Whistling problem figured out?

[Spooled]

I have searched and haven't found a definite answer to this. I do, however, have an idea about what it is. Here's the situation:

Ever since I had my turbo setup replaced under warranty for a stuck wastegate, I get a faint whistle at light load around 3000rpm. I thought it might be a vacuum hose or piping leak, but I have checked all of that and found nothing. Besides, it's when I'm not boosting, and seems to only happen for a short time.

When I got my car back, the first thing that I realized is that my boost is now at about 4.9psi (it used to be 6.5), and so I assumed that they didn't take the time to adjust the wastegate actuator rod. Not a big deal because I just popped my MBC on and dialed it to about 7.5psi, and it holds boost without a problem.

I think that the whistling is coming from the wastegate not completely closing. It only happens around 3000rpm (when the turbo is capable of full boost), and only while I'm on the gas a little bit. I think that since the rod isn't adjusted to the correct length, the gate is slightly open when it should be completely closed, and the air is sneaking past it causing a whistle and lower boost.

I thought I'd mention all of this to see what you guys thought, and to shed some light on the situation for others with the same problem.

[Spooled]

I will try adjusting the rod length while I'm putting my shifter in, then I'll let you know what happens. Just a note: I'm staying at 4.9psi boost until the problem is solved.

[pdhaudio83]

seems feasible that the WG is just barely open, causing the whistle...

[hazeXban]

Anyone got a how to one getting to and adjusting the wastegate. Out mazdaspeed tech in wayne nj told me how to adjust it to raise boost but I don't exactly know exactly what I am doing.

[Mike R]

I might be wrong, but if you are not boosting, then the wastegate would be all the way open. If the wastegate was closed, you would be boosting. The noise and low boost could because of the rod being misadjusted though. But, the adjustment would be off the opposite way you described.

[Spooled]

I might be wrong, but if you are not boosting, then the wastegate would be all the way open. If the wastegate was closed, you would be boosting. The noise and low boost could because of the rod being misadjusted though. But, the adjustment would be off the opposite way you described.
I think we are thinking the same way, but I didn't explain myself clearly enough. The whistling only happens between about 3000rpm and 3500rpm, and is most noticeable when at light-medium load. The wastegate is closing due to the vacuum in the intake manifold, but boost has not yet built. I think it's most noticable in this situation because it's lingering at the partially-open stage. If I get on the throttle, I can barely hear it for a split second if I listen for it. That's probably because it's only partially open for a shorter time when under a higher load.

Once I get in there and play with the actuator rod I should be able to see if that's the issue. I have a feeling that I didn't hear it with the old turbo setup because the WG would be closed all the way before the boost built to the same level.

[pdhaudio83]

I might be wrong, but if you are not boosting, then the wastegate would be all the way open. If the wastegate was closed, you would be boosting. The noise and low boost could because of the rod being misadjusted though. But, the adjustment would be off the opposite way you described.



the wastegate stays shut until you hit whatever psi you are pushing.
IE- once there is enough exhaust for the turbo to push 6psi, the WG will open and allow other exhaust to not push the turbine even more.

[Spooled]

the wastegate stays shut until you hit whatever psi you are pushing.
IE- once there is enough exhaust for the turbo to push 6psi, the WG will open and allow other exhaust to not push the turbine even more.
Oops, you're right. What am I thinking. I still think it's not shutting completely. The WG will start openning before it hits the target psi. This is because it's spring driven and doesn't act like an on-off switch. I bet that it's sitting slightly open (and whistling), and then stops whistling when the WG starts to open more. I guess this wouldn't explain why my boost is at 4.9psi... more research I guess.

[hazeXban]

No it does, depending on how tight the spring is the wastegate will open more to allow more out therefore reducing your psi to that level. I have the same whistle and am assuming I have the same situation. This weekend when I install my boost gauge I bet I am running like 4.5 psi which in that case mbc here I come.

[Mike R]

Ah, OK. Been about half a year since I've owned a turbo car..

[pdhaudio83]

right. the WG could be stuck open, and allowing air out too soon, and depending how many RPMs, only a small amount of air may be going thru the WG, thus the whistle.

[DSMConvert]

just posted a new thread my turbo was making more of a squeal but it was right around 4K like yours, ended up being shot bearings on the turbo shaft.....to adjust the wastegate you turn the nut on the acuator rod, make it shorter and it takes longer for the wastegate to open by increasing the distance the diaphram must inflate to push the rod, increase the distance and it opens sooner, or in extreme cases stays slightly open all the time. Actually I might have it backwards thats how it works on my DSM, but i think mazda has the little pivot point on the opposite side so reverse the directions if so....at any rate you lengthen and shorten the rod by turning the nut on it and that will adjust the boost level.....I dont recommend doing this in place of a mbc however as the flapper is designed to get rid of a certain amount of predetermined exhaust to prevent overboost, only use it to adjust 1-maybe 2 psi differences.

[Spooled]

just posted a new thread my turbo was making more of a squeal but it was right around 4K like yours, ended up being shot bearings on the turbo shaft.....to adjust the wastegate you turn the nut on the acuator rod, make it shorter and it takes longer for the wastegate to open by increasing the distance the diaphram must inflate to push the rod, increase the distance and it opens sooner, or in extreme cases stays slightly open all the time. Actually I might have it backwards thats how it works on my DSM, but i think mazda has the little pivot point on the opposite side so reverse the directions if so....at any rate you lengthen and shorten the rod by turning the nut on it and that will adjust the boost level.....I dont recommend doing this in place of a mbc however as the flapper is designed to get rid of a certain amount of predetermined exhaust to prevent overboost, only use it to adjust 1-maybe 2 psi differences.
Thanks DSM. I am only going to adjust it to get to about 6.5psi, which is what I boosted at with my last turbo. I don't think it's a shot shaft bearing (at least I HOPE not with only 2k miles on the new turbo).