Compressor Surge GOOD or BAD?

[TunedIS300]

so this is been a back and forth argument that i have seen and wanted to see what tst thought about this...compressor surge good or bad for the turbo...i know honda guys that swear by that they wont run a BOV...they say that runnin 10psi is too low and no need to blow off..

[TROLL]

uhh, who says its good? lol. its definitely bad for the turbo, no doubt.
i have some now and i'm not stressing cause its temporary and only at low boost, but yeah, its not good at all for turbo life.

[Foolinaround]

it causes the compressor to spin the opposite way,causing wear and tear on the turbine,and potential turbo failure.

[TunedIS300]

i was on different forums and some say it fine for the turbo if not running no more then 15psi...and some say it bad..i just boosted my Si and i have compressor surge at the moment till i get it fix cuz my BOV is not blowing off at all..hopefully its not that bad for the turbo if i dont get on it for the next week or 2. but wanted to see what other say.

[Foolinaround]

Can you post links as to where they actually used correct grammar, and English, explaining why it was ok?


The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side.
Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself.
Common conditions that result in compressor surge on turbocharger gasoline engines are:
A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
The outlet plumbing for the bypass valve is too small or restrictive
The turbo is too big for the application


The blow off valve (BOV) sits on the charge pipe between the two, discharging unneccesary air when the throttle plate is slammed shut. It is controlled by a vacuuming line, and when there is a change in vacuum pressure, it is pulled open, venting the air to aptomosphere.

Also, on (most all turbocharagers, with the exception of some race only applications) there will be a wastegate. The wastegate regulated boost pressure by opening a second channel through which exhaust gas may flow, reducing the pressure on the turbine wheel (thats the wheel in the exhaust side that powers everything) so that the turbo cannot spin faster.

Wastegates may be mounted internally, in the turbocharger, or externally, on the exhaust manifold. No matter where it is mounted, though, they all function in the same way: boosted air pressure pushes against a spring until it opens it to a certain point.

Boost controllers change when a wastegate opens and closes by modifying the signal (boost pressure) that the wastegate sees. Boost controllers (manual ones, anyways) generally function by the tightening of a screw against a spring to increase the pressure required to open it. Essentially the more pressure required, the more "boost" there is before the spring is compressed and air is allowed to reach the wastegate, opening it.

There are also "Diverter Valves" (DV) they function in the exact same manner as a BOV, excpet that they are used on cars which utilize a Mass Air Flow style air meter. The reason for this can be summarized as below:

Air -----> flow meter ---->turbo----(past BOV) ---->throttle body

In this situation, if the BOV discharges when throttle is dropped, the air vented to aptmosphere has already been metered by the ECU, and the computer still flows fuel for lost air, resulting in a rich condition. (So you basically get lots of nasty black smoke and bad gas mileage)

In systems like this a "Diverter Valve" is used. these valve instead of venting the air to aptomosphere recirculate it, after the airflow meter, but before the turbo.


and more on BOV's

A Blow Off Valve (BOV) is a valve that is mounted on the intake pipe after the turbo but before the throttle body. A BOV's purpose is to prevent compressor surge. When the throttle valve is closed, the vacuum generated in the intake manifold acts on the actuator to open the valve, venting boost pressure in order to keep the compressor out of surge.
Bypass valves are also referred to as compressor bypass valves, anti-surge valves, or recirculating valves. The bypass valve serves the same function as a BOV, but recirculates the vented air back to the compressor inlet, rather than to the atmosphere as with a BOV.

[assault187]

Adjust your BOV spring pressure or check your boost/vacuum reference to you BOV. Your turbo does NOT like compressor surge

[smelly240]

Originally Posted by Foolinaround

it causes the compressor to spin the opposite way,causing wear and tear on the turbine,and potential turbo failure.

spin opposite direction? really?

because... no it doesn't. you cant change the direction of a 120,000 RPM turbine if you wanted to - especially when the turbine still has exhaust spinning it...

Surge isnt good - but no BOV surge isnt as bad as wot surge... Either way - you arent spinning a turbo backwards.

[Foolinaround]

real compressor surge( or compressor stall) is the halting of the turbo spinning in on direction from the back pressure that is still built up when the throttle plate is slammed close and it has no where else to go.

[OutToWinPAHC]

The aussies love it... "dose" but yeah bad for the tubo hell yeah, sounds awesome, and boost stay up sure its win lose.

[Car6on14]

Originally Posted by smelly240

spin opposite direction? really?

because... no it doesn't. you cant change the direction of a 120,000 RPM turbine if you wanted to - especially when the turbine still has exhaust spinning it...

Surge isnt good - but no BOV surge isnt as bad as wot surge... Either way - you arent spinning a turbo backwards.

ya, i didnt think it could spin opposite either...

[Foolinaround]

maybe im mistaken,but i still did drop a good amount of info all about it,so suffice to say i have to have some idea of what im talking about?

[peteyturbo]

Originally Posted by Foolinaround

maybe im mistaken,but i still did drop a good amount of info all about it,so suffice to say i have to have some idea of what im talking about?

The copy and paste was nice, but the turbo is not going to spin backwards..However with no bov when the throttle plate closes the air will bounce back and fourth slowing it down quite a bit and thus making the noise.
I am guessing the OP is not referring to WOT surge rather just surge from no BOV. If it is driven on the street, just get a bov, it has a purpose.

[TunedIS300]

i have BOV i was just wondering how bad surge is when ur BOV isnt blowing off or is blowing half way or some sort and how it effect the turbo thats all just curious.

[Foolinaround]

is your bov adjustable?

[TunedIS300]

yup greddy type rs

[Foolinaround]

try loosening it,or i believe it says "soft", so itd open sooner,then adjust accordingly.

[M Solo]

as everyone else said
compression surge is terrible for turbo life
it killed the turbo on my tsi

[TunedIS300]

lol i adjusted it im good to go. i just wanted to see what people opinions were thats all.

[Renegade_]

Are you talking about true compressor surge, as in on load?

Or "compressor surge" as that flutter when you lift off?

On load compressor surge is absolutely terrible for your turbo and will eat seals, throw the wheel off center, and just in general **** **** up.

Off load surge or flutter you get from the BOV not opening will cause substantially less wear on the turbo than on throttle surge will since the shear on the center turbine wheel does not exist to the degree that it does with the prior scenario. The exhaust gasses aren't forcing a shear, but rather the flutter comes from the turbine stalling rather than a disproportionate amount of airflow on both sides.

Journal bearing turbos, as I understand it, are fine with some degree of surge. I have a T28 that I didnt let blow off until 8-9psi and all you heard around town was surge, all day, and then I drifted it all last season, pulled it out and no play outside of factory spec. Then again, whenever I did get full boost it did relieve the pressure... I dont want to test that theory. Ball bearing on the other hand I hear you do need to recirc/vent outright on all boost levels. Ive never owned one so I wont overextend myself.

Some people need to stop citing compressor charts and ish until you know how to read them...

[lagos]

Its "bad", but not something that will destroy your turbo after a week or two. Its the type of thing where 5 years down the road, the turbo with the surge will most likely have more shaft play than the one without it.