BOV compared to wastegate?!?!?!?!

[2DaTrakNow]

I dont understand exactly what a wastegate does and how the boost controller works. First off, i know that when you reach a certain psi or when you shift your blow off valve will let off the pressure. So, when i buy a boost controller will it hook up to my BOV because that is what will decide when to let off? OR...is it the wastegate? and how does that work?

 

[Wufei]

I'll try to answer it but not positive about all this: The wastegate controls the amount of boost you run. When it receives a signal from the BCS (or the manual boost controller that you're gonna put in), the wastegate will open and let out excess boost, thereby ensuring you're only boosting a max of # psi (which you set with the MBC or is at ~11psi with the stock BCS).

The BOV lets out excess pressure when you're shifting (engine doesn't exactly need compressed air then since it's just free reving).

 

[BlackbirdOfPrey]

I will try to explain it the best I can. The BOV functions when the throttle plate closes under pressure. Normally your compressed air would be going through the throttle body, but when you shift or let your foot off of the gas, the throttle plate closes shut, leaving the compressed air no where to go. Now if this air has no where to go, it will get over pressurized and damage the turbo, blow a pipe, etc and cause damage because the pressure will just keep building. The BOV reads the vacuum signal that is sent when the throttle plate closes (in the absence of pressure in a motor, there is vacuum), and the BOV opens to relieve the pressure, which is what creates the WHOOOOSH sound, it is pressurized air being relieved. The wastegate functions on pressure as well, but it starts to open once it recieves a certain amount of pressure signal from the turbo itself, therefore your wastegate is almost always open to some degree, and what it does is bleed excess pressure and keep you from overboosting. What the MBC does is delay the pressure signal to the wastegate, allowing you to create more boost. The reason these are usually T'd together is that they both operate on a vacuum/pressure signal, and that is just a common place to put it (especially good place because it reads pressure from the intake manifold) which is what actually goes into your engine.

 

[DiamondStarM]

Except the BOV line is not a good place to get the boost source, the closer to the turbo the better. Think of it this way, if you have a huge leak and you see 20psi on your gauge its because 20psi is getting to the motor but who knows how much is leaking out. This means the turbo may actually be pushing 25psi so by having the source closer to the turbo you have more acurate control over the turbo itself.

 

[BlackbirdOfPrey]

I wasn't saying it is the best place (heck I don't tap there) I'm just saying that line is the most common because it is easy to tap into. The best place is always as close to the turbo outlet as possible so you see ACTUAL boost.

 

[2DaTrakNow]

Alright, thanks for the info! its more clear to me now!!

 

[DGajre777]

What is a BOV?

BOV stands for blow-off valve, sometimes called a pop-off valve or compressor bypass valve. This is a spring-loaded valve mounted in between the turbocharger and throttle body that opens at a preset pressure. It's function is to provide an escape route for pressurized air trapped in the intake system when the turbocharger is spinning and the throttle place suddenly closes. Although many turbocharged cars lack a BOV, its presence makes the car more driveable. Opinion on whether it improves turbocharger longevity is divided.

The original DSM BOVs were designed to open at about 30 psi or so. Unfortunately for 2G owners, Chrylser replaced the metal 1G BOV with a plastic one that begins to leak at about 15 psi. This is a major problem for those 2Gers looking to up their boost, since the BOV will start to leak a lot of useful boost pressure back into the atmosphere. For this reason, 1G BOVs are a popular upgrade on 2G DSMs.

Hardcore 1Gers might also find the stock BOV to leak under higher boost pressures (more than 20 psi). To correct this problem, some owners crush their BOVs slightly, so they will open only at higher pressures.