Large blow off valves
02-12-2002, 07:00 PM
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Large blow off valves
Last season I kept blowing off the intake elbow from the throttlebody on up-shifts. I think it's time to upgrade to BOV. Any recommendations on something big, not a fortune, and overkill? 
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02-13-2002, 11:42 AM
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Car: 2000 Trans Am
Engine: LS1
Transmission: T56
Im not using a BOV this year.
I was given this advice by many people. Even Precision Turbo who is always trying to sell me something. They said they arent using one even on their 106mm race car.
He said I wouldnt need it...
Because, when you let off the throttle, your turbo should spool down and quit forcing air.
Its $250-$300 I dont need to spend, so I am not.
I HAD been looking at the turbonetics godzilla BOV.
If I have trouble, Ill just use a better method of keeping the tubes from coming off.
I was given this advice by many people. Even Precision Turbo who is always trying to sell me something. They said they arent using one even on their 106mm race car.
He said I wouldnt need it...
Because, when you let off the throttle, your turbo should spool down and quit forcing air.
Its $250-$300 I dont need to spend, so I am not.
I HAD been looking at the turbonetics godzilla BOV.
If I have trouble, Ill just use a better method of keeping the tubes from coming off.
02-13-2002, 05:32 PM
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Car: 84 SVO
Engine: Volvo headed 2.3T
Transmission: WCT5
Axle/Gears: 8.8" 3.73
Originally posted by Guido
Im not using a BOV this year.
I was given this advice by many people. Even Precision Turbo who is always trying to sell me something. They said they arent using one even on their 106mm race car.
He said I wouldnt need it...
Because, when you let off the throttle, your turbo should spool down and quit forcing air.
Im not using a BOV this year.
I was given this advice by many people. Even Precision Turbo who is always trying to sell me something. They said they arent using one even on their 106mm race car.
He said I wouldnt need it...
Because, when you let off the throttle, your turbo should spool down and quit forcing air.
guess they havent seen a turbo shear its impeller.....which "can" happen when the throttle slams shut after a run with the turbo at full spool..all that air slams into the closed throttle plates and trys to find a way out...either by popping the pipe off or back flowing thru the compressor (and shearing off all the blades or bending them backwards).
A BOV is a hell of a lot cheaper than killing a big buck turbocharger..
Oh...shelved my turbo setup for awhile, was draining too much $$ and it was either finish the car and drive this summer or finish the turbos and sit in the driveway...
02-13-2002, 06:59 PM
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Most folks not running a BOV are drag racers with automatic transmissions. You can stay WOT for the whole time, and then easee off the throttle. For a manual car, I'll be closing the throttle for every gear change. To have the impeller go from 100,000 rpms down to 2000 rpms and back to 100,000 in a fraction of a second isn't good. It also takes time to have it spool back up, and for every gear change, I'd like to save that energy. Drag racing you could probably get away with it, though. Why is Precision steering you away from them? Leaking boost?
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02-13-2002, 09:52 PM
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Car: 2000 Trans Am
Engine: LS1
Transmission: T56
I didnt think of it like that Andirs but that is right. You WILL need one.
They steered me away because I dont need it. They said they would sell me one if I wanted it, but that I WOULD NOT need it. I am using a TH400, and I am drag racing primarily so it isnt a big deal.
They steered me away because I dont need it. They said they would sell me one if I wanted it, but that I WOULD NOT need it. I am using a TH400, and I am drag racing primarily so it isnt a big deal.
02-14-2002, 01:28 AM
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Adris,I have a blow off valve I bought this yearit is a nice unit from Tial. here is the link:
http://www.angelfire.com/me2/tpi/bovalve.html
The picture doesn do it justice it is a nice piece.Just call for distributors in your area.I might be selling mine since im going another route.Let me know I will take a pic of it and send it to you.
http://www.angelfire.com/me2/tpi/bovalve.html
The picture doesn do it justice it is a nice piece.Just call for distributors in your area.I might be selling mine since im going another route.Let me know I will take a pic of it and send it to you.
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02-14-2002, 09:15 PM
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Car: 1992 B4C 1LE
Engine: Proaction 412, Accel singleplane
Transmission: built 700R4 w/custom converter
Axle/Gears: stock w/later 4th gen torsen pos
or this one from vortech
02-15-2002, 01:36 PM
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Mits. eclipse have a BOV that won't unseat until 15 to 20 psi boost, so go junkyard hunting.
Make sure that the outlet of the BOV is filtered, 'casue at idle and cruise, the BOV is open drawing air into the engine.
Make sure that the outlet of the BOV is filtered, 'casue at idle and cruise, the BOV is open drawing air into the engine.
02-15-2002, 02:01 PM
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Filtered?
The small mitsu valves might hold the pressure, but they don't have nearly enough flow for two turbos at full boost on a smallblock, unfortunately. I should rig up an auxiliary throttlebody that opens when the main throttlebody is closed. If it's linked off of throttle position, there isn't a worry of boost pressure unseating it, and the area can be made as large as necessary. I wonder if a solenoid could be powerful enough to quickly open and close it. Hmmm...
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02-16-2002, 10:17 AM
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Re: Filtered?
Originally posted by askulte
The small mitsu valves might hold the pressure, but they don't have nearly enough flow for two turbos at full boost on a smallblock, unfortunately. I should rig up an auxiliary throttlebody that opens when the main throttlebody is closed. If it's linked off of throttle position, there isn't a worry of boost pressure unseating it, and the area can be made as large as necessary. I wonder if a solenoid could be powerful enough to quickly open and close it. Hmmm...
A.
The small mitsu valves might hold the pressure, but they don't have nearly enough flow for two turbos at full boost on a smallblock, unfortunately. I should rig up an auxiliary throttlebody that opens when the main throttlebody is closed. If it's linked off of throttle position, there isn't a worry of boost pressure unseating it, and the area can be made as large as necessary. I wonder if a solenoid could be powerful enough to quickly open and close it. Hmmm...
A.
When is a BOV open??? When there is a vacuum applied to it.
What happens when a vacuum is applied to a BOV? It opens, either releasing boost or drawing in unfiltered air when not under boost, like during idle and part throttle cruise.
So the outlet of the BOV either needs to be plumbed to the air filter "box" or use valve cover breathers.
Last edited by a73camaro; 02-16-2002 at 10:23 AM.
02-16-2002, 11:29 AM
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Would you know the flow numbers for the mitsu BOV's? I've seen aftermarket BOV's advertising around 150 cfm... At idle, I'm actually having air blow out through the BOV. The turbos are pumping more air than the engine ingests, so the intake tract is somewhat pressurized at all times.
02-17-2002, 01:45 AM
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I think you should definately get one.... better safe than sorry ya know? plus it sounds cool!! vrrrrooom pppsssh!!! I say go with the HKS blowoff valves. I dont know what model blowoff valve but I do know that in the highly modified turbo supras they all use HKS. Might sound kinda silly looking to supras for ideas but thats what I do ... gotta admit they got some of the best turbo setups around. And if the HKS BOV's on the 900hp supras dont blow up they should be able to handle anything you can dish out. Good luck man!!
02-17-2002, 10:55 PM
#17
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I dont know if it applies for V8's or not, but I do know in a manual 4-cylinder car with a upgraded turbo, If that blow off valve doesnt blow off, goodbye turbo. Ask me how i know
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