How to make a homemade mbc????

Fox1486 · 09-22-2008, 01:00 PM

I can't seem to find a current link to a writeup for this. Anyone help me out. I remember it as the "home depot" boost controller. Thnx

snowborder714 · 09-22-2008, 01:04 PM

I've posted this on at least half a dozen other threads, so you should have been able to find it.
http://www.geocities.com/chmwatson/FAQs/mbc.html

tkelly27 · 09-22-2008, 01:09 PM

How to make a Manual Boost Controller....that works.

Also, I modified it a little bit. I used smaller fittings. It's a little more compact now. If you look a the plug you get from home depot, on the inside it tapers in. You can't do anything but get the hole right in the middle going from the inside. Tap it from the inside too (the tap doesn't care if you go in from the top or the bottom as long as you go all the way through). I didn't cut it off flush, and I used a 1/4-20 tap and nut and bolt set. 1/4-20 can be found nearly anywhere.

For the spring I used one from the inside of a pen. It fit right over the bolt, perfect, maybe some epoxy to keep it from wiggling free, but I've not had a problem yet. The ball, I used a 6mm plastic air soft pellet. This particular one was glow in the dark, but you could probably use any color you wanted. Ceramic balls? We don't need no stinking ceramic balls.

I've also found that I have not needed the small hole. Maybe I've been lucky, maybe I've been careless with sealing the fittings, I dunno. Mine holds 15psi just fine though.

DSMunknown · 09-22-2008, 02:06 PM

Locating the correct ball and spring was such a PITA for me when I was attempting this. $38 for a Joe P MBC was good enough for me, and I didn't have to go nuts hunting for all this crap. Just my four cents.

Fox1486 · 09-22-2008, 03:33 PM

Thanks for the quick replies. I did buy one but it was a while ago and I just wanted to make sure it was correct. The measurements are not the same, but the fundamentals seem to be the same, maybe the adjustment is just a little more or less sensitive? Anyways this is what I have:

The threaded ends seem to be taped though, both on the ends and the "T" fitting itself.

snowborder714 · 09-22-2008, 03:50 PM

Make sure it has the 1/32" bleeder hole (shown in the link I posted). And when you put it back together, make sure to use teflon tape on all of the threads so it doesn't leak.

Fox1486 · 09-22-2008, 04:00 PM

I've noticed that unlike the one above, the ball bearing actually seals off the end of the nipple thread instead of going past the threading:

As for the bleeder hole, I'm not going to be boosting past 15psi......

tkelly27 · 09-22-2008, 07:54 PM

The bleeder hole is important. When you let off the throttle that ball will shut and whatever boost was in there will continue to be in there. The next time you apply the throttle the WG will open at a lower boost pressure. So, mine does not have the hole, but it has enough leaks to allow it to work properly.

You don't need to have the hole if you have enough leaks in the system, it's just nice to have it to be sure. If you want one, and you don't want to drill, you can use a vacuum tee between the MBC and the WG off the tee you will put what's called an orifice, or restricter. It's a very small hole, some people use nitrous peices, other people welding orifices, I like to find them in cars at the junk yard. This will provide the exact same effect.

As long as the ball is sealing and can move around, you're fine. One thing I do with mine is I get it set up to the point where when I blow through it, the ball just vibrates a bit. This is something like 1-4psi and twisting it further will create useful boost. You're doing a few things there, more area is exposed to the boost pressure, but the spring is also under a lot more tension being so much closer. Should probaby work.