do you really need a blow off valve...

+ Reply to Thread
Results 1 to 20 of 20

Thread: do you really need a blow off valve...

  1. #1
    SupraForums Member KERR's Avatar
    Join Date
    Feb 2001
    Location
    Bristol VA
    Age
    36
    Posts
    2,618

    do you really need a blow off valve...

    just for fun lets discuss these blow off valves..

    Now i know we have all seen them both ways, with and with out on supras. I dont really care about other cars but have noticed some diesel trucks dont have them either.

    Anyway like the topc say... Do you really need one? and if you do how come the ones without blow off valves havent had problems?

  2. #2
    Banned
    Join Date
    Jul 2002
    Location
    Out of this World
    Age
    33
    Posts
    495
    I would say the are a neccesary evil if you want to prolong the life of your turbo. The concept behind the blow off valve is that when your intercooler piping is presurized and you close your throttle plate, the pressure will not just stay in the piping, it will end up exiting through your turbine blades, causing a reverse flow (in theory). Now your turbine blades will still be spinning in the normal direction but suddenly you have a 30psi back flow back through the blades, it is going to play havoc on your center section. Now this is in theory and maybe in real life, there is no harm, but I would rather spend 150 on a blow off valve, than 1800 on a turbo.

  3. #3
    SupraForums Member 955speed's Avatar
    Join Date
    Sep 2006
    Location
    Arizona
    Age
    31
    Posts
    479
    Yeah and they make that cool pssssssssssss..... sound

  4. #4
    Weapon of Mass Affection TrueSlideXL's Avatar
    Join Date
    Jul 2002
    Location
    Manhattan
    Posts
    3,780
    On a diesel truck and also in many European cars; a Diverter Valve can redirect that air with a vacuum line back into the intake or vented to the atmosphere as well. With that said if you car does not need a recirculating system because of it's MAF and ECU I think it's a safe bet to get a BOV only if your car is significantly modified to be looking into those things. So, in that diesel truck when the BOV vents to the atmosphere your ECU reads the MAF values as being out of spec; it will cause the truck to run rich as the ECU is measuring the flow of air that is no longer in the system. If the diesel truck is not making added power then the effect of venting to the atmosphere is useless.

  5. #5
    Defender of truth blue.label's Avatar
    Join Date
    Jul 2001
    Location
    87 41' N 78 97' W
    Posts
    4,120
    I hate the sounds of those.

  6. #6
    SupraForums Member KERR's Avatar
    Join Date
    Feb 2001
    Location
    Bristol VA
    Age
    36
    Posts
    2,618
    That they i understood how they worked as well. We have a friend that has some freaking fast buicks and typhoons. He said its not a big deal and he doesent run them. Granted his are just play toys but he said from the factory GM didnt use on.

  7. #7
    SupraForums Member
    Join Date
    Feb 2001
    Location
    Florida
    Posts
    3,098
    I haven't kept up with diesels in cars and light trucks lately, but the big diesels I'm familiar with (HD trucks, heavy equipment, etc.) don't have throttle valves.

  8. #8
    Weapon of Mass Affection TrueSlideXL's Avatar
    Join Date
    Jul 2002
    Location
    Manhattan
    Posts
    3,780
    Quote Originally Posted by Boost Junkie View Post
    I haven't kept up with diesels in cars and light trucks lately, but the big diesels I'm familiar with (HD trucks, heavy equipment, etc.) don't have throttle valves.
    Yes. The momentum of the airflow when fuel is not being sprayed would be when it could function like a gasoline BOV engine. When you do run into a BOV on these trucks it is used to eliminate surge during heavy towing. Is the elaboration coming from what I said? It is true that most factory turbodiesels will not need it but I was trying to find a good general example.

  9. #9
    OG Rich B's Avatar
    Join Date
    Aug 2001
    Location
    Houston
    Age
    51
    Posts
    1,093
    Quote Originally Posted by Boost Junkie View Post
    I haven't kept up with diesels in cars and light trucks lately, but the big diesels I'm familiar with (HD trucks, heavy equipment, etc.) don't have throttle valves.
    Steve is right - My understanding of Diesel engines is that they are controlled by metering fuel, not air, so they do not have throttle butterflies like gas engines, and hence no real need for a BOV .

    You hear, for example, rally cars with huge turbo surge, and they are fine...
    Cheers
    Rich B.
    '94 BL-61 6-spd

  10. #10
    SupraForums Member 1badsup's Avatar
    Join Date
    Oct 2003
    Location
    Los Angeles
    Posts
    2,578
    The Audi A4 Turbo doesn't have a blow off valve.

  11. #11
    I Solve Problems lis2k's Avatar
    Join Date
    Sep 2004
    Location
    Manhattan, New York
    Age
    34
    Posts
    4,205
    It has a diverter valve.
    Quote Originally Posted by 1badsup View Post
    The Audi A4 Turbo doesn't have a blow off valve.

    2000 Monaco Blue Pearl NSX-T
    1994 Twin Turbo 6 Speed Hardtop SOLD

  12. #12
    SupraForums Member
    Join Date
    May 2003
    Location
    Oslo, Norway
    Posts
    1,618
    The sound you get from turbo surge is awesome. I hate the sound of BOVs.

  13. #13
    Street Sleeper Buttmunch's Avatar
    Join Date
    Mar 2004
    Location
    Norfolk, England
    Age
    10
    Posts
    1,093
    Quote Originally Posted by Rich B View Post
    You hear, for example, rally cars with huge turbo surge, and they are fine...

    Yes but the turbo doesn't have to last 100,000+ miles
    Quote Originally Posted by OneJoeZee View Post
    Turbo lag is that moment when the car next to you thinks it's going to win.

  14. #14
    ಠ____ರೃ
    Join Date
    Jul 2004
    Location
    Freerice.com
    Posts
    7,192
    Can't believe this is even up for debate???

  15. #15
    Taxation is complicated
    Join Date
    Jul 2007
    Location
    CA
    Age
    27
    Posts
    973
    Well, I hear that technical debate is more fun than bowling.

  16. #16
    ESE CULO RemixPinoY's Avatar
    Join Date
    Apr 2007
    Location
    San Jose/Manteca/Livermore
    Age
    24
    Posts
    2,945
    I sometimes hate the noise too, is there any alternatives to BOV's?

  17. #17
    Akai Suisei - 赤い彗星 OneJoeZee's Avatar
    Join Date
    Apr 2003
    Location
    Chino Chills, CA
    Age
    28
    Posts
    10,376
    Recirc it to reduce noise.

  18. #18
    SupraForums Member
    Join Date
    Jul 2004
    Location
    California
    Posts
    314
    Quote Originally Posted by 1badsup View Post
    The Audi A4 Turbo doesn't have a blow off valve.
    it does. it's just called something else--a diverter valve. same exact function.

  19. #19
    ^____________________^
    Join Date
    Dec 2003
    Location
    Norway
    Age
    25
    Posts
    1,245
    Someone try and run without a BOV @ 30 psi... The surge would be truly awesome.

  20. #20
    SupraForums Member 97 Widebody's Avatar
    Join Date
    Oct 2003
    Location
    Purgatory aka: Houston, Tx
    Age
    41
    Posts
    2,238
    I've been testing stock twins on a Supra I currently have running 20psi with no BOV and so far no problems at all. In fact these OEM turbos seem to be in better shape than many I've seen with a lot more miles. I was about to pull them for a single so I figured I'd see how well they work without.

+ Reply to Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts