Blow Off Valve For Surge?
- Thread starter liv4gnz
- Start date
don't feel to bad .. your not alone
This is why I come here.:biggrin:
I thought that "fluttering" sound was compressor stall ?
I've never run a BOV on any of my cars and they've worked just fine.
Would it be a benefit to run a BOV ? That's anyone's guess, but I've never heard of a BOV creating a problem.
I don't like the flutter sound either, and can't see how stalling the compressor can be good for a turbo... but... that said... it's obvious that our GN turbos are overbuilt to some degree, since they've been surviving this stall condition since what ? 1986 ?
I've never run a BOV on any of my cars and they've worked just fine.
Would it be a benefit to run a BOV ? That's anyone's guess, but I've never heard of a BOV creating a problem.
I don't like the flutter sound either, and can't see how stalling the compressor can be good for a turbo... but... that said... it's obvious that our GN turbos are overbuilt to some degree, since they've been surviving this stall condition since what ? 1986 ?
BlackMetal
Active Member
- Joined
- Sep 29, 2005
I don't like the flutter sound either, and can't see how stalling the compressor can be good for a turbo... but... that said... it's obvious that turbos are overbuilt to some degree, since they've been surviving this stall condition since what ? 1986 ?
That's basically the case here. People want to argue and insult each other over this issue when there's no need for it. Are there 100k+ mile stock turbos out there that haven't blown up? Sure. Is it ideal to have air slam off the closed throttle blade and revert back into the turbo and force it to spin backwards? Probably not.
You DO get increased throttle response even on an automatic transmission, it just depends on the driving situation. Sure, a full throttle quarter mile blast isn't going to need it. If you road race or even drive on the highway, a situation where you're in boost, then get off the gas, then go back to accelerating... you'd benefit from the boost pressure not getting all backed up within the system.
A decent BOV can be had for $100 so if you feel like you want one it's not that big of a deal. Maybe if they cost $1000 it would be worth it to sit here and argue about whether or not it's really needed. I'm sure there are other parts that Buick owners blindly purchase without knowing that they need it.
I run a BOV and love it. No problems with stalling or engine stuttering like some people will try to tell you.
turbo nasty
Turbo Dojo / MNTR
- Joined
- Jul 19, 2001
Just put one on the GN today and it has stopped the throttle into boost let off bucking that its was doing at the same time as the compressor surge sound.
The surge and bucking had gotten old and it it is gone now.
You still here the compressor surge from a 20 psi plus lift but it is just a 1/3 of what it was and is over on in half a second or so. Ill try and post up pics.
I know I know the typical theory is ive never needed one and this and that.
Kinda different for my as I have had some high end turbo rice before and always had them. Even the autos have a byapss form teh factory in Japan...oh lord I have actually compared the GN to rice.
Smite me oh mighty smiters :biggrin:
The surge and bucking had gotten old and it it is gone now.
You still here the compressor surge from a 20 psi plus lift but it is just a 1/3 of what it was and is over on in half a second or so. Ill try and post up pics.
I know I know the typical theory is ive never needed one and this and that.
Kinda different for my as I have had some high end turbo rice before and always had them. Even the autos have a byapss form teh factory in Japan...oh lord I have actually compared the GN to rice.
Smite me oh mighty smiters :biggrin:
rodman99999
Active Member
- Joined
- Mar 25, 2004
rodman99999
Active Member
- Joined
- Mar 25, 2004
I thought one of the potential problems was the throttle plate closing too fast could cause the compressed air in the intercooler, etc. to push the turbo's impeller shaft shoulder against it's thrust, causing accelerated wear. Am I wrong here?
TURBOPOWERED68
David
- Joined
- Jan 31, 2006
i thought the same thing.:biggrin:
No way not on this subject they can and will be crewel. :frown:
I did a search and could not find any info on side by side testing. Do you have a link or key-word?
I just lost a rebuilt turbo with less then one year of use. Could it be that the factory turbos are built better then replacement turbos and that’s why OE turbos don't need any extra protection that a replacement turbo would need and should get?
I have had this problem with other replacement parts in the past where the OE part lasted a million miles but the (high end) replacements whir done in a year or less.
What exactly is it that happens? My guess is.
You are building boost and air flow from the compressor toward the engine. And all of a sudden the flow of air is stopped in its tracks and the pressurized air backs out threw the compressor and into the turbo’s inlet pipe.
Could this put a strain on the turbo? It “sounds” like it could.
But
Does IT put a strain on the turbo? YES or NO
IF yes does this strain accelerate or help promote turbo failure?
Would or does a Blow-off valve prevent this added strain on the turbo?
I don’t want to add more junk onto my car (more to junk to fix and adjust) but if something was to help prolong the life of MY turbo (second oil filter) I would go threw the trouble of putting it on my car.
What do turbo manufactures and rebuilders have to say about the use of a Blow-off valve?
Do they recommend them?
Does not having a Blow-Off valve void any warrantee / guarantee they offer on the turbos they make?
I think we're all Bozos on this bus!
obviously we have a BIG bus to hold us all
back to the BOV .. if ya want it do it .. no big deal.. just like some people NEED a front mount intercooler to run fast (oh and for the car show "go fast" look)
rodman99999
Active Member
- Joined
- Mar 25, 2004
Or: Lots of "short buses", if you know what I mean!obviously we have a BIG bus to hold us all
letting off the throttle cause the back pressure to hit that wheel spinning at thousands of rpms to almost zero. what do think is happening to the seals in that turbo when this happends.......this should be your deciding factor.
get yourself a good one (they are in the $300 range) and have it go back into the air intake.
get yourself a good one (they are in the $300 range) and have it go back into the air intake.
I never lost turbo due to lack of blow off valve and I have used MANY but...I never liked that noise either so ......I just order turbos with surge covers like the 6776RS I just sold or the better design surge cover on my 76GTQ , thats the way to go if you want to get rid off the surge ,my two cents
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1LowLeSabre
New Member
- Joined
- Mar 13, 2008
Where can one buy a BOV and what are some good ones or does it not matter?
DailyDrifter
The Slow and the Curious
- Joined
- Dec 5, 2007
TiAL. Go on google and search for the best price. Beware of Knock-Offs.
22lbChevelle
Member
- Joined
- Jan 14, 2005
I got a brand new one "type S" that I'm willing to sell cheap. I never used it cause I realized I liked the Buick surge sound and I wont be able to adapt it easily to my modified turbo piping very easily. PM with an offer
gnbooster87
its only a six
- Joined
- Aug 19, 2004
Blowoff valves are used to prevent compressor surge, a phenomenon that readily occurs when lifting off the throttle of an unvented, turbocharged engine. When the throttle plate on a turbocharged engine closes, the high pressure air in the intake system is trapped by the throttle and a pressure wave is forced back into the compressor. The compressor wheel slows rapidly and may even stall, and the driver will notice a fluttering air sound. The rapid slowing or stalling stresses the turbo and imparts severe turbo lag if the driver accelerates immediately after the surge event.
In the case where a mass airflow sensor is used and must be located prior to the blowoff valve, the engine control unit (ECU) will meter out excess fuel because the atmospherically vented air is not subtracted from the intake charge measurements. The engine then briefly operates with a fuel-rich mixture after each valve actuation.
The rich mixing can lead to hesitation or even stalling of the engine when the throttle is closed, a situation that worsens with higher boost pressures. Occasional events of this type may be only a nuisance, but frequent events can eventually foul the spark plugs and destroy the catalytic converter, as the inefficiently combusted fuel produces soot (excess carbon) and unburned fuel in the exhaust flow can produce soot in the converter and drive the converter beyond its normal operating temperature range.
One way to mitigate the problem is to reduce the boost pressure, which reduces the required venting volume and yields less charge overcalculation by the ECU. The air can also be recirculated back into the intake, a typical stock setup for cars with an upstream MAF sensor. The situation can also be corrected by switching the fuel metering system over to a manifold absolute pressure sensor, a conversion that usually requires a compatible aftermarket ECU or piggy-back fuel controller. The MAP sensor monitors the absolute pressure in the manifold at all times and will correctly detect the change that occurs when the valve vents, allowing the ECU to reduce fuel metering accordingly.
In the case where a mass airflow sensor is used and must be located prior to the blowoff valve, the engine control unit (ECU) will meter out excess fuel because the atmospherically vented air is not subtracted from the intake charge measurements. The engine then briefly operates with a fuel-rich mixture after each valve actuation.
The rich mixing can lead to hesitation or even stalling of the engine when the throttle is closed, a situation that worsens with higher boost pressures. Occasional events of this type may be only a nuisance, but frequent events can eventually foul the spark plugs and destroy the catalytic converter, as the inefficiently combusted fuel produces soot (excess carbon) and unburned fuel in the exhaust flow can produce soot in the converter and drive the converter beyond its normal operating temperature range.
One way to mitigate the problem is to reduce the boost pressure, which reduces the required venting volume and yields less charge overcalculation by the ECU. The air can also be recirculated back into the intake, a typical stock setup for cars with an upstream MAF sensor. The situation can also be corrected by switching the fuel metering system over to a manifold absolute pressure sensor, a conversion that usually requires a compatible aftermarket ECU or piggy-back fuel controller. The MAP sensor monitors the absolute pressure in the manifold at all times and will correctly detect the change that occurs when the valve vents, allowing the ECU to reduce fuel metering accordingly.
