Subaru WRX Forum banner
1 - 20 of 141 Posts

·
Registered
Joined
·
538 Posts
Discussion Starter · #1 ·
Unichip plus an MBC, any opinions?

OK. I've got the APS-COBB Club Spec kit and have experienced some boost-creep. I want to prevent over-boosting. Would an MBC limit the max-boost without affecting the boost parameters set by the unichip mapping?

Pros & Cons welcome.

Thanks,

Curtis
 

·
Registered
Joined
·
538 Posts
Discussion Starter · #2 ·
Hello, anybody out there?

Surely, with the vast knowledge present on this board, someone has answer for my question. Come on, don't be bashful.

Can I use an MBC in conjunction with my unuchip to limit the boost at a predetermined output?

Peace

Curtis
 

·
Banned
Joined
·
7,636 Posts
i don't know anyone here with the cobb chip. most have TxS, but i would guess it should help.

although some people report higher load throttle positions on just an mbc also spikes boost a little. maybe in conjunction that wouldn't be the case.

:confused:

dR
 

·
Registered
Joined
·
8 Posts
newb question: how does a MBC help performance exactly

mbc (manual boost control?) thats just a guess, how does it work ? and are vishnu and turboxs different companies that make this right? i hear people say they got a vishnu stage 0 or whatever, what does it all mean! tryin to learn here, fast. what changes in higher stages? etc etc. would be much apreciated if someone would explain all this to me.
 

·
Registered
Joined
·
310 Posts
The stock WRX doesn't go to full boost on 1 and 2 cause of the computer. The MBC force the boost to say higher and thus give you much better engine response. I might be wrong. hehe
 

·
Registered
Joined
·
41 Posts
should actually read up on all the forum threads, you'll learn a lot!!! the stage 0 or 1 or 2 kits mean that they come with a set of performance parts geared specifically for your car. should click on their link, and it'll show you exactly what the parts are. like for stage 0 it'll come with exhaust and intake, ecu chip and uppipe (just an example not a specific stage 0 kit)

you see the wrx comes with a turbocharger, and so the factory sets the ecu chip to go to about 14.5 psi per every gear. of course in real world applications, the chip doesn't allow it to go that high on 1st or even 2nd gear, and so that's where an mbc comes in.. or any BC for that matter. the turbocharger could actually withstand more psi to like 16.5psi or 17psi (a general consensus from this forum) so the BC is set this high thus giving you more boost even at the lower gears, which will give something better than the factory 9psi.

well if i'm wrong guys, feel free to bop me on the head and correct me

---RaCinWRX
 

·
Moderator
Joined
·
895 Posts
i wouldn't run 17psi stock...you'd have to do someothe mods, like uppipe, exhaust, fuel system, somehthing more before you do that. i think for stock wrx the safe bet is below 16psi
 

·
Moderator
Joined
·
895 Posts
WishIHadASuby said:
see this is why i love u guys. by the time a get a wrx in a year (if all goes as planned), ill be an expert....
yup!

i've had my wrx since november 2001, and in this time already i've learned so much about my car through clubwrx. its a great resource for car info
 

·
Registered
Joined
·
22 Posts
More Boost Controller questions (mbc)

Greetings all. I've been studying all the Subaru Forums regarding manual boost controllers. From what I've seen, most DIY ones either involve a bleeder valve or a pressure/vacuum switch valve. Also one common installation area is on the line between the turbo and the wastegate.

Before you flame me, please keep in mind that I am relatively new to Turbo cars and I've tried doing all the homework I can before I post this question, so here goes.

Fact Background:

A normal bleeder valve mbc works in a way that bleeds off pressure to the line going from the turbo to the wastegate, so that the wastegate thinks there is less pressure at the turbo than there really is, right? Then the pressure relief valve works in that the wastegate doesn't see pressure from the turbo, until the pressure is large enough to move the ball against the spring, right? OK, then there is the combination relief/bleeder mbc that uses a combo of both.

Here is my question:

Would the following work at all? Take the line between the turbo and the wastegate and put a brass tee in the middle, then put an adjustable pressure relief valve on the top tee connection (left and right connect to the line with hose barbs), and put the ball in the down position and the spring above that (making it a pressure relief valve and not a vacuum valve). Doesn't this make a pressure sensitive bleed valve? This is what I would imagine. With the spring compressed all the way, this is the same as stock (the valve cannot open because it would take more pressure than the turbo can generate to open it, so no change from stock). With the relief valve spring adjusted correctly, one can dial in a bleed ratio that will act like a bleeder valve MBC only when there is enough pressure going against the ball/spring to open it. So, at partial throttle, I'm imagining that the valve is either totally closed or barely open (depending on how much throttle). Then at wide open throttle, the valve opens and the right amount of bleed happens, making your wastegate think the turbo is generating less pressure than it really is. Thus giving more boost.

What do you think? Please do play devil's advocate, because I am actually planning to do this. Maybe I'm oversimplifying the process. So, if there is some not-so-mundane detail that I have not yet thought of, please bring it to my attention. Thanks in advance.

TonyK
 

·
Registered
Joined
·
42 Posts
help with Identifying turbo/engine componets PLEASE (for new MBC install)

can someone help me identify the follwing componets, im installing my boostvalve tomorrow and new some help (i tried a search already). I thought i once saw a picture of the engine bay with these componets outlined. Here's what im looking for:

compressor-outlet
wastegate
control solenoid hose
factory bypass bvalve
wastegate actuator

if anyone has a pic with these items on them or any other guidance i would appreciate it!

-Joe

:)
 

·
Registered
Joined
·
310 Posts
I hooked up my boostvalve MBC a while back. The pic they show is
pretty good if you know about engine. Read my instructions and
then look at the pic from the MBC installation guide to get a better
idea.

1. Connect the tee fitting to the BOV hose and add a 1 1/2 inch
hose and reconnect to the BOV. From the tee add a hose
long enough to connect to the MBC (look at the pic showing
the MBC tie to the left side of the intercooler )

2. From the MBC add a hose which will connect to the factory
wastegate.

3. Disconnect the factory hose from the wastegate and connect
wastegate to the hose added on step 2.

4. capped off the factory hose disconnected from step 3. This is
to keep dirt from getting into the factory hose. ( You need
to reconnect the factory stuff when you bring the car for
service). Make sure you use the clamp ***.

5. Remove the cover on the passenger side (close to the air box)
the one with the two plastic wing nuts. Now you can see the
factory boost control solenoid.

6. Disconnect the two hoses and cap them both and use the
clamps to keep the caps from backing out.

7. Set the MBC 5-6 threads out. Short shift from 1st to 3rd
on the highway or a long road. Have your friend watch
the boost gauge. You want to set it a 15.5 - 16 psi on
a normal warm day ( not cold ). Set the screw 1/2 turn
at a time, when it get close to 15 psi do it 1/4 turn at a
time. When it is set a 16 psi on 3rd take it to 4th and
5th and make sure you don't go 2 much over 16psi.
With the bleeding hole build in it doesn't spike much at all
if any.

8. Have fun and watch the HT/FP thingy. When it is working
fine then try my boostvalve/dwaes setup.

9. Good luck.
 

·
Registered User
Joined
·
2,210 Posts
Re: help with Identifying turbo/engine componets PLEASE (for new MBC install)

ElectronBlueSi said:

..
compressor-outlet
wastegate
control solenoid hose
factory bypass bvalve
wastegate actuator

if anyone has a pic with these items on them or any other guidance i would appreciate it!
..
Standing at the front of the car, look at the engine bay (so I will refer to right being the left side of the vehicle, and vice-versa). Find the turbo - it's to the left of the intercooler under an aluminum heat shield that has embossed the picture of a hand with a cross (hot - no touchy).

1. Compressor outlet: Identified by a black plastic hose exiting the right side of the turbocharger and disappearing under the intercooler.
2. Wastegate: Internal, so you cannot see it.
3. Control solenoid hose: On the turbo you will notice a thin tube that runs from the compressor outlet to the wastegate actuator. It has a T connector along it's length, with a tube that runs to the control solenoid.
4. Factory bypass valve: Look at the intercooler. On the right-hand side at the front you will see a device bolted onto the intercooler. This device has a large hose connected to the bottom and a smaller hose exiting the right-side. This device is the bypass valve.
5. Wastegate actuator: Look at the hose mentioned in (3). It runs from the compressor outlet to the actuator, which is a shiny cylindrical device mounted on top of the turbo. It has a rod exiting the back of it, which is connected to the internal wastegate.


Hope that helps,

-Pace
 

·
Registered
Joined
·
42 Posts
thanks a lot guys! you guys rock!
 

·
Registered
Joined
·
42 Posts
install went great, 1st gear is now officially scary! whats next? maybe a uppipe.....hmmm

thanks to all
 

·
Registered
Joined
·
310 Posts
Yes the uppie will improves spool up by 500 rpm. Also it will reduce
the EGT and make the exhaust a little ---> louder <--- :D

Look at PlatinumWRX's rex, it is running 13's with a MBC and a few
mods :D
 

·
Registered
Joined
·
42 Posts
yep, i fixed my sig.
 
1 - 20 of 141 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top