Part throttle compressor surge with a small 16g?

[knochgoon24]

Is it even possible to get compressor surge with a small 16g on our cars? I've been noticing a weird sound as I merge onto the highways with some fervor. Usually, I'm at about 4000rpm and I'll give it a little gas and the turbo just spools instantly at that rpm. Past 15psi but still part throttle is when the noise happens. I'm running a 6cm^2 exhaust housing if that makes a difference.

I don't know if the microphone on my camera is good enough to capture the sound if I try and record it tonight.

 

[turbosax2]

We get exactly the same thing on Brian's car with a small 16g - especially at his track days a couple weeks ago where it was basically surging all the time. Very interested to hear expert's opinions on this.

 

[knochgoon24]

With the 6cm hotside, the spool is really quick. Almost too quick. As soon as it hits 10psi it's then at whatever I have the MBC set to (17psi right now). It makes the throttle a bit touchy under boost. I really don't need to make a scene as I merge into highway traffic. So I try to moderate the throttle, and the noise starts. It's not that chirping sound that's said to be "true" compressor surge. Maybe the intake pipe and filter is muffling that some.

I'm actually thinking about going to a 7cm housing. I broke a bolt off in my current one. It still seals fine with the other 3 in tight, but I need to either drill the broken bolt out or replace the housing.

 

[turbosax2]

Agreed on the spool being almost too quick. But hell, that's why I love the turbo We're running ~22psi if it makes any difference. At the track (road course), we turned it down a few psi which seemed to help with the surging so it wasn't constant at least. When it was at 22psi the surging was present almost all the time.

 

[turboglenn]

You'll know if it's an actuall surge, the noise will be loud and spook you the first few times you hear it, probably to the point of letting off the gas. It's a loud high pitch bark almost sounds like a squirrel bread with an attack dog lunging at you

SUrge can ahppen about any time the turbo is pushing more air than can get through the TB or into the engine for the matter, the only mystery to me has been why i've never seen one surge under WOT, that always seems to solve it.. My 57 trim will surge on the highway if i'm part throttle goping up a hill in 5th and it builds too much boost (well it did with the .48AR turbine housing, now that i got the .63 on it can't spool enough at those RPM's to get any good surge going that i've yet to see)

but i would say that when i think about it i could see a 16g spoooling fast enough at part throttle to give one or 2 quick barks, so i would say Yes, entirely possible

 

[knochgoon24]

Here's a video. You can kind of hear it starting at 0:14.

http://www.youtube.com/watch?v=wBPKkGX4KRA

I forgot my camera so I shot that with my cell phone. I'll try to get a better video/sound with my camera later.

 

[JusMX141]

Wow Wes, that's definitely surge under load. I have no clue what would be causing it unless, like stated above, the smaller turbine housing is helping to spool the turbo too quickly under load at low RPM in high gears on the highway.

Interesting that this was never an issue before....have you changed anything recently like BOV, intercooler piping, etc? One thing's for sure...guys have killed turbos from surge under no load (BOV too stiff, etc), so surge under load could definitely be fatal if not addressed.

 

[knochgoon24]

I don't know what's up. The only reason I now noticed this is because I leave the overdrive off when driving in the city. To get to work, I merge onto a highway. The speed limit is only 55mph, so it doesn't take a lot of throttle to get up to speed.

I have an in-car mount I'll attach my camera to. The video quality should be good enough that I can see gauges with it.

I'll also try to get a log so I can pinpoint where it's happening. I have no clue how plot my airflow on a compressor map, so maybe some help with that would lead to a prognosis.


The only things that have changed are the ambient temperatures. I have added some more timing to the spool up region though. Only about 3* more than I had before. But it's on par with the Evo 6 TME maps as far as timing goes. I've seen a lot more timing.


I wonder if this is what managed to make those bearings look the way they did in that last turbo...

 

[thilaksharma]

i had similiar issue that i faced last year , tht i posted here too
mine was solved by switching the synapse bov to another unit
im nt sure if its the same, bt mine at part throthel, it was confused between open up the bov or closing it , causing lot of surge

 

[knochgoon24]

I'm running an HKS SSQV v2. I have a 1g BOV, and I think I have the parts laying around so I could use that. If that might fix it, I'll give it a shot.

Until then, I'm just running WG pressure (~7psi). I need my car in one piece to get to and from work. Plus, it's kind of nice hearing the sound of the exhaust for a change instead of the turbo screaming over it.

 

[romeen]

Wes, are you absolutely sure it's not a boost leak. A couple years ago my car was making a similar sound only after a certain psi was reached. It ended up being a large crack (at a seam/weld) in one of the IC pipes.

 

[knochgoon24]

Hmmm.... I'll have to check. I'm out at college, so I'm going to need to track down an air compressor first.

 

[Ceddy]

Are you using ECU Boost Control with the Evo8 ECU?

If so you can use the TPS WGDC Correction table to get rid of part throttle surge. It will basically lower boost if you aren't WOT.


Not sure what is causing your surge, my previous turbo was a S16G with a 6cm @ 22 psi housing and don't think I had any part throttle surge.

 

[knochgoon24]

I'm using a MBC. I haven't hat time to mess with ECU based boost control yet. That does sound nice though.

 

[tektic]

My small 16g does the same thing. Ever come up with a good resolution? I'm looking at a turbosmart Bob for a replacement.