Installed MBC, now I have a funny buzzing sound???

[skid542]

As the title says, I installed a ball/spring MBC the other day and now I have a strange buzzing sound coming from the drivers side when I get above 6-7 PSI. It almost sounds like it's coming from in the cabin but I'm not sure.

At first I thought it was a boost leak as my boost gauge needle was shaking pretty badly, so I replace all my clamps with nice T-bolts and torqued it all down. However, I still get this buzzing.

You ever take a piece of wax paper and comb and play space invaders when you were young? Well that's about the sound I'm hearing. It goes away the second I left off the throttle.

I've noticed a fuel odor in the cabin when I hit boost hard in 1st/2nd gear but had attributed it to a hole in my firewall I haven't plugged back up, just having air from the engine compartment making it's way into the cabin. I should note that I've smelled this odor since I did my pedal swap and left the hole open, so it isn't anything new, but....

Now I'm starting to wonder though. My initial setup of the MBC did cause me to hit fuel cut a few times. I have it adjusted now such that it doesn't considering I'm still on the stock VF11, I can't imagine I blew anything in the motor. I let the motor get up to temp and be all happy before I got on the boost to set the MBC. I also recently, 350mi. ago, replaced my HG's.

I'm just at a loss right now trying to figure out why I didn't have this before at stock boost levels and am now getting it a 6-7+ psi.

The car pulls strong, doesn't miss or hesitate, seems happy. All my sensors are ready nominal and nothing's out of whack, albeit my MAF is maxing out but that happened when I installed my TMIC.

I'm open to all suggestions at this point in time.

Thanks in advance.

[Legacy777]

Did you leave the wastegate solenoid plugged in?

How do you have the MBC hooked up?

[skid542]

Josh,

I did unplug the solenoid as that was my first thought.

I just came back in from lunch where I took another car enthusaist friend for an extra set of ears and eyes.

We think it's the wastegate fluttering. It starts right at 7 psi and is worst at part throttle.

I think I have the MBC hooked up right. Perhaps though I made a rookie mistake and put it backwards. Below is a rough diagram.

__
_|_
| | |___
| s ___ - To wastegate
| s |
| O|
T T
||
To compressor outlet

The 's' represents the spring and the 'O' represents the ball.


Is it possible that the initial boost spike broke the wastegate diaphram?

Thanks.

[Legacy777]

Plug the wastegate solenoid back in just for kicks & giggles.

It looks like you have things hooked up right, and it may be wastegate flutter. Does the MBC vent to atmosphere? If so, how big is the hole it vents through?

What kind of MBC is it?

[skid542]

Thank you.

When I get home I will plumb the factory boost control back up and see if that alleviates the problem.

The MBC does have a vent to the atmosphere, approx. 1/4" above the ball. The vent is approximately 1/32" - 1/16", probably closer to the 1/32".

Here is the controller, and as a forewarn, yes it is a cheap Ebay item and feel free to comment . I went cheap because I wanted to see the difference of the extra boost and I didn't know what controller I wanted to go with. I'll be going to standalone at some point and would like to have a nice EBC system so I didn't want to spend a lot of money I didn't need to. So here it is - http://cgi.ebay.com/ebaymotors/NXS-MANU ... dZViewItem

[skid542]

Well I changed it all back to stock and... same thing. It's not quite as loud but once I hit about 7 psi I start getting the noise again.

So now I'm thinking maybe I spiked my boost during the initial setup and killed the old diaphram? I never recall seeing the boost get over about 16-17 psi, momentarily, on the very first go.

Any suggestions/comments?

It's not possible to easily change just the wastegate is it?

[Legacy777]

Yeah you can change the wastegate actuator pretty easily. Just a couple bolts. I've got one from a vf11 sitting in the garage if you want it.

Did your boost actually hit 16-17 psi?

You shouldn't have been able to go above 13 psi based on fuel cut.

[skid542]

Good deal. Do I need to remove the turbo in order to do such? I have another VF 11 from my recent parts car that I'll grab.

I only think I saw it get high very very momentarily. But then again I was more focused on the road than on the boost gauge. I thought fuel cut only came in after boost got above the threshold for a brief, but measurable, time span.

Does this sound like a plausible cause/effect?

[Legacy777]

I think you should be able to remove the actuator without removing the turbo.

I'm not positive if the boost spike could cause your problem. I'd check the actuator with a vacuum/pressure hand pump before you remove it.

Did you get my email?

[skid542]

Okay. Thanks, I'll try to give it a shot this week.


Negative on the email. I tried sending one to you this morning after my post. My usual account's been acting up though.

[Legacy777]

Yeah, I replied to your email. I will send you a pm to reply.

Thanks

[skid542]

Well I should have followed Josh's advice and tested the diaphram before replacing the actuator - which you can do with the turbo still mounted. Bit of a PIA but doable.

So now I have a 'new' actuator on, and I'm still getting that dang buzzing sound. It's weird, up until around 7ish psi all you can hear is the rushing air through the TMIC and then the buzz comes in and drowns out the wooshing sound. I know I'm getting slight blow-by around my nipple for the BOV as evident by the oil residue is leaves but it seems to be a small leak. I wouldn't think it'd cause the buzzing noise.

So at this point I'm a bit stumped. I guess I need to do a pressure test on the system and find my leak . Very agrivating that it was happy until I put on the MBC and now even below stock boost levels I get this noise, AAArrrrggg......

[SubaruNation]

is it the worst noise in the world?
does it affect the car negatively at all?

and just to make sure, check that your bypass valve is all plugged in right.

i know my car made that weird sound like you are describing i think, and it ended up that my BPV was cracked. lil' pressure leak

[smh0101]

I'm going to bet its the boost gauge.

Mine makes buzzing noises... but it is a $25 POS Gauge... but works good enough to have a MBC.

[skid542]

I know it's not the boost gauge because I've tried plumbing it out of the system with no change.

The BOV could be a culprit I suppose. The one on the parts car had the little nipple broken off so it's a little hard right now for me to swap in another.

I can't tell if it's having a real negative effect on the car or not. My boost is jumping a tad and I'm right on the verge of fuel cut and occasionally am slamming into it. Interestingly enough, if I'm at a stand still and just floor it - it'll make it through first and second gear at around 12 psi just fine. However, if I'm just rolling at part throttle it'll jump right up to over 14 psi pretty quickly. This leads me to believe it's a leak.

This weekend I'll grab my spare charge pipe and plumb out the TMIC and put everything back to stock. If the noise is still there... well then I'm not sure where to go from there. I've checked all my bolts/nuts and everything's tight, including the intake manifold.

Thanks for the suggestions guys, keep them coming.

[Legacy777]

Interestingly enough, if I'm at a stand still and just floor it - it'll make it through first and second gear at around 12 psi just fine. However, if I'm just rolling at part throttle it'll jump right up to over 14 psi pretty quickly. This leads me to believe it's a leak.

You're seeing more boost when you accelerate from part throttle because your engine load higher, therefore will build more boost.

This can also manifest at freeway speeds in 4th & 5th gear where the engine is more loaded.

There's not enough load on the engine in 1st & 2nd gear to produce the same boost levels. This is the draw back of a MBC, and why with an EBC, boost levels stay pretty consistent, regardless of engine load variences.


BTW, did you get my latest email about the wastegate solenoid and the clip/clamp?

[skid542]

I don't think was clear on the high boost issue. If I'm at a stop light and give it light throttle to start and then maintain that setting, say 20%, once the turbo starts spooling it slams into fuel cut super quick. If the turbo can reach those pressures at light throttle, either accelerating from a stop or a rolling start, shouldn't it be able to at full throttle? This would be irregardless of MBC vs EBC (ultimately I want a good EBC).

I need to do some searching, but it was my understanding the VF11 is capable of maintaining 13 psi to redline in 2nd gear?

I went out at lunch and had my friend drive it as well. Right now the feeling is a definative boost leak so I'll be trying to address that this week. Figure out a good way to do a pressure test on the system with it installed.


Josh - I am assuming you mean the email requesting the clip/clamp? Is there something else, is the solenoid no good? If you mean just the clamp - I've been deliquent in getting it to the P.O. but it's sitting beside me now and will be dropped off this evening. My apologizes in not getting shipped monday like I said I would .

[Legacy777]

I don't think was clear on the high boost issue. If I'm at a stop light and give it light throttle to start and then maintain that setting, say 20%, once the turbo starts spooling it slams into fuel cut super quick. If the turbo can reach those pressures at light throttle, either accelerating from a stop or a rolling start, shouldn't it be able to at full throttle? This would be irregardless of MBC vs EBC (ultimately I want a good EBC).

I need to do some searching, but it was my understanding the VF11 is capable of maintaining 13 psi to redline in 2nd gear?

I went out at lunch and had my friend drive it as well. Right now the feeling is a definative boost leak so I'll be trying to address that this week. Figure out a good way to do a pressure test on the system with it installed.


Josh - I am assuming you mean the email requesting the clip/clamp? Is there something else, is the solenoid no good? If you mean just the clamp - I've been deliquent in getting it to the P.O. but it's sitting beside me now and will be dropped off this evening. My apologizes in not getting shipped monday like I said I would .

Yeah.....I'm not sure I follow 100% of what's going on. It sounds kind of funky. There is the part throttle full boost thing.....

Yeah....the clip/clamp is all I need. Thanks!!

[SubaruNation]

I know it's not the boost gauge because I've tried plumbing it out of the system with no change.

The BOV could be a culprit I suppose. The one on the parts car had the little nipple broken off so it's a little hard right now for me to swap in another.

I can't tell if it's having a real negative effect on the car or not. My boost is jumping a tad and I'm right on the verge of fuel cut and occasionally am slamming into it. Interestingly enough, if I'm at a stand still and just floor it - it'll make it through first and second gear at around 12 psi just fine. However, if I'm just rolling at part throttle it'll jump right up to over 14 psi pretty quickly. This leads me to believe it's a leak.

.

my BPV's nipple came off and i was losing air like crazy i guess b/c i am getting shitty MPG. well, was i guess. i haven't driven since i installed it yesterday i know it can't be good for you either way

[skid542]

The current one on my car is fully intact. My 'spare' is the one that's broken.