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Goddamnit!

Tonight I started hearing a lot of compressor surge.

I have NO idea what's causing it, but it's starting to worry me.

It didn't do it before tonight, and it seems to only happen at partial boost.

Could this be a sign of my turbo going out, maybe the wastegate? If so, then I'm going to be upset .

I was getting a lot of surge with my stock BOV. Now I've got the HKS unit, and it just started doing it again.

Hopefully I can tune the BOV to prevent surge, but we'll see.

The surge was loud enough that my girlfriend noticed it! Sounds like a goddamn Supra or something.

Ok...

Now I wish I knew what compressor surge sounds like...

Uh oh, time for a turbo upgrade!

No really, if you're getting comp surge then I would think something is wrong with the BOV setup. A couple guys here are running similar boost as you without any DV or BOV setup at all and aren't having real big problems.

How can you have compressor surge at part throttle unless you have some kind of huge restriction in the intercooler or piping? Are you sure you don't just have a high-pressure leak in the plumbing somewhere, which might sound like compressor surge?

QuickDrive - Compressor surge to me sounds like a loud flapping noise.

Thanks Vrg3.
I'm good then.

I swapped the 10 core IC and thats when I started noticing it.

I'll swap my 15 back on and see what happens.

Matt - I've already got a line for a TD05-16G from a 95 WRX

yeah it might just be the intercooler is damaged.

My boost makes a fluttering sound anytime it goes above 4-6 psi. So I am safe to assume this isn't some sort of sound the wastegate is making? Everything runs perfect. No boost creep up in high RPM's and holds boost great in between and in each gear.

BAC5.2 wrote:
Matt - I've already got a line for a TD05-16G from a 95 WRX

NOOOOOOOO! You can't get a 16G! You're car won't be any different then mine except for your bolster mod. *sigh*

No really, that's cool as hell if you get a 16G. When are you doing that?

Going to talk to a friend. I am going to buy it from him when he is ready to sell it. I've come to realize that our cars, although almost identical in mods, have completely different manners.

William - Sounds exactly like my car. Holds boost until redline, which is weird because Matt's bleeds off. I can run 10psi to 6600 in every gear (except 1st. I'm out of gear before I reach 9 pounds).

BAC5.2 wrote:Going to talk to a friend. I am going to buy it from him when he is ready to sell it.

Sweet, when do you think you might get it.

I've come to realize that our cars, although almost identical in mods, have completely different manners.

I know that your engine sounds a little different, your clutch is a lot better and your shifter bushings are in a lot better shape but do you really think they're that different?

William - Sounds exactly like my car. Holds boost until redline, which is weird because Matt's bleeds off. I can run 10psi to 6600 in every gear (except 1st. I'm out of gear before I reach 9 pounds).

Hehehe, well the reason mine bleeds off is because I'm running A LOT more boost then you Phil. If I run at 10 psi, I can pull that boost all the way to redline too. It's that fact that our turbos won't support much more then 11-12 psi after 4800 rpm that mine drops from 15 psi to 11 psi at higher rpm's. Once you get your FCD fixed and raise your boost I gaurantee you'll have the same problem.

I dunno, your car just feels ... different. Driving yours was WAY different than my car. Maybe it was the clutch?

ETA on the turbo remains to be seen. It SHOULD be a direct bolton affair. Don't the WRX turbo's have the exact fittings we need? Just need the DIY BEP and I'll be boostin big

Hows this for weird. I just started getting surge as well, a few days after installing atmos. bov. Found that the bov control hose had a hole melted in it from the coolant tank, and I also set the bov a bit looser. It still surges a tiny bit though...mebbe aftermarket bovs help old turbos die faster? haha

Havn't had any boost problems though...nice quick spool and holds boost fine, just as before...

Exactly, I think it might just be the BOV fluttering and not necessarily surge.

I set my BOV loose, and then tight, and it got a little better when I tightened it up.

I'm gonna go fuck with it for a little while, maybe swap my good intercooler back on and see how it goes.

I dunno, I am getting it all the time, I was just not noticing it before.

At partial throttle, no-boost, 0" VAC, I can hear it flutter when I get off the gas. At WOT, I can hear it flutter pretty loud (which makes me think its the BOV).

If I blow my turbo, I'm going to be upset

Hmm.

The first part sounds like compressor surge. If you're at part throttle and manifold pressure is atmospheric, your compressor is definitely making boost. And then when you slam the throttle shut, if the blowoff valve fails to do its job, you get surge that sounds like flutter. That's exactly what I experienced when running without a blowoff valve.

The second part doesn't, though, since at WOT the compressor shouldn't ever really be starved for airflow... so a leaking BOV might indeed be the culprit.

Both things sound like the BOV not doing the right thing.

How does your blowoff valve work?

http://hksusa.com/products/more.asp?id=792

I think I don't have enough spring tension, and it's leaking as I build boost.

I'm not sure I understand.

So chamber A is connected via a vacuum line to the intake manifold?

What's chamber B connected to? Is it some sealed pressure reference or something?

What's special about the "sequential" action? It just allows for two stages of opening, depending on the degree of pressure differential between the compressor outlet and the intake manifold, right? That shouldn't make much difference for us, should it?

I guess the special thing about this valve is that instead of being activated by a pressure differential between the manifold and the compressor outlet, it's activated by a pressure differential between the manifold and this other chamber.

Without knowing what's going on in chamber B it's hard to understand how this valve works.

But I don't think it can leak under boost. Even regular blowoff valves like our stock one don't really leak under boost, from what I understand. They just leak when pressure drop across the intercooler gets too great, since they open when the pressure differential between the compressor outlet and intake manifold exceeds a certain threshold. But your valve doesn't seem to use the compressor outlet pressure as a reference against a diaphragm.

There is a reference line that plumbs into the same line that connects to our BOV. See the nipple up on top of the picture? That's what the line comes in from.

Isn't that line connected to chamber A?

Are there two vacuum lines connected to the valve?

may be slightly related, but i am having a bov issue also. What is happening is that the bov will leak boost during cruising and some acceleration. For certain reasons i had to make my stock BOV vent to atmosphere. I installed a checkvalve on the bov return line. It opens under pressure, but will stay closed when there is vacuum. My boost gauge is tapped from the manifold.

Here is an example of the problem: Cruising on the highway, ~90mph, i will be 0-5psi of boost pressure. I can hear air leaking through the check valve, and the gas mileage is TERRIBLE, ie 10mpg. if i step on the gas and accelerate, the check valve does not leak. If i let off the gas, it vents, then stays closed.

MK

FYI, about the HKS valve....Sport Compact Car bolted like 10 bov's to a talon and datalogged pre-throttle pipe pressure with each during a 1-2 upshift. The HKS valve had the worst looking graph in the test...even after they fiddled with the valve adjustments, it still allowed for 3 or more compressor surge cycles before opening.

I just adjusted it, and it works perfectly now. No surge at all.

Awesome! =)

Tonight I heard:

"Why does your car make that breathing sound all the time?" <girl>

"Why are you making that pshh noise when you change gears?" <another girl>

and

"Hey, it kinda sounds to me like there's an air leak on your engine..." <guy>


Hooray for atmospheric!