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Discussion Starter #1
I purchased a used valve on Ebay with the correct T hose for the Esprit.

I went to install it this weekend and realized I really dont understand how they work when I started puzzling over the vacuum connection.

After reading up a little bit it dawned on me that the spring pressure holding the valve closed needs to match the characteristics of the car. It needs to match the boost and the vacuum at idle and low boost, otherwise it may leak boost or bypass air when not on boost.

Do I have that right?

Seems odd that many dump valves can work on many cars with out some adjusting/changing the spring

The valve I purchased looks like a quality piece but I am not familiar with the brand. I might be able to figure out what spring it has but wondering what spring is needed for an Esprit.

Probably should of bought one from one of the vendors that has done the research... :)
 

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Dose it work? When screaming down the road and you take your foot off the gas pedal, you should hear it blow off the pressure.
 

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Ok Erik, i'll give it a go:
The key to the function of a BOV is the correct connection of the Vacuum hose, without vacuum the valve should remain closed so you can easily test it on or off the car. As the Esprit produces relatively low boost (around 10 PSI under normal conditions) blow-by, where the boost pressure lifts the valve against the spring pressure, should not be an issue with the Bailey valve which unfortunately does not have any adjustment of the spring. Under normal conditions the intake plenum on a turbo car is under pressure, not under Vacuum like a naturally aspirated engine. When under acceleration (boost) there is positive pressure both before and after the throttle flaps but when you let your foot off the gas the flaps close causing a vacuum downstream of the flaps, it is this vacuum that opens the BOV against the spring pressure and releases the stalled boost pressure on the other side of the flaps, this stops the turbo from slowing down/stalling due to excessive back pressure which is still being produced by the spinning turbo. This release of pressure allows the turbo to continue to spin freely so that when you again apply the throttle the turbo is already spooling and will apply boost quicker than if it was slowed due to back pressure. The key for you is to make sure that you connect the vacuum line downstream (after) the throttle flaps, i have seen more than one connected via a 'T' on the boost pressure line at the rear end of the intake plenum (line that feeds the transducer) :ROFLMAO:.
Graphic explanation:
 

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Discussion Starter #6
Great, thank you!

I have seen some installed with a one way disc valve on the vacuum line. Is that necessary? Does that help ensure the dump valve stays closed during low/no boost situations?
 

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That valve is known as a check valve or one way valve that allows flow in only one direction (vacuum or pressure) On earlier/cheaper BOV's the topside of the diaphragms didn't like pressure which occurs under boost, later valves are designed to take advantage of the boost to ensure complete closure of the BOV under boost until the Vacuum occurs when the throttles are closed. It wont hurt to have it, so if you have one go ahead, but its not really necessary on newer BOV's. The only downside to the Bailey valve is that on most of them there is no adjustment, this means that its essentially an on/off switch. Some have a Philips screw than can be adjusted but its not ideal. The ideal situation is to bleed off some of the boost but maintain pressure in the chargecooler so that when you re-apply the throttle there is minimal lag between hitting the gas and re-boosting. This explains it well, but stop it after 7 minutes unless you want to watch boy racers at work :ROFLMAO:
 

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Correct, though the Esprit does have a MAP and MAT sensor! Another decision on that valve is do you want the 'whoosh', or do you want to recycle the air back through the intake by running a hose from the BOV discharge to the intake?
 

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Erik
The valve you have redirects the air. If you want the "whoosh", you need one that ventilates to the atmosphere. The spring should be rated 5-11 psi (yellow)
 

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Discussion Starter #11
Well - got scammed. Tried to install today and the tee hose is not the correct size for the Esprit intake. Fortunately it was very cheap. I guess I will look at purchasing the tee hose section, I have seen just the tee for sale somewhere before.
 

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Discussion Starter #12
Ebay has the tee hose in various sizes. The hose that came with this dump valve (shown in the picture above) is 2" ID. Any body know what size is correct to stretch into that oval shape?
 

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Erik
You have to measure the diameter in millimeters. Also check PNM , they have those silicone tees.
 
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