# The real diy information on MBC/n75



## 514passatvr6 (Dec 5, 2004)

After spending a few hours reading up on mbc's options I was not able to find any real good diy information on the mbc mod in various applications. 
I was hopping to compile some information on each set-up to hopefully later on develop some good write-up material for the FAQ section. 
Here are the options:
N75 with MBC running in line.
N75 bypassed with MBC, N75 still plugged in
N75 bypassed with MBC, N75 not plugged in
N75 ran in parallel with MBC known as "overboost kit"
N75: in either stock form, J or H.
Please give feedback, pros and cons for each set up that you have experience with. 
Hopefully we won't get people telling me go check the search or this topic has been killed before. This is the only topic in existence that actually lists all the possible combinations. If you don't have something nice to post, please don't post.


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## QuickK03Crap (Oct 5, 2004)

*Re: The real diy information on MBC/n75 (514passatvr6)*

Different setups react differently on different cars. And you can't run w/o the N75 electrically plugged in, ECU doesn't like it. I mean I guess you CAN if you want to, but.....lol


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## AVANT (Jun 25, 2001)

*Re: The real diy information on MBC/n75 (514passatvr6)*

a) N75 with MBC running in line. - Inceases boost, stupid part throttle (on/off feeling)
b) N75 bypassed with MBC, N75 still plugged in - Feels like option a.
c) N75 bypassed with MBC, N75 not plugged in - Don't do it as the ECU will hate you.
d) N75 ran in parallel with MBC known as "overboost kit" - Used to LIMIT boost, NOT to increase, different purpose when compared to option a and b.


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## 514passatvr6 (Dec 5, 2004)

*Re: The real diy information on MBC/n75 (QuickK03Crap)*


_Quote, originally posted by *QuickK03Crap* »_Different setups react differently on different cars. And you can't run w/o the N75 electrically plugged in, ECU doesn't like it. I mean I guess you CAN if you want to, but.....lol 

It has been done by a few members, they claimed it pulled really hard, part throttle was awful though. It will throw a fault naturaly. Some report though the car run's crazy. 
Overboost kit to be used with N75 H with an aggresive chip. 


_Modified by 514passatvr6 at 4:37 PM 10-18-2005_


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## TSTARKZ123 (Oct 1, 2004)

how would you do A and D? I though they were the same.


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## QuickK03Crap (Oct 5, 2004)

*Re: The real diy information on MBC/n75 (514passatvr6)*


_Quote, originally posted by *514passatvr6* »_
It has been done by a few members, they claimed it pulled really hard, part throttle was awful though. It will throw a fault naturaly. Some report though the car run's crazy. 


Mine was in instant limp mode.


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## ruso (Jul 29, 2004)

*Re: The real diy information on MBC/n75 (AVANT)*


_Quote, originally posted by *AVANT* »_d) N75 ran in parallel with MBC known as "overboost kit" - Used to LIMIT boost, NOT to increase, different purpose when compared to option a and b.

Could this be used with say a TurboXS Dual Stage Boost controller to limit boost at two different PSI? COuld you leave one wide open for maximum requested and another for daily driver mode?


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## AVANT (Jun 25, 2001)

*Re: The real diy information on MBC/n75 (ruso)*


_Quote, originally posted by *TSTARKZ123* »_how would you do A and D? I though they were the same.

They are not the same, you generally don't need both A and D. However...
For example:
If your N75 causes a spike to 22psi and holds 17psi, you can use option A to boost PAST 17psi, while using option D to LIMIT the psi to 20psi (As in to never boost past 20psi). Obviously you can play with the numbers a little, but that's the only reason I can think of to run A and D.
It would be better to just use option B and set it to your desired boost level as it will feel just about the same and it'll save you a from more routing and $$ for another MBC.

_Quote, originally posted by *ruso* »_Could this be used with say a TurboXS Dual Stage Boost controller to limit boost at two different PSI? COuld you leave one wide open for maximum requested and another for daily driver mode?

If you mean running the dual stage MBC in overboost mode, yes that would work. But why? It'll only be used to limit your boost, not to increase it. If your car is chipped, invest in the smoothest N75 for your car and you already have a decent part throttle for daily driving conditions.


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## TSTARKZ123 (Oct 1, 2004)

*Re: The real diy information on MBC/n75 (AVANT)*


_Quote, originally posted by *AVANT* »_They are not the same, you generally don't need both A and D. However...
For example:
If your N75 causes a spike to 22psi and holds 17psi, you can use option A to boost PAST 17psi, while using option D to LIMIT the psi to 20psi (As in to never boost past 20psi). Obviously you can play with the numbers a little, but that's the only reason I can think of to run A and D.
It would be better to just use option B and set it to your desired boost level as it will feel just about the same and it'll save you a from more routing and $$ for another MBC.
If you mean running the dual stage MBC in overboost mode, yes that would work. But why? It'll only be used to limit your boost, not to increase it. If your car is chipped, invest in the smoothest N75 for your car and you already have a decent part throttle for daily driving conditions.

I think I know how to route the BC for D...could you explain how it would go inline for A. Thanks for the help thus far!


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## ruso (Jul 29, 2004)

*Re: The real diy information on MBC/n75 (AVANT)*


_Quote, originally posted by *AVANT* »_If you mean running the dual stage MBC in overboost mode, yes that would work. But why? It'll only be used to limit your boost, not to increase it. If your car is chipped, invest in the smoothest N75 for your car and you already have a decent part throttle for daily driving conditions.

I'm running the APR Stage III+ which is full 20 psi all the time. It'd be nice to be able to trunicate it down to say 16 psi for the sake of the engine and switch to 20 psi when I feel like messing around.


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## tsuter (Dec 25, 2003)

*Re: The real diy information on MBC/n75 (514passatvr6)*

I know these have been posted 1000 time but once more won't hurt.
Boostvalve.com
1. MBC in line or series with N75. Raises boost...by holding pressure back from the N75 until the MBC limit is reached.








2. MBC bypassing or in parallel lowers boost. Used to trim limp causing boost spike by passing air around the N75.








3. Both in line and parallel. Usually done with an MBC in line to raise boost and a needle valve in parallel to trim spike. Can be done with two MBC.









Mine is picture 3.








Leaving the N75 plugged in is recommended unless you like CELs on your cluster.



_Modified by tsuter at 8:09 AM 10-19-2005_


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## judoGTI (Mar 5, 2002)

*Re: The real diy information on MBC/n75 (514passatvr6)*

You have to be kidding me that you couldnt find any real good DIY information on here about this.
Its been beaten to death on here, with many diagrams pictures and written experiences.


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## 514passatvr6 (Dec 5, 2004)

*Re: The real diy information on MBC/n75 (judoGTI)*


_Quote, originally posted by *judoGTI* »_You have to be kidding me that you couldnt find any real good DIY information on here about this.
Its been beaten to death on here, with many diagrams pictures and written experiences.

Did you read my 1st thread? Obviously you did not. If you don't have something good to say then keep quiet. I never said anything about diagrams or pictures. And no there is not 1 thread at all which discuss' all the possible set-ups. I just spent 3 hours searching, please. 
Back to the topic:
I was thinking maybe trying an H valve, and limiting my boost down to 20 as one option to try.
Currently my boost goes to 20, and some times goes to 18 then back 20, then again to 18, till it settle down to 15 then to 12-13 at redline.
Am I hitting soft limp and surging at the same time?


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## TSTARKZ123 (Oct 1, 2004)

awesome...ends up I knew how to do A all along


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## RichB (Jun 7, 2003)

*Re: The real diy information on MBC/n75 (tsuter)*


_Quote, originally posted by *tsuter* »_
3. Both in line and parallel. Usually done with an MBC in line to raise boost and a needle valve in parallel to trim spike. Can be done with two MBC.
Mine is picture 3.










Does the needle valve help any in aleviating part throttle surging???


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## sxorpyon (Jul 6, 2004)

*Re: The real diy information on MBC/n75 (RichB)*

I ran stock programming for a year at 18 psi dropping to 12 redline. Do this:
option B + 4.3v diode + bypass n249 + buy 30 dollar vag cable + log and use lemmiwinks to get as close to safe as ya can.
You will never have part throttle unless you have a solenoid which you switch between a line running to the MBC and running to the n75. It's not hard to do - there are a lot of threads on it i'm sure or you could just figure it out. wire to a switch in dash that lets you flip between the n75 or the mbc. Also you can adjust the WG arm. I ran the stock n75 with stock programming with a tight WG arm for several months.


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## 514passatvr6 (Dec 5, 2004)

*Re: The real diy information on MBC/n75 (sxorpyon)*

I just received both my n75 race, and my MBC.
Had no had time to install mbc, but the n75 race works like butter.
results= [email protected], stock downpipe stock exhaust.


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## MoBlueTT (Aug 17, 2002)

*Re: The real diy information on MBC/n75 (tsuter)*

Mine is Option # 4







Not the cheapest, but nothing works better IMHO...


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## El Romano Loco (Sep 8, 2000)

*Re: The real diy information on MBC/n75 (MoBlueTT)*

Could explain how this is connected on the engine? 
Thanks!
Also, what is the metal tube thing?
Adrian


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## RichB (Jun 7, 2003)

*Re: The real diy information on MBC/n75 (MoBlueTT)*


_Quote, originally posted by *MoBlueTT* »_Mine is Option # 4







Not the cheapest, but nothing works better IMHO...









The Mod Shcack Boost machine... have read the details on the mod shack website about this item and it looks like a really neat device, but I could not gleam if it worked on smoothing out part throttle surging issues.


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## gls:maverick (Oct 18, 2005)

*Re: The real diy information on MBC/n75 (RichB)*

The place to go in Louisville sells these things option#4 and aparently they work awsome. When i get all of my winter mods out of the way and I drop it on the dyno in the spring I will probably put one on to fine tune the system.


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## vwturbowolf (Nov 28, 2003)

*Re: The real diy information on MBC/n75 (gls:maverick)*

do any of you guys have big turbo setups running mbcs to get more boost.
i have a gt28 with revo stage3 and only at 17 pds. i want to get to 21. the guys that did my software said its made to run with a boost controller.


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## kroutbrner (Nov 2, 2009)

*Re: The real diy information on MBC/n75 (QuickK03Crap)*

There is a "diode mod" for this purpose. 
Get a 4.7 Volt diode and hook it up to your N75. This allows the ECU to see no more then 17psi, there for keeping you from hitting limp mode. There is a DIY for this somewear on here. Im sure you could find more info with a quick search.
Good Luck! 
Cheers








-Ross


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## technician (Jun 29, 2009)

*Re: The real diy information on MBC/n75 (kroutbrner)*


_Quote, originally posted by *kroutbrner* »_There is a "diode mod" for this purpose. 
Get a 4.7 Volt diode and hook it up to your N75. This allows the ECU to see no more then 17psi, there for keeping you from hitting limp mode. There is a DIY for this somewear on here. Im sure you could find more info with a quick search.
Good Luck! 
Cheers








-Ross

I thought that was for the MAP sensor. . .


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## jeffcoan (Jun 24, 2009)

*Re: The real diy information on MBC/n75 (technician)*


_Quote, originally posted by *technician* »_
I thought that was for the MAP sensor. . . 

You are right. That other guy is


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## dubinsincuwereindiapers (Jan 16, 2008)

*Re: The real diy information on MBC/n75 (kroutbrner)*


_Quote, originally posted by *kroutbrner* »_There is a "diode mod" for this purpose. 
Get a 4.7 Volt diode and hook it up to your N75. This allows the ECU to see no more then 17psi, there for keeping you from hitting limp mode. There is a DIY for this somewear on here. Im sure you could find more info with a quick search.
Good Luck! 
Cheers








-Ross


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