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Items required:
Dump Valve
Air Filter Bung (28mm)
Tools required:
Socket Set
Flat Head Screwdriver
Spring Clip Pliers
Clean Cloth
Estimated Time:
1 hour.
Difficulty Rating:
Very Easy.
WARNING: AS WITH ALL WORK YOU DO ON YOUR CAR, PLEASE BE CAREFUL AND USE COMMON SENSE - IF IT'S HEAVY, DON'T LIFT IT ON YOUR OWN. IF IT'S HOT, DON'T TOUCH IT, OR USE A RAG TO PICK IT UP. IF IT'S SHARP, WEAR GLOVES. IF YOU NEED TO DISTUB ANY ELECTRICAL COMPONENTS, MAKE SURE YOU DISCONNECT YOUR BATTERY FIRST AND IF IT'S ACID - LEAVE IT WELL ALONE!
The fitting of an aftermarket Blow Off Valve or Dump Valve is one of the most common and usually one of the first modifications done by owners of Turbo cars including the GTI-R.
The purpose of a Dump Valve is to ensure that the turbo is not put under undue stress due to compressor surge. Without a Dump Valve, when the throttle is released suddenly, such as when changing gear on boost, the blades of the turbo will stall as the throttle flaps shut, forcing the boost back down to the turbo, and stopping the blades. This will eventually cause the thrust bearings to fail. By releasing the boost at a point very close to the throttle when changing gear, the turbo is allowed to continue spinning. This also helps turbo spool up faster after a gear change, because the turbo is still spinning and requires less time to spool up.
The Dump Valve works by using the vacuum line from the engine (normally taken from the inlet manifold) to pull up a piston, to release the boost. Most modern Dump Valves have two pistons, an inner piston and an outer piston. During idling, when the inlet manifold registers vacuum, the outer piston of the Dump Valve is drawn up, but the inner piston remains locked in place so that no un-metered air can enter the system. As the car comes on boost, the pressure at the inlet manifold rises, and becomes positive - this effectively holds both pistons of the Dump Valve shut against the pressure building from the turbo.
When you suddenly release the throttle, the throttle flaps close, immediatley sending the inlet manifold into vacuum, however the inlet tract from the turbo to the plenum is still at a positive pressure. The vacuum from the inlet manifold coupled with the boost from the inlet tract forces the inner as well as the outer piston open. This then releases the boost either to the atmosphere or re-circualtes it back into the inlet tract, until there is no longer enough pressure to hold the inner piston open at which point it closes, leaving only the outer piston open. This whole process takes around 1 second from start to finish.
There are many different types and variations of Dump Valve. The two main varieties are the Recirculating Dump Valve and the Atmospheric Dump Valve. The Recirculating Dump Valve is the type fitted to the GTI-R as standard. Once the excess air from the turbo has been released from the Dump Valve, it is returned back into the inlet tract and is used again. The Atmospheric Dump Valve, on the other hand, releases its waste air into the atmosphere resulting in a 'Phssssh' sound.
Since the standard Dump Valve is a recirculating Valve, it is assumed that most people, who replace the standard item, do so with an Atmospheric Dump Valve. This Tutorial has been written as such. Dump Valves cost anything from £40 up to £300. Different people have different opinions of Dump Valves - some say that more money = better Dump Valve. I use a Forge Motorsport Dump Valve which costs around £120 and I find it to be more than adequate.
Instructions:
Perform the installation with the engine cold if possible to avoid burning your hands on the engine.
1. With the engine switched off, lift the bonnet and prop it using the bonnnet support bar.
2. Prise the Throttle cable from its seating in the intercooler frame on the Driver's side.
3. Using a 10mm Socket, remove the 4 small bolts that hold the Intercooler cover to the intercooler core. One of the bolts on the Driver's side, is recessed and may require an extention bar to enable you to remove it.
4. Using the same socket, slacken and remove the bolt on the drivers side of the intercooler cover that holds a 'p' bracket with a green metal pipe running through it. It should now be possible to lift the intercooler cover clear of the core.
You should now be left with the black frame with the core attached. Before you remove the frame and core, note the small rubber pipe at the top of the frame, running from the intake manifold, through the frame, and down to the actuator. This pipe is used to regulate and restrict the boost. It will be necessary to,
5. Slide the spring clips, on the pipes, away from the intercooler frame to enable the pipes to be pulled free, thus enabling the removal of the frame and core.
BE AWARE; THIS PIPE USES AIR PRESSURE TO FORCE THE ACTUATOR TO OPEN AT A SPECIFIC LEVEL OF BOOST. IF THIS PIPE IS NOT CORRECTLY RE-ATTACHED AFTER INSTALLATION, THERE WILL BE NO AIR PRESSURE TO FORCE OPEN THE ACTUATOR AND BLEED OFF THE BOOST. THIS WILL RESULT IN 'UNLIMITED' BOOST AND WITHOUT THE CORRECT FUELLING AND MAPPING - SEVERE DETONATION AND A DEAD CAR.
Once this pipe has been unplugged,
6. Remove the four 12mm bolts that hold the frame to the black brackets and inlet manifold.
7. slacken the jubilee clips that attach the intercooler core to the rubber hoses which connect core to the inlet manifold and the tubo outlet pipe.
8. Using moderate force, rotate the core and frame slightly, in a clockwise direction to help the rubber pipes slide off, freeing the core and frame.
You should now have easy access to the Dump Valve.
The Standard Dump Valve has 3 Pipes attached to it. The replacement atmospheric Dump Valve should only have 2 (The small pipe Which is the vacuum pipe which opens the Dump Valve at maximum boost and the vertical large pipe which is the boost pressure pipe from the Plenum) The other pipe which attaches to the angled join, will not be required as this is the pipe used to recirculate the waste boost air back into the system; this air will now be released into the atmosphere, resulting in a nice "pshhhhh" sound.
9. Unbolt the standard Dump Valve from the block using a 10mm socket.
Once the Dump Valve is clear,
10. Slide the spring clip away from the join on the small pipe and unplug the small pipe from the top of the valve. Slacken the jubilee clip that connects the bottom of the Dump Valve to the inlet manifold and unplug it. Do the same for the pipe connected to the angled pipe on the valve.
It should now be possible to remove the Factory fitted recirculating Dump Valve.
11. Take the Bung provided with the new Dump Valve and insert it fully into the large pipe that was attached to the angled arm on the standard Dump Valve. This pipe is used to recirculate waste air and is no longer needed.
12. Replace the clip on the pipe, securing the bung in place.
13. Reconnect the other 2 pipes to the new Dump Valve and tighten the Jubilee clips and spring clips.
The Dump Valve should not need to be physically attached to anything as the pipes which it is connected to are fairly rigid and should provide support. If you find that the valve rattles against the rocker cover or anything else, it is acceptable to attach a cable-tie around the base of the Dump Valve and tie it to one of the other fixed pipes nearby.
Once the valve is in place, reverse the above process to re attach and reconnect the intercooler:
14. Begin by bolting the intercooler core and frame frame to the supports and inlet manifold. MAKE SURE YOU RE-ATTACH THE ACTUATOR CONTROL PIPE TO AVOID DISASTER!
15. Reattach the rubber hoses which connect the Core to the Turbo outlet pipe and the inlet manifold.
16. Tighten all of the jubilee clips firmly.
17. Place the Intercooler cover over the core and replace the 10mm bolts, including the 'p' clip.
18. Re-attach the Throttle cable in its seating within the intercooler frame.
CONGRATULATIONS!
The operation is now complete and your GTI-R should not only sound 'better', but you should also notice better turbo response when changing gear. You can also live happily knowing that you are extending the life of your turbo.
HAPPY MOTORING!