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After installing my front mount setup on my comptech the bov no longer has the clean woosh sound.
It has more of a chatter sound.... cha cha cha flutter kind of sound.
Can centrifugal blowers have compressor surge like turbo's?
heres the setup: before the intercooler it was non aftercooled with the same BOV
Compressor surge happens when the throttle body is shut too quickly with a turbo setup. Going from high-load to no-load instantaneously results in the throttle body closing before the turbine has time to slow down. (The inertia of the turbine effectively makes it so the turbo is still making boost after letting off the throttle, which is not the case with a SC).
With a SC, the instant you let off the throttle, and the throttle plate closes, the SC stops boosting immediately (as it is tied directly to the crank, which drops to idle (no boost) when the throttle plate closes).
Is that a synchronic BOV? If so, just turn the setting to a softer setting... That noise you are hearing is like compressor surge, in that there is pressure in the charge pipe that needs to escape. It is not because of the compressor "surging", though, and is probably due to your BOV being set too "hard."
Compressor surge happens when the throttle body is shut too quickly with a turbo setup. Going from high-load to no-load instantaneously results in the throttle body closing before the turbine has time to slow down. (The inertia of the turbine effectively makes it so the turbo is still making boost after letting off the throttle, which is not the case with a SC).
With a SC, the instant you let off the throttle, and the throttle plate closes, the SC stops boosting immediately (as it is tied directly to the crank, which drops to idle (no boost) when the throttle plate closes).
Is that a synchronic BOV? If so, just turn the setting to a softer setting... That noise you are hearing is like compressor surge, in that there is pressure in the charge pipe that needs to escape. It is not because of the compressor "surging", though, and is probably due to your BOV being set too "hard."
John
thanks, its a HKS SSQV and its the second version with no spring settings so i cant set it... And the second the throttle is closed that supercharger is still spinning for sure it doesn't immediatly drop to idle.
And i dont know if youve felt the air coming out of one of these at idle but its alot...
Im thinking it may be because of where the bov is, and air is escaping now from the superchargers direction and back up from the throttle plate, we'll se if it changes when i put on the 9psi pulley.
Or maybe since i have such a long vacuum hose its now not opening quick enough?
(The inertia of the turbine effectively makes it so the turbo is still making boost after letting off the throttle, which is not the case with a SC).
With a SC, the instant you let off the throttle, and the throttle plate closes, the SC stops boosting immediately (as it is tied directly to the crank, which drops to idle (no boost) when the throttle plate closes).
I'm afraid you're way off on this one.
With a centrifugal supercharger the instant you let of the throttle the SC does NOT stop boosting immediately (unless you put your clutch in and let the rpms drop to idle). If I take 4th gear to redline and then let off the engine doesn't immediately drop to idle, instead it's going to have to gradually slow down because I'm still in gear. The SC is directly coupled to the crank and is going to still be spinning its ass off due to the revolutions of the engine regardless of if the throttle plate is opened or closed. If anything the SC is going to continue to boost and surge longer than a turbo would due to its mechanical connection to the crank. A turbo would spin down much faster since it is driven by exhaust gases which should be drastically reduced when the throttle closes.
With a centrifugal supercharger the instant you let of the throttle the SC does NOT stop boosting immediately (unless you put your clutch in and let the rpms drop to idle). If I take 4th gear to redline and then let off the engine doesn't immediately drop to idle, instead it's going to have to gradually slow down because I'm still in gear. The SC is directly coupled to the crank and is going to still be spinning its ass off due to the revolutions of the engine regardless of if the throttle plate is opened or closed. If anything the SC is going to continue to boost and surge longer than a turbo would due to its mechanical connection to the crank. A turbo would spin down much faster since it is driven by exhaust gases which should be drastically reduced when the throttle closes.
I am afraid you are incorrect. A turbo will wind down slower than a SC, because it is not tied DIRECTLY to the motor (assuming you go from 100% load to 0% load). The crank will drop RPM faster than exhaust gas volume. Exhaust gas volume will fall, but only proportionately to the RPM. We are talking semantics (fraction of a second) in terms of which one loses boost faster.
However, turbo's suffer from boost-creep (i.e. - boost still builds AFTER you go from 100% load to 0% load), which usually results in compressor surging, as the creep occurs first at the compressor housing, and then moves to the throttle body. SC definitely does not have this problem.
If you are at low load, and go to no load, yes, a turbo will probably wind down faster. However, when going from high-load to no-load (when compressor surging happens... it never happens at low load, as turbos usually do not build much boost at low loads), the turbo will wind down slower (assuming turbine wheels the same size, etc... a GT40 will obviously wind down much slower than a gt28rs...).
Centrifugal SC is tied directly to the crank (RPM only). Turbo boosts proportionately to load / RPM. In high-load to low-load situations, large turbos will unspool slower than a SC due to boost creep properties (not necessarily creeping, but the same physics are present to keep the wheel spinning, if not generating more boost after the load is dropped to 0%). Small turbos might unspool faster, but I am not sure. The physics point to turbos unspooling slower in high load to no load situations (like on a dyno, or finishing a drag pull) than a centrifugal SC, and unspooling faster in medium/light load to no load situations (due to the lack of real boost being generated to begin with by the turbo at low load situations).
Supercharger compressor surge
