Question about BOV's - Subaru Enthusiasts Car Club of the Sierras

ArthurS · 2003-01-29, 10:23 PM

I look all over NASIOC for some answers, but you get so many mixed results.

Do BOV's actually help performance at all? Or are they basically just to make noise? IF they help performance, which ones are amoung the best?

I was kinda looking at the MRT GFB Bov, which says it:

Quote:

Unique design allows both venting to atmosphere to give that unique "whoosh" noise as well as part venting back to inlet to stop over fueling and poor idle.

Are they really worth it? How loud are they? Sorry bout being such a n00b, but these are fairly new to me.

AtomicLabMonkey · 2003-01-30, 09:29 AM

Quote:

Originally Posted by ArthurS

I look all over NASIOC for some answers, but you get so many mixed results.

Do BOV's actually help performance at all? Or are they basically just to make noise? IF they help performance, which ones are amoung the best?

I was kinda looking at the MRT GFB Bov, which says it:

Quote:

Unique design allows both venting to atmosphere to give that unique "whoosh" noise as well as part venting back to inlet to stop over fueling and poor idle.

Are they really worth it? How loud are they? Sorry bout being such a n00b, but these are fairly new to me.

I believe the purpose of the turbo wastegate (blow off valve) is to relieve the overpressure in the intake path that happens when you lift off the gas pedal, since the throttle plate closes up but the turbo compressor is still spinning. That sudden high pressure downstream of the compressor can slow down or even stall the compressor, so when you get back on the gas it takes more time to spin back up, hence "turbo lag". So, it helps in both reducing turbo lag and also in reducing physical stress on the turbo components. This article is fairly descriptive.. http://www.syclone.freeserve.co.uk/blow.htm

ArthurS · 2003-01-30, 10:27 AM

Thanks. That makes more sense. I thought I heard that they were bad sometimes because sometimes they would release the pressure (or something like that) and you would get no boost.

AtomicLabMonkey · 2003-01-30, 11:04 AM

It shouldn't, unless the valve is malfunctioning or adjusted wrong.

AtomicLabMonkey · 2003-01-30, 11:06 AM

Of course, I've never owned or worked with a forced-induction car, so this is all theoretical for me.

ArthurS · 2003-01-30, 12:07 PM

This is pretty much my first also. I had a 87 supra turbo, but never did anything to it. Before that it was all n/a cars.

ArthurS · 2003-01-30, 02:40 PM

Okay, I thnk I am going to go with the GFB BOV. I have read now for awhile that it is the most suttle at 100% atmosphere until you go WOT then it get pretty loud. Also has the 50/50 setting i guess. They are fairly cheap, but how hard are they to install?

MattR · 2003-01-30, 03:33 PM

Save your money Arthur...You will notice no performance gains at all from a BOV. And, the sound is really less noticeable because you don't have to let off the gas to shift. I think the stock BOV is the mosty efficient for the motor, but also the quietest...good luck.

Matt

ArthurS · 2003-01-30, 04:09 PM

So its more for a manual then a auto? Only reason why i am inquiring so much is one was offered to me for really cheap.

sperry · 2003-01-30, 08:17 PM

The stock BOV is actaully a really good BOV. Plus it's recirculating, which means the compressed air that the other (loud whooshing) BOVs just vent to the atmosphere gets put back into the intake.

Recirculating some or all of the air helps keep lag down during shifts because the compressed air is still in the system while the turbo is not compressing (i.e. during a shift, or when you get off the gas).

On a 4EAT, the BOV doesn't make quite as much of a difference as the 5MT because you can keep on the gas during shifts. If you want the cool sound, check out the 50%-50% recirculating BOVs, since they vent half the air back to the intake. I think that GFB one might be a 50-50, but check to make sure.

Also, don't listen to the monkey... he's all hopped up on fumes from his big-ass 5.0! Acutally, all the stuff he said about the BOV is correct... with this addendum: no BOV = bad, vent to atmosphere BOV = good (and sounds cool), vent to intake (recirculating) BOV = better.

The reason you hear the "psssst!" sound on rally cars is that they run vent to atmosphere BOVs *and* an anti-lag system. No need to keep that compressed air in the system when you're intentionally backfiring the motor to spin the turbo! Get of the gas in one of those cars and you hear: "PSSHHHHHT!! BANG! BANG! BANG!" But then you have to replace the turbo after every weekend.

ArthurS · 2003-01-30, 08:34 PM

Thanks for the input. The GFB is a 50/50 bov I have heard, or a 100% bov. I will instead save my money for the stage 0 package instead.

Have you gotten the Vishnu Silicone Intercooler Hose Kit? It says that it increases horsepower by about 5-7. Thats pretty good considering the price.

sperry · 2003-01-30, 08:47 PM

Quote:

Originally Posted by ArthurS

Thanks for the input. The GFB is a 50/50 bov I have heard, or a 100% bov. I will instead save my money for the stage 0 package instead.

Have you gotten the Vishnu Silicone Intercooler Hose Kit? It says that it increases horsepower by about 5-7. Thats pretty good considering the price.

Yeah, I got my Stage 0 with it, but my butt-dyno isn't good enough to pick out the extra 5hp when the car goes from 227hp to 280hp hehe. I just wish you could see them better since they're really high quality (even better than the Samco ones I hear). I may have to get some cooling system hoses just to dress up the engine... plus I'm sure they flow better... awe who cares, they look cool! <flame-suit on>

AtomicLabMonkey · 2003-01-31, 11:12 AM

I knew I should have opened the garage door when I was doing that motor-tune... *cough* *choke*

2003-01-30, 11:04 AM	#4
AtomicLabMonkey Nightwalker Real Name: Austin Join Date: Dec 2002 Location: Oshkosh, WI Posts: 4,063 Car: '13 WRX YGBSM	It shouldn't, unless the valve is malfunctioning or adjusted wrong. __________________ "None of you seem to understand. I'm not locked in here with you.. you're locked in here with me."

2003-01-30, 11:06 AM	#5
AtomicLabMonkey Nightwalker Real Name: Austin Join Date: Dec 2002 Location: Oshkosh, WI Posts: 4,063 Car: '13 WRX YGBSM	Of course, I've never owned or worked with a forced-induction car, so this is all theoretical for me. __________________ "None of you seem to understand. I'm not locked in here with you.. you're locked in here with me."

2003-01-30, 08:17 PM	#10
sperry The Doink Real Name: Scott Join Date: Nov 2002 Location: Portland, OR Posts: 20,335 Car: '09 OBXT, '02 WRX, '96 Miata Class: PDX/TT-6 The way out is through	The stock BOV is actaully a really good BOV. Plus it's recirculating, which means the compressed air that the other (loud whooshing) BOVs just vent to the atmosphere gets put back into the intake. Recirculating some or all of the air helps keep lag down during shifts because the compressed air is still in the system while the turbo is not compressing (i.e. during a shift, or when you get off the gas). On a 4EAT, the BOV doesn't make quite as much of a difference as the 5MT because you can keep on the gas during shifts. If you want the cool sound, check out the 50%-50% recirculating BOVs, since they vent half the air back to the intake. I think that GFB one might be a 50-50, but check to make sure. Also, don't listen to the monkey... he's all hopped up on fumes from his big-ass 5.0! Acutally, all the stuff he said about the BOV is correct... with this addendum: no BOV = bad, vent to atmosphere BOV = good (and sounds cool), vent to intake (recirculating) BOV = better. The reason you hear the "psssst!" sound on rally cars is that they run vent to atmosphere BOVs and an anti-lag system. No need to keep that compressed air in the system when you're intentionally backfiring the motor to spin the turbo! Get of the gas in one of those cars and you hear: "PSSHHHHHT!! BANG! BANG! BANG!" But then you have to replace the turbo after every weekend. __________________ Is you is, or is you ain't, my con-stit-u-ints?

2003-01-31, 11:12 AM	#13
AtomicLabMonkey Nightwalker Real Name: Austin Join Date: Dec 2002 Location: Oshkosh, WI Posts: 4,063 Car: '13 WRX YGBSM	I knew I should have opened the garage door when I was doing that motor-tune... cough choke __________________ "None of you seem to understand. I'm not locked in here with you.. you're locked in here with me."

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2003-01-30, 10:27 AM	#3
ArthurS EJ207 Join Date: Dec 2002 Location: Reno, NV Posts: 3,707 Car: 2011 Chevy Battle Wagon	Thanks. That makes more sense. I thought I heard that they were bad sometimes because sometimes they would release the pressure (or something like that) and you would get no boost.

2003-01-30, 12:07 PM	#6
ArthurS EJ207 Join Date: Dec 2002 Location: Reno, NV Posts: 3,707 Car: 2011 Chevy Battle Wagon	This is pretty much my first also. I had a 87 supra turbo, but never did anything to it. Before that it was all n/a cars.

2003-01-30, 02:40 PM	#7
ArthurS EJ207 Join Date: Dec 2002 Location: Reno, NV Posts: 3,707 Car: 2011 Chevy Battle Wagon	Okay, I thnk I am going to go with the GFB BOV. I have read now for awhile that it is the most suttle at 100% atmosphere until you go WOT then it get pretty loud. Also has the 50/50 setting i guess. They are fairly cheap, but how hard are they to install?

2003-01-30, 03:33 PM	#8
MattR El Matador Real Name: Matt Join Date: Dec 2002 Location: Reno, NV Posts: 10,660 Car: 2012 Toyota Tacoma Class: ?	Save your money Arthur...You will notice no performance gains at all from a BOV. And, the sound is really less noticeable because you don't have to let off the gas to shift. I think the stock BOV is the mosty efficient for the motor, but also the quietest...good luck. Matt

2003-01-30, 04:09 PM	#9
ArthurS EJ207 Join Date: Dec 2002 Location: Reno, NV Posts: 3,707 Car: 2011 Chevy Battle Wagon	So its more for a manual then a auto? Only reason why i am inquiring so much is one was offered to me for really cheap.

2003-01-30, 08:34 PM	#11
ArthurS EJ207 Join Date: Dec 2002 Location: Reno, NV Posts: 3,707 Car: 2011 Chevy Battle Wagon	Thanks for the input. The GFB is a 50/50 bov I have heard, or a 100% bov. I will instead save my money for the stage 0 package instead. Have you gotten the Vishnu Silicone Intercooler Hose Kit? It says that it increases horsepower by about 5-7. Thats pretty good considering the price.