miatamad

Hi - Here is my problem,

I have a MBC installed between the housing on the turbo and the wastegate.

If I have the w/gate can set to 5PSI - I cannot change boost at all higher regardless of the amount I dial in the MBC - even all the way. Seams that its simply not having any impact.

When I adjust the can I get higher boost -- ??? again independent of the MBC setting.

Then when I was checking it this morning a ball and spring fell out - anyone know what order I put them back in?

C

jwarriner

Make sure you have it hooked up correctly (as in not backwards) the boost source should be going into the ball. Secondly it goes screw, spring, ball, in that order. Some of them, like a Halman, sometimes have a little disk, this goes between the screw and spring.

left field

iTrader: (1)

https://www.miataturbo.net/forums/showthread.php?t=5403

miatamad

OK - so I did have it installed the right way around and I put it back together correctly - same problems exist.

?? This is doing my head in. I'm thinking that it may be a problem with the MBC?

samnavy

iTrader: (7)

OK, clarify a few things.
Your turbo setup was working perfectly fine and would adjust accurately on wastegate spring alone prior to installing the MBC.
You have just bought this MBC, installed it, and it's not doing anything?
Is it new? What is the brand?

You say you can still adjust accurately with the wastegate spring even though the MBC is installed?

Hmmm.... that is strange. I vote that you reassembled it wrong... but it's a pretty simple device and you say you've got it right. Post a couple of pics of the setup... maybe we can narrow it down with a visual. Take the MBC apart and lay the pieces out in the order you're installing them and post a pic of that too.

Braineack

iTrader: (62)

is there anything inside the MBC?

jwarriner

Well an MBC is a simple device, unless the spring is bad/crappy, or it's a poor design, then I can't see it being a "bad" MBC. They don't just go bad or have "bad batches." Does it have a bleeder so that the wastegate can close when you go off boost?

My thoughts are that the wastegate is blowing open. Do a run with no boost source going to the actuator, if you can't get over 5psi then it's the actuator.

lazzer408

iTrader: (1)

Does the mbc come with a pill built into it?

lazzer408

iTrader: (1)

VERY carefully!! Your going to be using your foot to control the boost!! BAD advice imo. If he cant get over 5psi with no boost to the actuator it could be a bad turbine fan, bad bearings, ect ect. Not a good way to diagnose the problem jwarriner.

magnamx-5

iTrader: (7)

If the WG was failing then the failure would be apparent with out the MBC in place. It is not occuring like that is you read the original posters posts. his problem is a MBC doing nothing, look at the faq it explains how to reassemble and check your MBC. Nice try newb bad MBC is the answer. If he had it fail vented he would see to much boost if it failed open with no vent he would have what he has now. And if it failed closed with no vent he would see to much boost. This is simple logic people

jwarriner

If this is a homemade MBC then I could see it just being a crap MBC. There is a science behind choosing the correct spring. Too loose and it'll bind and get stuck, too tight and you'll have no resolution in your adjustment. If it's a good MBC, assembled correctly, and hooked up right, then I don't see how it could just fail. It makes no sense. He must have put it together wrong or just got a poor design. Crap MBC? Yes. Improperly installed/assembled MBC? Yes. MBC failure? Not a ******* chance.

Bad wastegate actuator my have been poorly concieved but random MBC failure is just as dumb.