IanM

So...what does compressor surge feel like / sound like?

If I set my boost controller to 15psi, boost comes on and holds with no problems. If I set boost to 17psi, boost will hit 17psi then start to flutter madly. Boost gauge needle will bounce between 16-18psi, and I hear a fluttering sound - really hard to tell if it's from under the hood or not.

I took my Tial wastegate apart, in case it was a torn diaphragm - no. I pressure tested my intercooler pipe in case my 1G Talon recirc. valve was leaking - no. I checked all my vacuum lines, they're all fine, and my vacuum/boost gauge sits steady at 18 in. Hg. at idle. I bought a Greddy ebc and replaced my mbc in case that was it - no. I'm running a Garrett hydrid turbo (T04E 60 trim, #8 hotside w/ a Stg2 turbine wheel). It was rebuilt last year (was in perfect condition upon disassembly), and the rebuilder installed a slightly bigger 60 trim compressor wheel (bigger exducer size?). Anyways, I can't figure out what the problem is, and I think I've pretty much tried everything.

JET951

i think you just found the problem. if you have too big of a compressor wheel, you will get surging. it sounds like a flutter, from when you are at full throttle it is at its loudest and steps down from there. it is detrimental to the turbo itself, as the compressed air cannot be forced through the engine because of the restriction in the exhaust housing of the turbo, and such forced back through the compressor housing causing the sound, and stuttering you are getting. there are a few options, get the turbo rebuilt with a bigger exhaust housing, or use only 15psi where it doesnt surge, or get a smaller compressor housing.

Rogue_Ant

A 1G DSM BOV will only hold ~16-18psi or so. You might need to 'crush' it a little bit to get more spring tension (common in the DSM world). This could be the fluttering sound your hearing.


Rogue

ross255

IanM

People are running that turbo compressor, but if I remember, they use a stage 3 wheel.
Slightly longer to spool up i suppose, but then you wont get surging.

toddk911

I would say the BOV is the issue. Since the "fluttering" sound is usally the BOV anyway, it sounds like yours is not holding. So yo ucan "crush" it or upgrade it.

I have a bigger compressor than he does, 67mm, and #8 at 19psi and no compressor surge or fluttering.

JET951

blow off valve doesnt sound anything like compressor surge, although if the bov is not big enough or is sealed closed it will cause compressor surge around the 3 grand mark. but it will keep reving.

bov sounds like a psssh, fluttering sounds like a helicopter blade slowing down.

toddk911

Well, are we talking BOV or DV?

BOV = pfssssss

DV = fluttering (turkey gobble)

Trucho-951

At what engine RPM does it surge? If it is compressor surge, then boost is comming in too early for your the engine size, and the engine cannot swallow that much air flow. Can your EBC be staged? Say 15 psig at < 4,000 RPM, then higher boost at higher RPM?

IanM

I've already crushed my recirc valve. I took off the intercooler pipe with it still attached and pressurized the pipe to 30psi - thing holds boost with no leaks (yes, this is with the vacuum line into the recirc. valve also pressurized).

It only flutters at full throttle and high rpm. I may need to pay the turbo rebuilder a visit, I can't remember this happening before the rebuild, but it's tough to say as I normally only run 16psi and it doesn't happen until I hit 17psi.

Rich Sandor

That makes sense to me, but didn't Shaun at Kinetic say the opposite... that you weren't flowing enough air at the top?

Ian, take me for a ride tomorrow. I wanna hear it.