Subscribe now
Subscribe now and be the first to hear about new products and exciting news!
Free Fuel System Planning Tool
Fuel System Sizing Calculator
Size your fuel pump, injectors, lines and regulator correctly the first time. Enter your target power and fuel type and get precise component recommendations, before you buy a single part.
Fuel Pump Flow
An undersized fuel pump causes lean conditions under load. We calculate the exact litres-per-hour your engine needs at full power, with a safe 20% headroom built in.
Injector Sizing
Injectors running above 85% duty cycle risk inconsistent fuelling and heat damage. We size your injectors to keep duty cycle in a safe operating window at peak power.
Lines & Regulator
Fuel line diameter and regulator capacity are often overlooked. Restrictions here cause pressure drop at the rail. The root cause of many tuning headaches.
Why Fuel System Sizing Matters
Your fuel system is only as strong as its weakest link. The pump, injectors, lines and regulator must all be matched to your engine's actual fuel demand at full power — not just close enough, but correctly sized with proper safety margins. An undersized fuel pump starves the engine under load. Oversized injectors lose resolution at idle and make tuning difficult. The wrong line diameter creates restriction that drops rail pressure exactly when it matters most.
This calculator models your complete fuel system from pump to rail. Enter your target flywheel horsepower, choose your fuel type — petrol, E10 or E85 — and get precise specifications for every component. Whether you're building a 400 bhp LS3 street car or a 750 bhp supercharged LT4 track weapon, the maths is the same. BSFC determines fuel demand, injector duty cycle determines safe sizing, and flow rate determines line and pump capacity.
Typical Use Cases
- LS and LT engine swaps — sizing the fuel system to match a new crate engine's actual output
- E85 conversions — E85 requires approximately 40% more fuel flow than petrol at the same power
- Forced induction builds — supercharged and turbocharged engines need significantly larger pumps and injectors
- Upgrading from carburettor to EFI — calculating correct injector size, fuel pressure and line diameter
How to use the calculator:
01
Set Your Target
Enter your flywheel BHP target or choose an engine preset to auto-fill values.
02
Choose Your Fuel
Petrol, E10, or E85. Each requires different flow rates and injector sizes.
03
Review Results
Get exact fuel pump, injector, line and regulator specifications with safety margins.
04
Shop the Parts
Jump straight to the right products in our catalogue. No guesswork.
Size Your Fuel System
Enter your engine details below or choose a preset to get started.
Engine Setup
Enter your realistic target. Factory crate or tuned output.
43.5 PSI (3 bar) standard for most EFI
80% is safe. 85% is aggressive. Never exceed 90%.
Enter your engine details and hit Calculate
Or select a quick preset to get started instantly.
Fuel Demand Summary
Based on your target power, fuel type and safety margins.
Total Fuel Flow Required
-L/hr
Total Flow (incl. 20% safety)
-L/hr
Per Injector Flow Needed
-cc/min
Injector Duty Cycle
-%
Recommended Components
Minimum specifications for reliable operation at your target power level.
System Safety Margin
How much headroom your fuel system will have above demand.
Calculation Breakdown
Formulas Used
Fuel Flow (lb/hr)BHP x BSFC
Fuel Flow (L/hr)Flow (lb/hr) / Fuel Density (lb/L)
Injector Size (cc/min)Flow (lb/hr) / Cylinders / Max Duty x 10.5
Fuel Line ID (AN size)Based on flow rate and max velocity of 1.5 m/s
Safety Margin20% added to total pump flow requirement
Ready to Build Your Fuel System?
Browse our complete range of fuel pumps, injectors, regulators, AN fittings, lines and fuel cells. All in stock and ready to ship across the UK.