Home Made MBC [Merged 9-7] depot

[eyeculookn]

whats up everyone? i've just recently entered the DSM world with a newly acquired 91 Talon AWD 5 spd. car. it has 195,xxx on the body with a rebuilt engine (around 50-60,xxx on rebuild) & is totally stock(except for the wheels). i've not even driven the car yet as i'm in the process of pulling the motor/tranny out right now. i bought the car for $700 but it needed a clutch. i read up on alot of "how-to" articles and decided to pullthe motor/tranny and: remove balance shafts, install clutch of course, and port/polish various turbo parts (the lip from ex.mani. to turbo mainly). anyways, on to my question....

it seems that all a manual boost controller does is cut off some of the air flow to the wastegate, correct? as you tighten down the valve, it slowly blocks off some of that air, correct? well i found a valve at the hardware store that has 3/8 barbs on either end and the knob has to be spun around about 2 complete turns to allow full air flow. it appers to be very heavy duty. it look like a small water shut off valve but with 3/8 inch barbs instead of threaded ends. i dunno, gimme some comments as i'm new to this stuff.

 

[candela]

not to bust on you or anything, but damn, you must have little cash and a lot of money... you pull the motor for shafts, clutch ... i understand budget racers( like myself ) but unless you are getting serious they really don't need removed...just my.o2$

 

[Boosted1gDSM]

Yeah, ur better off just droppin the $25 and gettin a quality MBC. if you dont wanna do that u can go to www.c-speedracing.com and find instructions for a homemade MBC that uses two plumbing components, a ball bearing, and a spring.

 

[Slanted J]

Ive done a search but couldn't find anything really relevant.

From what I understand, the basic idea is to reduce the psi goign to the wastegate accuator, thus keeping it closed longer and generating more boost. So what is the advantage of using a ball bearing and spring valve for a MBC versus something like a flapper valve. I would think that a flapper valve (or any other valve that doesnt require a ball bearing and spring) would give a more consistent and better result instead of having to expieriment with different springs.

When I searched around, it seems that everyone is hell bent on using the G-valve, and when asked why...no response.

Can anyone clue me in?

Thanx,
Slanted J

 

[L2RTSiAWD]

Becasue a flapper valve is known to cause major spikes and creep becasue is cannot open the wastegate as fast as a ball/spring type. Why? I don't know they just do.

later,

 

[L2RTSiAWD]

Actually after reading your post again you have the concept wrong. The MBC's job is to open the wastegate at a certain psi. the reason you get boost spoke is becasue some MBC's cannot do this in time and boost spikes then settles down. A ball/spring can open the wastegate quicker with less spikes.


Later,

 

[Slanted J]

Ive heard the same thing, but cant get anyone to tell me why a ball/spring MBC would not cause boost spike. If anything I would think that a ball/spring MBC would create a boost spike because of the spring. Where as a flapper valve stays in the same position regardless of PSI changes.

 

[BatmanGSX]

Dear god... none of you even know how an MBC works. First you have a spring in your actuator that compresses at a certain PSI. Whatever, let's say it's 7psi. The actuator will not open without some sort of signal (unless extreme exhaust gas pressure pushes the flapper door open). So to increase boost you can "bleed" some signal off so that it requires more boost to actually get the actuator to see 7psi (the wrong way that will cause spiking).

Or you can use a ball and spring MBC. What you are doing now is blocking all signal from reaching the actuator until enough pressure builds up to open the spring in the MBC. Once the spring opens all that pressure goes to the actuator and opens it up. Remember, the actuator will not open without a signal but it will open at 7psi or above.

As you compress a spring it's rate increases. When you screw the MBC in the boost pressure goes up.

 

[L2RTSiAWD]

Originally posted by BatmanGSX
Dear god... none of you even know how an MBC works. First you have a spring in your actuator that compresses at a certain PSI. Whatever, let's say it's 7psi. The actuator will not open without some sort of signal (unless extreme exhaust gas pressure pushes the flapper door open). So to increase boost you can "bleed" some signal off so that it requires more boost to actually get the actuator to see 7psi (the wrong way that will cause spiking).

Or you can use a ball and spring MBC. What you are doing now is blocking all signal from reaching the actuator until enough pressure builds up to open the spring in the MBC. Once the spring opens all that pressure goes to the actuator and opens it up. Remember, the actuator will not open without a signal but it will open at 7psi or above.

As you compress a spring it's rate increases. When you screw the MBC in the boost pressure goes up.

Thanks. I was having a brain fart and knew how I wanted to explain it but it didn't come out right.

Later,

 

[Slanted J]

BatmanGSX, I know how a MBC works. But I dont know why one is better than the other, apparently you dont either.

Ok, lets say that the Waste Gate Acuator opens the waste gate when it recieves a signal of 7psi.

Now if were using a ball/spring MBC, that has been calibrated to open at 12psi, there will not be a signal (air flow) to the WGA until 12psi is reached because the ball and spring will only let air by when 12psi is reached. Thus you get your 12psi of boost. Great.

If were using a flapper valve, we are basically just restricting the amount of air flow, which in turn drops the pressure. So there is always air going through the Flapper valve MBC. Now the WGA will not open until 7psi, but since there is a pressure drop caused by the MBC, it will delay the opening of the WGA. THus you get your 12psi of boost. Great

You get the same PSI just by a different means. Why is one better than the other. I KNOW how both works. I woud think there is something potentially problematic with the flapper valve idea being it always lets air through, but not sure. Thats what my question is about.

 

[BatmanGSX]

Originally posted by Slanted J
BatmanGSX, I know how a MBC works. But I dont know why one is better than the other, apparently you dont either.

Uh-huh. If you knew how they worked you would understand why a bleeder will cause boost spikes. It's because the pressure that bleeds off isn't static. A different ammount of pressure will bleed off with different engine loads. The only way it would work would be if the bleeder was dynamic and used some sort of stepping motor, controlled by a pressure sensor.

But whatever. Why don't you go ahead and try a bleeder. Because nobody else, including myself, has ever tried to make a $0.50 boost controller and we have no idea what will happen. You will be a pioneer. Report back with your findings.

 

[Slanted J]

I dont quite understand what your tyring to say when you say "the pressure that bleeds off isn't static".

 

[BatmanGSX]

The pressure that bleeds out of the orifice you have added to the signal line is not going to be the same per gear, temperature (and about five hundred other variables). Therefore the actuator may be opening at different manifold pressures. The 7psi required to open the actuator will not occur at the same actual manifold pressure pretty much ever.

A bleeder will increase boost but it doesn't control it by any means.

 

[GreenGSX]

A ball and spring MBC spools a turbo faster because the wastgate stays shut until the spring force is overcome. That means no boost leaks until you hit full boost. When using a bleeder, the wastgate opens before the full boost and thus isn't as fast. The bleeder is always leaking boost and that's never good for fast spooling. Not much of a big deal say at 12psi but at 20psi its a night and day type of thing. Also, boost spiking can be caused by using to stiff of a spring or to big of a bleed hole your home made MBC. Hope this helps.

Tim

 

[Slanted J]

I think my understanding of the way the Waste Gate works is messed up. Does the waste gate open and close like a light switch (on/off) or can the Waste gate partially open?

 

[BatmanGSX]

It works better if it is like a light switch (better spool). Ball/Spring MBC will make it like this. Some EBCs and Bleeders may open the wastegate progressively. This is bad for spool time as not all the exhaust gas is being used to spool the turbo.

 

[Slanted J]

I gotcha. Thats where I was getting confused with your explanation BatmanGSX. Now using a Ball/spring MBC makes PERFECT sense. For some reason, the fact that the waste gate can open partially, didnt occur to me until Tim posted his explanation. Thanx Tim.
Thanx for straigthening me out BatmanGSX, even though it must of been REAL frustrating .

 

[Bohrn]

yep, Batman is right.

Ball and spring is better, as your car gets FULL boost to the engine until the boost pressure overcomes the spring pressure allowing the signal to reach the waste gate actuator. This allows you to have better throttle response, nicer part throttle driving and a less "wishy washy" engine. It just works better. It also holds a much more steady pressure. Mine holds 16 psi. Not between 13 and 18 like a bleeder valve will. I do get a small spike at first(1psi for one second) but that is all. It is my first attempt at an MBC. I had never heard of one 2 weeks ago, let alone made one or understood one.

Just be VERY careful with your right foot when testing/calibrating it. VERY careful. Watch that boost guage like a hawk. You do have an after market boost guage that accurately reads up to at least 20psi don't you. If not, do not make an MBC! Really! You can destroy your motor in a heartbeat!! Game over!

I attached a simple pic of how to make one in another thread. It is called ?? about my homemade MBC or something. I used a "T" instead of a 90deg elbow, but the rest is the same. Oh and I made it smaller. The sizes he has there are enormous!! That is the basic idea, just make it about half size. Brass is better than steel or iron. And don't forget the 1/16th" bleed off hole or it will spike and then not hold too much. I figure it is because the high pressure air can't get outta the dang system and holds the ball shut. As soon as I drilled that hole, all was well in my neigbourhood.

best of luck and have fun.

 

[Slanted J]

Thanx for the advice Bohrn, and yes I most certianly have a after market boost guage

You wouldnt happen to have the url for that particular thread? I did a search, or the best I could since you cant use MBC in the search criteria.

 

[ProjectGSX]

These days, there is really no reason to build your own MBC. Prices have gotten so low lately. Dawes Devices sells a ball and spring MBC for $35.

http://www.dawesdevices.com/boost.html

 

[Bohrn]

Well slanted, I just went back a couple of days, and found my name as the thread starter. Here it is

http://www.dsmtuners.com/forums/showthread.php?s=&threadid=2441

also, note that I did not use an "L" fitting, but a "T" fitting. Also I made it smaller. The sizes he uses would be friggin huge!

and yea, at $35 it is a pretty good deal, and the JoeP and Hallman ES can be had for $45 at www.boostcontroller.com, but after duty, s&h, various taxes and us/canada exchange, I was lookin at over $130 for a $45 part,so I built my own for $13.58 canuck bucks. about 7cents us??

besides it is kinda fun to build your own hot rod parts. Kinda adds to the feeling of accomplishment. Anyone can buy a new Porshce and whoop anyones ass, but someone who builds up an old car and beats the high dollar car really feels cool about it. I know this is at a smaller scale, but to me, its the same idea.

have fun

 

[Slanted J]

Yeah, I know there getting cheaper, but if there something that I can make myself, then thats what im going to do. Just for the fun and knowledge of it all.

thanx for all the help again.


Jon

 

[eyeculookn]

if you had the tools to MAKE a 20g for $200 instead of buying one for $1000, wouldn't you make one? i mean, these MBC's are nothing more than a few pieces that these guys have put together and sell em for a fair but very profitable price. just like cell phona antenna boosters, i can get like 1000 em for $100 and sell em for $5 a piece.......$5 is a fair price but anybody could find them for a dime a piece.

 

[gstspyder1998]

Does anybody else have a link on how to make an MBC???

 

[Captain Morgan]

hey I went out and built me a mbc. I didn't drill a bleeder hole in it, and im having trouble boosting over 13psi, I was running 15lb without the controller. I read somewhere that not drilling the hole will not allow you to boost over 15, but I can only squeeze 13 out of it with it screwed all the way in. shoud I go ahead and dril a 1/32" hole in it to bleed?