Modifications

[see also RISKS, RETURNS (performance data) and INSTALLATION]

I now have an HKS EVC IV installed (by Graydon Stuckey) in the S4.What this does is replaces the wastegate frequency valve (WGFV) with a fast and powerful valve actuator run off a separate boost controller. It learns how to sense how much boost the turbo can handle, and holds the wastegate shut until max boost (specified by the driver) is reached, and then only opens the wastegate enough to bleed off the excess air. If boost starts to fall, it re-shuts the wastegate to try to maintain maximum boost.

• Q: "Doesn't the WGFV do the same thing?"
• A: "Essentially, yes, but less powerfully, less swiftly, and with no user-control"

The result is that boost should come on sooner, and remain stronger across a much wider rev-range.

The effect is incredible. The sheer pull of the car is now phenomenal (and I had the TAP stage 1 chip/exhaust/K&N filter beforehand) and very smoothe. The old "lump" of power at 3200 rpm is now smoothed out, and power is retained _far_ better up the RPM scale.

Qualitative Improvements:
(UD=user definable)

1) Boost at part throttle about 3000rpm is instantaneous. No lag. This was particularly noticeable when driving my car against Chuck Price's S6, back to back.

2) Boost is cockpit-controlled: The EVC has two stored boost settings (UD), high and low, which can be alternated at the flip of a switch. I currently run 1.25 bar+ and 0.6 bar+ (as a "valet mode")

3) Overboost is replaced by "scramble mode" which adds, when you push the scramble button, for a period of time (UD) an increased (UD) level of boost. If, during scramble or normal operation, the EVC detects excessive (UD) boost levels, it warns you. I have yet to see it overshoot the mark I've set by more than 1-2%.

4) Digital boost guage... I need to re-mount this where I can see it, because currently testing this thing is a 2 person job.

OTHER MODIFICATIONS

Geoff Jenkins
Email: gj_os@pacbell.net URL: http://home.pacbell.net/gj_os

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