Recirculating BOV w/CA18DET (where do I output the bov line to?)

[flohtingPoint]

I have some of the materials needed to recirc my Blitz DD, but I am at a loss as to where to recirc it too. My motor setup is entirely stock, as I just recently got this 200SX (euro RS13) and I am unfamiliar with CA18's right now. I know it has to go in behind the MAF, but I'm unable to find where I can output it to. Any help is appreciated.

Thanks,floh

[c-rad]

I don't know the answer to your question, but I didn't know European S-chassis had a 240 km/h speedo...

[flohtingPoint]

I don't know the answer to your question, but I didn't know European S-chassis had a 240 km/h speedo...

Some people get sick on the autobahn... My CA18 is pretty abused from its previous owner driving down it thinking that she was an F1 racer =/

[Nunook]

Doesn't the stock intake pipe (from the AFM to the turbo) have a connection for a hose from the valve cover? NOT SURE... i never saw the stock piping in person.

If it does, u can put a breather filter on the valve cover side, and use the connection on the intake as the output from ur BOV.

EDIT: now that i think of it, that might be too small. It might give u ideas though, lol.

[originalsin]

I don't know the answer to your question, but I didn't know European S-chassis had a 240 km/h speedo...

I don't know the answer to your question, but I didn't know European S-chassis had a 240 km/h speedo...

and the tach goes to 9k

[81na ZX]

A recurculating BOV will always dump back between the AFM and the turbo. Between where it was metered and where it can be recompressed.

[originalsin]

A recurculating BOV will always dump back between the AFM and the turbo. Between where it was metered and where it can be recompressed.

so its recurculating bov's that make that very fast sputtering sound? there arent a ton of boosted cars in my area and a friend with an srt4 has the stock bov with makes a very fast like sputtering, not like a bad sound but i never understood it

[iliketocrash]

a sputtering sound? sounds more like mild compression surge to me. i've never heard a stock srt4 do that.

[f s t caz]

so its recurculating bov's that make that very fast sputtering sound? there arent a ton of boosted cars in my area and a friend with an srt4 has the stock bov with makes a very fast like sputtering, not like a bad sound but i never understood it

that would be the sound of the compressor coming to a violent/abrupt stop, aka compressor surge. The reason it happens is that a lot of stock recircs aren't made to handle above stock air flow (above stock boost levels) and thus they can't dump enough volume of air fast enough to stop the compressor surge from happening (or atleast thats what makes sense in my head)

[xyster]

that would be the sound of the compressor coming to a violent/abrupt stop, aka compressor surge. The reason it happens is that a lot of stock recircs aren't made to handle above stock air flow (above stock boost levels) and thus they can't dump enough volume of air fast enough to stop the compressor surge from happening (or atleast thats what makes sense in my head)

I'm sorry, I hate to nitpick, but compressor surge is not really the wheel stopping... It's actually the point where the compressor impeller can no longer overcome the pressure of the air in the pipe. It happens when the throttle plate suddenly slams shut, and the turbo is still pushing air...the piping and compressor housing rapidly pressurize, and the wheel is still spinning, just not moving any air (cavitating, I think is the word). Some of that pressurized air bleeds off through a BOV, back out the turbo, wherever, just enough so the wheel starts pushing air again, the piping pressurizes, and the cycle starts anew...all this happens in a fraction of a second, makes the "ch-ch-ch-ch" noise. I work with large industrial multistage centrifugal blowers, and I deal with surge all the time...except surge on a 5-ton, 20k CFM blower is a little more exciting than on a turbo...heh

[81na ZX]

Cavatation is what happens when a propeller creates eddys or air bubbles instead of acting on a liquid. A compressor wheel is a propeller, and I think you described it correctly, but I got lost in your post

Cavatation can just cause noise and slow a boat down, or it can add air into a water pump due to poor design at really high RPMs.

I've always been told and read that compressor surge is when the TB closes, the pressureized air has no where to go but back to the turbo, crashing into the wheel causing bearing damage.

[xyster]

Cavatation is what happens when a propeller creates eddys or air bubbles instead of acting on a liquid. A compressor wheel is a propeller, and I think you described it correctly, but I got lost in your post

Cavatation can just cause noise and slow a boat down, or it can add air into a water pump due to poor design at really high RPMs.

I've always been told and read that compressor surge is when the TB closes, the pressureized air has no where to go but back to the turbo, crashing into the wheel causing bearing damage.

I did a little checking on my own post, and I might be wrong, but I still think cavitation is the right word. Sorry, my post might be a little unclear...I haven't had to explain surge to a customer in about a year (been activated with my reserve unit), so I'm probably a little rusty. You're essentially right, the pressurized air has nowhere to go, so it goes back through the turbo, pressurizing the compressor housing, just like the piping. In that instant, the housing is more or less just another piece of piping, until the pressure can drop enough for the impeller to overcome it and begin moving air again, which happens in a fraction of a second. The damage is done by the air/pressure rapidly slamming back and forth against the wheel. Now, speaking solely from my experience with large machines, it tends to create a high radial load (along the line of the shaft), which, in turn, puts a high strain on the bearings. It can cause impellers to crack or actually be pushed back into the casing. All our machines use ball bearings, and it can put a tremendous strain on the bearing...I've seen ball bearings explode from persistent, violent surge. Also, a machine run in surge a lot will run significantly hotter. Pressure is directly proportionate to the temperature of the air charge, and surge means higher pressure. Again, that's all talking about general centrifugal compressors, it may or may not apply to turbos. I work on these:

[KaZ (VaBch)]

It is still called "Compressor Surge" in the automotive industry... it basically has to push air back out the intake to compensate for the stopped air flow from the throttle body... the turbo doesn't necessarily spin backwards per say, but it does STOP, which is really rough on the turbo... it should be avoided at all costs if you want to prevent shortening your turbos life... I think the term surge comes from the surge of air that comes back out from the turbocharger... not based on what's actually happening...

Something I found on Blitz's website about their blow off valves:

"The Blow-off valve is essential to all turbocharged vehicles. The purpose of the BLITZ Blow-off Valve DD is to relieve compressor surge without reducing compressor speed. It controls boost pressure that is built up by the turbo and vents it into the atmosphere when the car is not under load (in between shifts). This prevents pressure from backing up into the compressor housing, causing the turbo impeller blade to rapidly stop or even worse, to spin backwards (compressor surge or backspin). Doing so can be potentially destructive to the turbine wheel and shaft. Repeated stress over time can cause eminent damage to the turbo charger and eventually lead to turbo failure. A blowoff valve is actuated by pressure changes only, ensuring quick valve responses and complete closures at idle. The BLITZ blow-off valve not only improves performance and response, but also increases the life of the turbocharger."

[float_6969]

I would almost have to see it with my own eyes to believe that the compressor blade will spin backwards or even stop. And if the air pressure great enough to cause those events to happen and to travel backwards through the suction side of the turbo, what do you think would happen to the MAFS reading? It would actually count the same air twice since it counted it once when it was drawn into the turbo and then again when it was forced out. You also have to remember this. A gasoline engine is, in it's simplest state, an air pump. That means that as long as it's turning, it should be moving air. For the blades to be able to stop or spin backwards, there would have to be enough force present on the compression half of the turbo to overcome the forces on the exhaust (turbine) half of the turbo. I won't say that it isn't possible, but just highly unlikely.

The sound that you are all making reference to actually stems from the sound of air molecules slamming into eachother and the tips of the compressor blades in the turbo housing. As was stated before when the turbo is still spinning and the throttle plate shuts, the turbo is still trying to compress the air. At some point the pressure of the air inside the compressor housing becomes so great that the compressor blade is no longer able to continue to pressurize the air any more. THAT is when the "Ch-ch-ch-ch-ch" sound is made.

[xyster]

ok, again, the compressor wheel DOES NOT STOP during surge on a centrifugal compressor...which is exactly what a turbo is. That's a common misconception....let me say this again...the damage to the bearings is caused by the high radial load on the shaft, caused by pressure slamming back and forth against the compressor impeller. On the centrifugal machines I work on, which work on the same principles as turbos, just on a larger scale, a hard surge will slow down the rotation by about 50 rpm...that's it.