Nikos

What would happen if you took out the spring and ball?

Would it run minimum PSI or maximum?

Around midnight yesterday, I pulled over to set my boost and lost both the ball and spring.... I don't have a boost gauge so I don't know what is running/ (I used one to set the boost at the highest setting possible and marked it)

So tell me, without the spring and ball, how should it run?

Thanks,

Nikos

DragII

it should run whatever your wastegate is set to

X2BOARD

Not exactly sure on what you are asking.... but from what I gather, I believe that that would allow all of the boost signal to pass thru the MBC, therefore it should be upping the boost from the standard W/G setting. I think you would be seeing maximum, not minimum boost.

X2

Nikos

That's what I thought but I am experiencing minimum boost.

Can somebody explain how a MBC works.

X2BOARD

The basic function of an MBC:

First you gotta understnad how a W/G works. It (W/G) is basically an exhaust bleeder controlled by a piston and shaft or a ball OR a butterfly style valve. There are 2 ports on a W/G... One for boost signal and One for Vaccum. The boost port is on the exhaust venting end and the vaccum on the opposing end. Both ends are sealed from each other.
An MBC is basically a bleeder valve that allows boost signal (which is actually boost pressure) to pass thru it at a set rate (wherever you set the MBC). As you turn the MBC in the 'UP' direction, it bleeds more boost to the vaccum port, assisting the W/G to place more tension on it's bleeding mechanism, in turn forcing the W/G to remain MORE closed...forcing more exhaust pressure to spin the turbo.
If you were to turn 'DOWN' the MBC, it would allow less boost signal to reach the vaccum port, in turn allowing the internal spring of the W/G to function at it's 'stock' setting.

I hope I explained this clearly, as I am not able to post diagrams.

X2

DragII

if there is no spring, and no bearing....then there is nothing stopping the wastegate from seeing boost hense it will open up at the minimum.

the ball keeps the wastegate from seeing boost...if it's not there, it's like you have no boost controller at all.

Nikos

Thanks guys. Better go find a tiny metal ball and spring then......

X2BOARD

I thought he lost the valving for the MBC, not the W/G ??

True, if there were no spring in the W/G, he would see no boost... but maybe some clarification is needed.... these parts are missing from where ? The MBC or W/G ?
How in the world did you lose them anyways ?

X2

Nikos

I pulled over in a gas station around midinight yesterday and I took the MBC screw out becaue I suspected that the spring was stuck.... (I was experiencing wheel spin on 3rd gear which is not normal)
Indeed it was stuck but when I tried to get it out and dropped... My MBC is in a weird position...

I could not find either parts because the car was hot and I suspested that the spring and ball drop inside the fan somewhere... I couldn't put my hands to look.

Therefore I put the screw back and drove home..... This morning I looked but couldn't find anything...

My brand new 16G needed a break anyway.

Thanks to both of you for replying.

DragII

I am refering to the MBC

X2BOARD

I would assume a missing spring would be the equivalent of just leaving the MBC fully open. (max boost)

Gunna disassemble an MBC tonite...... again...

DragII

nope, see wide open would mean full boost signal is reaching the w/g, which would then open the w/g to bleed off boost.

the ball closes the valve and boost pushes it open, allowing some boost to slip by "tricking" the w/g into thinking it is in low boost and staying closed.

therealciviczc

The sping holds the ball against the hole in the MBC. The sping is what forces the ball to hold the boost back from the WG. No spring = no resistance to boost = WG seeing all of the boost as it buids just as thought the MBC wasn't there.


Signal in ---> ==0////////////////===== sginal out

O = ball
/// = spring

Usually the boost out is on the side, but the principal remains. The ball blocks the line, and the sping holds it there. Without the sping, the ball would just be pushed back by the boost.

SIDE NOTE!!! If you have the ball, leave it out. It could drop down in to the the boost exit and block the boost from exiting the MBC which would be really bad.


BTW: Don't you have a boost gauge???


[Modified by therealciviczc, 4:50 PM 7/10/2002]

Nikos

No. I know , I know, I should......

I used a comression gauge to set it......

Yes,I set it by driving the car with a big *** line coming off my hood into the cabin......

I know it's stupid..


[Modified by 2 B 4GO10, 12:38 PM 7/10/2002]

DragII

aaahahah Post a pic, I gotta see that.

Nikos

That's how I set it. Only did that for a day. After I hit 18 psi... I marked the screw thread and set it at 15 psi....

DragIIDigital was nice enough to give me agreat price on a Boost gauge and a turbo timer but mecahnical problems set me back.

Now my rings are all messed up and I am going to be driving the SOB till it dies.......... or till I sell it....... Therefore I don't mind that much that the BC is not working........

Of course when I get owned by a Z24 on a red light I will mind and that's why I will put a new balland spring in there.....