Removing & Blocking the Standard Dump Valve on Nissan 200sx (S14a)

This is the valve that releases compressed air from your intake when you take your foot of the throttle. Nissan fitted this as standard to help meet emissions standards and also to prevent the lovely rally-esque flutter noise. This noise is created as the compressed air does an about-turn back through your spinning turbo blades

The standard dump valve is believed to leak at around 1 bar (14.5psi) and your options are to buy an aftermarket one or to get shut altogether.

Removing the valve *should* be safe when running relatively low boost pressures (<1.4bar) although some really good information can be found here if you're unsure. Note: I wouldn't recommend doing this if you still have your CAT fitted. Without a fuelling computer, your car will overfuel on lift-off causing unburnt fuel to pass through into the exhaust system and could foul the CAT.

The Dump Valve itself - located just behind the battery

All three of the above pipes will be disconnected and bunged up.

Pipe 2 above needs unbolting from the rocker cover. There's only two or three 10mm screws attaching it.

Undo the jubilee clip at point 1 above. You can now pull the hard plastic pipe away and block the hole up with something suitable. The internal diameter is about 27mm.

(if you want it to look neater, you can actually remove the airbox and the intercooler intake pipe and remove that elbow pipe altogether but that would add an extra bit of time to the job)

Pipe 2 ducks down and the other end is connected to the "DV Exit Pipe" in the 1st picture.

At this stage, access to the DV was going to be a problem so I disconnected and removed the battery. To do this, unscrew the Live Terminal first, then the negative and finally unscrew the bar going across the battery holding it down. This should now lift out easily.

Next, undo the jubilee clip attaching the DV Exit Pipe to the DV (1st pic) and remove this flexible pipe and the hard plastic pipe(2). That's half of it done.

Now, this is the bit that took the most time:

You need to unscrew the jubilee clips on either end of this DV Intake pipe (3) and try to remove it. However, because it's not a flexible pipe, this is pretty tricky and made especially so because the right hand bit has some plastic going in for about an inch. If you're a big strong fella (or lady) this will probably be a doddle.

However, the way I did it was to unscrew the Dump Valve from it's two connecting points and twist this and the pipe around and pull it off.

Once removed, block the pipe up (this is about 30mm) and tighten very securely. I had to use a piece of shovel handle to block it up with. Hey, it works!

Finally, block off the thin actuating pipe (I used a fat screw in the end for this) and tidy it away somewhere - make sure it can't get stuck in the fan!

And the end result is:

One pigeon installed and ready to warble!