BogusSVO

iTrader: (1)

You should have to use compressed air on the actuator to move the rod out about 1/8 inch to get the rod on to the WG flapper. if you can just drop the rod and not have to fight it on, your too loose and the WG flapper is not fully closed.

I am running about that same turbo on my old Turbo Ranger...

f1luva92

iTrader: (3)

really? my old rx7 TII wastegate i could move even easier and it built boost just fine.

BogusSVO

iTrader: (1)

Think about it, the WG is a door, if not fully closed, it leaks

Maybe you had a diffrent style of actuator that pulled the rod tight. IDK

I know I had a no boost problem once, and the rod was not pulling the WG tight to seal.

Clocked the turbo a bit to put some tention on the rod, therefor the WG... boosted great after that.

f1luva92

iTrader: (3)

its got a good amount of tension on it, but not enough that i cant pull it by hand with some effort.

BogusSVO

iTrader: (1)

Can you blow a small amount of compressed air in one the nipples and see the rod move?

When you install the rod on the WG lever pin, to you tug on it some to get it to go on the lever pin?

It should take a bit of effort to get the rod on.

How old is the turbo?
Has it been abused?

I wonder if the WG hole has cracked badly and even with the flapper fully shut, exhaust gasses are getting around it

fooger03

iTrader: (2)

You'd pretty much have to lose the flapper to see almost no boost - a crack wouldn't do it. Also, it doesn't matter if the MBC is on there, if you're not building enough boost to open the wastegate, you could run the MBC fully closed or fully open and it wouldn't make a difference. Better idea: disconnect the signal line from the wastegate actuator altogether to see if you can build boost that way.

Faeflora

iTrader: (2)

Make or buy a boost leak tester

Savington

iTrader: (31)

WG flapper leak or boost leak. You have one of these problems.

f1luva92

iTrader: (3)

well i disconnected the mbc which made no difference. also i pulled the downpipe off and the flapper does appear to be closing fully. i'm planning to build a boost leak tester tonight.

devin mac

iTrader: (2)

This.

Otherwise you're just going to keep grabbing at straws. Plus, you'll now have it on hand for the future if you ever run in to problems again.

Toddcod

iTrader: (8)

I literally just went through this. Flapper door seemed to work fine. 2-3 psi with wastegate vac hose disconnected.

The rod had moved out of position on wastegate. Once dp was removed. I instantly seen it. I tapped it lightly with a hammer back into place. Never had a problem again.

sixshooter

iTrader: (12)

Intake manifold shouldn't have any hisses. Find your leak.

Braineack

iTrader: (62)

mbc mounting bracket is ingenious. +1.

BogusSVO

iTrader: (1)

I think that is about the best way to mount a MBC, It is very responsive that way.

All you do is remove the hose barb and replace with a pipe nipple (1/8 npt)

The trick is you have to shave a few threads off the nipple on the end that screws into the MBC, or you will not be able to get any adjustment from the spring.

devin mac

iTrader: (2)

it's ingenious except it keeps you stuck with the worst possible place to take a boost reference for a MBC...


that said, i still like it if you don't mind the boost taper towards redline. ;-)

f1luva92

iTrader: (3)

what do you mean it moved out of position? when i pulled my dp off, everything looked to be alright.

BogusSVO

iTrader: (1)

Why is it the worst place for a MBC?

It is set at 22psi, no boost creep or taper.

devin mac

iTrader: (2)

it's taking a pressure reference from the source, not from where the charged air enters the engine.

if you have something like an IC in the path between the compressor outlet and the intake manifold, the amount of restriction that item represents becomes greater as the airflow increases. It's a non linear relationship.

The way to think about it is with a narrow drinking straw. if you blow through it lightly, it seems to present no restriction. However, the harder you blow, the more of a restriction it becomes.

We have a thread about it somewhere. I'll find and update this post.

EDIT: here we are. https://www.miataturbo.net/diy-turbo-discussion-14/boost-sag-no-you-dont-need-ebc-47532/

Braineack

iTrader: (62)

i still prefer sourcing boost from after the IC, but props nonetheless.

devin mac

iTrader: (2)

that was the core intention of my post, as well, i just was less direct about it