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BOV Flutter at high RPMs? - I swear I'm not an idiot

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doubleclutch

doubleclutch

10+ Year Contributor
830
175
Jun 26, 2009
Canton, Michigan
I recently installed a punishment racing knock off BOV. I have the removed the larger spring and have the light spring set fairly light. The car blows off nicely and low and mid boost levels, but at high levels (20+) it flutters some. My understanding is that flutter should be under low boost not high? I will be attempting to very slowly soften the setting, but I am not sure how much softer I can go as I previously had it set so soft it would blow off without lifting off throttle. It would vent simply by holding throttle steady.

I know there are a million threads on this because i have read most of them. I also don't want your opinion of "crank that S^%$ down" because we all should know that doesn't help.

Thanks
 
So it couldn't be that your boost is just over powering the spring and boost source on the BOV? Just a question that went through my head (its pretty empty). :)
 
1990TSIAWDTALON said:
So it couldn't be that your boost is just over powering the spring and boost source on the BOV? Just a question that went through my head (its pretty empty). :)
Click to expand...

No, sorry i thought i had mentioned that it flutters on lift off. It seems to function perfectly fine as far as when it releases, it just flutters at high boost.
 
Have you done BLT yet? I would suspect it's leaking somewhere with your funny behavior only happening at high boost. Leak my be the BOV itself too.
 
BOV definitely holds boost better than the uncrushed 1g i had on there. Builds boost faster and builds more of it for the same duty cycle. This would make me think that it isn't a high boost leak in the BOV. Only thing that has changes since last BLT is the BOV.
 
Do I have this right? You changed to a new BOV & got funny behavior, then posted here without doing a BLT?
 
Mello said:
Do I have this right? You changed to a new BOV & got funny behavior, then posted here without doing a BLT?
Click to expand...
I'm willing to entertain you boost leak theory if you are willing to explain how a boost leak could cause a BOV flutter issue only at high boost. While i agree that a BLT is a great thing to do on these cars as a first diagnostic step, there are too many people who post that as a fix to everything without actually providing any plausible logic behind why it needs to be done. Please elaborate and keep you patronizing to a minimum if possible.
 
Vegas smith said:
Boost leak test or turn the boost down......and did you search? And stop buying knock off parts. :talon:
Click to expand...

Vegas, i did read if you read the OP i mentioned that. Everyone has issues with the BOV being too tight at LOW boost. No one mentioned issues at HIGH boost. Can you explain how high boost this effects BOV function?

Hard to not try a knock off when it was free. Not to mention multiple people have used these successfully.
 
doubleclutch said:
Vegas, i did read if you read the OP i mentioned that. Everyone has issues with the BOV being too tight at LOW boost. No one mentioned issues at HIGH boost. Can you explain how high boost this effects BOV function?

Hard to not try a knock off when it was free. Not to mention multiple people have used these successfully.
Click to expand...
Just messing with you dude. Sorry, don't have anything constructive to add to the thread yet.
 
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And If there is a boost leak or a vacuum leak at the blow off valve that only leaks at higher boost / vacuum pressures, that could throw off the operation of the valve. I'm not going to go into pressure differences, vacuum operation, blow off valve function, and all that.... but it can happen. Even if its only at a higher boost level. If you don't want to check the car / blow off valve for a boost leak then that's on you, but it would be the first thing that I did.

However, buying a knock off blow off valve is the last thing that I would have done. So my first recommendation regardless of the function is to get a strong and reliable one.
 
I have what's essentially the same valve on my 2G GST daily driver because the intercooler piping doesn't allow anything else to fit next to the fuse box, and I absolutely hate it. The next time I have the piping off I'm modding a 1G valve to fit the Greddy flange and that's going back on because this valve has been nothing but problems since the day it went on.

The first day it was on the car the o-ring at the base of the valve piston, where it seals against the housing, fell off and it became an enormous boost leak...so I took the valve back off and glued the o-ring to the piston. Solved that problem. Luckily it rolled up and over the valve so it was stuck on the stem instead of ending up in my engine.

Ever since I cannot get the valve to do what it's supposed to do properly whatsoever. I've added springs, removed springs, had the adjustment screw in every direction, replaced the diaphragm, changed the hose nipple on the valve to a full 1/4" barbed nipple to hopefully allow quicker action and no matter what will either cause the turbo to surge at low load because it's not opening properly or not even sound like it's working at all no matter what the boost level is and there's no "happy medium". As it is right now it will surge a little under extremely-light throttle situations which is annoying in traffic with on/off boost situations in higher gears because it interrupts the MAS signal and causes the car to buck...and anything below 10psi it doesn't even sound like the car has a BOV on it at all- it just makes no noise whatsoever. At 15-20psi or so it sounds just like your traditional Greddy Type-S which I assume is normal function for this piece of garbage.

Bottom line...a blow off valve should absolutely not need this much tinkering to work properly. I'm glad I got it for free because it's either getting launched over the hill or becoming a paper weight at my earliest convenience and I'm going back to a 1G valve that I don't have to constantly screw with.
 
Isn't the punishment racing bov a fake Freddy type S?

A real type S or the ngr version will not hold over 20psi, and has real problems with turbos with high cfm rates

You will need to upgrade to a real blow off valve to hold the boost, at 18psi on a 16g I remember a real type S would sound like a boost leak pop and whistle, on a t25 it's just a nice annoying whistle.

Way back in the day I can remember supra guys running dual hks ssq blow off valves to handle the extra pressure. Now I'm pretty sure all of them run Tial or specialist boost pressure valves.

So you're not crazy, it's a cheap blow off valve. Besides on a factory turbo the blow off valve was very weak and sensitive. Why do you think Greddy stopped making them?
 
Last edited:
JusMX141 said:
I have what's essentially the same valve on my 2G GST daily driver because the intercooler piping doesn't allow anything else to fit next to the fuse box, and I absolutely hate it. The next time I have the piping off I'm modding a 1G valve to fit the Greddy flange and that's going back on because this valve has been nothing but problems since the day it went on.

The first day it was on the car the o-ring at the base of the valve piston, where it seals against the housing, fell off and it became an enormous boost leak...so I took the valve back off and glued the o-ring to the piston. Solved that problem. Luckily it rolled up and over the valve so it was stuck on the stem instead of ending up in my engine.

Ever since I cannot get the valve to do what it's supposed to do properly whatsoever. I've added springs, removed springs, had the adjustment screw in every direction, replaced the diaphragm, changed the hose nipple on the valve to a full 1/4" barbed nipple to hopefully allow quicker action and no matter what will either cause the turbo to surge at low load because it's not opening properly or not even sound like it's working at all no matter what the boost level is and there's no "happy medium". As it is right now it will surge a little under extremely-light throttle situations which is annoying in traffic with on/off boost situations in higher gears because it interrupts the MAS signal and causes the car to buck...and anything below 10psi it doesn't even sound like the car has a BOV on it at all- it just makes no noise whatsoever. At 15-20psi or so it sounds just like your traditional Greddy Type-S which I assume is normal function for this piece of garbage.

Bottom line...a blow off valve should absolutely not need this much tinkering to work properly. I'm glad I got it for free because it's either getting launched over the hill or becoming a paper weight at my earliest convenience and I'm going back to a 1G valve that I don't have to constantly screw with.
Click to expand...

Ive never had any problems with my NGR blow off valve. Should be similar in size and holds boost really well.
 
Everything seems to work fine other than flutter during liftoff at 18+psi. It definitely holds better than my uncrushed 1g. I am debating hooking up the lower nipple to see if that fixes my problem. I did soften it a tad more yesterday and so far no issues. Essentially i followed wobble's guide on this site by softening it till it just opened at idle.
 
chrysler kid said:
Isn't the punishment racing bov a fake Freddy type S?

A real type S or the ngr version will not hold over 20psi, and has real problems with turbos with high cfm rates
Click to expand...

Don't know why you would say this. I have not had any problems with mine and hit 23psi regularly. Genuine Greddy that I've had for over 15 years before knockoffs started appearing on the market. Only thing I would suggest is not to hook up the lower nipple as that can cause it to open too early. Only the top nipple for vacuum and boost is connected to my intake manifold port.
 
My crushed 1g holds (or held, car is down now) an amazing 30+ lbs. It will flutter at 35 but I took my NGR off after a week and put the 1g crushed back on, ran great for years.
 
Last edited:
1990TSIAWDTALON said:
My crushed 1g holds (or held, car is down now) and amazing 30+ lbs. It will flutter at 35 but I took my NGR off after a week and put the 1g crushed back on, ran great for years.
Click to expand...

Any idea what causes flutter at high boost?
 
chrysler kid said:
the ngr version will not hold over 20psi, and has real problems with turbos with high cfm rates
Click to expand...

I have to disagree. I'm not saying NRG is the best brand you can buy, but it holds just fine for me on my HX40 at 35psi. Hasn't leaked a bit in 4 years.
 
In my case it is just boost over powering the BOV spring plus boost source pressure. I could see it on my logs, at max boost it appeared to open and close rapidly, like a EKG readout but not so spikey. I still pushed a max of 44lbs but had a hard time holding it steady. My waste gate had 3 springs in it and would hold 33 lbs on its own. Just my experience.
 
1990TSIAWDTALON said:
In my case it is just boost over powering the BOV spring plus boost source pressure. I could see it on my logs, at max boost it appeared to open and close rapidly, like a EKG readout but not so spikey. I still pushed a max of 44lbs but had a hard time holding it steady. My waste gate had 3 springs in it and would hold 33 lbs on its own. Just my experience.
Click to expand...
Crushing the valve is a cheap/easy way of increasing the spring pressure and holding power of the valve by overpowering the quick-release feature a tad, but eventually the quick-release feature will still effect the valve's holding power. The only way to disable the quick-release feature altogether is to do the Dodge Garage Mod and route it to the exterior of the valve then the valve can hold whatever boost you want to run because the pressure in the chamber at the top will always be the same as the pressure pushing against the piston in the piping.


A stock, unmodded 1G valve will hold 20-25psi or so at the max depending on your setup and how tired the valve is. A crushed 1G valve will give you another 5-10psi over that. A Dodge Garage Modded 1G valve will hold whatever boost you want to run but may give you a little surge at low boost. A crushed Dodge Garage Modded 1G valve is ruined and should be thrown away as there's not enough vacuum to draw the valve open with no quick-release feature once it's crushed, especially if you have cams. If a 1G valve's piston is too small to safely control surge and relieve pressure enough to effect turbo performance between shifts, you need a 50mm TiAL. Anything else isn't worth using unless you're going specifically for a certain sound...at which point us old men like me and Marty would likely call you a ricer and make fun of your mudflaps. :p
 
THE turbo guru has spoken! :sneaky:
 
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