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Discussion Starter · #1 ·
Hi All,

As per title really. I want to control the issues I have with surging on my 1.8T (on full boost, it boosts up to 26PSi, then falls back to 15PSi, then swings up and down between the two). Needless to say, this really spoils the drive. The car has had everything turbo related checked now, from new Forge DV with yellow spring to new N75E valve and all is clear of leaks, etc etc.

So, having had a long chat with one of the guys from The Phirm, they suggested the best course of action is to fit a manual boost controller. As I already know the car can hold 26PSi of boost without issue, I can gently ease it up to this in steps myself and be sure not to get the old issues with surging - this will also then mean that the car is running the boost that it is mapped for.

My only question is: who on here uses one and which do you recommend?

Ta,

Wigster.
 

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Wigster that sounds like horrendous surging issues. Is your N75 faulty? Pull it off and see if you can blow through it all 3 ways, that is one thats definaltey knackered...some dont do this but still dont work.

Dan
 

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Discussion Starter · #4 ·
Chris: Cheers. Do ya know of a particular make? Anything you've got experience of?

Dan: No - there was no fault with my original N75 (have tried two on it now). TBH, I'm sick of having problems with this turbo set-up now and the manual controller finally provides me with a simple solution. I've had the car checked over time and again and all recommendations have been followed at great cost. For a very few quid, the MBC will provide me with the stability I want, as the car is already mapped to handle this level of boost.

Wigster.
 

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why don't you run the mbc in parallel with the N75, i've read on scn that this can help with surge, also it could be the spec of wheels used in your hybrid causing flow issues, and the wastegate could need porting....

Another thing to note is the actuator, is it uprated? If so i'm led to believe that a 9 psi spring should be used or if you have a forge actuator a yellow spring, otherwise you will have issues running with the n75.

These are all things i have read on SCN forum
 

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Is it surge the car is suffering from?

I really hate using MBC's on cars controlled by N75's. The ECU cant predict properly whats going to happen so part throttle conditions and general driving just becomes a right nightmare although in somecases (possibly mine in the future) you can't get around it. If you really have to running one in parallel with the N75 is the best way to go. You essentially use it as a bleed valve to bleed the excess boost coming from the turbo to the actuator to make sure its fully open depending where you have set it.

Varying between 15-26psi really indicates a fault and wants getting to the exact cause of the problem first. What boost should it be running under full load? If it wants 26psi fitting an MBC in parallel isn't going to help you as it will still surge between the two.
 

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If you have to use one a decent one is the Forge UNOS one but you can use the cheap ebay ball and spring ones (do not get a bleed valve, it wont work).

You could also look into an electronic boost controller with duty cycle dependant upon load/rpm - good but expensive and you will still suffer the problem of hesistation on part throttle.

Dan
 

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Discussion Starter · #13 ·
Wow - loads of useful info there. T hanx everyone.

Basically, I want to stop the car running too light on boost, so I want the 26PSi to remain constant. (On rare occasions, the car still achieves this in the right atmospheric conditions).

I already have a Forge 007P with yellow spring. The N75 valve is a new N75E (the latest replacement for the original C valve), although this also made no difference to the running. R-Tech advised me that there was a slight pass on my original Bailey DV and I have since replaced this. The car does initially boost harder, but having a fully working DV has actually made the problem worse, not better.

The car is custom mapped by R-Tech.

Dan - I really appreciate all the advice so far. I've had the car checked by three different places now (including R-Tech when they set-up the car and once since) and, despite a slightly passing DV that has now been replaced, it still just won't boost right. There are no boost or vacuum leaks, the N75 is new, the DV is new as are many other items. I'm basically looking to bridge out the N75 altogether, as I am informed that running the boost controller in parallel won't solve my issue - what I apparently need to do is physically instruct the ECU what boost to run, hence the manual controller.

Effectively, I want to be able to take control of the boost to ensure the car is forced to run the 26PSi it is set-up to run on the K03s hybrid that is now fitted.

Ta,

Steve.
 

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Discussion Starter · #15 ·
If you going to use a MBC, then leave the N75 plugged in. That way ECU wont play up with error codes.

Im not sure.....and this is a total random suggestion, to split the boost piping so there is a feed to both the MBC and the N75.
I did consider this. Only worry is, if I split the piping and leave the N75 in, surely there is still the possibility of it surging? What I want to do is take complete control of the boost off the ECU and instead run it through a pre decided manual setting (ie - the 26PSi the car is set-up to run). Do you think this will still work with the N75 still connected?

In theory, I could set the manual boost level to slightly lower than the 26PSi the car can run, but still achieve a manageble, smooth level of boost without the constant fluctuation that spoils the drive of my car.

Steve.
 

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Discussion Starter · #20 ·
I mean leave the actuator line off the N75 valve disconnected but have it plumbed into both boost and atmospheric pressure on the intake.

That way, the ECU knows what boost is getting to it if in case it needs a boost reading for things to operate properly.
Magic - so, am I right in thinking that with this set-up, the setting chosen on the manual boost controller will determine the actual amount of boost generated, because the N75 will no longer be able to open the waste gate to bleed off excess boost as this will now be controlled by the manual controller?

Wigster.
 
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