The RFD Fiesta ST is strapped in and ready to roll.

One of the most overlooked modifications to any performance vehicle is the ECU tune. By tuning the vehicle, signals sent from the computer are adjusted in real-time to optimize engine performance. A custom tune can enhance your car in ways you probably didn’t think. Video at the end.

I recently visited PTUNING in Manassas, Virginia to witness the wonders of custom tuning first hand on Kevin’s Fiesta ST.

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This particular Fiesta ST is a street car. It’s not a race car, but Kevin wants to get the most out of the Ecoboost 1.6 liter engine and has come to PTUNING for a little #tunedbytoan, a premier custom tuner in the DC area. Toan and PTUNING have been developing tunes for the Fiesta ST since their release. They use a Dyno Dynamics load bearing dyno that allows for simulation of all engine loads and allows for quick turn around of custom tuning adjustments.

Kevin brought his Fiesta ST in with a handful of basic modifications. The turbo was fed by a CPE Xcel air intake, with piping wrapped in heat-deflecting material. Mishimoto charge pipes and Depo Racing intercooler kept intake temperatures low. Exhaust flows through the factory downpipe and catalytic converter and exits out a FSWerks 2.5 inch catback. The ECU was tuned with COBB Tuning’s Access Port and an unnamed off the shelf tune.

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The car ran great but Kevin was expecting higher numbers. Keep in mind the Dyno Dynamics dyno typically reads lower, but the base line dyno pull was 188 WHP and 206 WTQ and was consistent.

Next up, Toan tuned the Fiesta ST for 93 octane, which would be used for one of the two maps that could be selected on the fly from inside the car using the steering wheel. The other would be an E30 tune, which is a mix of 93 octane and E85.

Toan at PTUNING, working magic on the Fiesta ST

BIG GAINS

Even on 93 octane we were shocked by the improvements made with the custom tune. The final results tune blew away the off-the-shelf tune but it’s not only about the peak numbers. Power under the curve was substantial.

We saw a measured 20 or more horsepower and torque bump in the low end, with the gap tapering off as the turbo simply ran out of steam on the top side. This means more power, sooner.

The factory turbo was maxed out however introducing E30 still has great benefits. While horsepower stayed roughly the same, the E30 fuel provided a richer air-to-fuel mixture and resulted in reduced internal temperatures. This allowed for more engine timing and even more boost.

When all was said and done, Kevin’s Fiesta ST received over two dozen custom tuning revisions. Opting to go with custom tuning via an E-Tune could achieve the same results but would take weeks, if not months. That’s something to consider when looking to get your ride back on the road.

For those interested, we found that the Fiesta ST’s factory fuel system will support about 240 whp. A larger turbo will reduce low end torque but offer more top end horsepower.

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