Compressor Surge help

[Dknits782]

hey i have a 05 sti i just got an ap and a spt intake i think im getting comprssor surge how can u tell besides the sound? and how can i fix it?

[Nick Koan]

Do you have a boost gauge?

[Dean]

Loose the intake if you don't have a ProTune.

And what do you mean by compressor surge?

[Kevin M]

You don't get compressor surge on a stock turbo.

[cody]

The intake will definitely cause Turbo/Bypass Valve sounds to become much louder. The SPT should be ok, but I personally would stick with the stock intake with the silencer removed (optional) as it will be safer until you get tuned. Ed had the SPT intake fall off during a dirt drive which caused the death of his stock motor and it was starting to come off on his new motor too so he went back to the stock intake. He said the car performed much better on the stock intake and now he said he'll never use that intake again.

Usually it's only an issue that results from adding a more free flowing exhaust, but it could be wastegate flutter.

http://www.scoobymods.com/forums/showthread.php?t=3654

[Dknits782]

well i have hks blow off and axel back blitz nur exhaust. what else could be the problem if its not compessor surge

[Nick Koan]

Originally Posted by Dknits782

well i have hks blow off and axel back blitz nur exhaust. what else could be the problem if its not compessor surge

What symptoms are you experiencing? If its just more noise, than that's pretty normal for an intake.

Is the HKS blow-off valve atmospheric? or is it recirculating or 50/50?

[Dknits782]

no after the blow off it makes a strange sound i cant tell it its air or something else sounds like its coming from more of the left side of the engine

[Kevin M]

The intake is fine if he's running the proper AP map from Cobb.

It seems that all you're hearing are the sounds that the bypass valve and convoluted stock intake are there to silencer (hence the term silencer for the milkjug in your fender). If you get a bellmouth or divorced downpipe, you'll hear much more noise from the turbo from where you are now.

[sperry]

Your problem isn't the intake (not that the intake is helping anything). Your problem is the BOV. Ditch it until you're making 400+hp at the wheels and you might need it.

[Dknits782]

if i keep the bov then will it hurt my engine or turbo? what map should i run with my ap?

[Dean]

To the best of my knowledge, there is no Cobb AP map for any after market intake, and they make a significant difference in intake flow.

If you BOV is anything other than recirculating, dump it.

If all you have on the exhaust side is an axle back, it is unlikely to be anything turbo/wastegate related.

I can't imagine anything on the left side of the engine that could make noise... Intake and exhaust is all on the passenger side... It is likely just more noise due to the intake which is no big deal, but unless you are tuned for it, I would remove it as well.

[sperry]

Originally Posted by Dknits782

if i keep the bov then will it hurt my engine or turbo? what map should i run with my ap?

If the BOV vents to atmosphere, you're throwing away metered air that the ECU is expecting to be in the cylinders, which means running rich when you shift, as well as causing a loss of power after shifting waiting for the turbo to re-spool to re-generate the pressurized air you just threw away making a neat-o PSSSHT sound.

The only reason ever to use anything but the stock BPV is if you're running insane levels of boost that the stock valve can't handle, or if you're a ricer that wants your car to make lots of whooshing noises. So, unless you've got a massive turbo running 30 psi, or neon-underglow, stick to the stock valve. I'm running 22psi of boost on a stock WRX valve w/o issues, other people are running more.

[kidatari]

Originally Posted by sperry

The only reason ever to use anything but the stock BPV is if you're running insane levels of boost that the stock valve can't handle, or if you're a ricer that wants your car to make lots of whooshing noises. So, unless you've got a massive turbo running 30 psi, or neon-underglow, stick to the stock valve.

[100_Percent_Juice]

Originally Posted by sperry

as well as causing a loss of power after shifting waiting for the turbo to re-spool to re-generate the pressurized air you just threw away making a neat-o PSSSHT sound.

I thought that both a bpv and a bov are in the closed position when the gas pedal is depressed? How does that effect the turbo spooling? I thought the only downside to the bov was running rich for a split second when you push in the clutch to shift.

[Nick Koan]

Originally Posted by 100_Percent_Juice

I thought that both a bpv and a bov are in the closed position when the gas pedal is depressed? How does that effect the turbo spooling? I thought the only downside to the bov was running rich for a split second when you push in the clutch to shift.

You almost repeated exactly what Scott said.

With a atmospheric BOV, whenever it triggers the car to lose metered air the ECU thinks is present in the system. This causes you to run rich after a shift and running rich will cause the car to lose some power for a split second or so.

[100_Percent_Juice]

Originally Posted by nKoan

This causes you to run rich after a shift and running rich will cause the car to lose some power for a split second or so.

I understand about it running rich but scott said that the car loses power because you have to wait for the turbo to respool not because its running rich. Thats what I had a question about.

[Nick Koan]

Originally Posted by 100_Percent_Juice

I understand about it running rich but scott said that the car loses power because you have to wait for the turbo to respool not because its running rich. Thats what I had a question about.

That's the same thing. If you lost air to the atmosphere, you have to wait for the turbo to spool to regain it. If you are short on air, you will run rich. If you are running rich, you lose power because leaner = more power.

[100_Percent_Juice]

Once you shift doesnt the turbo have to re-spool reguardless? Also if the rich period is between shifts would you ever be able to tell there is a power loss other than in theory or on paper? And just know that im not trying to defend bovs or be a pita, im just trying to explain it to myself I guess.

[sperry]

Originally Posted by 100_Percent_Juice

Once you shift doesnt the turbo have to re-spool reguardless? Also if the rich period is between shifts would you ever be able to tell there is a power loss other than in theory or on paper? And just know that im not trying to defend bovs or be a pita, im just trying to explain it to myself I guess.

With a BPV, the pressurized air in the system is returned to the intake pre-turbo. So for the turbo to respool to the target pressure, it's already got an injection of pressurized air to work with. With a BOV that vents to atmosphere, the turbo has to respool to pressure only with the 1 atm air from the intake.

It's not a lot more spooling with a BOV, but it's there. It's especially noticeable when you're on and off the throttle mid-corner under boost... w/o the recirculating BPV you'll quickly kill off the boost in the system.

[Nick Koan]

Originally Posted by 100_Percent_Juice

Once you shift doesnt the turbo have to re-spool reguardless? Also if the rich period is between shifts would you ever be able to tell there is a power loss other than in theory or on paper? And just know that im not trying to defend bovs or be a pita, im just trying to explain it to myself I guess.

The rich period is shortly after the shift, not during. I think that's where you are getting confused.

[100_Percent_Juice]

Originally Posted by sperry

With a BOV that vents to atmosphere, the turbo has to respool to pressure only with the 1 atm air from the intake.
It's not a lot more spooling with a BOV, but it's there.

So with a bov like the hks-ssqv that is partial recirculating its not as bad compared to a full atmospheric.

Originally Posted by nKoan

I think that's where you are getting confused.

yeah I was. I read a whole bunch of stupid crap on nasioc and obviously I was mislead. thanks bitches

[sperry]

Partial recirculating is better than 100% atmosphere, but the only reason for something like that is to make the noise. That's basically saying "I know I shouldn't be blowing to atmosphere, but I really want to make the noise"... which means you can't even claim ignorance on being a ricer.

[Dean]

Originally Posted by sperry

It's not a lot more spooling with a BOV, but it's there. It's especially noticeable when you're on and off the throttle mid-corner under boost... w/o the recirculating BPV you'll quickly kill off the boost in the system.

This is really the key more than the post shift time IMHO. One of my students at Miller in an '04 STI had a atmospheric BOV and his mid-corner response was madning. It bascially makes throttle steering nearly impossible because there is a significant hiccup do to the lost air and sudden rich condition, and you are never sure when it is or isn't going to happen.

And while I wasn't logging, I would bet that if you are in closed loop, the ECU sensing the rich condition then pulls fuel resulting in a lean condition shortly there after when the BOV closes.

[Dknits782]

oh thanks for all the info i dont have the bov for the sound so im just going to put the stock back on. and i found out that the sound was my wastgate dumping.