general forced induction question

[95_bowtie_s10]

Ive been thinking about this for a while.

Why is it that Blow Off Valves and boost controllers are used in turbo systems, but not with superchargers?
Also, what benefit is there for a BOV on an automatic?

 

[GM TURBO]

Re: general forced induction question

Boost on a turbo is run by exhaust gas. The more exhaust gas the more the turbo wheel spins. The more the turbo spins - the more exhaust gas. The more exhaust gas.....enter the wastegate.

A supercharger is run by engine speed and a pulley. Getting more boost out of a SC is done with a pulley change.

There isn't much need for a BOV on an automatic.

 

[SeattleSy#1255]

Re: general forced induction question

BOV saves your turbo, what does it have to do with auto or manual? When you let off the gas, and you TB slams shut, the pressure doesn't destroy your blades by bleading off the air. I believe some guys do use BOV for other types of blowers such as a vortec centrifugal. Could be wrong on that one. Superchargers are operated by belts, not "work" by exhaust.

 

[GM TURBO]

Re: general forced induction question

BOV saves your turbo when you quickly let off the gas. It helps maintain boost on the shift instead of sending all that 'forced air' back through the turbo when the throttle blades close. On an automatic - you stay in the gas on the shift.

I have 120K miles on the stock turbo. It sees max boost every time I drive it. I don't have a BOV.

 

[schrgds]

Re: general forced induction question

Besides alleviating compressor surge... on a centrifugal s/c setup without a bpv or bov the engine wont idle properly due to too much air flowing out of the supercharger vs how much air the engine required to idle. This would also occur if the bov or bpv wasnt large enough to bleed enough air coming off the supercharger. This is mainly due to the supercharger is always compressing air even at idle since it is turned with the belt. Since a turbo doesnt begin spooling (compressing air) until a certain rpm above idle this isnt an issue allowing you to get away with not having a bov.

 

[vortecfiero]

Re: general forced induction question

Also the Bosch type recycling valve (blow off) is always open under vaccum
therefore at cruise it is open allowing the turbo to spin
at a higher rate since the boost it has somewhere to go
so spool up is faster

craig

 

[TYHOGG]

Re: general forced induction question

BOV saves your turbo when you quickly let off the gas. It helps maintain boost on the shift instead of sending all that 'forced air' back through the turbo when the throttle blades close. On an automatic - you stay in the gas on the shift.

I have 120K miles on the stock turbo. It sees max boost every time I drive it. I don't have a BOV.

Yeah Yeah, and mine craps out at 32k, so i buy a 20g. But the BOV does sounds kool, haha.

 

[95_bowtie_s10]

Re: general forced induction question

yeah, the basic "propulsion" of the two compressor methods i got, but since there isnt really a time when you let off the gas during a run (unless you lift) with an auto, i figured it wouldnt do much. Thanks for the information.

 

[THEMADTYPH00N]

Re: general forced induction question

Compressor surge is much more harmful in a blower car then it is in a turbo car. It not only affects the blower but the motor as well. Specifically the crank. When that pressure wave comes back trying to turn to compressor wheel backwards it also tries to turn the crank backwards making for a horrible twisting force placed on the crank snout.

On the subject of boost control I've seen some NMRA Outlaw and Pro 5.0 cars use what look to me like wastegates to control boost on the line. I have no idea how they control it but they are used to bleed off some of that air pressure so they can leave the line at a certain boost level. So boost control in blowers does exist.

 

[95_bowtie_s10]

Re: general forced induction question

those outlaw guys are sick!! they run, what, like 9.0 on 10" tires?? I saw an outlaw guy run 10.50 on 10" DR's and two license plates down in maryland. Thats insane

 

[QUICK STORM]

Re: general forced induction question

:syty: i like turbos better

 

[THEMADTYPH00N]

Re: general forced induction question

those outlaw guys are sick!! they run, what, like 9.0 on 10" tires?? I saw an outlaw guy run 10.50 on 10" DR's and two license plates down in maryland. Thats insane

10.5"

 

[95_bowtie_s10]

Re: general forced induction question

eh, outlaw 10.5, my bad

 

[TheNeek]

Re: general forced induction question

Superchargers have different configurations as well. I purchased a twin screw off a MKI toyota MR2 way back in the day to supercharger my BMW with. It was pretty slick with a AC clutch type pulley on it to engage or disengage the charger. During cruise or big vaccum (idle) the charger would turn off and there was a bypass valve that simply turned the whole engine into an NA setup. Real slick and funny that they dont' do stuff like that more often. My friends MR2 would run 12.5 all day. Not blistering fast, but definately surprised a bunch of people. Including a GN until about half track Superchargers have their place... dissapearing in turbo cars rearviews.

 

[ghettosled]

Re: general forced induction question

outlaw and pro cars use the wg on the intercooler pipe to basically overspeed the turbo by creating a huge vacuum leak. When they finally launch the gate slams shut and pumps all the air straight into the intake.. Extrememly hard on turbos, but thats one of the ways they get those massive turbos to come onto boost with an automatic.

As for the 10.5" cars, where have you been?? Tim Lynch has been in the 6s on 10.5", and drag radial is going 7.60s.

 

[THEMADTYPH00N]

Re: general forced induction question

outlaw and pro cars use the wg on the intercooler pipe to basically overspeed the turbo by creating a huge vacuum leak. When they finally launch the gate slams shut and pumps all the air straight into the intake.. Extrememly hard on turbos, but thats one of the ways they get those massive turbos to come onto boost with an automatic.

Thanks for the explanation I never really could figure out how that worked.

As for the 10.5" cars, where have you been?? Tim Lynch has been in the 6s on 10.5", and drag radial is going 7.60s.

Right, at the World Ford Challenge this year I saw Mike Keenon's Wild Street car make the 30 mile qualifying cruise then bust a 7.80 pass on a Drag Radial.

 

[95_bowtie_s10]

Re: general forced induction question

As for the 10.5" cars, where have you been?? Tim Lynch has been in the 6s on 10.5", and drag radial is going 7.60s.

I only saw one down at the track I was at. I dont normally follow the outlaw guys, OutlawProMod maybe, but thats a VERY different story. Besides, I was a little more interested in watching Top Sportsman guys run 7.60's and stopping on a 1/4mile shutdown area.