Wastegates and Boosting

[eclipytic~ice]

I was wondering what is the Waste gate supposed to act like? Because I'll build boost up and it will hit 15psi then it dumps everything down to 7, then build it back up again to 15 then dump. all in the same gear. espically in fourth. That's only with WOT, if I hold out on the gas just a little it will hold it at 15psi through the whole gear. So Have I got a problem or is it supposed to be that way?

I had to put my car away for two years and forgot what it's like to have my turbo, so I can't remeber if this is normal or not. so a little help would be nice?

 

[howdeyjake]

BOOST LEAK TEST!!!!!!!!! vfaq.com

 

[Newlogics]

BOOST LEAK TEST!!!!!!!!! vfaq.com

You consider this sufficient help?
What's with people blaming EVERYTHING on boostleaks lately... jeez.



First off, does your car sound/feel normal when that boost fluctuation happens?
Any missfire, sudden power loss, smoke etc.. ?

What needs to be determined here, is if your boost drops because your engine missfires or runs into another similar issue, or if it is, in fact, turbo/wastegate that's doing it.

Also, can you note RPM at which boost goes up, drops down, and goes up again?

 

[eclipytic~ice]

As far as it feels when it happens, it will hit the 15 psi and drop, feeling like I ran into something then when it drops to 10psi it builds again to hit 15 psi thus again it feels like I hit something. I'll have to get back to you on the rpm levels at which it drops and raises.
I've done a boost leak test and the only thing that showed was a vacum leak in an emmison hose. Fixed that still does it.

 

[oldman]

What's with people blaming EVERYTHING on boostleaks lately... jeez.

Are you threatening me?

 

[1GawdJunkie]

I had a similar problem last month when I changed my external wastegate. I thought I had turned the MBC down enough to re-tune back to 18psi. My symptoms were I would hit 15 drop to 10 then spike to 20. It was very strange when I backed off another 2 full turn on the MBC I was hittin 18 all day long.

Just a thought.

 

[Newlogics]

As far as it feels when it happens, it will hit the 15 psi and drop, feeling like I ran into something then when it drops to 10psi it builds again to hit 15 psi thus again it feels like I hit something. I'll have to get back to you on the rpm levels at which it drops and raises.
I've done a boost leak test and the only thing that showed was a vacum leak in an emmison hose. Fixed that still does it.

Well, it just sounds like a plain ol' fuel cut to me.

 

[eclipytic~ice]

See I've wondered myself if it's fuel cut, but yet when the boost does cut it's not exactly very hard it sputters. and jerks a bit, then builds again. And I've always hear that it's like hitting a brick wall, So I might have yes to retract my statement early of ":It feels like I hit something" But it is like hitting a dog or something kinda a ruff stutter.

 

[Newlogics]

See I've wondered myself if it's fuel cut, but yet when the boost does cut it's not exactly very hard it sputters. and jerks a bit, then builds again. And I've always hear that it's like hitting a brick wall, So I might have yes to retract my statement early of ":It feels like I hit something" But it is like hitting a dog or something kinda a ruff stutter.

Have you logged it to see what's happening with knock/timing etc. ?

 

[tranceman]

See I've wondered myself if it's fuel cut, but yet when the boost does cut it's not exactly very hard it sputters. and jerks a bit, then builds again. And I've always hear that it's like hitting a brick wall, So I might have yes to retract my statement early of ":It feels like I hit something" But it is like hitting a dog or something kinda a ruff stutter.

Believe me, you will know if you hit fuel cut.. It is just like hitting a brick wall. If you hit fuel cut, you would think your car just blew up. Much worse then just hitting a dog or something.
Could you be starving for fuel? Bad Spark?
Just throwing out ideas.

 

[eclipytic~ice]

Ok this is getting ridiculous, it seems to have fixed itself I guess? I go now and it just goes, when I hit 15 it stays there. I'm clueless now....