How Much Does It Really Cost to Build a 450–550 bhp ST250 in the UK?
Written by a UK Focus ST owner planning and documenting a real-world high-power ST250 engine build. All costs reflect UK fuel availability, UK labour rates, and proven EcoBoost limits.
One of the most common questions in the UK Focus ST community is:
“How much does it actually cost to build a high-power ST250?”
The honest answer is: it depends how far you go — but there are very clear cost bands, and there are no shortcuts once you move beyond mild upgrades.
This guide breaks down the realistic UK costs of building a Ford Focus ST250 (R9DA EcoBoost) at different power levels.
Before planning any build, it’s essential to understand the ST250 EcoBoost engine weak points, as many of the costs below exist purely to fix known reliability limitations.
Understanding Power Stages (UK Reality)
| Power Level | Description |
|---|---|
| ~300 bhp | Safe fast-road setup |
| ~350–360 bhp | Upper limit of stock / hybrid turbo |
| ~420–450 bhp | Forged internals + big turbo |
| 500–550 bhp | Full build, diminishing returns |
Each step up increases cost non-linearly.
Stage 1: ~300 bhp (£1,000–£2,000)
This is where the ST250 is happiest on stock internals.
- Front-mount intercooler
- Intake and panel filter
- Uprated recirculation valve
- Conservative custom map on 99 RON
Total: £1,000–£2,000
Stage 2: ~350–360 bhp (Hybrid Turbo) (£2,500–£4,000)
This is the absolute ceiling of stock-based turbo setups.
- Hybrid turbo
- Intercooler (mandatory)
- Exhaust and intake upgrades
- HPFP internals
- Custom dyno calibration
Total: £2,500–£4,000
⚠️ Reliability margins begin to shrink here.
Stage 3: ~420–450 bhp (Forged Build) (£6,500–£9,000)
This is where costs rise sharply — but reliability can return if done properly.
Mandatory components
- Forged pistons and rods
- Performance bearings
- ARP head and main studs
- Big turbo system (G25-660 / GTX3076R)
- Upgraded fueling and cooling
This stage is covered in detail in my ST250 engine build planning guide.
Total: £6,500–£9,000
Stage 4: 500–550 bhp (£9,000–£12,000+)
This is where diminishing returns become unavoidable.
- Larger turbocharger
- Return-style fuel system
- Twin-plate clutch
- LSD and drivetrain upgrades
- Extremely conservative calibration
Total: £9,000–£12,000+
Labour vs DIY
- Engine removal/refit: £800–£1,500
- Full engine build labour: £1,000–£2,000
DIY saves money but only if you have space, tools, and patience.
Hidden Costs People Forget
- Gaskets, seals, fluids
- Broken fasteners
- Heat shielding
- Multiple mapping sessions
- Insurance changes
Expect an extra £500–£1,000 in real builds.
Planning Beats Power Chasing
Most expensive ST250 builds fail due to poor planning, not excessive power.
If your engine already needs rebuilding, doing it properly once is always cheaper than fixing it twice.
Related Guides
- ST250 EcoBoost Engine Weak Points (UK)
- ST250 Turbo Upgrade Guide (UK)
- Ford Focus ST250 Engine Build (UK)
Written by a UK Focus ST owner documenting real-world EcoBoost build costs.