how to...

Fit a new dump valve

by James N

The Coupe 20v turbo already has a dump valve - a small plastic Bosch valve. This uses a diaphram which can eventually split.The spring inside the dump valve can become weak and either of these problems will lose valuable boost pressure. I suspected mine was leaking boost as it was making a humming sound at times so I decided to replace it with a better valve. This guide shows the fitting of the Bailey DV30 but is applicable to the Forge range of valves too.

The engine bay. The dump valve connects between Pipe 5 and the turbo compressor inlet hose (after the airflow meter 3)and is situated amongst the pipework. 6 shows the approximate location. The dump valve is difficult to get to, but this can be made easier by removing the Airflow meter 3 and airbox pipe 2. Remove pipe 5 too. This needs large hoseclips of 3in diameter to replace the non reusable Fiat clips. The airbox connection uses a conventional hose clip which can be undone with a screwdriver. The airflow meter to compressor pipe needs the hose clip cut off which can then be replaced with a conventional hose clip when put back together.

The Airflow meter and inlet pipe removed. Store this in a safe place as the sensing element is very delicate. Don't be tempted to remove the plastic mesh at the inlet to the AFM as this is important to its correct operation. It's also advisable to stuff a clean rag into the pipe which leads down to the turbo charger to stop any foreign objects accidently going down the hose while you are working on the engine.

The dump valve can now be removed. It sits between the the top hose (top *) and the inlet hose (lower *). The top hose hose clip needs to be removed. The other hose clip is on the valve outlet to compressor pipe connection at the base of the dump valve. The hose clips are very fiddly and I found the easiest way was to twist the main body of the clip at it's clamp point and then cut the clip with wire cutters. If anyone has a better solution then please let me know. Pull off the small pipe at the top of the valve and remove the valve from the engine bay.

The two dump valves. The bosch one on the right has had its inlet hose removed and transfered to the shiny new Bailey valve. The Fiat hose clamps have been replaced  by standard hose clips.

The Bailey valve fitted. Rub a small amount of washing up liquid on the valve pipes to make it easier to slide the Fiat hoses onto the valve. Tighten the hose clamp clamping the Bailey valve into the compressor hose. Ensure all connections are tight and remember to refit the small hose to the top of the new valve.

Another view of the valve. Appologies for the photos but the engine bay is too crowded to get good clear photos. Refit the airflow meter and ensure all the hose clamps are tight. I found that pickup was much better and boost was developed lower down the rev range due to the stronger spring keeping the valve closed more effectively. It sounds good too with my modified airbox.