Tech Analysis: VW

Intercooling is often overlooked in the initial stages of upgrading a 1.8t-powered Volkswagen. A stock, 150-hp 1.8t will heat soak its intercooler by the end of third gear, so when starting with the 180-hp version, or adding a chip, performance gains are almost certain to be realized. european car recently tested one such upgrade, the prototype for Autobahn Designs' front-mount Golf/Jetta MkIV intercooler, on ABD's 2002 GTI 337, and quantified the improvements. This was the first modification to the car; it was otherwise stock at the time we carried out the tests.

Autobahn Designs' 1.8t front-mount intercooler was installed while ABD's GTI 337 project was strapped to Primedia's dyno. It is clearly visible from the front of the car, if that is important.

Autobahn Designs (ABD) had two primary objectives in the design of its Golf/Jetta 1.8T intercooler: improved performance and ease of installation. Some performance benefit was virtually guaranteed by using a larger, front-mount design. A pipe returns the cooled charge to the passenger side of the car, allowing the stock intercooler pipes to be used, rather than cutting a hole on the opposite side of the car to route new pipes. Thus, the installation of ABD's intercooler is fully reversible. Whether it will be necessary to trim the front bumper plastic depends on what bumper is used. Only very minor trimming to the rearmost portion of the stock 337 front fascia was required.

Installation
We installed the intercooler while the GTI was strapped to our dyno. With Dave Anderson, proprietor of Autobahn Designs, helping, it didn't take long. There were some non-obvious details, however, which is why we recommend having a Bentley workshop manual for your car handy before performing almost any task.

Roughly, here are the steps: Remove the front bumper, right hand (passenger) side headlight, remove the stock intercooler and install the ABD intercooler. Tighten the hose clamps only after all the plumbing is in place, and be sure to double-check each one. Install the bumper cover, check to see if trimming is necessary and reinstall the remaining factory parts. More photos of this procedure are available at www.europeancarweb.com.

Testing
Before beginning our test, we filled the GTI 337's tank with 91-octane Chevron gas. Whether it's urban legend or truth, there is a consensus in Southern California's performance community that Chevron gasoline consistently sucks less than some others.

We plugged in Ross-Tech's VAG-COM (see "Select Gear," 12/02) to monitor coolant and intake air temperatures and drove around, noting readings under various conditions. VAG-COM displays the ECU temperature readings; Germans use SI units, so all temperatures are in degrees Celsius.

At a steady 70-mph cruise, we saw the coolant at 93*C, the intake at 46*C. Idling at rest, intake temperature was near 57*C and dropped to 46*C when the throttle was fully opened. This information provided context for testing with the Primedia Tech Center Dynojet 248. Idling on the dyno with the dyno fan blowing at the front of the car, coolant temperature was 94*C and the intake was 61*C. We can't replicate 70-mph airspeed over the whole front of the car.

Our dyno procedure for 1.8t's includes spraying the intercooler with water from a hand squirt bottle. It's a bit of a cheat, but it's the only way we've found to achieve repeatable results. The resulting intake air temperatures are within the range seen in on-road testing. Testing is repeated until the measured power and torque figures stabilize and repeat.

Results
Temperatures and measured power and torque can be found in accompanying charts. With the Autobahn Designs intercooler installed, intake air temperature was 5*C cooler at the beginning of the pulls and 10*C cooler at the end of pulls. The intake air temperature increase was reduced from 15* to 10*C.

Observed peak-to-peak output gains were 5 hp and 1 lb-ft of torque. These figures are slightly misleading due to the typically rough nature of 1.8t torque curves. For the same reason, the slight change in engine speed at which the peaks occurred is not significant. More telling is the fact that there was an average gain of 2.8 lb-ft between 3000 and 6700 rpm. While not amazing, these gains are real and significant, and are likely to become larger as other components on the engine are modified.

Conclusion
Autobahn Designs' Golf/Jetta 1.8T intercooler is easy to install and requires no cutting of metal components, or any part of the unibody. On an otherwise stock, 180-bhp factory-rated engine, it provided a real performance improvement throughout the useful engine speed range.

Autobahn Designs
(909) 351-9566
www.abdracing.com

Ross-Tech
(215) 361-8942
www.ross-tech.com