psi in 3rd and settles back down to 10psi, then spikes to 12.5psi in 4th, and settles to 10psi, then 5th gear it holds 11psi. That sounds more like a problem with tuning or with the turbo than the mbc. It seems like it just doesn't have enough time/energy to spool the turbo. You might want to check your turbo (which I think is new) or work on tuning somemore. I have run three different types of mbc's and they all act differentely but have found the dawesdevice and a home depot designed mbc to work the best. I would think that if the threads were on the inside the spring would have a chance to catch so why would any one design it that way? I guess just didn't have the right parts or time. I think I have a dawesdevice mbc somewhere in my garage if you are interested? I would give it to you for cost of shipping. PM if you are interested mobythevan. Quote Link to comment Share on other sites More sharing options...
zguy36 Posted February 12, 2006 Share Posted February 12, 2006 The small bleed after the MBC is CRUCIAL to proper operation and consistent boost. I have been building these things for years and have had great luck with them. Right now, mine is set at 15psi. I get 15psi at 3200rpm in 1st, 2nd, 3rd, 4th, 5th and that holds clear till redline. No spikes, no drops, just consistent boost. My design does have internal threads, but they don't go full length inside the controller, so the spring does not touch them. The bleed valve greatly effects your results. Without one, whatever your boost spikes to is what your controller is set to. When pressure finally pushes past the ball and spring, it opens the wastegate fully open. Fully open is too far open for your wastegate as it will oscillate until it settles at the correct openining for your desired boost level. Well, when the boost starts to drop with the wastegate wide open, the ball and spring controller shuts and traps the pressure on the wastegate and it remains open, dropping your boost level below your desired. A small slit on the hose, or a small bleed after the controller will bleed off this pressure and allow the wastegate to shut again. Keep in mind, these oscilations happen very quickly and are very small motions, so they aren't detectable when your controller is working properly. Another note for consistent boost controllers. When I first started building these things for my friends, I had the ball seat metal to metal inside of the controller. I figured that this was a good enough seal for the ball to seat against, but was wrong. If the ball doesn't have a perfect seal against its seat, then you will also get inconsistent boost. I modified mine so that the ball seats against a rubber o-ring and had much better luck. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted February 13, 2006 Share Posted February 13, 2006 I'm running a JoeP MBC http://www.joepmbc.com/ Hmm.. how big of a hole should I drill ? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 13, 2006 Share Posted February 13, 2006 okay to clarify, I had already tapped a small bleed hole like .020" into the outlet end of the MBC... BEFORE I added a second, much larger bleed inline which was just recently. But yeah, you need SOME kinda bleed or your actuator is just gonna stick open. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted February 13, 2006 Author Share Posted February 13, 2006 I want to try zguys recommendations of the bleed hole and the o-ring for the ball to seal against. It may be a couple weeks before I get back to that, I have to check some other things out first on the car before adjusting the boost again. Quote Link to comment Share on other sites More sharing options...
zguy36 Posted February 13, 2006 Share Posted February 13, 2006 Moby, I have had the best luck gluing the o-ring in with JB-quick, or JB-weld. The quick sets up a ton faster so you can see right away if it is going to work or not. Just be very careful to not get any of the glue on the sealing surface of the o-ring and that the o-ring is seated perfectly flat in the bottom of the fitting or else it won't seal for beans. Here's another interesting though for these types of controllers. I traded my ball and spring controller last year for a rising rate fuel pressure regulator ($10 traded for $60 and couldn't find a suitable ball to build another one. I took a grabber screw and carefully ground all of the threads off of it and left about half an inch of the shank. These have a really nice tapered underside to the head of the screw which was the perfect diameter and seated great against the o-ring. The shank stuck through the fitting and acts as a guide for it to slide and not pop out of position. Since the top of the screw is flat, it is perfect for the spring to seat against. Just more ideas for these cheap controllers. For the bleed, I am not sure exactly what size you need for proper function. All that I did was take my knife and put a small slit in the hose ~1/4" long. That way it seals when there is no pressure and releases pressure when it needs to. Quote Link to comment Share on other sites More sharing options...
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