Wondering if anyone knowledgeable on turbo surge can help me out. From what I've read; surge (under load) occurs when either the engine cant consume what the turbo is pushing or that there is a leak where the turbo is having to work harder to flow the desired pressure and therefore over spins. But every mention of this has said to generally only occur on larger turbos. I have checked for boost leaks and I cant seem to find any and have even tightened up the BOV just in-case it was leaking but no change.  

The turbo started surging one afternoon after a long day driving (It has been performing fine since mid-2013 with no real modifications since then). The turbo was fine and then all of a sudden it was making the surge sound. It has been gradually getting worse also. It started out only doing it at 14psi+ then a week later it would start as early as 7psi and now it whines as low as 4psi. The CT20B I have is bog stock standard. It was rebuilt in Japan with a steel wheel at some point and has less than 50,000kms on it. Im hoping the turbo isnt cactus as its basically new but I would appreciate if anyone can point me in a direction of why it could be occurring before I book the car into a workshop. 

Thanks in advance.

Check your spark plug gap. You may be experiencing "spark blowout" it happened on my volvo and at full throttle under boost it would stutter. The gap had opened up on the plugs and i just had to close them back up to spec

I'm no expert but I do have a turbo with on-boost surge. It's in for a region or replacement. My surge would disappear with higher revs (engine taking in more airflow). Not sure what would change for you for surge to appear, for me it was post- engine rebuild and change of intercooler. The turbo has the exhaust wheel clipped so it's not got the best low-mid range efficiency. Does the boost gauge flutter like crazy? That would be surge, not sure about whining noises though...

*rebuild, not Region lol

MR PLOW
I'm no expert but I do have a turbo with on-boost surge. It's in for a region or replacement. My surge would disappear with higher revs (engine taking in more airflow). Not sure what would change for you for surge to appear, for me it was post- engine rebuild and change of intercooler. The turbo has the exhaust wheel clipped so it's not got the best low-mid range efficiency. Does the boost gauge flutter like crazy? That would be surge, not sure about whining noises though...

Im unsure either as it just started happening one afternoon after it worked perfectly the whole day. It got me thinking either something has dislodged causing a severe boost leak (as there were quite a few large bumps I hit across the day) or the turbo has given up the ghost. Hoping for the former rather than the latter. 
Couldn't tell you as my gauge isn't in position that allows me to keep an eye on it constantly. But watching it when it starts to surge (4psi+) it begins this horrific whining sound that would make anyone who loves their car cringe and goes on to struggle to build boost. I dont really push it as the sound is enough to make me think  Im doing damage so I really cant say how unstable it is. 

could it be a restriction in the exhaust somewhere? Blocked cat or something?

Mrskylighter
could it be a restriction in the exhaust somewhere? Blocked cat or something?

Actually thats a fair point. Have noticed the exhaust isnt the cleanest. Think Ill whip the dump pipe off and have a look. Cheers.

Maybe take the intake piping off to see if the turbo spins nicely, or if there's movement in/out or side/side, also look for scoring from the blades around the inside of the turbo.
Doesn't sound good, good luck

Ill take a look at that too. Thanks!

I decided to take it for a drive again today. It's boosting fine, holds boost strong and doesn't budge. So it's not surge as all it does is whine.

Pulled the intake off and there's no scoring but there is a bit of radial movement. Enough to make a tapping noise.

I did a bit of research on turbo whine and it seems it could be either a bad boost leak or an unbalanced shaft/worn bearing. But if it was a boost leak I wouldn't think I would be making my set boost target. :confused: