The Way of the FiST – Part 6: Dyno Baseline and Mods For Power

The Way of the FiST – Part 6: Dyno Baseline and Mods For Power

So far in our “The Way of the FiST” series, where we are taking a 2019 Ford Fiesta ST and trying to turn it into an autocross champion, we ran it in stock form at a drag strip and an autocross before we lightened the car a bit, and slapped on some sticky Yokohama tires. Then we added a few driver comforts to the interior for racing and went back to an autocross to test (taking first place in the H Street class). The little Fiesta is turning out to be a fast car around the cones, but we know we can always go faster. Our next step is to see if we can find some more horsepower and torque out of the little turbocharged 1.6-liter Ford EcoBoost engine. Time to head to the dyno.

Dyno Baseline

Here is the Mustang chassis dyno at Performance In-Frame Tuning where AJ Gracy works his magic making cars faster on a daily basis. Whether you have a front-wheel-drive car or rear-wheel-drive car will determine if you pull forward or backward onto the chassis dyno.

We had made a few interior mods and added lightweight wheels, lightweight lugs, and sticky tires, but we hadn’t done anything to the drivetrain of the Fiesta other than change the oil. Our first run on the dyno would be a legitimate baseline test in stock form. We even put the heavy stock wheels and OEM tires back on for the tests. For consistency, we ensured the front tire pressure was at 32 psi, as tire pressure can change dyno results. To make sure we were ready for our dyno day and ensure that things would go smoothly, we followed the advice from TURNology‘s Tips To Prep For The Chassis Dyno and headed to Performance In-Frame Tuning in Napa, California.

AJ Gracy, owner of Performance In-Frame Tuning, takes the time to carefully strap down the rear wheels of the Fiesta to ensure the car doesn’t jump off the dyno during a high-speed pull.

Chassis dynos measure horsepower and torque at the wheels of a vehicle. Dynos are excellent tools for determining if a modification actually improves the car’s performance. There are plenty of aftermarket companies that claim that their bolt-on parts improve the performance of a vehicle, but nobody really knows for sure until they slap the car on a dyno to prove it as a fact. That was our goal at Performance In-Frame Tuning. We wanted to get stock baseline numbers and then try some engine modifications that would be legal upgrades per the SCCA H Street Rules. Our list of mods would include installing a cat-back exhaust from FSWerks, testing three different air filters from K&N, Cobb and Green Filter, trying a colder spark plug from Denso, and adding an oil catch can from Mishimoto.

With the FiST safely strapped onto the dyno in completely stock form, it was time to get some numbers. We put the car into Fourth gear, hit “test” on the dyno, and flattened the gas pedal.

Dyno numbers are a finicky thing because every dyno is different, weather has an effect, tire pressure makes a difference, even how tight you strap the car onto the dyno can change results. For bragging rights, people always want to see the biggest number they can find so they can post a picture on Instagram (#horsepower). We were less concerned with what the initial number was, because what we wanted to do was ensure that we improved the car in some measure by modifying it. But for you “dyno nerds” out there who want all of the parameters of the test, here they are: the 2019 Ford Fiesta ST was tested on a Mustang Gladiator Dynamometer on February 19, 2020, in Napa, California, which has an elevation of 20 feet above sea level. The barometric pressure was 29.95 psi, the temperature was 63 degrees Fahrenheit, and horsepower and torque were measured in Fourth gear between 2,500 and 6,300 rpm. Tire pressure was at 32 pounds per square inch and I was wearing Fruit of the Loom underwear. Boxer briefs, not tighty whities.

The dyno needs to know what the RPM are during a test run, which is usually done via a sensor on the number one plug wire. Because the Fiesta has a coil-on-plug (COP) setup, it doesn’t have plug wires. Removing the plastic sheathing on the wires going to the number one cylinder coil, we were still able to get a signal to the dyno.

To ensure that we were getting accurate and repeatable data, we would conduct three separate tests and then average the three tests together. Our bone stock baseline tests resulted in the following average:

Stock Results (SAE): 168.6 horsepower, 200.4 lb-ft of torque

Once we had those numbers as our baseline, it was time to start modifying the car for more power. Our first step was to replace the stock Ford exhaust system with a cat-back bolt-on system from FSWerks. We chose this particular exhaust because it didn’t have a resonator (which is located near the front of the exhaust system) and that meant it would be lighter than the stock system. This was also the same exhaust that the 2019 SCCA National Champion, Philip Mitchell, used on his H Street class Fiesta ST. We pulled the car off of the dyno and headed to Napa Valley Muffler to swap out the exhaust.

Cat-Back Exhaust

This is the stock resonator which will be replaced with a smooth flowing and lightweight straight pipe from the FSWerks exhaust system.

Steve Cardwell at Napa Valley Muffler made quick work of removing our stock exhaust by using a Sawzall to cut the system in half for ease of removal over the rear axle. Once we had the exhaust off the car, we weighed the stock system. Then we weighed the FSWerks system and found that the FSWerks piping was lighter. Awesome!

Steve Cardwell gets busy with the Sawzall (left) while the lightweight FSWerks cat-back exhaust is laid out ready to bolt on.

The FSWerks Fiesta ST exhaust system bolted up with ease. Steve from Napa Valley Muffler, who works on exhausts all day everyday, said the FSWerks system was one of the best ones he had seen. The bends were in the right spots, the attachment hardware was high quality, and everything lined up correctly. We had the stock system off and the entire new FSWerks system bolted on in 30 minutes thanks to a handy lift, power tools, and years of exhaust installation experience.

With the FSWerks exhaust quickly installed, it was time to hear what she sounded like. The system has a nice, raspy sound but won’t wake your neighbors up when you head to work in the morning.

We knew the FSWerks exhaust system was lighter, and it sounded good, but did it actually make our Fiesta ST faster? Performance is our ultimate goal. We aren’t interested in just revving our aftermarket exhaust at a stop light. It was time to strap back onto the dyno at Performance In-Frame Tuning and find out the fruits of our labor (and money).

AJ Gracy rows through the gears in the Fiesta with his wireless keyboard on his lap, as he sets up the dyno for another three runs to find out if our new bolt-on exhaust was worth the effort.

With the new pipes on the FiST, we ran three dyno pulls and grabbed data from those runs to find out we picked up 5.8 horsepower!

Cat-back exhaust results (SAE): 174.4 horsepower, 200.4 lb-ft of torque

Good news, we were heading in the right direction to make our Fiesta ST a better autocross racer. We made it lighter and we gave it more horsepower — WIN-WIN. Next it was time to try some different air filters.

Air Filters

All of the modifications we were making during our dyno day with the FiST were in accordance with Sports Car Club of America (SCCA) Street Class rules. Those rules allow for an aftermarket drop-in air filter element. There are aftermarket cold air intake systems that could probably make more gains on the dyno, but they weren’t an option for us as we wanted to ensure our car remained legal for SCCA national competition. Since we couldn’t do anything more with induction than a new air filter, we decided to buy three different ones and try them all out.

We purchased drop-in air filters from K&N, Green Filter, and Cobb. Our plan was to dyno test all three filters and then use the best one for racing.

The three different filters we chose were from K&N, Green Filter, and Cobb. Each of the filters were the washable/reusable type, which means they would be the last filter you would ever need to buy for the car, and now we had three of them. Swapping out the filter was relatively simple, but did require the use of some special tools, namely a Torx screwdriver to remove the top of the airbox.

By removing five Torx screws and unplugging the mass airflow sensor wire, the top of the airbox came off and the stock paper air filter could be removed.

We slapped in the Green Filter first and made three dyno pulls, which averaged an increase of 0.4 horsepower, but no gains on torque. Next we installed the Cobb filter and made three dyno pulls, which averaged an increase of 1.1 horsepower over the Green Filter (1.5 horsepower total over the stock paper filter) and a gain of 1.5 lb-ft of torque. The next filter we put in was the K&N filter, and did three more dyno runs, which averaged an increase of 0.6 horsepower over the Cobb filter (2.1 horsepower total over the stock paper filter) and gained another 1 lb-ft of torque (for a total lb-ft gain of 2.5 over stock).

Air filter & cat-back exhaust results (SAE): 176.5 horsepower, 202.9 lb-ft of torque

Since the K&N filter tested the “fastest,” picking up 2.1 horsepower, we left that one in the airbox. Our plan is to use the Cobb filter for daily driving, putting a lot of miles on it, and then drop in the clean K&N filter at the track.

Laid out in a row of performance by the numbers from left to right: K&N wins, Cobb second, and Green Filters third. Each of the filters was better than stock and they were all within nearly one horsepower of each other. But since autocross races are won within thousandths of a second, we will be racing with the K&N.

Spark Plugs

Another powertrain modification we can make within SCCA Street Class rules is spark plugs. Taking advice from the folks at FSWerks, we ordered a set of Denso Iridium spark plugs that are one step colder than the stock Ford Motorcraft iridiums that came from the factory.

FSWerks suggested the Denso Iridium plugs should be gapped at 0.28 of an inch. We carefully gapped each plug before installation.

We waited for the engine to cool down which was a good excuse to grab some lunch before we installed the new spark plugs. After we scarfed down some fast food, we had to unplug and unbolt the four individual coils to access the spark plugs. With the new Denso spark plugs gapped and installed, it was time to start rolling on the dyno again.

Large fans at the front and rear of the car during dyno runs help replicate moving air for the drivetrain as tests are conducted, not to mention evacuate all that exhaust from the dyno cell.

We conducted three more runs and averaged those runs together, and found more good news: more power! We picked up 1.2 horsepower and 0.1 lb-ft of torque with the new plugs.

Plugs, air filter & cat-back exhaust results (SAE): 177.7 horsepower, 203.0 lb-ft of torque

Things were looking good. Everything we added to the car made it perform better and made it lighter. Our next step was to add an oil catch can, another modification that is allowed under the SCCA Street Class rules.

Oil Catch Can

We picked up a baffled oil catch can system from Mishimoto. The reason for this modification was to limit the amount of blow-by oil that was being funneled into the induction system. We want air and fuel (which is combustible) going into the cylinder, not oil. The stock system recirculates blow-by into the engine through the intake. Over time, this can cause oil deposits on the intake valves making them heavier and less efficient. Since we are building this car for racing, we want efficiency.

The baffled oil catch can system from Mishimoto for the 2014-2019 Ford Fiesta ST is a thorough kit, providing everything you need for an easy installation.

We chose the Mishimoto kit because it was built specifically for the Fiesta, taking away a lot of R&D time on our part. We simply ordered the kit and bolted it in. The hoses were the perfect length and even had O.E.M. fittings to plug into the stock components, replacing two stock hoses.

A few simple tools, a half an hour, and this Mishimoto oil catch kit was installed with ease.

Once the kit was installed, we ran the car on the dyno and didn’t see any net gain or loss results, which was to be expected. An oil catch kit isn’t something that you would think would change performance instantaneously, but we weren’t taking any chances. If the kit harmed performance, we would have removed it. Since it didn’t show any net change on the dyno, we kept it on there to help the performance of the engine over time, especially during high speed autocross runs with high RPM on slalom courses.


We used our three run averages to measure improvements along the way. One of our better single runs, once we had all of our bolt-on goodies installed, was a run with 175.3 horsepower and 207.3 lb-ft of torque.

Overall, it was a great day at the dyno (not all days at the dyno go this smoothly). We were able to bolt on easy-to-install parts and improve our 2019 Ford Fiesta ST by an average of 8.7 horsepower and 2.6 lb-ft of torque. That is a 5% increase in horsepower, which is significant in SCCA autocross Street class, where the rules for engine modifications are extremely limiting. The next thing to do was to take the car to an autocross to see if our powertrain adjustments made a difference.

After our day at the dyno, we picked up another H Street class win and finished second out of 89 in the PAX index. Autocross photo by Anthony Topalian.

At the autocross, I could feel the 5% increase in power as it was testing the adhesion of the Yokohama Advan A052 tires during acceleration. The car was fast, and we took another H Street class victory. But what was a better measuring stick for the car’s performance was how it finished in the PAX index. PAX index measures all of the cars at an autocross event, from heavily modified Z06 Corvettes to stock Fiesta STs, by adjusting the finishing time of each competitor based on an index of that car’s specific SCCA class. At the event we attended, there were 89 competitors, and the FiST, with its newfound power at the dyno, finished second overall.

That may sound like a victory, but we lost the top stop by a mere 53 thousandths of a second. Remember, second place is the first loser. The good news is we are still developing the car. We haven’t even touched the suspension or brakes yet, and there are boxes of parts currently being shipped across this great nation of ours to make the Fiesta even better. Motion Control Suspension remote reservoir dual adjustable struts are on the way, as are new alignment tools from Smart Racing Products, a CD-5 digital dash and data logger from AEM Electronics, and Carbotech sticky brake pads. Will those things make the Fiesta 53 thousandths of a second quicker? Oh, hell yes they will. Stay tuned.

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About the author

Rob Krider

Rob Krider will race absolutely anything. He is a multi-national champion racing driver and is also the author of the novel, Cadet Blues.
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