KA-T Won't Stop Comp. Surging!

[HolyShiznit]

As stated in a previous post I got my new Type-S bov today and I hooked it up in all manner of different combinations of vacuum lines. Some before the throttle body some after.....the bov opens at the setting we have it on, and it doesn't leak. The problem is that it seems like it is delayed in opening. When I hit boost and left off the throttle, I hear the compressor surge but it is cut short by the BOV opening.... kind of like chi, chi, chi, PSSSSSSSSSSSSTTTTHHHH. I don't get why the hell it is doing this. Like I said I have tried almost everything, I have it on the softest spring setting which seems to work, we tried tightening it a bit but the bov wouldn't even open then. I have the smaller of the nipples (the bottom most one) with a line running pre-throttle body hooked up to it and the top one is ran from a line I t'ed off from the intake manifold. I have good vacuum according to my gauges and testing of the lines.

I am wondering if my placement of the BOV is causing this. For reference here are pics......the Type S is situated exactly where the RFL is pictured. Does anyone have any ideas! Please help!

http://northwestnissans.com/bo...18314

Jon

[huguetpj]

I'm guessing you have... but have you tried leaving one of the two ports open to the atmosphere? Don't really know but I'm thinking something along the lines af how a wastegate is actuated.

[C-Kwik]

The BOV fluttering is not an uncommon occurence. My car does it as do many other turbo cars I've dealt with. The fluttering sound you hear is not surge. It's the BOV preventing surge from occuring.

[HolyShiznit]

C-Kwik, I respect your knowledge and I have followed it myself with my car but are you sure the fluttering isn't compressor surge.....

Because when I let off the throttle, the chi chi chi sound comes from my open element filter. After about a second of this the BOV opens. It's not really a flutter coming from the BOV, it seems to be coming from inside the turbo as we can hear it from the filter. This is also the same noise that it made when my RFL did NOT open at all. I really don't get this at all.

[C-Kwik]

I see what you might be saying now. Depends. If the fluttering sound you get sounds like the BOV opening and shutting, it is the BOV. If not, it could be surge. It would be concievable if your BOV is not opening until after a second after you close the throttel. If your BOV is adjustable you may need to loosen it up. The BOV should open as soon as you close the throttle. What may be occuring if the BOv is responding that late is that it's responding to a very high pressure ratio. Without a BOV a compressor will surge each time you close the throttle on just about any turbo that is spinning fast enough to create boost at low throttle. If it opens late the turbo is going to surge until the BOV opens. And if the BOV is set too tightly, then it may be opening when a certain pressure is reached in the pipe. I can't say for sur that this is actually the case. Sounds can be a bit hard to understand in words.

[95_240sx]

I think you just need to buy my s14 because mine is fine

j/k I have comp surge on my car, but minimal, and i deal with it. True compressor surge is a deep loud rumble coming from the exhaust as far as i know.

Rick

[HolyShiznit]

I am so confused right now.....

I drove it a little tonight and it seems like if I drive it real hard like rev it up, hit boost, then shift then slam throttle again it "appeared" that the bov didn't even really open. It's like it waits for me to pause then it comp surges then it opens. But...goddamn, it's getting annoying, oh well.

As for tightening/loosening, the bov opens.....just late. It also doesn't leak at idle or anything like that so I am pretty sure that the BOV is set right, but who knows at this point.

[C-Kwik]

I think you just need to buy my s14 because mine is fine

j/k I have comp surge on my car, but minimal, and i deal with it. True compressor surge is a deep loud rumble coming from the exhaust as far as i know.

Rick

Surge occurs at the compressor, not the turbine.

[C-Kwik]

I am so confused right now.....

I drove it a little tonight and it seems like if I drive it real hard like rev it up, hit boost, then shift then slam throttle again it "appeared" that the bov didn't even really open. It's like it waits for me to pause then it comp surges then it opens. But...goddamn, it's getting annoying, oh well.

As for tightening/loosening, the bov opens.....just late. It also doesn't leak at idle or anything like that so I am pretty sure that the BOV is set right, but who knows at this point.

Again, the BOV should open pretty much right when you release the gas pedal. You can set it a little tight to promote keeping the intake pressurized, but this is not really recommended unless you are running a ball bearing turbo as bb turbos can take more thrust loading from surge than a standard bearing.

If it opens late, the compressor will surge. Surge essentially occurs when the pressure is high and the flow is low. It varies based on what turbo you have, however every turbo will surge if there is no flow and boost exists. And for some time, the turbo will still be spinning and trying to force more air into the intake. So if the BOV does not open right away, it will surge until it does open.

[MikeMurphy]

As stated in a previous post I got my new Type-S bov today and I hooked it up in all manner of different combinations of vacuum lines. Some before the throttle body some after.....[/url]

I take it your current setup is after the TB right?

[HolyShiznit]

The BOV is mounted 5-6 inches in front of the throttle body.

[andrave]

I think he meant your vacuum lines for the bov.

I remember in SCC's blow off valve test a year or two ago they showed that some of the more popular valves on the market allowed compressor surge before they opened... HKS ssqv, for one...I think the type S did very well in their tests tho.

[HolyShiznit]

The one vacuum line that is supposed to be after the throttle body is coming from a tee that was spliced into a line on the far back left side of the intake manifold, the other vacuum line that is supposed to be pre-throttle body(the smaller and lower of the two nipples) is reading right off of the compressor itself. My turbonetics has a small screw part that we used to put a little nipple on it.

[MikeMurphy]

Your saying you have one right next to the compressor inlet that is supposed to be in front of the TB?

Isnt that supposed to be on the pressurized side of the turbo?

I really dont know. I think im pointing out the obvious here but it seems to make sense to me. This would also explain why there is a delay since it may take a moment for the vaccuum between your compressor and your filter to "devaccuumize" and thus create the differential needed for the BOV to open.

Someone tell me im wrong.

[HolyShiznit]

Wait, I think your right....I was thinking about it wrong when I put it on. So maybe I need to make another nipple on my cold pipe side and run that to the nipple that is currently ran to the compressor inlet of the turbo. Mike.....good call man.

I will try this tomorrow.

[huguetpj]

Turbonetic turbos have a screw tap on the outlet of the compressor, not the inlet... I know mine is like that. Are you sure you have it on the inlet of the compressor? Don't really know how would a compressor inlet have a screw tap.

If the signal should be pre-TB I'm pretty sure it should be on the pressure side, so definitely not on the inlet. Also if it were on the compressor pressure screw tap, I would move the signal closer to the TB since pressure build up starts at the TB when you close it.

If the other signal is after-TB then that's the vacuum signal.

[240_2NR]

i dont know if this helps but my friend has a DSM w/ a GReddy Type-S BOV and he doesnt have the bottom nipple (from BOV) hooked up to anything at all and it never surges, The vacumm line after the Throttle Body is hooked up just not the bottom one that u say is supposed to be pressurized

[ftrs13]

that would make sense though, because the vacuum sucking it up, and the pressure pushing it up together might be what opens it up, because I know its pretty stiff. if that is the case, it would only release on vacuum + boost underneath, which is where you want it.

[HolyShiznit]

Well I screwed around with nearly every damn thing I could today, I tore the crap out of everything and re-routed, re-drilled, tapped from different spots, and generally tried everything including testing vacuum on nearly all my lines. I still have weird compressor surge and THEN the BOV opens. At this point I am stumped....everything is where it should be, the last thing I am guessing is that my secondary butterfly valves are screwed up and they are messing with the vacuum.....but at this point, I am completely lost.

EDIT: Doesnt' make much sense that the butterfly thingies would do anything to screw stuff up. I have 0 clue at this point.

[Gofast1]

Holy,

We experienced this on a couple of our kits with customers running the Type-S BOV. We found two things out:

1. The BOV doesn't need the bottom line hooked up and it should be set to it softest setting possible without leaking. On our Stage 2 car the set screw is on like one thread into the BOV case.

2. Check your oil feed line. This may sound crazy but on our kits we had to change to -3 feed lines because the -4 lines were letting too much oil into the turbo, which made a surge sound when we let off the throttle. The sound ended up being the turbo trying to cycle all that oil. We changed to -3 lines and set up the rest of our Greddy Type-S BOVs at the softest setting we could before leak and none of our kits have had surge since.

I don't know if this will help or not, but it solved what we thought was surge. Check em out man, can't hurt

Marc

[HolyShiznit]

Did your cars have the delay problem that I have though?

BTW: I have it on the same setting you said, mine is one thread in, literally. And I will try the oil thing, I am using the JGS tools oil kit but I don't know what you mean by -3 or -4 lines....

[Gofast1]

Did your cars have the delay problem that I have though?

BTW: I have it on the same setting you said, mine is one thread in, literally. And I will try the oil thing, I am using the JGS tools oil kit but I don't know what you mean by -3 or -4 lines....

Yeah we had the delay as well.

What I mean by the -3 or -4 is the size of the line. In AN military sizes. -3 is just a slightly smaller line.

[Kotir]

2. Check your oil feed line. This may sound crazy but on our kits we had to change to -3 feed lines because the -4 lines were letting too much oil into the turbo, which made a surge sound when we let off the throttle. The sound ended up being the turbo trying to cycle all that oil. We changed to -3 lines and set up the rest of our Greddy Type-S BOVs at the softest setting we could before leak and none of our kits have had surge since.

Interesting... I'd assume a line restrictor would work aswell as changing the whole line eh? I've heard of too much oil leaking through the oil seals and making the car smoke smoke etc, but not making a noise...

How and which vacuum signal lines do you use/share with your kits? Out of curiousity? I have no idea how many nipples are on the KA intake manifold and it seemed like he had alot of **** tee'd off one line. I don't think that'd make a difference though would it?

(This is a local friend of Holy btw... I have a aftermarket turbocharged Impreza 2.5RS, so I kinda know about the trials and tribulations of a N/A car w/ a turbokit on it)

-Tim

[Gofast1]

Interesting... I'd assume a line restrictor would work aswell as changing the whole line eh? I've heard of too much oil leaking through the oil seals and making the car smoke smoke etc, but not making a noise...

A line restrictor would have worked, but we figured we would fix the problem at the source.

How and which vacuum signal lines do you use/share with your kits? Out of curiousity? I have no idea how many nipples are on the KA intake manifold and it seemed like he had alot of **** tee'd off one line. I don't think that'd make a difference though would it?

We T off the fitting on the intake manifold below the runners, to the right of the idle control screw for the BOV line. Shouldn't make a huge difference, but there are differences in pressure/vacuum between different lines in the engine.

(This is a local friend of Holy btw... I have a aftermarket turbocharged Impreza 2.5RS, so I kinda know about the trials and tribulations of a N/A car w/ a turbokit on it)

-Tim

Aye, turbocharging 2.5 RSs is fun isn't it? NOT!LOLBut well worth it in the end, they make unreal power

[C-Kwik]

1. The BOV doesn't need the bottom line hooked up and it should be set to it softest setting possible without leaking. On our Stage 2 car the set screw is on like one thread into the BOV case.

I would focus on this...too stiff a setting will cause the intercooler pipes to have to see a certain amount of pressure before it opens. With such a high pressure ratio and low airflow(throttle is closed remember?) that will easily put you way over on the left side of the surge line of any compressor map.

[HolyShiznit]

Well, tried the oil line thing and it didn't do it. Hot damn this sucks. Nothing really makes sense at this point, we are going to try one more time tomorrow to rig up a vacuum canister and check valve to basically try to force the valve to open after I release the throttle. But that's basically where I am at right now......

BTW: My Greddy Type S has BOTH vacuum lines hooked up correctly and with BOTH springs inside the BOV(like it normally has) and it is on the last thread and it still won't leak....so I dunno if I am getting bad vacuum or what, but it just delays opening......so I dunno, I have explained it as best I could.

[DaveEEE]

I had a very similar problem with my KA-T.... Drove it like that for 4 months and pissed me off just about everyday. When the BOV would open and flutter the car would stutter, unless I was WOT. Made daily driving a pain.......... Turns out it was a simple rubber hose clamp on my ic pipe. Go figure. We had ran a pressure test, we didn't hear it. But, sure enough it was torn.

[HolyShiznit]

I tried routing a more direct line from a vacuum source to the BOV and it still didn't work. I dunno if I have a vacuum leak that is causing my car to not have enough vacuum to open the BOV up or what. The car idles fine though. I dunno, if it is something simple ama be pissed. I don't think tapping directly into the intake manifold and making a direct port for the BOV is a good idea either because if it isn't drawing enough vacuum as it is now, then why go through all the trouble.

Once again, I am stumped.

[ftrs13]

you problem with the BOV stems from the fact that it is sprung to high for our engines. its all explained here, and how to fix it.

http://forums.freshalloy.com/u...40202

[HolyShiznit]

you problem with the BOV stems from the fact that it is sprung to high for our engines. its all explained here, and how to fix it.

http://forums.freshalloy.com/u...40202

I thought that was for recirculating cars only, though. Oh well may as well try it.