MBC Issues...

New members MUST post a new intro thread before they can access the rest of the forum.

Re: MBC Issues...

Postby Skurneha » Wed Aug 14, 2019 10:10 pm

Junctrac wrote:There's a good chance you have the mbc from twosrus or atleast a spring and ball one that works the same, I would look through these install directions and check the routing and see if the tvsv line is capped.

https://www.twosrus.com/Articles/Instal ... ctions.PDF

Basically the the mbc goes inline between turbo compressor outlet and wastegate. When turbo pressure is greater than mbc spring pressure the ball moves and allows pressure to go to wastegate which then opens. I have this mbc and after the car sat for along time i think its spring became slightly weaker because I had to turn it in to get back to the same psi I was at before. Like underscore said you could hook up a compressor and regulator to the line going to mbc and see where it opens. If its above 12-13 then its probably the exhaust leak holding you back.


I actually found the issue and you’re not going to believe it. It was a dud boost controller that was feeding a SECOND ONE. I rechecked the vacuum lines and found it was connected to another boost controller so the one I was messin g with wasn’t increasing boost because it was already opened up and the second one it was connected to is what was controlling it.
Fucked up stuff. Either way issue solved! I’m going to have to install an electric boost controller anyway though so I can have two stage, I don’t want to be running high boost all the time
Members don't see the above ad. Register now - it's free!
Skurneha
Newbie
 
Posts: 13
Joined: Mon Aug 05, 2019 9:40 pm

Re: MBC Issues...

Postby Junctrac » Wed Aug 14, 2019 10:29 pm

Well thats an interesting tactic haha, glad you got it sorted.
Junctrac
Newbie
 
Posts: 13
Images: 4
Joined: Tue Jan 24, 2017 11:41 pm

Re: MBC Issues...

Postby Skurneha » Wed Aug 14, 2019 10:50 pm

Wouldn’t’ve found it without the suggestions, thanks!
Skurneha
Newbie
 
Posts: 13
Joined: Mon Aug 05, 2019 9:40 pm

Re: MBC Issues...

Postby underscore » Thu Aug 15, 2019 3:35 am

I'm assuming someone installed the hidden MBC, and a later owner added the one you found not knowing about the first one. Otherwise one can only guess at what somebody would've been trying to achieve with two lol :crazy:
★ 1991 GTFour RC ~ "Rebel Scum" ★
It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
underscore
GTFour God
 
Posts: 4269
Images: 0
Joined: Mon Apr 09, 2007 11:29 pm
Location: Kelowna, BC

Re: MBC Issues...

Postby Skurneha » Thu Aug 15, 2019 3:42 am

underscore wrote:I'm assuming someone installed the hidden MBC, and a later owner added the one you found not knowing about the first one. Otherwise one can only guess at what somebody would've been trying to achieve with two lol :crazy:


Looking at the signs hidden around the car and in the box of parts I got with it, the second owner (I’m the fourth, the third garage kept it and it started to die, and the first was just an old doctor wanting a slick car) rally or autocrossed it. Dings and dents, respray on rear quarter that barely doesn’t match stock super white paint, mashed undercarriage, and spare set of labeled rims and tires.
Guy probably cobbled together something that worked for him I guess, maybe. No idea. All I know is that I’m going to turn this car into my project daily driver so no huge shit just small tweaks.
Skurneha
Newbie
 
Posts: 13
Joined: Mon Aug 05, 2019 9:40 pm

Re: MBC Issues...

Postby SLC Punk » Thu Aug 15, 2019 11:00 pm

Your car sounds like my old one. Is it a 92 white? Josh was the owner after me. Let me know, I might be able to help
-Travis
1992 ST185- sold
2014 4Runner Trail
2018 Audi S5 Sportback
1978 F250-for sale
SLC Punk
Club Member
 
Posts: 276
Joined: Mon Aug 09, 2004 1:09 pm
Location: Maryland

Re: MBC Issues...

Postby Skurneha » Fri Aug 16, 2019 3:14 pm

SLC Punk wrote:Your car sounds like my old one. Is it a 92 white? Josh was the owner after me. Let me know, I might be able to help


Small world! Yeah that’s me, bought it from josh in May.
Skurneha
Newbie
 
Posts: 13
Joined: Mon Aug 05, 2019 9:40 pm

Re: MBC Issues...

Postby Andy » Sun Aug 18, 2019 1:17 pm

The TVSV is Not a bleed-type boost controller, I believe that is what the MBC is...

The TVSV is open or closed.... it is never half or quarter way open.

As a test.... (did this years ago, look back in my history...)
I used a syringe and a vac/boost gauge to put controlled pressure into the sensor...
Engine off, key on.
Apply "boost" to sensor...
When it hits the "limit" the ECU will open the valve and remove the pressure from the waste gate to limit boost.
Then pressure drops off, TVSV is closed again for boost....
You should hear the TVSV click open...
A a further test....
Use an air compressor to apply about 10-12 lbs of pressure to the hose (the one that gets blocked off with a MBC) going to the TSVS valve.
Repeat the first test.... the valve should open and the air will flow thru TVSV into the intake manifold.

The boost/pressure gauge will show what pressure this occurs.

You might find my thread from a while back interesting.
My DIY Electronic Boost Controller
viewtopic.php?t=32605

Also, Temperature and humidity play a significance role.
If I dialed in my MBC (or EBC...) to be just under Fuel Cut on a hot afternoon.
That setting would be "to High" the next mourning with Cold Damp air....and I would hit FC.
In the afternoon, hot and drier, like when I set it, it was working as expected.
So if adjusting and comparing, be aware, weather matters.
Andy
Club Member
 
Posts: 333
Joined: Sat Oct 30, 2004 12:50 pm
Location: Ohio

Previous

Return to New Member Forum

Who is online

Users browsing this forum: No registered users and 1 guest