Turbos are nothing new when it comes to vehicle performance. Using the speed of exhaust gases to spin and pressurize air going into an intake creates massive horsepower gains. But with all good things come some bad things.
Exhaust gas is hot, which means turbos get hot and the transfer through the turbo creates intake temperatures that are not optimal for performance. Air also warms as it is compressed. Cold air is denser — has more molecules — and thus creates more horsepower. To combat heat, engineers added intercoolers to cool the air before it goes into the engine.
Intercoolers are great, but they can only do so much. They work like the radiator in your vehicle. When the car is rolling down the track, air moves through the intercooler, chilling the contents inside. But what about when the car isn’t rolling down the track? Radiators have fans behind them to pull air through regardless of whether the car is moving. Most intercoolers do not have a fan. If the car isn’t moving, then air is not moving through the intercooler and thus the intercooler isn’t really helping improve intake charge temps.
As a turbo car is run hard and then shut off, like in qualifying, Time Trial and autocross, heat soak sets in and everything under the hood gets hot. When you go back out on track to go fast again and you want peak performance out of your intercooler and engine, you may find the intercooler is unable to cool the intake temps as you want. The intercooler is heat soaked. We decided to find a way to help the intercooler before a Time Trial run using the same concepts a radiator has — air flow and water.
For this performance upgrade on our Ford Fiesta ST, we didn’t purchase anything from Ford Performance, instead we went to Home Depot. We headed down the aisle where the tools are for getting your backyard ready for barbecue season. We grabbed a Hudson sprayer — normally used for herbicides — and a leaf blower. We also grabbed an extra battery for the blower, and all said and done, we were out of there for around $200.
Our hypothesis was this: To battle heat soak, we were going to spray the intercooler with cold water and then run air through the intercooler using the blower to get the intercooler as cold as possible before a qualifying or Time Trial run. To ensure the water in our sprayer was nice and cold, and not just ambient temperature, we packed lots of ice with us to the track. The ice played double duty to keep our Double Nickel Nine IPA beers cold and to keep the intercooler cold. We put ice in the sprayer bottle so the water hitting the intercooler would be as chilly as possible.
We used a data logging tool to read what the intake charge temperature was between runs so we could gauge if this whole cooling theory worked. We found that after just two autocross runs — around one minute of hard driving per lap — the intercooler was heat soaking fast. We know that if intake temps aren’t low enough, the engine computer will limit boost. We want as much boost as possible, so we needed to keep the temps low enough to get the computer to give us the green light to go fast.
Once we had data with the intercooler in stock form, we started to add water and air. Our engineer, Stephen Young said we needed to spray and spray and spray ice water, “You can’t spray it enough. Water that intercooler until it grows!” Once we had lots of ice water on the intercooler, we started using the blower to push air through it while we waited in the paddock between runs.
While standing there running the blower, our engineer monitored intake charge temps. The good news is they were falling fast. The process was working. We found that the best results showed when we alternated between ice water and air over and over again. When we stopped, heat soak from the engine would start to creep down to the intercooler and the temps would go up again. This resulted in us going through lots of ice and multiple batteries on the blower.
For a Time Trial racer, an auto crosser or a road racer getting ready to qualify, our test indicated that cooling down the intercooler with a simple sprayer, some ice and a leaf blower resulted in lower intake temperatures and thus more horsepower. And we all know more horsepower is a good thing!