sick of compressor surge??? Synchronic BOV

[Crucible]

Check these new bovs out, seem really responsive. They do a couple of demo's and compare them to the Tial - 50mm Valves,

http://www.youtube.com/watch?v=Ffj01k64AZI
http://www.youtube.com/watch?v=gvnBDlXy ... h_response

...and the HKS SSQs.

http://www.youtube.com/watch?v=MU5Y6d9rh1k

I have personally used both types on my car, didnt have much luck at all with the ssq, it didnt vent at all, bad comp surge!!!!. I currently have a Tial 50mm and it seems ok, but still get surge at low rpm just like the video, even with dedicated vac line and cut down spring.

hmm.....could be worth looking into

[Quirky]

Interesting....
My cousin has a Celica GT4, put one of those imation HKS bov in his car (shop welded it on to factory intercooler) and it makes that "compressor surge" sound. He always thought it was cool, didnt know it was pretty much screwing the turbo.

[Crucible]

Ive seen a comp wheel nut spin off on a TD06 once, couldnt figure out how the hell it happened, until someone told me that comp surge was the cause.

damaged it beyond repair, he was using a ssq copy

[Quirky]

My cousin is quite adamant that it allows him to BOOST more, thus making the car faster. Bone stock ST185.

Plus i tell him that the BOV works when your off the throttle anyways...and from what i can see in its design, is just a sort of safety feature for the turbo...

[bluemaumau]

semi o/t

whats the best BOV for dumping lots of boost

some say
Greddy Type R
50mm tial

?

[touge rolla]

I have a GReddy Type RS on my MR2 and it is fine as long as I don't come off the throttle gently. It won't surge at all with it set a little softer, but then it sometimes opens when idling. Friend has a GFB on his GT-Four with no detectable compressor surge. (but seeing as ST185's don't have BOV's standard it wouldn't be too bad if it did)

These videos are rigged advertising, and it would be possible to compare any two BOV's against each other and create whatever result you please all with a simple spin of a spanner

http://www.youtube.com/watch?v=8-JTfgpF ... ed&search=

[Crucible]

These videos are rigged advertising, and it would be possible to compare any two BOV's against each other and create whatever result you please all with a simple spin of a spanner

http://www.youtube.com/watch?v=8-JTfgpF ... ed&search=

maybe so, but they seem pretty genuine to me.

I can tell you from experiance the ssqs are crap, been there tried that. The 50mm one I have, doesnt respond like the one in your link. I have 10mm dedicated line and Ive actually cut the spring to try and make it more responsive to the point where its actually opening at idle.

when I first fitted it, I got bad surge and it wasnt opening at all!!!. Venting on 19psi its fine, does the job no prob, but on quicker shifts it doesnt respond fast enough and I get surge, others Ive talked to have the same problem even with bling Tial originals.

of course i never had a nice row of differant rate springs to try, and last time I checked they were like 70 bucks each, maybe the guy in the link you put up did??

[ollieboy]

Ive seen a comp wheel nut spin off on a TD06 once, couldnt figure out how the hell it happened, until someone told me that comp surge was the cause.

reminds me of my friends race car- the compressor wheel? I guess you call it(I don't know anything about turbo's) fell off and rolled round in the housing then fell out the exhaust. Was a really small turbo on really high boost so I guess things were spinning really fast.

[KinLoud]

I'm really puzzled???
Stupid blow off sound = compressor surge?
So if you don't have a blow off valve it won't surge? Well I learn something new every day!

I would have thought that you would need to measure pressures and temps before and after the compressor. Also need to know the compressor rpm.
You then take this info and plot it on a chart and end up with something that looks like this:

more info about compressor surge etc:
http://www.google.co.nz/search?q=compre ... =firefox-a

Silly me - all this time I could have just listened to the stupid blow off sound!

Ken
Ham
021 408 863

[gleem]

so how do you know if your bov is surging or not i have a blitz one on a caldina

[FrEsH]

if your BOV chatters, its surging
as in ch-ch-ch-ch- instead of ccchhhhh

[KinLoud]

Are we talking about compressor surge or blow off valve surge? Big difference!!!
One affects the sound and the other affects power! Hmmm I wonder which one I'm more worried about?

Ken
Ham
021 408 863

[Crucible]

I'm really puzzled???
Stupid blow off sound = compressor surge?
So if you don't have a blow off valve it won't surge? Well I learn something new every day!

Im not to sure what you mean? if you dont have a BOV fitted or its not working correctly it WILL surge (cha cha cha cha)

Compressor surge is caused by a blow off valve not releasing pressure fast enough when the throttle snaps shut, the pressure has nowhere to vent so backtracks back past the comp wheel, stalling it, and out through the air filter (ie - cha cha cha cha).
I know alot of people think this is the blow off valve making the noise, but its NOT, its actually the BOV not doing its job. If its working correctly you will only hear (psssssh) as all the air is exiting out the BOV and not back through the turbo housing.

Are we talking about compressor surge or blow off valve surge? Big difference!!!
One affects the sound and the other affects power! Hmmm I wonder which one I'm more worried about?

lol now Im getting confused , maybe your understanding of comp surge differs from my understanding of what it means?? so what your saying is that people are getting confused between the two meanings? as in comp surge is actually BOV surge? and comp surge is terminology only used on a compressor map???... is that correct??

[fivebob]

Compressor surge is caused by a blow off valve not releasing pressure fast enough when the throttle snaps shut, the pressure has nowhere to vent so backtracks back past the comp wheel, stalling it, and out through the air filter (ie - cha cha cha cha).

That's not really compressor surge, and it isn't compressor surge when you have the throttle partially open and it makes that sound, IME that's just the BOV opening and closing due to the slight pressure differential between the turbo and the manifold.

Real compressor surge occurs at full throttle when the turbo is too big for the engine and the engine cannot flow the amount of air that the compressor is producing. That is the point at which it gets unhealthy for the turbo.

The only reason that a BOV would produce surge would be if it is too small, and then the surge would only occur at the point where the throttle was shut. If your BOV make the phhssst noise when you close the throttle, then IMO it is correctly sized. If it make the "surge" noise at partial throttle openings then it's because the pressure differential between the manifold and the turbo is not enough to caus ethe valve to open.

I know alot of people think this is the blow off valve making the noise, but its NOT, its actually the BOV not doing its job. If its working correctly you will only hear (psssssh) as all the air is exiting out the BOV and not back through the turbo housing.

IME it is the BOV making that noise, stock Toyota bypass valves always make this noise and in the situations they do it's not at a point in the compressor map that is anywhere near the surge line

Are we talking about compressor surge or blow off valve surge? Big difference!!!
One affects the sound and the other affects power! Hmmm I wonder which one I'm more worried about?

lol now Im getting confused , maybe your understanding of comp surge differs from my understanding of what it means?? so what your saying is that people are getting confused between the two meanings? as in comp surge is actually BOV surge? and comp surge is terminology only used on a compressor map???... is that correct??

IMO Kinloud is correct, what you are describing is not compressor surge, and in most instances is not harmful to the turbo. Hell some Toyota's didn't even come with a BOV from the factory and they don't exhibit compressor surge even when you lift off the throttle

[touge rolla]

I can tell you from experiance the ssqs are crap, been there tried that.

yes a mate has one on his cefiro, set as soft as possible and it surges all the time. (it's a genuine one as well not a cheap knock off)

blow off valves can make a noise similar to compressor surge, but it is fairly simple to tell the difference if you have heard both before.

edit: mild compressor surge can be hard to detect with standard air box

[fivebob]

edit: mild compressor surge can be hard to detect with standard air box

IMO there's no such thing as mild compressor surge, it's either surging or it's not. Compressor surge is the stalling (and sometimes reversal) of the airflow over the compressor wheel. It is very loud and sound's nothing like the noises shown in the video.

What most people call surge is actully valve flutter, and in fact is the valve doing the job it was designed to do. True compressor surge sounds totally different, and it's not something you'd ever confuse with valve flutter if you'd ever actually heard it

[touge rolla]

^by mild I mean from a lower boost setting ie 10psi compressor surging as oppose to 18psi.
but yes I agree

[Lith]

What most people call surge is actully valve flutter, and in fact is the valve doing the job it was designed to do. True compressor surge sounds totally different, and it's not something you'd ever confuse with valve flutter if you'd ever actually heard it

I'd call a lot of what is being talked about here compressor stall, which is more or less compressor surge if you look at the physics thats going on. If you close the throttle when you have no positive pressure, the valve may not be pushed open as there is no major pressure difference across the BOV *but* the compressor could still have some speed on it, pumping more air than the system can use.

One way or another, the stall noise is caused by the system failing to use the air - that could be the compressor out pumping the motor, or the compressor pushing against a closed throttle and no open BOV to releive pressure.

[fivebob]

I can't see how you would ever get true compressor surge at 10psi on a properly sized turbo. The BOV certainly wouldn't cause it.

e.g. look at the surge line in the compressor map that Kinloud posted. at 10psi the surge line is around 5lb/min or about 50HP. I can't think of any engine that would cause surge at that point, unless it was really small (<500cc)

[touge rolla]

rb20det, no bov, made compressor surge noise when throttle closed. Could feel the air flowing back out of the filter.
Turbo was in perfect condition, now stuffed. Seems very compressor surge like to me.