Here is an A to B comparison of two of the dyno runs to show a typical power and torque difference between the stock and the Garrett intercoolers. The numbers stated before are the average gains. As you can visually see here, the gains are huge and across the board, with a lot of area under the curve. With fat gains like this, the power increase is readily felt in the seat of the pants as soon as you step on the throttle. The turbo spooled faster and the car had more easily felt power everywhere.
Looking at the logged temperatures for the intercooler inlet and outlet you can see the dramatic difference between the Garrett part and the OEM intercooler. The OEM intercooler is logged in the top chart. As you can see the stock intercooler drops the charge air temp by around 200 degrees. From around 350 degrees to 150 degrees. The post intercooler temps mimic the inlet temps, going up and down with each dyno pull. Also note how high the compressor discharge temps are, a sign of a small compressor being worked really hard. In the case of this car, the intercooler is very critical for the power output and safety of the engine. Ford engineered a small fast spooling turbo to blast boost at low RPM to get the torque up and is relying on an effective intercooler, direct injection and very active engine control to keep detonation at bay.
The bottom chart is the Garrett intercooler. Note that it keeps the outlet temp at around 85 degrees or a little above ambient in our case. The temp is reduced by around 260 degrees. Most notably, look how stable the intercooler outlet temperature is. There is hardly any run to run fluctuation. We attributed this to the Garrett intercoolers much higher thermal mass. We ran the Garrett intercooler through as many as 18 back to back dyno pulls to see if we could heat soak it and cause the outlet temperatures to climb. As you can see the temps remained stable. We were amazed, this is the best performing intercooler we have tested to date!
Our conclusion is that the huge power gains that we saw were the result of a perfect storm, a really effective intercooler being run on an engine whose design and calibration depends on the use of an effective intercooler to begin with.
We were pretty impressed that reducing the charge air temperature really made the car a lot more consistent. We think that the cooler charge air temperature makes the engine less on the edge of detonation so the ECU does not need to be as active.
You can see the new Garrett front mount through the grill with the shutters removed.
Overall we were thoroughly impressed with the Garrett intercooler for the Focus ST. The fit and finish were great, the installation was fairly easy and most of all the gains in power and torque were very impressive. Besides the dyno results, you could really feel a seat of the pants improvement in power and response out of the engine. By just adding the intercooler you are truly getting something for nothing.
With the charge air temps much lower, with some creative tuning, we are confident that more power will be easily obtained on the Focus ST with Garrett’s intercooler. Perhaps low-end torque won’t improve as much because the engine is already pretty much at the detonation limit but more boost and timing can easily be applied at higher rpm which will provide a good increase in power. We feel that this intercooler is a great bang for the buck and a must have if you own one of these cars!