fixed mbc hookup now this!!!

[jw_55_55]

Well i just finished fixing my MBC lines because they werent hooked up right! start that car up and take it down the road for a drive. my MBC is set to 13 psi and i go to step on it in second rises up normally then spikes to 20 psi!!! I stopped checked to make sure everything was hooked up still and then tried driving again this time watching the throttle and psi at all times. Only gave to 7 psi in all gears then i go to fourth and hear this weird noise....now my car wont idle right and smells funny! Drove it home going 15 mph with it sputtering all the way!....what did i do or could have done? Fried my ecu or blew an injector? Just installed a 190 as well! dont know what happened or what i did!

 

[Talesin]

My guess is that the boost controller still wasn't hooked up right, and you may have either (best case scenario) blown an intake pipe or hose off (check them all, if one's hanging loose the car will barely run, and run stupid rich or lean), or (worst case scenario) overboosted and detonated. Which can crack a piston into chunks if it's bad enough.

An MBC isn't exactly an exact thing in the first place. You need to set it to minimum spring tension (or zero bleed if it's one of that type) and slowly increase the spring tension/bleed, doing a pull or three after each to make sure everything's working right, and that you haven't exceeded your 'safe' boost point, and won't surge past.

My guess is that if it's a spring and ball type, you hooked it up backward and robbed the wastegate actuator of all boost signal, so it never opened. Bang, overboost. Hopefully you had a semi-loose clamp somewhere in the intake tract and the hose slipped off, instead of toasting the engine.

 

[xi Talon ix]

I put a MBC on my 90 TSI and went down the road and spiked to 26 psi. The next day my car started to run really bad and sputter. Sounded like a Subby. Found out that the ball in my MBC fell out and I burned an exhaust valve. Well...best of luck to you.

 

[jw_55_55]

Ok well first off how will i know if i toasted the engine??? and secondly how do i properly hook-up a MBC? I was told that it was compressor nipple and waste gate nipple to the MBC and then the vacuum line from the intake mani to the BOV. Is there anything i missed or didnt hook-up correctly?

 

[Talesin]

Yes, it goes from the compressor outlet nipple to the MBC to the wastegate actuator. But there are two nipples on the MBC. On a spring-and-ball type MBC, you have to hook up the correct nipple to the correct side, otherwise the pressure coming in just forces the ball down against the air path to the other nipple harder, and none ever gets through.

Generally if the MBC is a ball and spring type, there'll be one nipple on the end directly away from the adjustment screw. That end is supposed to be hooked up to the line from the compressor outlet elbow, so incoming air will push the ball up and compress the spring a little against the adjustment screw before slipping around and going out the other nipple (generally much closer to the actual adjustment screw end) which goes to the wastegate.


Before you start worrying too much, check ALL of your intake tract piping/hoses. From the sound of it, I'm guessing that one just popped free and is hanging off, making the air meter useless. You can try unplugging the MAS and see if the car runs any better in limp mode. If it's a dramatic change for the good, you almost definitely have an intake tract pipe/hose off somewhere. Even if it doesn't you may still have one off.
Generally to find out if you detonated and destroyed the engine, just pull the spark plugs, do a plug read, then compression test the engine. If one of the cylinders is at zero, or close to it... well. Time for some work.

 

[Mr Peepers]

When my wastegate actuator came unhooked and my car overboosted, it backfired and shook the entire limp home I got lucky and it was only a spark plug with a broken insulator, allowing it to slide back and forth on the electrode. New plugs and problem solved.

If it's not a loose intake pipe as Talesin suggested, take the plugs out and inspect them. You'll need to anyway to do a compression check if thats not the problem

Good luck

 

[MrBoxx]

Don't use the BOV line for a boost source.

On MOST ball-spring MBCs, the nipple OPPOSITE the adjustment knob is for the pressure source, which should ideally come from as close to the compressor housing/IC piping as you can get. Most people tap the J-pipe or lower intercooler pipe and install a threaded nipple fitting for this. The MBC's "side" nipple usually routes directly to the wastegate. This is the simplest, most effective setup.

If your setup had multiple vacuum lines or tees, as it sorta sounds like it did, you may have inadvertently set up an infinite boost situation.

A picture or MSPaint diagram of how you have your MBC hooked up would help.

 

[Mr Peepers]

Here's a pic I made in paint for one of my friends on how to connect a mbc. This was for a t25, so the only difference is the hose will be coming from your J-pipe(or wherever your pressure source is) instead of the compressor housing. Do NOT "T" off the BOV line.

 

[Talesin]

Pretty sure that's what I'd just said above, MrBoxx. :b And he'd noted that he has a seperate line from the intake manifold to the BOV(/CBV), as compared to the pressure source for the MBC, coming from the 'compressor nipple'.

 

[MrBoxx]

Sorry, John. I'm half-asleep right now and must have just glossed over almost everything in the thread. Luckily, I've answered questions like this so many times, I pretty much have the wording memorized.

Peepers, that is the most awesomest Paint diagram I have ever seen. Would you like an apple?

 

[Mr Peepers]

Mmmbah!

If you don't know which end of the mbc is supposed to hook up to the wastegate, there will be a small extra hole on that side if its a ball and spring type. With the screw turned in enough to make the ball seat, blow into each side, and the side that leaks air is the side that should be connected to the wastegate actuator. I'm almost certain every ball and spring type has this hole to keep it from acting like a check valve and not letting the wastegate close.

p.s. Am I the only one who routed this hole back into the intake tract after the MAS and before the turbo inlet, seeing it as a boost leak when the wastegate opens? I didn't like the idea of a 1/16" hole whistling out metered air after I spent time with soap and water making sure my clamps weren't leaking

 

[jw_55_55]

Thanks for all the replies....ill get back on here when i have time to see what happened!! All i have had time to do was re-do the MBC lines again and then started it up....it sounded ok but still something is wrong especially when i rev it up a little...3-4000 rpms it sounds like its struggling, but better than the ride home. So i will investigate and pull out the spark plugs and what not thanks for the pics and everything...greatly appreciated!! Also i will give you guys an update on friday mornin when im off till 2...hope to have it figured out by then!!