
Weakest Links
Our previous journey to Buttonwillow with the Fiesta ST in its first stage brought a significant improvement in lap times, two full seconds quicker than the car could pull off in factory trim. The additional power, shorter shifts and grippier brake pads worked together to benefit the speeding up and slowing down, however, there was more to be desired through the corners. Yes, the Fiesta ST holds a strong reputation for how it darts into the turns, but there was still room for improvement. When it came to power, the little hatchback came alive in its midrange RPMs in the first stage. This helped greatly in most of the medium-to-low speed corners, but not enough on the long straightaways or really tight corners. With the search for more power in mind, we called up mountune USA and Bill Knose of Delicious Tuning to help us on our way.(1) and (2) Mountune’s Sport CAT Down Pipe combined with its High Flow Cat Back Exhaust sheds weight while freeing up available power. (3) The mountune Intercooler Upgrade features a seven-row extruded tube and fin core design.
Respiration Evaluation
The first stage utilized a mountune Induction Upgrade Kit and ECU recalibration to raise the power from 183whp to 193whp and the torque from 211lb-ft to 254lb-ft. For stage two, we installed a mountune Intercooler Upgrade, built with a seven-row extruded tube and fin core to increase the heat-fransfer efficiency of the air-to-air intercooler system. On the other side of the engine, we swapped out the factory exhaust for a mountune High Flow Cat Back Exhaust and Sport CAT Down Pipe. Mountune designed the down pipe to reduce exhaust back pressure at the turbocharger to allow for faster response and in turn, more power. The five-inch diameter catalyst sits between the three-inch tubing that mates to the turbocharger and exhaust. The cat back exhaust system delivers the spent gasses through its 2.5-inch stainless-steel tubing, through the Helmholtz chamber design rear silencer and out the 3.25-inch polished stainless-steel tips.With the pieces in place, Bill Knose of Delicious Tuning stepped in to help extract the full power potential of the stage two power upgrades via Cobb Accessport. It was no surprise that the power figures went up, however it wasn’t in the way that we expected. After the Fiesta ST took to the new ECU mapping, it wrung out 204whp and a whopping 296lb-ft torque. This demonstrated a 6-percent increase in wheel horsepower and a 39-percent increase in torque.
Stage 1 (Blue)- 193.54 WHP @ 5,350 RPM 254.37 lb-ft @ 2,800 RPM
Stage 2 (Red)- 204.20WHP @ 5,250 RPM 295.96 lb-ft @ 2,700 RPM
Stage One vs Stage Two
Stage One | Stage Two | |
Curb Weight | 2,560 lbs | 2,560 lbs |
Horsepower | 193 whp | 204 whp |
Torque | 254 lb-ft | 296 lb-ft |
Top Track Speed | 106.3 MPH | 106.9 MPH |
Highest Lateral Acceleration | 1.14 g | 1.16 g |
Best Lap Time | 2’12.497″ | 2’11.716″ |
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Around the Bends


Gain Some and Lose Some
Making use of lessons learned from the previous stage tests and our day of tire pressure tuning (issue #160), we set the tire pressures for the track conditions and set out to lay down some laps. The first few laps on track revealed a very different car from what we tested before. That does not necessarily mean that the car felt better, nor did it feel worse, the handling characteristics of it simply changed and called for a different style of driving.Keeping track of tire pressures, temperatures and wear patterns can tell you nearly everything you need to know about the effectiveness of your car’s chassis and suspension setup.
Both subjective and objective notes were recorded before, after and during each track session. This information combined with the raw data acquired from the vehicle and track gives great insight to the vehicle’s performance.
Section by Section

Debrief Session
Once acclimated to the different driving style that the stage two Fiesta ST demands, there’s no denying that the car found more speed. Utilizing mountune’s intercooler and exhaust upgrades with a retune, paired with Eibach’s springs and rear sway bar sent the car around Buttonwillow Raceway nearly a full second quicker. While the first stage saw a best time of 2’12.497”, the second stage build consistently delivered lap times in the high 2’11s with a 2’11.716” topping our list. The Fiesta ST in its second stage build still brought streetable qualities (minus the deleted passenger and back seats). The car handled dips and bumps in the road with little discomfort, and maintained a throaty exhaust note without pushing any limits of comfortable volumes. Taking notes on the car’s strengths and weaknesses on track, we proceeded to build the to-do list for the next stage. We aimed to approach this stage with an even stronger focus on the car’s overall handling performance. This meant stepping up the brakes and suspension to a whole new level, while making the car as light as a feather. Stay tuned for stage three of the DSPORT Ford Fiesta ST.
Stage Two Parts List
Manufacturer | Product (Part No.) | MSRP |
Eibach | Pro-Kit Performance Springs (35143.140) | $349.10 |
Eibach |
Anti-Roll Single Sway Bar Kit – Rear (35140.312)
|
$319.00
|
mountune |
Sport CAT Down Pipe (2364-DPSC-AA)
|
$579.00
|
mountune |
High Flow Cat Back Exhaust System (2364-CBE-AB)
|
$739.00
|
mountune |
Intercooler Upgrade (2364-IC-AA)
|
$799.00
|
MSRP Total: $2,785.10 DSPORT Street Price: $2,367.34 – $2,506.59 |
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