Compressor Surge on s14 sr20

[s15 sr20 guy]

I have a s14 sr20 and i am having a little surge problem. I am running a Sard r2d2 bov. Running my car at 7 psi everything is fine and there is little to no compressor surge. When I up my boost to 12 psi i I am getting compressor surge when i shift around the 10 psi range or higher. the compressor surge is very noticeable too. The weird thing is that my bov is still blowing off. i tried adjusting the bov softer but it didnt seem to help. do i need to set my bov to be tighter? what should i do? by the way this is my first turbo car. i also looked though alot of the threads and none of them seem to have my problem because my bov is blowing off fully but its surging to.

[jspaeth]

There is always a compromise between compressor surge, and how "easily" it blows off.

IF you tighten it, it will mean that it takes more boost and subsequent throttle let off to blow off.

If you loosen it, too much, your idle will be bad and you will run really rich, but the looser you make it, the easier it blows off.

Again, there are a ton of variables....how much boost you are at, and how quickly you let off the throttle.

A little surge under light loads isn't too bad.....if you try to make it blow off too easily, it will probably leak to easily

[s15 sr20 guy]

so if i tighten the bov will it lessen the compressor surge at higher boost levels and increase compressor surge at lower boost levels?

[jspaeth]

If you tighten the bov, you will in general have more surge.....the "break-even" point where the bov opens will be slightly higher, requiring a larger difference between manifold pressure and hot pipe pressure.

Tighten---->requires larger pressure difference to blow off.....too tight, and it won't blow off for medium amount of boost build up, leading to more surge.


Essentially, tightening it always creates more compressor surge (well, it shifts the regime where you get surge down farther to lower boost levels).


Try LOOSENING it first to eliminate surge, but you don't want to completely get rid of surge....in other words, at very light boost levels with easy throttle let off, some surge is okay...

IF you loosen too much, you aren't going to hold boost well and might have bad idle.

[s15 sr20 guy]

ok. i will losen the bov as much as i can and then adjust from there.

[tt99ol]

really you should loosen it as much as you can just so it wont leak at idle, then leave it there, thats as good as its gonna get, well loosen it all the way, then tighten it back up until it doesnt leak anymore

[s15 sr20 guy]

I have adjusted my bov every which way and nothing seems to help the compressor surge. i also took apart my bov and made sure it was working good and it is. the bov is opening all the way and blowing off hard. like i said earlier, it only surges at any boost at or above 10 psi. it still bows off hard. the thing that gets me is that i have seen cars running a higher boost then mine and they dont have compressor surge. i am only running 12 pounds of boost. the only thing that i can think of is that i am running a ball and spring manual boost controller and that may be the cause of the compressor surge. one time i rigged up a turbonetics boost controller made for an external waste gate and had it set for 10 psi and there was no compressor surge. could it be my boost controller or am i just reaching?

[garagelu]

My car actually does the same thing. I have a sard r2d2 mounted on the cold pipe. It actually surges and then blows off when you let off at partial throttle. I bet yours acts the same as mine. I dont really consider it a problem because I think it sounds completely awesome. I run a ball bearing turbo so I am not too worried about it.

My theory is if you mounted the bov on the hotside, you will get less compressor surge. Where do you have yours mounted?

[khilgers]

I had an issue with my Blitz BOV surging. I took it all apart, cleaned the piston walls, re oiled the seal, RTV'd the top back on and it has worked great from that day. It may help to take it all apart and give it a good cleaning. I bought mine used from a friend that had only around 6K miles on it, but it did help to give it a good cleaning. They are not hard to take apart, just watch out for the large spring when you take the top of. Good luck.

[s15 sr20 guy]

My bov is mounted on the cold side as well. i realized after i took it apart that i didnt take one part off so i am gonna take it aprat right now to nothing and rebuild it again and hopefully my problem will be solved.

[khilgers]

I've got mine mounted on the cold side for my S14 sr and after I cleaned the BOV my problems went away.

[tt99ol]

it actually could have something to do with the boost controller, if it bleeds out air too fast the wastegate slams shut and all the exhaust gasses spool the turbo more, where is your vaccuum source to your actuator? from the manifold?

[s15 sr20 guy]

all of my vacuum sources come from the intake manifold. i have taken my bov apart, what is the best thing to oil it with? i have a sard r2d2 bov.

[khilgers]

I just used a very small amount of 5/30 oil. Just enough to coat the cylinder walls lightly so that the piston can move freely.

[garagelu]

well I know exactly what your blow off valve is doing because I have the same one. Honestly I dont think coating it with oil will do anything. I bought mine brand new and even before I installed it, I took it apart to make sure the piston moved freely. And the problem isnt that the bov isnt releasing any air at all. It actually surges and then blows off. It kind of acts like there is too much preload on the bov but I have the screw as loose as it will go and it still does it.

I think placing the bov closer to the turbo will fix it. Try oiling the piston wall barely and see if it fixes it. I cant remember when I took mine apart if it was already prelubed. Its been a while. But if that doesnt work its either the placement of the bov or just the design of the bov.

[khilgers]

now that I think about it the SARD bov on my buddys STI swapped impreza does the same thing. It will first make the fluttering sound like compressor surge, then the woosh of the air being released. Like garagelu said, you can try moving it to the hot side, oiling it and go from there. But from my understanding you are supposed to put the BOV on the cold side of S14 SR motors.

[s15 sr20 guy]

its not the bov making the fluttering sound. it is the turbo compressor surging. the bov is clearly blowing off. it blows off and surges at virtually the same time. it will blows off and then a split second later it will surge, but it is blowing off and surging at the same time. am i making sense?

[s15 sr20 guy]

I also want to know will the surging damage my turbo. it's not horrible compressor surge because my bov is still blowing off. i just want to make sure that i dont hurt my engine or turbo in any way.

[jspaeth]

maybe if you could take a video and post that, it would help....

if it's surging when you have a lot of boost built up, that isn't good.

minor surging at small throttle inputs/letoffs isn't terrible and is practically unavoidable

[GabeS14]

The little compressor surge you are hearing, is fine....it will not damage the turbo..It mostly happenes when you release at a pressure so low that the BOV didn't even open....(too low to cause any damage).. many guys run no bov with much bigger turbos, for a few years with no prob, so if you have a stock turbo, dont worry.

I had comp surge for 2 years on the Stock T28(S14), till I upgraded the turbo, and the turbo was in almost perfect condition when I pulled it out.
I boosted about 14-17 psi all the time.
Whenever you do boost hard the majority of the air is released by the BOV so the little surge you hear, actually is very light.

[s15 sr20 guy]

i'll post a video tomorrow after i put my bov back together

[tt99ol]

try running your wastegate actuator vacuum source from a nipple on the coldpipe because once your throttle plate closes your wastegate gets 0psi or even vacuum readings and shuts completely, on the charge pipe it will only close once there is no pressure in the pipes, or after the bov lets it all out, it wont have as harsh of a boost spike either so it will feel smoother coming on to boost

[s15 sr20 guy]

here is a video: the bov is blowing off and i could hear it when i was driving but u cant hear it in the video because the compressor surge is louder.

the video is on youtube

[ame]http://youtube.com/watch?v=GmDpxmSHCHQ[/ame]

[GSXRJJordan]

Doesn't sound like it's blowing off much at all. Ready for the shocker...

It has nothing to do with your BOV.
(as long as the BOV is blowing off at all, it's working. Note about the SARD: no rubber seals. It's just a metal piston against a metal wall, and gets lubricated by the small amount of oil blown through the hotpipe. On the first boost after a long period of sitting, it'll stick. Once it opens, you're in business.)

Now back to the issue: your vacuum setup. Either you've got your BOV tee'd off on some other vacuum source (like the MBC), or your manual boost controller is absorbing some of the change in pressure. MAKE SURE YOUR BOV HAS IT'S OWN VACUUM SOURCE FROM THE COLDPIPE/INTAKE MANI.

Oh, and one more thing - BB turbos are weaker than journal bearing, not stronger. That doesn't mean you've permanently damaged your S14 BB turbo - as Gabe said, many people run their turbos hard (with compressor surge) for years before it becomes a problem.

Fix your vacuum source, and your problem will go away.

/thread. That's one more Zilvia tech problem solved before breakfast

[McRussellPants]

Originally Posted by GSXRJJordan

Oh, and one more thing - BB turbos are weaker than journal bearing, not stronger.

BB turbos don't have the same issues with surge.


I don't see surge as an issue, this isn't the stone age, half the people rabbling about surge read it out of SCC who read it out of Maximum Boost which was written in the 70s.


Fucking Buzz words.

[jspaeth]

^ I'm sure you are right, but it OBVIOUSLY isn't great for the turbo to have a force acting on it suddenly trying to make it move in the opposite direction

[McRussellPants]

Originally Posted by jspaeth

^ I'm sure you are right, but it OBVIOUSLY isn't great for the turbo to have a force acting on it suddenly trying to make it move in the opposite direction

lol.

turbos don't just flip it and reverse it. Turbos are not missy elliot.



you get small boost spikes.

interestingly enough, you get the same first spike with a blowoff valve.

without the bov you just get little tremors and it doesn't bleed boost as quickly.

[jspaeth]

hhah

Yeah I agree.....although your video doesn't really show you building much boost before letting off the throttle, but either way, it doesn't sound like it's blowing off.


Your MBC in should be connected to a nipple as close to the turbo as possible, and the out should go to the wastegate nipple

Your bov nipple should run to a vacuum source in the intake mani, as previously said.

It doesn't sound right at all....I would loosen the spring and make sure you have everything set right.

Also, a video where you floor it and hold, and THEN let off would be helpful I think


Also, some people said to run the wastegate source from the coldside, and I guess that maybe this is better for MBC????......for an electronic boost controller, which can respond quickly, you are better using a boost source as close to the turbo as possible, as pressure changes coming from the turbo are picked up the CLOSER you are to the turbo

[s15 sr20 guy]

I know you cant hear the bov in the video but it is blowing off hard. remember the turbo is right in front of me and the bov is on the cold pipe side that why it cant be heard in the video. nothing is tee'd off everything has its own source. the bov source is the manifold, and the MBC source is the nipple on the intercooler. does the surge sound bad and should it be something i worry about?

[jspaeth]

i mean your turbo isn't just going to all of a sudden blow up, but over time it adds wear on the turbo....try to reduce it