The HPG/Garrett R30 turbocharger and cast exhaust manifold
Real World Driving
How does the new turbo system work in the real world? Regardless of what the numbers say, I can tell you the delivery of power is smooth and strong. After starting the engine, I was pleased to learn there were no codes thrown or engine lights brightening the dashboard once the ECU finished its checks. It idled as smoothly and quietly as it did before, albeit a little higher at 750rpm (when warm). I assume this is necessary due to the reduction in engine compression. One of the aspects of this system I was quite surprised with (besides the power) was that I have lost nothing off-boost (this is demonstrated nicely by the dyno curve overlays in Figure 9).
With the engine fully warmed up, the car is just as easy to drive around town. Throttle sensitivity is nice, linear yet responsive, making the power easy to modulate. As I use a bit more pedal, I enter into the lower boost range. There are some interesting but satisfying whirrs and swooshes up front. The steep torque curve between 2100 and 3800rpm does appear ominous, but, because of the excellent throttle sensitivity and response, accelerating at any desired rate through this rev range in any of the lower gears is not an issue.
Dual TT intercoolers with beautiful stainless steel boost piping
Full stab on the throttle in second gear builds boost nearly instantaneously and you're rewarded by a rocket-like thrust squashing you into the seat. Be absolutely sure to have a clear, straight road and both hands firmly on the wheel. The sound begins as the gentle VR6 hum we all know and love, then transforms from growl to roar to shriek, like a cross between a race car and jet fighter. The car accelerates feverishly toward 60 mph, as the tach races towards to the new 7000rpm redline in a blink. Fortunately, with 4Motion, there is no lack of grip, so none of this power is wasted on burning up tires. A quick shift to third is rewarded by a similar sound and an almost equally forceful thrust of acceleration when hard on the throttle. Before you can say "80mph" you're doing it.
Stepping off the throttle in either gear will throw you forward, due to the loss of acceleration, and cause the recirculation valve to make a minor rumbling and rubbing noise that is slightly audible through the dashboard. This is normal. For full throttle runs starting in first gear, the rate of acceleration is obviously sky-high. In these instances, be sure to have the corner of your eye on the tach.
The finished product
I identified the stock clutch as a weak point on getting my new-found power to the pavement. To rectify this I ordered the HPA/Sachs R32 Racing pressure plate and unsprung organic friction disc, for strong, yet streetable, clamping power (see Figure 10). This setup is designed to work with the stock dual mass flywheel and does so extremely well. When driving around town, it is virtually indistinguishable from the stock unit, due to its light pedal feel. The unsprung organic friction disk provides smooth and quiet operation. Note that this is the same pressure plate used for HPA's early 450-plus bhp twin turbos, so I am not worried about slippage in higher gears.
In order to retain the expensive aftermarket stainless exhaust system (2.5 inch diameter) described in Part Three, HPA recommended the installation of a computer-activated exhaust bypass valve. This works via vacuum line in much the same way as the OEM R32 exhaust flapper. Once activated at 3100rpm, the bypass valve redirects the exhaust flow, half through the muffler and half through the bypass dump (see Figure 11). The change in sound is fairly minimal (but nice all the same) and this releases the back pressure on the exhaust system, thus increasing power in the top end. Unfortunately, this gain cannot be seen realistically on the dyno chart (which drops quite drastically), due to the artificial loading and airflow during the dyno run.
Next, the lower rearward engine/transmission mount, often called the dogbone, was another item to be addressed and strengthened. HPA has a new solution for this as well. A proprietary set of bushings was designed to replace the OEM rubber in the dogbone (see Figure 12). This modification was noticeable the first time out of the parking lot, as I could feel the more direct connection of the drivetrain to the road in first and reverse gears. An additional plus is that it provides as much vibration damping from the engine as the stock rubber, so your eyeballs remain unshaken.
With the increased performance, it was now necessary to more closely monitor my engine's condition, so I decided to add some aftermarket gauges. In a MkIV VW it is possible to install up to seven gauges: two in a steering column pod, two in an A-pillar pod-mount, and three above the stereo (if you are planning to upgrade the stock double-decker stereo unit with a single-level aftermarket piece). However, it should be noted that A-pillar pods should not be used on MkIVs equipped with A-pillar airbag systems (like my car), as they will become projectiles during airbag deployment.
A closer look
With the guidance of Rob Leech at Tunerworks Performance Parts House in Calgary, I selected gauges from Auto Meter's Sport Comp line. Having strong confidence in HPA's tuning abilities, I opted not to add EGT and A/F gauges necessary in most custom turbo applications. The simple solution was the Auto Meter two-gauge steering column pod mount with the bare minimum. This comprises a combination vacuum/boost gauge and an oil temperature gauge (see Figure 13).
The extremely stealth R28 Turbo is proudly shown in Figure 14. I would like to say that, as a VR6 and R32 enthusiast, this turbo system is well beyond my expectations. Power delivery is ultra smooth and surprisingly easy to modulate at any engine speed, and it can be absolutely fierce when desired, with around town off-boost driving as silky as the stock VR6 engine (with an aftermarket chip, i.e. no drive-by-wire delay). It is truly like driving a stock car with a 'magic' throttle-controlled power release. Also, in this application, turbo lag is negligible, and gas mileage was over 27mpg (US gallon) during a day of highway driving with many trips into the boost range. With all of this performance, I think 'My R32 Blues' have now completely faded away.
Stay tuned for Part Five, the last installment of the series, when the R28 Turbo gets some new shoes, thanks to Neuspeed and Toyo Tires, and a few more finishing and handling touches. Also, a full track review will be included and the complete specs listed.
The R28 Dyno plot compilation
Sachs/HPA performance clutch assembly
Computer-controlled exhaust by-pass
HPA dogbone mount
Steering column gauge pod
The stealth R28 with 17-inch winter wheel setup