Why No Blow Off Valve?

[Red C5]

well in most arguments there are 3 sides.... their side, our side, and the TRUTH

i dont care for "wives tales" and i dont care to make cool noise when i let out of the throttle.

I DO CARE about the longevity of my turbo and assicociated parts. that being said when thought about for a bit, the BOV becomes a necessary part of any turbo system. most buick guys will tell you that the BOV doesnt make the car go any faster which is true, in fact if set up wrong, the BOV will only slow a tubo car down. the secret is to set it up correct as to not bleed out boost while under WOT and to fully evacuate excess pressure when the throttle "snaps" shut

currently on the auto industry, every auto manufacturer on planet earth that produces a turbo car has a BOV built into the turbo system (auto or manual), also known as a recirculation valve. if every major auto corporation puts cash into installing a recirculation valve (BOV),than shouldnt we? im talking about companys that wont waste a dime on anything that wont improve the product at hand either in mpg, value, performance, saftey, or reliability.......

stock car manufacturers install BOV's for a reason, 99% of outlaw 10.5 racers install BOV's for a reason, and so will I

What about the millions of turbo diesel trucks out there? Do they have a BOV?

 

[TurboDave]

Here's what we know..... This arguement will never be resolved to everybody's satisfaction, why? Because proponents of BOV's will forever argue in their favor, and those apposed will argue in agianst them.

What are the facts? Can they help save a turbo's life. No definative proof, but I'll give ya a maybe. Were they designed for that? No.
Can they help cars with standard tranny's keep the turbo spooled up during shifts? Yes. Were they designed for that? Yes.

I'm not going to speak to whether they are good for the longevity of a turbo, because I've never suffered a turbo failure due to the lack of a BOV. The 44 on my 86 has been there having the snot beat out of it since the early 90's....STill going strong.
The 49 on my 87 has been there having the snot beat out of it since the early 90's.....Still going strong.

As a matter of fact the ONLY turbo failure I've EVER suffered was not due to the absence of a BOV, but rather debri from a Champion spark plug that came apart and went through the turbine. That was on the 87 and the reason the 49 got replaced way back in the early 90's by another.

As for the arguement that virtually the entire automotive industry is using them, hogwash, and B.S. Ford is now the largest nameplate that's turbo'ng (over half their automotive line), show me their BOV's. Diesel trucks...also none.

I choose not to run any for common sense reasons. Those of you that like them, spend away.

 

[slimtastic]

What about the millions of turbo diesel trucks out there? Do they have a BOV?

they sure dont have a BOV...but they also dont have a throttle body to regulate the engine power/rpm...their power/rpm is regulated by the fuel injectors themself which change the ammount of fuel to increase or decrease the "throttle".

 

[slimtastic]

As for the arguement that virtually the entire automotive industry is using them, hogwash, and B.S. Ford is now the largest nameplate that's turbo'ng (over half their automotive line), show me their BOV's. Diesel trucks...also none.

which car specifically are you speaking of that doesnt run a BOV/recirculation valve?


diesel trucks dont run BOV's cause they are throttled by the fuel ingested, not the air......the air injestion comes later "technically"

diesel to gasloline is kind of an apples to oranges comparo.

 

[87-WE2]

which car specifically are you speaking of that doesnt run a BOV/recirculation valve?


diesel trucks dont run BOV's cause they are throttled by the fuel ingested, not the air......the air injestion comes later "technically"

diesel to gasloline is kind of an apples to oranges comparo.

Us dummies and noobs are clear as a bell now!! I wondered the same thing, but didn't realize this issue was a hornet's nest!!

 

[charlief1]

Well...technically big trucks do have BOV's, but it's called a jake brake. It's only used to slow the engine and slow the truck down not to help with shifting or turbo life.

 

[longball]

I don't use one on my GN because Kenny Duttweiler told me not to on automatic cars. That was good enough for me.
Peter

That is the best reason not to use one that I've heard so far!

 

[slimtastic]

Well...technically big trucks do have BOV's, but it's called a jake brake. It's only used to slow the engine and slow the truck down not to help with shifting or turbo life.

a BOV is not exactly what yor talking about in reference to a "jake"... a BOV is a valve in the intake track just befor the throttle body that lets excess pressure out when a throttle body closes.

a jake brake is a series of valves that basicly uses the engines pumping losses as a mechanical brake though the drive line. essentally using the exhaust valve in a "gloriously late opening cycle" to use the comression stroke as an " engine brake"...

the other BIG TRUCK engine brake is basicly a large restriction thats activated in a trucks exhaust path that also uses the engines pumping losses to slow the engine down...which in turn (while in a drive gear) slows the industrial truck down

 

[charlief1]

I know that, but was trying to simplify it. The purpose of them isn't the same and the design isn't the same but it's about as close as you'd get for the application, which was my point.

 

[kidglok]

dont the newer cars use "recirculation valves" ??

 

[smoke20]

I don't use one on my GN because Kenny Duttweiler told me not to on automatic cars. That was good enough for me.

Peter

Just got a new engine from him today with a new 6766 no bov huuuummmmmmmm if it needed it he would have added it. made over 900 hp and 100% street driven

 

[slimtastic]

I know that, but was trying to simplify it. The purpose of them isn't the same and the design isn't the same but it's about as close as you'd get for the application, which was my point.

ahh ok

dont the newer cars use "recirculation valves" ??

yes...which is basicly the same in principal. the only diff is that BOV dumps the excess to atmosphere...a recerculation valve dumps into the intake tract...typically just behind a mass air flow meter

 

[wiseman]

well in most arguments there are 3 sides.... their side, our side, and the TRUTH

i dont care for "wives tales" and i dont care to make cool noise when i let out of the throttle.

I DO CARE about the longevity of my turbo and assicociated parts. that being said when thought about for a bit, the BOV becomes a necessary part of any turbo system. most buick guys will tell you that the BOV doesnt make the car go any faster which is true, in fact if set up wrong, the BOV will only slow a tubo car down. the secret is to set it up correct as to not bleed out boost while under WOT and to fully evacuate excess pressure when the throttle "snaps" shut

currently on the auto industry, every auto manufacturer on planet earth that produces a turbo car has a BOV built into the turbo system (auto or manual), also known as a recirculation valve. if every major auto corporation puts cash into installing a recirculation valve (BOV),than shouldnt we? im talking about companys that wont waste a dime on anything that wont improve the product at hand either in mpg, value, performance, saftey, or reliability.......

stock car manufacturers install BOV's for a reason, 99% of outlaw 10.5 racers install BOV's for a reason, and so will I

What size spring do you run in your bov?

 

[slimtastic]

thats kindof a tough question for me to answer. i run a "light spring" that holds enough pressure to keep the BOV closed at idle...but if i were to rev and hold the engine rpms to just over 2000 prm. the engine vacume and the "light" boost presure being built will start to pull the BOV open, now that being said when i go wide open throttle the spring pressure in the bov holds the valve shut.

this setup probably wont work for a mass air flow equipped car

 

[spooledyou]

if one were to run a BOV, which one is best suited for our cars, i also have a simalar problem" among others" ever since i added a large FM, when i accelerate at mid throttle " no where near wot" before my car shifts it to does a wierd boggle like wobble wobble wobble unitl i lift and then begin to gas it again, never had this issue with a slic, so i guess a bov would get rid of this, wouldnt it..??

 

[slimtastic]

i think your runnign into an issue with the fact that your turbo is building boost from the abundance of exhaust flow, but since the throttle isnt wide open to invelope all the added air charge, surging and bucking occures. the added "interior space" of a front mount makes the problem worse, you might hear a sneezing sound with some light turbo chatter as well.

the only BOV's i have ever used or recommended are from Tial...more specific is the Tial 50mm BOV. if youve ever held one, just by looking it over you know its all buisness. it doesnt make any stupid "whistle" sound, but by the sheer valve size alone its fully capable of evacuating alot of air in quick order.

i run a single Tial 50mm and and have a front mount core size thats 26*24*3.25 without end tanks, ive never had any chatter or suge problems

 

[WIKEDV6]

I don’t have a degree in physics nor conducted any study on what happens to an air pump that pumps air in one direction then all of the sudden the air has to back up against the pump’s direction of flow to release the excess pressure .The air/excess pressure that backs out from the front of the Throttle body all the way though the IC, the compressor, the inlet pipe and out of the K&N filter leads to the horse sneeze sound. The only thing in the way of that is the compressor wheel spinning the opposite direction of the back flow. I am sure that this may create some kind of distress on the turbo no matter how big or how minute it is. In my opinion it will help the longevity of the turbo regardless if it’s an auto or stick trans even though you get on and off the gas less in an automatic. Then again the way I drive a Buick, it just might be same lol.

I don't have one on my car yet but I am installing one on my stage build. Most of my driving is on the street. I would hammer it and get off quickly sometimes if I am not able to just ease off the gas due to traffic and what not. Every time I hear that horse sneeze it bothers me. I have been driving around with an old school 63-1 for the past 12 year with hard miles and she is still going but maybe getting ready for a freshen up. So far it lasted 12 years maybe if I had a blow off valve it may have given me 13…who knows.

Just my $.02
Prasad

 

[DoubleD]

Here is my take on everything from a physics/rotating equipment standpoint

You will have a thrust imbalance when the compressor surges, similar to any process gas compressor. The air has no place to go, so it tries to equalize in pressure, moving bacwards through the impeller to the lower pressure side (suction side) once the downstream pressure balances, the flow shifts the other direction, and the phenomenon repeats until the energy is dissipated. I would expect turbochargers to have relatively good thrust capabilities because of the nature of the system they are working in (variable flowrates on both intake and exhaust side). Since the weigh of the shaft is small, the inertia of these small turbos isn't extremely high, you don't have a violent surge phenomenon like you would with a 10 ton compressor rotor. This is likely the reason that they will last a very long time doing this. The longevity of the turbo itself should be increased by a reduction in the amount of surge the turbo sees though.

It could all be a wash though, because maybe you get 100,000 miles out of a stock turbo that surges all the time versus 200,000 on on that doesn't. No one here seems to have any data to compare anyway, and who is really going to care.

I can tell you that you do not want to surge a process gas compressor... bad things happen. The same should apply on something that is just smaller scale.

My $.02

 

[YouLikeThat]

My brother installed mine. Not much money compared to my billet turbo. I'm not sure why all the haters out there, it's not a ricer thing.

 

[GNVenom]

I installed a BOV in my twin turbo Spyder, because without it, I was getting some serious slamming on the compressors. I believe it's a good thing to have for certain applications.