ok so i just installed an authentic greddy type rs bov. before , i had a knock off from ebay that i had removed the small spring from, reducing the spring load on the bov . the bov was making high pitch wistleing noises under light boost and a quick psh noise under full boost, 8psi.

i replaced the knock off with a readl type rs and it seems i simply just get compression serge fluttering. when its all the way loose i can hear light fluttering on throttle let off. i tightened it half way and i hear louder fluttering on throttle let off .


when all the way loose it doesnt ,make flutter sound untill after i build 5-8psi. doesnt make any sound.

when tightened half way it makes fluttering noise even at 0-5psi and louder 5-8psi.



this video sounds just like what i have going on
http://www.youtube.com/watch?v=2TzQRbUuAho

this is how mine is sounding. my bov has both springs in it. the bov is located between intercooler and throtle body. and i am running a stage 3 style hybrid turbo "high flow" turbo.


my questions :


is this type of air escaping threw the blade, called turbo serge, damaging to the turbo?

is it a good idea to remove/play with the spring set up for this bov?


if i remove the spring wont i just reduce the audible qualities of this bov? thus reducing the distinct sound of the greddy rs bov?



how can i get this rs bov to sound like an rs bov... whats the trick...

 

If your rx is making the same noise as the car in the vid, then yes, that is compressor surge. Unfortunately thats all the help I can offer until some more of the veterans step in. I've got no experience with after market bov's....

 

to add, heres is a video of TRUE compression surge, the type of surge that is most damaging, caused when the turbo is spooling,
http://www.youtube.com/watch?v=nCj6Spwl1CU

there are 2 types that i knwo of. surge caused by bov not opening and the fluttering sound that makes when the throttle is closed. and the surge caused by wot and overloading the turbo

 

Hook the vacuum port on the Type RS to the bottom port on the front of the UIM near the throttlebody, or the bottom port on the back of the UIM. Those are better vacuum signals.

 

screw the back ports all together. run it right off the uim, off the nipple under the BAC

 

That second vid, I don't think thats surge. That sounds more like the compressor wheel binding in the housing. Could be caused by excessive shaft play? I could be all wrong.

 

no that video shows exactly what compressor surge is. its basically pressure building up in the charge pipes because the motor can't inhale more air than what the turbo is putting out. the little bit of fluttering a turbo does inbetween shifts can damage a turbo but will more than likely never do anything noticable.

 

+1

 

The first vid is DEFINITELY surge. The second one, that sounds NOTHING like surge, and you can physically see the turbo shifting the entire motor. That high-pitched squealing sound is usually synonymous with metal binding against metal.

I have NEVER heard surge sound like that.

 

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

heres another instance were theres load type compressor surge

 

Sounds more like binding metal to me. But I'm not a turbo guy.

 

lol, binding, surging, stalling, theres many non technical names for it all. but the fact of it is what causes it. wot or on closing of throttle.


both are surging of different kinds. one i have even heard called stalling, where the air splits back over the turbo once you close the throttle. in the video for the evo, that can be called stalling. and the video of the skyline, can also be called binding since the turbo is "surging " under load causing what you see, to happen.



i talked to a friend last night and the actual stalling isnt bad for the turbo it just simply is slicing the air thats going back over the blades. now the video of the skyline, that IS bad and thats where you get vibration on the shaft and thats very damaging


but who knows, this is just what i have heard from a few people.


i will go ahead and find a new vaccume source. i think i already have it set up wehre ya'll told me but i will play around with everything and figure it out.

 

Also you don't "need" a bov.

 

no you dont. it basically is a 2ndary waiste gate to prevent building to much boost.

like for instance. greddy have a 22lb dual spring. holds 22psi of boost , in theory, if boost reaches over 22lb the bov will release the extra boost lowering and preventing the bad type of surging.


thats in theory what a bov really is. there is a really good article that enplanes this.

 

http://www.myspace.com/87rx7chick/videos

heres a video of my old bov. the greddy knock off type s. it was sounding like this for a long while untill i re-adjusted it .

 

Have you tried tightening the spring?

 

this may be a stupid question but, if i tighten the spring how will that help it opening at low boost.


its not opening when i rev the car up. like in the video above, the bov opens even while reving while idleing IE no load.


the vaccume alone is not strong enough to pull open the bov. usually if the bov is perfectly set up for the car then the highest peek of vaccume will pull open the bov. under idle, idle is usually less strong vaccume then when you initially take your foot off the throttle hence why the bov is not open while your idleing. its that threshold of vaccume between idle and max vaccume produced while you take your foot off the throtle while your driving.

that is what initially opens the bov.

if you tighten the spring wont you tighten the strength or vaccume required to pull open the bov? so in theory tightening it will not help it open under correct boost?


just a thought...

right now its all the way loose and its not opening while revving it up. like the video above shows.

 

ok a few min ago i went out on some back roads after changing the location of my vaccume source from the upper nipple to the lower nipple on the front of the uim. that may have been the reason my last bov stopped making the squeeky noise. since i did change the vaccume source. so i changed it back per some ones recomendation above.


after this change i went out and i still have the agressive fluttering where i should here my bov .


i went ahead and removed the bov. unscrewed the bov top and removed the smaller spring.

there is noticable difference when pressing up on the plunger, as now its easier to press upward then before.

i will be test driving it tonight or tomorrow to see if this infact improves the fluttering.

if i get no fluttering it means the bov is opening. if the fluttering goes away and my bov is opening but i hear no distinct blow off valve noise, then it means the spring mod worked but the spring mod sucks and it takes away the distinct noise of the greddy bov.

hopefully tomorrow i get answers....


seems the greddy bov is not entirely user friendly and you dont always get that signature sound like you hope for when buying the greddy bov...

 

Idk how different the Type-RS is from the old type-s one, but the thing I hate about the stupid BOV is the whistling sound it makes whenever I let off the throttle at low boost. How much vacuum are you pulling at idle?

 

idle is STRONG. 22 when i let off and about 15 at idle. when i had a vacuum leak it was at 9 under idle. idle is very very solid too, no variations indicating vacuum leak

the bov look identical in construction i am sure the difference is just the tone they make by splitting the air? no idea. but it was the same exact design...

 

ok i think i figured it out. i have a vacuum pump since i rented one from autozone. since i took out the small spring i reduced the pressure nessasary for opening the bov.

on an rx7, we idle at about 12-15 vacuum. on a piston engine they idle at about 20, or so.

alot of different engines idle at different vacuum pressures. and the pressure has alot to do with how the bov opens.


i would assume, the best way to get sound from this bov is to get the bov to open minimally so the split of air is more extreme causing more force from the air passing over the split that causes the signature noise.


while playing with the vacuum pump i have set mine to open at about 18 vacuum.

tomorrow i will do more trial and error but so far i think i have a better idea of what exactly is going on.


if i am still having fluttering issues after doing this test with the vacuum pump, then i have obvious vacuum source issues and need to tap into the bacv block off plate to get a true source of vacuum

 

http://www.evomoto.com/tech_info.php?tPath=1&tech_id=7

vital information

 

i used to have the type rs bov and a type s, they both make two completely differnet sounds. the type s sound like the usual greddy whistling. the type rs sounds like a blitz bov just a exhale of air

 

Just to clarify on compressor surge.




Surge line: The map width is limited on the left by the surge line. This is basically "stalling" of the air flow at the compressor inlet. With too small a volume flow and too high a pressure ratio, the flow can no longer adhere to the suction side of the blades, with the result that the discharge process is interrupted. The air flow through the compressor is reversed until a stable pressure ratio with positive volume flow rate is reached, the pressure builds up again and the cycle repeats. This flow instability continues at a fixed frequency and the resultant noise is known as "surging".


taken from : http://www.rbracing-rsr.com/turbotech.html

 

surging, stalling, who's the ruler of these terms.

like i said above, it doesnt matter what its called, it matters what is causing it and what is the result. i can call what i have going on either surging or stalling, both make sense, in a sense, and the skyline can be called surging or stalling, it makes sense depending on what you are thinking about,t he blade motion or the air motion they both surge or stall in either situation.

surging is stallng, stalling is surging, its either under throttle or closed throttle that matters.

and if any one doesnt agree, then oh well. it makes sense in my head and the names are just nascence.

i dug deep and found my own answers on this bov issue, and i am pleased with the results.