MK3 Focus ST Diesel Tuning Guide — Stage 1 & Stage 2 | Wayside Performance
The Focus ST Diesel is one of the most underrated performance cars Ford has ever built. While the petrol ST250 got all the magazine covers and forum hype, the diesel version quietly offered something the petrol couldn't match — relentless, effortless torque delivery, genuine 50mpg+ fuel economy on a cruise, and a chassis that's every bit as sharp as its petrol sibling. It was Ford's answer to the VW Golf GTD, and in many ways it bettered it.
Under the bonnet sits a 2.0-litre TDCi Duratorq diesel engine — part of the Ford/PSA DW10 engine family that also saw service in Peugeots, Citroëns, Volvos and Jaguars. In ST form it produces 185PS (182bhp) and a massive 400Nm (295ft/lb) of torque, peaking at just 2,000rpm. That wall of low-down torque gives the car an addictive in-gear punch that makes overtaking completely effortless and transforms the car on a B-road.
The ST Diesel was only ever offered in the facelift MK3 (2015–2018), with a choice of 6-speed manual or 6-speed PowerShift automatic gearbox. It shares the same ST chassis, body styling and interior with the petrol ST250 — meaning it handles identically, with the same upgraded suspension, Recaro seats, and aggressive exterior package.
It also happens to be an outstanding platform to tune. The factory calibration is very conservative — Ford deliberately softened the power delivery compared to the petrol ST, leaving a huge amount of performance on the table. A remap wakes the car up in a way that has to be experienced to be believed.
This guide covers the two stages of tune we offer, with our recommended hardware at each level. Every remap is a custom dyno calibration carried out on our in-house rolling road — never a generic flash file.
Stock PerformanceFactory baseline — 185PS / 400Nm
The stock ST Diesel makes 182bhp and 295ft/lb of torque from just 2,000rpm. Ford's claimed 0–62mph time is 8.1 seconds with a top speed of 135mph — respectable numbers, but they don't tell the full story. The real-world pace of this car is far more impressive than the figures suggest, because all that torque is available almost immediately and stays there right through the mid-range.
That said, the factory power delivery is noticeably conservative. Ford softened the calibration compared to what the hardware is capable of — the power comes on gently, the turbo response is deliberately dulled, and there are flat spots in the throttle map that blunt the car's natural urgency. It makes the car feel refined and easy to drive, but it also leaves it feeling a bit too relaxed for something wearing an ST badge. This is where a remap makes a transformative difference.
The engine itself is fundamentally robust. The DW10 platform has been in production across multiple manufacturers for decades, and the bottom end is well proven at power levels significantly above what Ford run in the ST. The variable-geometry turbocharger responds well to increased boost, and the Siemens piezo injectors give us excellent control over fuelling at higher power levels.
Stage 1 — 230–240bhpRemap only — no hardware required
Stage 1 is a remap only — no hardware changes are required. With careful recalibration of boost pressure, injection timing, rail pressure and fuelling, we take the standard 182bhp up to 230–240bhp and 360–370ft/lb of torque. That's a genuine 50–60bhp increase and over 70ft/lb of additional torque — on a car that was already torque-rich to begin with.
The difference in the way the car drives is night and day. The lazy, softened factory power delivery is completely transformed. Throttle response sharpens up immediately, the turbo spools harder and earlier, and the flat spots in the mid-range are cleaned up entirely. You get a smooth, progressive surge of power from low down that pulls relentlessly through to the redline. The in-gear acceleration becomes genuinely rapid — the sort of effortless overtaking pace that would embarrass a lot of petrol hot hatches.
This is the best bang-for-buck modification you can make to an ST Diesel. No additional hardware is needed, the DPF stays in place, and the car remains fully road legal. The standard intercooler, exhaust and fuelling system all cope perfectly at Stage 1 power levels.
Stage 2 — 240–250bhpDPF removal + intercooler upgrade required
Stage 2 pushes the standard turbo to its safe limit. With the DPF removed and an upgraded intercooler fitted, we can extract 240–250bhp and a massive 380–400ft/lb of torque from the factory turbocharger. The torque figure in particular is staggering for a four-cylinder diesel — that's the kind of mid-range shove you'd normally associate with a six-cylinder engine.
The DPF is the single biggest restriction on the exhaust side of the engine. Removing it and fitting a straight-through replacement pipe allows the variable-geometry turbo to spool faster, flow more efficiently, and sustain higher boost levels without the backpressure that the DPF creates. The result is noticeably sharper turbo response, a broader powerband, and more power at the top end where the standard DPF was choking the turbo off.
The intercooler upgrade is equally important at this level. The increased boost pressures generate more heat, and the stock intercooler can't keep up. An upgraded unit keeps intake temps down and ensures the ECU isn't constantly dialling back fuelling to protect the engine.
- DPF replacement pipe — removes the single biggest exhaust restriction
- Upgraded intercooler — essential for consistent power at higher boost
Exhaust UpgradesDPF-back options for sound and flow
One of the few criticisms of the ST Diesel is how quiet it is from the factory. While the stock exhaust is perfectly functional, it does nothing for the driving experience. A DPF-back (or cat-back on Stage 2 cars) performance exhaust transforms the soundtrack — giving the car a deeper, more purposeful note under load without being obnoxious around town. It also reduces backpressure downstream of the DPF, helping the turbo breathe a little easier.
We stock Cobra Sport rear performance exhausts for both the hatchback and estate bodystyles. These are a direct bolt-on replacement for the rear section of the exhaust and work with both the standard DPF and the R-Sport replacement pipe.
Keeping Your ST Diesel HealthyMaintenance tips for tuned 2.0 TDCi engines
The 2.0 TDCi is a proven, reliable engine — but like any turbodiesel, it benefits from proper maintenance. Here's what to stay on top of.
Timing belt: Unlike the 2.0 EcoBoost in the petrol ST, the diesel uses a timing belt — not a chain. Ford's replacement interval is around 100,000 miles, but many owners do it earlier for peace of mind. Critically, the 2.0 TDCi also has a secondary wet belt that drives the high-pressure fuel pump. This must be replaced at the same time as the main timing belt. If the wet belt fails, fuel pump debris enters the engine and the damage is catastrophic. Don't let a garage do one without the other.
Dual mass flywheel (DMF): This is the most common wear item on the ST Diesel, and one that tuned cars accelerate. The extra torque from a remap puts additional load on the DMF, and over time it wears. The classic symptom is judder when pulling away from a standstill — a vibration through the drivetrain that gets worse as the flywheel deteriorates. If you're feeling judder after a remap, the DMF is the likely culprit. Budget for it as a maintenance item rather than a surprise, especially on cars with 60,000+ miles.
DPF health (Stage 1 cars): If you're keeping the DPF in place on a Stage 1 car, make sure the car gets regular longer drives to allow the DPF to regenerate properly. Short journeys where the engine never gets fully up to temperature are the enemy of diesel particulate filters. If you're predominantly doing city driving, keep an eye on the DPF warning light and consider a forced regeneration if needed.
Oil: Use a quality fully synthetic diesel oil that meets Ford's WSS-M2C913 specification. Change intervals should be shortened to 7,500–10,000 miles on a tuned car — the increased fuelling and boost pressures mean the oil works harder. A tuned diesel generates more soot than a standard one, so fresh oil is important.
EGR valve: The exhaust gas recirculation valve can clog over time, particularly on cars doing short journeys. Symptoms include rough idle, hesitation and reduced performance. Regular motorway driving helps keep it clean. On Stage 2 cars with the DPF removed, the EGR is typically disabled in the software.
Complete the LookStyling upgrades for the MK3 Focus ST Diesel
The ST Diesel shares the same aggressive body styling as the petrol ST250 — the same front bumper, rear diffuser, roof spoiler and twin exhaust tips. But there's always room to take it further. Whether it's a splitter upgrade for a sharper front end, side skirt extensions to fill the gap between the sills and the road, or a rear spoiler extension to finish off the profile, the right touches make a tuned ST Diesel look as good as it drives.
Quick ReferenceAt-a-glance comparison of each stage
| Stage | Power | Torque | Hardware Required |
|---|---|---|---|
| Stock | 182bhp | 295ft/lb | — |
| Stage 1 | 230–240bhp | 360–370ft/lb | None (remap only) |
| Stage 1 + Intercooler | 235–245bhp | 370–385ft/lb | Intercooler upgrade |
| Stage 2 | 240–250bhp | 380–400ft/lb | DPF removal + intercooler (off-road only) |
*All figures measured on our in-house dyno. Individual results may vary based on vehicle condition and ambient temperature. Stage 2 figures require DPF removal which renders the vehicle non-road-legal.
