As many of you are aware, the 944 Turbo has a single port wastegate with electronic boost control. Many of you are also aware that the Wastegate on the 944 Turbo gets weak with time and there are rebuild options that can cost about GBP 700.00. However, even a new or rebuilt factory KKK wastegate for the 944 Turbo has a major weakness - it is overcome by exhaust pressure at high RPM. This means that it is very difficult to achieve more than 0.7 bar of boost at high RPM. With the standard wastegate, there is no problem reaching an increased (and brief) over boost condition at 3,000 to 4,000 rpm - but to achieve considerably more power is not possible (safely) using a factory wastegate. Power requires RPM. If your car is not making boost at high RPM - it's not reaching its true power potential.
Most of you will have noticed how your Boost Gauge falls back as the revs rise - the factory gauge reacts very slowly, but with an accurate boost gauge you would be surprised as to how much the boost tails off. In the majority of cases, beyond 4,500 rpm - the boost tails off on the 944 Turbo using the factory wastegate (both 220bhp and 250bhp models). Recently a test was performed on a standard 250 bhp 944 Turbo with new factory wastegate (these retail at GBP 1,350.00!). A maximum boost of 0.82 bar was achieved and the boost rolled off to 0.7 bar and decreased further beyond 6,000 rpm. This car made an indicated 242 bhp. This was with a new Porsche supplied factory wastegate.
The factory wastegate is a single port wastegate meaning the signal pressure air is only applied to one side of the actuator diaphragm. The spring pressure is also weak on the factory unit allowing it to open with boost pressures as little as 0.1 to 0.2 bar (especially as the wastegate spring weakens with age and use). Being limited to one port and having a weak spring means the wastegate opens early. Also, the rate at which it opens and closes is not adjustable.
The Dual Port configuration allows for a second air signal on the opposite side of the diaphragm; the spring side. By adjusting the air pressure with a regulator (Variable Boost Controller) either up or down (on the spring side), has an effect like changing the spring pressure. To increase the boost? The pressure is raised on the spring side and the wastegate closes. To achieve less boost? The pressure on the spring side is lowered and the wastegate opens.
A Variable Boost Controller is required to adjust the Dual Port Wastegate (or any other dual port wastegate). A Manual Boost Controller is available which enables in car control of your desired boost level. Other electronic options will be available also. Holding 1 bar or more of boost in high gears is no problem for the Dual Port design. Not only that, you can also turn the boost down to as low as 0.5 bar when conditions require (for example, in the wet). The ProMAX Dual Port Wastegate is a direct bolt on replacement for the standard factory wastegate.
The ProMAX Dual Port Wastegate is manufactured utilising the original wastegate. The factory unit is rebuilt with the modifications added to it. Hence, the Dual Port Wastegate is supplied on an exchange basis (for the original factory unit). There is a core deposit that is fully refunded when the original factory unit is received (as most would rather remove the original wastegate and fit the new Dual Post wastegate at the same time - rather than remove and send the original first).
The Wastegate can be installed with a few basic tools in about two hours. The exact time will vary as the bolts can be rusty and snap, or they may come undone. It takes around 3\4 hour to install the Manual Boost Controller. The Boost Enhancer (if fitted) and cycling valve should be removed / disabled - neither are required when using the Dual Port Wastegate. Turbo lag is greatly reduced with the DPW as the wastegate valve is unable to open prematurely - due to pressure on the spring side of the valve keeping it firmly shut as the engine revs build.
Using the standard Dual Port Wastegate and with a K26 6/8 turbo (the K26/6 is fitted to the 220 bhp car, the K26/8 to the 250), the boost level can be set to 1.0 bar (i.e. 1.0 bar to the redline in all gears) or as low as 0.5 bar. It can also be set as high as 1.5 bar, but the boost would fall off to 1.2 bar in 4th and 5th (due to strength of the standard spring). Boost levels using a Dual Port Wastegate and a hybrid (e.g. K27 hot housing and K26/8 cold housing) turbo have yet to be determined, but expect higher maintained boost. Same applies to later ceramic ball bearing turbo units.