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1999 V70T5M- Overboost Is Killing Me, And I Have Tried It All


fst aslp

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I am losing it.

I have attached a video and you can clearly see that i am hitting fuel cut out.

I have replaced the following:

Stock TCV and IPD HD TCV (although I couldn't complete the learning on it)

BPS

All Vacuum Lines are silicone, new and as short as possible

Blue port is going to fresh air inlet

Red port is on compressor housing

Yellow Port is on Wastegate

Stock ECU

^^^^^I have checked these connections a million times and also all clamps are tight.

I have adjusted the wastegate to 4.5 PSI as IPD calls out and it make it worse, so I lengthened the rod to make it come on slower.

I have connected the compessor to the WG actuator, and it will not overboost it builds to about 9, but this is on city streets, and not maintained as if it were highway.

I used the IPD wastegate tool and the actuator is fully open at 12 PSI.

I have another wastegate actuator to try but it is a 300/70 and for my 18t when I install that. I am afraid this would only make the problem worse.

Current mods are as follows:

Stock 16t Turbo

EST Intake/ Snaab Inlet Pipe

3" DP/no cat/est cat back

stock plugs gapped to .028

Please help as I don't know what else to do.

Video of the situation:

http://youtu.be/X4D2oRVH64g

You see it overboost to cut off then it over boosts again but not hitting cutoff.

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What do you think about this setup:

Run a MBC and TCV. I would put the MBC on a tee coming from the trubo compressor line to the inlet of the MBC and then the outlet of the MBC would tee into the TCV-Wastegate line.

By doing this, I could allow the car to control lower boost as intended and then use the MBC to control top boost if I set it at 12 PSI. This should eliminate the spiking right?

post-44312-0-18418900-1348175076_thumb.j

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What do you think about this setup:

Run a MBC and TCV. I would put the MBC on a tee coming from the trubo compressor line to the inlet of the MBC and then the outlet of the MBC would tee into the TCV-Wastegate line.

By doing this, I could allow the car to control lower boost as intended and then use the MBC to control top boost if I set it at 12 PSI. This should eliminate the spiking right?

No.

I have overboost but I think its due to my speedtuning tune and I run an online mbc with my tcv to keep from going over the intended target. It won't work the way you have diagrammed. There's nothing diverting the pressure to the mbc or tcv. Its just one big loop. You need two more things in that setup to make it work. I have a pressure activated electrical switch bought on ebay and another tcv from my spare parts bin. When pressure hits 10lbs it activates the switch, which puts 12v to the spare tcv, which cuts off flow to the real tcv and diverts it to the mbc. When flow goes below 10lbs, the switch is off and the pressure flows back through to the real tcv. Google around and you will find a diagram if the description doesnt make sense. But just try the mbc on its own first before getting fancy. Plus there shouldn't be any reason to need this setup on a stock tune. The mbc just might help diagnose a wastegate issue. And if you do try the mbc alone, be sure to keep the tcv plugged in or you'll throw a code.

Edit: I believe this was the diagram I went off of when I did my setup. http://forums.vwvortex.com/showthread.php?3832253

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Are you running an aftermarket bov and venting to atmosphere? If so...problem solved. ME7 cars have to run recircs or you'll get what you're running into. Mine sounded the exact same way as well until I recirced it back into the intake just after the maf. Just a thought.

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I have removed the hood insulation. I think it is due to that and the intake and snaab pipe.

I will try the MBC tonight, but I am a bit worried about it after the stories I have read.

Can anyone try an experiment on their t5 and let me know what they boost when they run the compressor straight to the actuator? I am afraid I have the wrong actuator and that is why it is so slow, like perhaps the PO put on a 300/70.

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Well I am going to try my parallel idea. I actually found a better drawing where someone else tried it and Lucky said it should work:

8010274045_d2425518da.jpg

mbc_parallel by FST ASLP, on Flickr

From MVS:

As for MBC in parallel to a turbo control valve; If your intention is to use the MBC to control spikes then you have it setup correctly. If I'm understanding you correctly you're on a stock tune still so 8-9psi is about all you'll see with the MBC setup in that fashion.

Thanks guys, hit me with any other ?'s you have!

-Lucky

I have my MBC set at 10psi so it will take the edge off then once the pressure bleeds off, the TCV should open and route the compression feed through. At that point the MBC should reset to closed and all air will go through the TCV.

This is only to get rid of the spike not increase boost.

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  • 4 weeks later...

Just as a follow up, I have been running this setup with a Vibrant MBC and it is working perfectly. I have it set about 10PSI so it opens just before the TCV. This completely smooths out the boost building too quickly and the car holds perfectly at 12 psi.

Once I get a tune I will try to run with out it and see how it does, but for now it is running great.

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