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Joined: Jun 2001
Posts: 4,777
Hard-core CEG\'er
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Hard-core CEG\'er
Joined: Jun 2001
Posts: 4,777 |
Originally posted by zm830101:
as i understand it, you want the blow off valve as close to the throttle body as possible. this is so that when the throttle plate slams shut, the BOV can release the pressure before it is forced back into the spinning turbo. matter of fact you don't even really NEED to use one with anything less than 10 psi, just ask any mazdaspeed protege owner. why you would even put it on the intake pipe is beyond me. it isn't actually doing its job there. also, there is a huge difference between a recirculating bypass valve and a BOV.
bypass here . . .
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Joined: Jan 2005
Posts: 2
Newbie
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Newbie
Joined: Jan 2005
Posts: 2 |
Originally posted by Horse:
Originally posted by Dustyn:
People throw stupidchargers on v-8's because they are fed by the ad's and just want bolt on power.
What is wrong with bolting on power?
the difference between turbo vs a super? super has NO LAG
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Joined: Sep 2000
Posts: 3,223
"Absolut Rara."
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"Absolut Rara."
Joined: Sep 2000
Posts: 3,223 |
Originally posted by DemonSVT:
Originally posted by Dustyn:
The BOV is before the MAF so its not unmetered air. When the car is idling its in full vaccum 19hg.
So in full vaccum you have the BOV diaphram being sucked up causing the valve to be open. If the valve were closed the system would keep building pressure. 
That's a horrible place to put it.
So you are back flowing the surge of air charge past the MAF in reverse!!! 
Not only does the double meter the air you are then "loosing" but the meter is NOT designed to flow air in reverse. This can damage the meter which means very erratic or no air metering in the near future. 
Your description and thinking of a bypass/blow off valve is completely wrong as is everything you have posted about it.
While some {IMO} improper supercharger setups also use a bypass valve to control maximum safe boost they are truly designed & used for surge control. It is for protecting the compressor from the reverse surge of air flow when the throttle plate closes and the pressure spikes & reverts.
Using it as a "safety" valve for engine protection is more understandable but any time you are using it for normal boost control you are just over tasking the compressor and adding more heat, compressor rpm, & lower efficiency. (i.e. why I state it's improperly used that way)
A turbo setup NEVER uses it for boost level control. That is the entire purpose of the wastegate.
I know this thread is over a week old, but Dustyn's dyno thread made me start looking around a bit.
Anyway, Demon, I think you are being way too hard on Dustyn here, and way overstating some issues.
Quote:
That's a horrible place to put it.
So you are back flowing the surge of air charge past the MAF in reverse!!!
Not only does the double meter the air you are then "loosing" but the meter is NOT designed to flow air in reverse. This can damage the meter which means very erratic or no air metering in the near future.
I disagree. Ideal? No, but horrible? Not so much. Because the BOV valve is between the MAF and the Turbo doesn't mean it definately is reversing flow in the MAF, it depends on a number of other system factors. Further, even if it is, backflowing air through a MAF won't really damage it, it will just make it read erratically while air is being backflowed (remember, most MAFs are just hot wire sensors). If he's not having idle driveability issues, then its probably a complete non-issue here.
Personally, I think the pre-MAF location is much more desirable than a post-MAF location, so that you don't bleed off metered air.
Quote:
Your description and thinking of a bypass/blow off valve is completely wrong as is everything you have posted about it.
. . . A turbo setup NEVER uses it for boost level control. That is the entire purpose of the wastegate.
Again, I disagree. I can really only assume that you are referencing two things here; Specifically, that the valve is open at idle, and that you think he is using it for boost control duty.
First, having BOV valves open at idle is pretty common. BOV valves open because of a pressure differential across them. When there is pressure in the intake tract, it pushes the valve open, and when there is no pressure, a vacuum signal across the back of the valve pulls it open, and everywhere in between during various operating conditions. Having the valve open during idle, allows the turbo to keep some of its velocity up (rather than stalling or surging) Not always ideal, but perfectly acceptable in many applications. personally, I'd run a bypass valve, and have it open under idle as well, unless I couldn't get good driveability out of it.
As far as the second, I think you've completely misunderstood, I don't believe he is using the BOV for boost control at all; merely for overpressure control and turbine speed management in off-load conditions.
Fwiw, often pure drag race applications will use the blow-off valves to control boost during staging to allow full boost at launch.
Further, the guy bought a kit, he didn't design it; That doesn't make him an instant expert on every aspect of its design. I wouldn't be surprised at all if he can't explain all the details perfectly clearly.
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