Lotus Esprit V8 Turbine Bypass Valve Upgrade

Before or immediately after you do any form of BOOST tweaking, you must consider your turbo chargers health and longevity.  At high boost levels, turbo back pressure is substantial and when you slam that throttle shut between gear changes, it pounds back against those little Garrett T25's.  This greatly reduces the turbine life, not to mention that the bearings also take a real beating. As we are increasing constant BOOST levels to almost 3 times what Lotus intended for this Esprit ('97, '98 & '99 model years), this modification was NOT considered an option!  The valve output must be connected to the air filter boxes to finish off the installation, as it keeps the turbos fully spooled between gear shifts and get rid of the Shhhhhhhhhhhhhhhhhhhh...... generated by the valves when vented to atmosphere.

All items listed assume the person(s) doing the modifications have a complete set of up to date Lotus workshop Manuals.

The steps we performed are as follows:

• Open the tailgate as far as it will go without disconnecting the struts and support it. (we used a rope to the roof of the garage through the rear wing)
• Disconnect the battery.
• Remove the rear cargo bay, this is an easy task and involves removing a few bolts, 2 Allen Screws, Loosening the Radiator filler reservoir and slicing through the black silicone sealant with a utility knife.  It then simply comes out through the tailgate.
• Drain the Radiator.
• Remove all pipes, hoses wires and sensors that are in the way of the left and right turbo manifolds. The following picture shows the engine from the rear with all the pipes removed. (The manifolds were also removed by this time and put back just for this shot. You will notice some cork and plastic plugs that we used to protect all the exposed holes to the engine from debris. You will notice some black marking on the turbine manifolds, these were where we had to weld the valve inlet ports. The white towel was used to protect the plenum when we put tools on it.

The left and right manifolds can clearly be seen here.

• Once all the pipes etc. are out of the way, all the bolts removed, the manifolds can be coaxed off. This is a lot easier said than done, but they come off with the help of washing up liquid (dish soap) for lubrication (to help us get the attaching rubber joining hoses off). The main problem was getting the left (as seen) manifold off. The short 2" in diameter rubber connection hoses have a very small gap between the pipes, as you can see in the next photo, especially the lower one that connects the manifold to the turbo charger outlet (you cannot see that one).  But with the mentioned washing up liquid liberally placed around  the joints they came off quite easily.... considering. We thought they would be murder to get back, but the new blue silicone hoses  we used were much more flexible and they just popped back on.

Here you can see one of the small gaps between the manifold and the throttle body

Here you can see the left manifold removed

• Now the manifolds are removed you need to get the ports welded on. This next photo shows the manifolds all marked up. We put one 1.25" OD alloy barb on each manifold at the positions marked with the black dotted rings. Ignore the other marks and black dots for now they are for the H2O injectors (only one was used on each side).   We drilled and tapped them at the same time. The large circle on the left manifold and the lower of the 2 on the right manifold were what was finally decided as optimum.   They need to be marked for maximum clearance from the exhaust re-circulating return line (the left side).  The right one is a lot easier to mark because there is a lot more room. You will need to re-do your own to find the best location, and double/triple check it.

Turbo charger manifolds, ready for welding

• Once the ports were welded, the manifolds were re-installed on the car, with their new sparkling blue silicone couplers. The hoses were aligned and put back into place. Extra tie wraps were used where needed to keep the cables and pipes from fouling each other, and we were now ready for the valve installation.

At this point we are short of pictures as we did not take any photos of the finished valve installation with the cargo compartment out. The next time we take the it out we will update this page with the installed finished photos. The following text bullets and photos show the final installation.

• Blue silicone 90 degree 1.25" tubing was used to connect the welded ports to the GREDDY Type "S" valves.  Standard stainless steel clamps were used to secure all new hose fittings. The GREDDY valves were the best fit for this application. Mitsubishi Eclipse mounting flanges were used as they were the most appropriate "off the shelf" parts available without going custom.

• The valves were mounted to the engine by 2 custom made aluminium brackets which were very easy to fabricate. They were bolted onto the inner valve-to-flange mounting bolt on each valve, and in turn clamped to the air return tube with modified small aluminium cable clamps. (a very close fit)

• One last item to mention. The valves require a vacuum supply to open and function. A "T" was placed into the plenum vacuum outlet that goes to the air recalculation system.  This is located on the right hand front side of the plenum as you stand at the rear of the car. A 1/4" plastic hose was run into, then through the right hand bulkhead cavity, (where the ECU lives) and back into the engine bay at the rear of the plenum. Then Tie wrapped to the fuel lines and "T'd" once again into the valve inlets.

Plenum vacuum "T" to valves

Here are some photos of the valves and their associated parts:

NOTE: The returns from the valves are disconnected for viewing and should be connected to the left and right airboxes for best results.  They can be run without but make sure your airboxes are sealed as shown, if you do so. (We did for testing)

The Mitsubishi Eclipse GREDDY valve flange

This is a GREDDY Type "S" Turbine Bypass Valve installed, the custom mounting bracket is also visible

Left valve installed with 90 degree silicone connection hose, notice the vent to atmosphere

Left valve mounting bracket

Left airbox return plugged for testing

Right valve custom mounting bracket

Both valves installed and operational (Left valve in foreground)

We hope you found this text interesting.  If you have any more questions please leave email  and we will be please to respond.

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