Losing Boost Pressure...

[Maverick3169]

My boost falls off usually 2-3 psi after exactly 5000rpm in every gear... also seems to spike pretty bad. I have tried everything to fix this, and tested for boost leaks up to 30psi with nothing leaking (except the CBV at 23 psi). Also, sometimes the needle on the boost gauge vibrates when initially going into full boost... this does not happen everytime though.

One thing that I just noticed is that my manifold to turbo gasket is leaking... could this cause these symptoms? I'm really running out of things to try. The only other thing that I haven't tried is replacing my magnacore 8.5mm wires. But I'm not getting any drivability issues at all, and I don't break up.

 

[Talesin]

What boost level are you running? It sounds like it could just be a bit of boost surge working itself down, possibly.

The leaking manifold/turbo seal should be taken care of; not only is it slowing your spool by a bit, mine was doing the same thing... and it turned out to be that one of the bolts had fractured. A second one went before long, and it sounded like a Honda on accelleration after that. :b Also sent a good portion of the exhaust gasses into the engine bay, and melted a couple of things (upper timing belt cover, part of the belt, O2 sensor wire).

 

[Maverick3169]

What boost level are you running? It sounds like it could just be a bit of boost surge working itself down, possibly.

The leaking manifold/turbo seal should be taken care of; not only is it slowing your spool by a bit, mine was doing the same thing... and it turned out to be that one of the bolts had fractured. A second one went before long, and it sounded like a Honda on accelleration after that. :b Also sent a good portion of the exhaust gasses into the engine bay, and melted a couple of things (upper timing belt cover, part of the belt, O2 sensor wire).

I'm trying to run around 20psi... but it ends up spiking to 23, resting down at 21, then after 5000rpms it goes down to 18.5 psi. This happens at any boost level I've tried... 15psi, 16, 17, 18, 19 psi, it always happens.

 

[Talesin]

The surge is likely too-long vac lines on your boost controller, given that you've got a ported exhaust housing. The drop past 5K is unlikely to be turbo overrun (obvious reasons), check your boost controller again, and fix that gasket leak... if it's a broken bolt, it could be seperating at higher RPMs as more exhaust gas is forced through, making the leak bad enough to drop your spool a bit.

MBC or EBC, by the by?

 

[Maverick3169]

MBC... and the lines are as short as I can get them.

By the by???

 

[CanadianTSi]

Either Exhaust leaks or it could be your flapper blowing open, try putting more tension on the wastegate actuator.

 

[Maverick3169]

How to I do that?

 

[Talesin]

More tension on the wastegate actuator? The heck are you talking about? The only ways to do that are replacing the spring or the actuator, and those don't go bad too often... and certainly not at a defined RPM level. That or lowering the boost level, which shouldn't make a difference.

By the by = by the way.

And my money is currently on the leaking manifold/turbo gasket. Figure out why it's leaking, and fix it. If it's a bolt blown, or if the turbo is somehow pulling away from the manifold at a certain flow level, that'd definitely drop your boost. How did you figure out that it's leaking, anyway?

 

[CanadianTSi]

You can use washers to shim it...

 

[Maverick3169]

A buddy of mine who owns a exhaust shop found it while fixing a couple of other leaks (bolt holding the exhaust manifold to the head, and O2 housing-downpipe gasket).
I'm pretty sure its not a broken bolt, because they(two of them) recently somehow backed themselves out a little, so we had to tighten then back down.

 

[Maverick3169]

You can use washers to shim it...

What would that do?

 

[CanadianTSi]

What would that do?

Put more pressure on it so it won't blow open as easily.

 

[Maverick3169]

Put more pressure on it so it won't blow open as easily.

Ok, now where do I put the washers. I know I have to put them somewhere on the actuator, but which part, and how many washers?

 

[Maverick3169]

No one knows?

 

[project_tsi]

No one knows?

http://dsmtuners.com/forums/showthread.php?t=179987&highlight=actuator+shim

AND NO BUMPING

 

[Maverick3169]

Well thanks for the link.
I wasn't trying to just bump my thread, I was serious... I want to fix this problem.

 

[Maverick3169]

Put more pressure on it so it won't blow open as easily.

Well I put one washer on each bolt, and it pretty much stoped losing pressure.
It still spikes to 23ish psi, but then it settles down to 20 psi and holds there up till redline (maybe fluxuating a half pound or so).

Thats amazing that small solution fixed this for me.
Thanks a lot CanafianTSI... that was kind of a PITA(I have big hands), but well worth it.
I'm still going to swap out the gasket, I should be doing that within the next couple of days.

 

[oldman]

As for the boost spike, if you're tapping the BOV line for your mbc pressure source, try tapping of the compressor housing/j-pipe instead while shortening the hoses even more and see if it helps, I have seen this making a difference several times.

 

[Maverick3169]

As for the boost spike, if you're tapping the BOV line for your mbc pressure source, try tapping of the compressor housing/j-pipe instead while shortening the hoses even more and see if it helps, I have seen this making a difference several times.

Well, I'm tapping from the TB port.

 

[CanadianTSi]

Well, I'm tapping from the TB port.

Thats a long way to go, I would suggest something closer.

And I'm glad the solution worked for you.

I have about 4 washers on each bolt for my actuator, that bi*** is tight

 

[oldman]

Well, I'm tapping from the TB port.

The best place to tap is the compressor housing. I just received my TO4S with anti-surge compressor cover and it came tapped for 1/8 npt straight from Garrett. There is no good reason to tap the manifold pressure because the boost gauge is tapping the manifold anyway.

 

[Maverick3169]

Well, thats the best that I could do with out drilling a hole in the compressor outlet elbow. Would it be worth going through the trouble of tapping a hole there and threading a nipple on? I mean, how much would that really help out?

 

[Maverick3169]

Thats a long way to go, I would suggest something closer.

And I'm glad the solution worked for you.

I have about 4 washers on each bolt for my actuator, that bi*** is tight

Yeah man, thanks a lot!
How do I know how tight I should make it? It was a tight enough fit just trying ot put one washer on each bolt.

 

[oldman]

Well, thats the best that I could do with out drilling a hole in the compressor outlet elbow. Would it be worth going through the trouble of tapping a hole there and threading a nipple on? I mean, how much would that really help out?

Only you can make that decision for youself, will it solve your spike? I don't know, is there a chance that it will, yes. All you need is a 11/32 drill bit, 1/8 npt tap and a 1/8 npt to 1/4" fitting. This was posted in another thread on the subject of bov/manifold vs compressor/j-pipe, obviously #2 soes not apply here.

1. The main argument for using the intake/BOV source is that it's controlling the manifold poressure (what goes into the engine) so it's more accurate when in reality it doesn't matter because the boost level you see on the boost gauge is always tapped into the manifold anyway, the only difference is a slight adjustment with the mbc due to pressure drop after IC.

2. The accuracy of vacuum and boost signal to the BOV is very crucial to the proper functioning of the BOV. Most mbc will vent to the atmosphere one way or another either through a bleeder type mbc like the TurboXS Standard mbc or through the wastegate relief hole on a ball and spring type when you go WOT. This will change the pressure level on the BOV line and cause the BOV to either open too late when letting off or open too early during boosting.

3. Tapping off the compressor/licp will greatly reduce the chances of boost spike due to short route pipping.

4. In the case of serious boost leaks, it will help preventing over spinning the turbo.

5. If you own a bleeder type mbc (TurboXS) or a poorly designed ball and spring type mbc where the ball does not fit tightly with the housing allowing air to flow around the ball, tapping off the BOV/intake lines will create a vacuum leak.

 

[Maverick3169]

Thanks for that oldman... I think I'll try it out pretty soon.