BOV or no BOV?

[Brett]

Or, man up and run it aspirated :Giggle

[Grant Monkhouse]

Or, man up and run it aspirated :Giggle

That\'s why I\'m going na 13b pp in my rx4! Maybe embarras a few turbo boys up the drag strip when it\'s done!

[Brett]

That\'s more like it

[STU13 B]

3 years on my 200sx at 1 bar and then the last year at 1.2. As soon as i get my fd3s im ditching the ssqv and releasing the pigeons!
 
Oh and its not wastegate chatter, its called compressor surge.

[jackaleks]

3 years on my 200sx at 1 bar and then the last year at 1.2. As soon as i get my fd3s im ditching the ssqv and releasing the pigeons!
 
Oh and its not wastegate chatter, its called compressor surge.

you mean compressor stall, surge sounds like this and is very very bad (it\'s when gas flows backwards through the compressor whilst it\'s operating, i.e. on full boost):

True Compressor Surge

[STU13 B]

Axi-symmetric stall or compressor surge
Axi-symmetric stall, more commonly known as compressor surge; or pressure surge, is a complete breakdown in compression resulting in a reversal of flow and the violent expulsion of previously compressed air out through the engine intake, due to the compressor\'s inability to continue working against the already-compressed air behind it. The compressor either experiences conditions which exceed the limit of its pressure rise capabilities or is highly loaded such that it does not have the capacity to absorb a momentary disturbance, creating a rotational stall which can propagate in less than a second to include the entire compressor.
The compressor will recover to normal flow once the engine pressure ratio reduces to a level at which the compressor is capable of sustaining stable airflow. If, however, the conditions that induced the stall remain, the return of stable airflow will reproduce the conditions at the time of surge and the process will repeat.^[1] Such a "locked-in" or self-reproducing stall is particularly dangerous, with very high levels of vibration causing accelerated engine wear and possible damage, even the total destruction of the engine.
 
http://www.youtube.com/watch?v=LZUbo_mNDZM
 
Thats compressor surge.

[fil_auto]

interesting chat / debate occurring.. the latter vid shows a decent amount of engine movement too.... am thinking it might need some new mounts! :chat

[BlitzBoy]

http://www.youtube.com/watch?v=LZUbo_mNDZM
 
Thats compressor surge.

Thats compressor stall, the throttle plate is being "shut" during lift off of the throttle causing the compressed air going through the compressor wheel causing the noise

True Compressor Surge

Correct this is true compressor surge, in this instance the throttle plate is "open" but the amount of compressed pressurised air is not being fully ingested by the engine normally caused by a restrictive intake manifold or incorrect sizing of the compressor housing on the turbo

[STU13 B]

Haha, your not wrong, but its a retro fit. The 200sx s13 never came with an SR20DET, it had the CA18DET. The 180sx silvia had the red top SR20 fitted as standard. Useless info on a rotory forum but you might be intrested lol
 
The later in the paragraph is what Jack is on about, if you get that.... bang as his vid shows. Ideally if your going to do this you should have a ball bearing turbo so it dosnt put to much strain on the shaft when it stalls. There are lots of myths and old wife tails that compressor surge will route your turbo blah blah blah .... but as said mind has never missed a beat the whole time ive run no bov.

[trotter]

Thats compressor stall, the throttle plate is being "shut" during lift off of the throttle causing the compressed air going through the compressor wheel causing the noise



Correct this is true compressor surge, in this instance the throttle plate is "open" but the amount of compressed pressurised air is not being fully ingested by the engine normally caused by a restrictive intake manifold or incorrect sizing of the compressor housing on the turbo

excuse my ignorance here, but my understanding of it was that compressor stall was when the pressurised charge downstream of the turbo had the effect of \'slowing\' or stalling the turbine off-throttle, thus making it harder to spool again as it\'s working against backpressure rather then a vacuum??

The thermodynamic definition of compressor surge is where (for whatever reason) the compressor can no longer push enough mass flow through to sustain the discharge pressure. This results in the flow reversing direction and forcing its way back through the turbine. What happens next is that the reverse flow then re-pressurises the intake side and normal flow direction is recovered. If the original cause is not corrected, this pattern continues many times per second and puts massive stress on the turbine blades as the flow goes back and forward.

I\'m agreed that compressor surge is indeed worse, i\'m a process engineer and i\'ve been standing next to north sea gas compressors (variants of the RB-211s which used to power commercial jet planes) when they\'ve gone into recycle mode (essentially a recirculating BOV) to protect against surge and it sounds like the end of the world!! I\'ve seen a video of a $6mn compressor actually hitting surge when the recycle valve failed and vibrating itself clean off it\'s mountings!!

The anti-surge (or recycle) control systems that these babies have are usually worth in excess of £1mn, which goes to show that its a problem that\'s taken seriously in industry. For that reason alone I will always go for a BOV.

graeme

[yiug412]

excuse my ignorance here, but my understanding of it was that compressor stall was when the pressurised charge downstream of the turbo had the effect of \'slowing\' or stalling the turbine off-throttle, thus making it harder to spool again as it\'s working against backpressure rather then a vacuum??
 
The thermodynamic definition of compressor surge is where (for whatever reason) the compressor can no longer push enough mass flow through to sustain the discharge pressure. This results in the flow reversing direction and forcing its way back through the turbine. What happens next is that the reverse flow then re-pressurises the intake side and normal flow direction is recovered. If the original cause is not corrected, this pattern continues many times per second and puts massive stress on the turbine blades as the flow goes back and forward.
 
I\'m agreed that compressor surge is indeed worse, i\'m a process engineer and i\'ve been standing next to north sea gas compressors (variants of the RB-211s which used to power commercial jet planes) when they\'ve gone into recycle mode (essentially a recirculating BOV) to protect against surge and it sounds like the end of the world!! I\'ve seen a video of a $6mn compressor actually hitting surge when the recycle valve failed and vibrating itself clean off it\'s mountings!!
 
The anti-surge (or recycle) control systems that these babies have are usually worth in excess of £1mn, which goes to show that its a problem that\'s taken seriously in industry. For that reason alone I will always go for a BOV.
 
graeme

Agree on that. My lecturer (auto eng, lufbra uni) explained to me why the BOV is needed from his past rally car experience. to put it simple it is there for perfomance, to keep the turbo spinning,and the sound:D
 
ofc theres a lot of theories behind that. there\'s always a reason why the stock FC\'s or 200SX have the recircu valve as stock.
 
Louis

[SiH]

Agree on that. My lecturer (auto eng, lufbra uni)

Just out of interest, don\'t know a guy called Alan Baker do you?

[BlitzBoy]

Agree on that. My lecturer (auto eng, lufbra uni) explained to me why the BOV is needed from his past rally car experience. to put it simple it is there for perfomance, to keep the turbo spinning,and the sound:D
 
Louis

Ask you lecturer why most turbo rally cars dont run a BOV then?

[BlitzBoy]

Also F1 turbo cars in the 80s did not run BOVs, two reason, one a BOV would have a hard time not leaking under 3-4 BAR of boost, second the time lost in recompressing the air in the intake system which be lost when vented by a BOV versus the time gained in keeping the turbo spinning , they found it was better to have the performance advantage of not venting the already compressed air.

[BlitzBoy]

there\'s always a reason why the stock FC\'s or 200SX have the recircu valve as stock.
 
Louis

Yes noise surpression in the case of recirc valves