TunerBench learning center
Understand the math behind the build
Worked examples, primary sources, and practical limitations—connected directly to calculators you can rerun with your own numbers.
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Research-backed guidance
Better answers for real build decisions
New practical guides added regularly · Follow new releases via RSS
Responsible modification
EPA Emissions Tampering Rules and Aftermarket Parts
Understand the federal tampering and defeat-device prohibitions, the idea of a reasonable basis, and why a “performance part” label is not compliance evidence.
Performance testing
What Changes a 0–60 Time Besides Horsepower?
Separate power-to-weight from launch traction, gearing, shifts, rollout, surface, weather, and timing method.
Vehicle technology
How Wheel, Tire, and Ride-Height Changes Can Affect ADAS
Understand why geometry changes may affect camera, radar, steering, braking, and calibration without assuming every modification has the same result.
Electrified powertrains
How an Electric Car Powertrain Works
Follow energy from charge port to battery, inverter, motor, reduction gear, wheels, and regenerative braking.
Everyday ownership
The Full-Tank Method for Accurate Gas Mileage
Calculate real-world MPG or L/100km with two repeatable full fills and understand why the first entry is only a baseline.
Vehicle identification
VIN Decoder vs. Factory Build Sheet: Which Shows the Options?
Separate standardized VIN identity from manufacturer production records, option codes, recalls, and modifications found on the physical vehicle.
Drivetrain math
How to Calculate RPM from Speed, Gear Ratio, and Tire Diameter
Use the standard gearing relationship, understand the 336 constant, and identify why real road RPM can differ from the nominal result.
Performance measurement
SAE, STD, and Uncorrected Dyno Numbers: A Fair Comparison
Understand atmospheric correction modes, reference conditions, and why converting a screenshot cannot make two test procedures equivalent.
Data literacy
Why Datalog Review Should Start with Target vs. Actual
Build a defensible log-review order around commanded targets, operating state, units, and sustained differences instead of universal thresholds.
Fuel-system fundamentals
Lambda vs. AFR When the Fuel Blend Changes
Use lambda as the fuel-independent mixture ratio, convert to fuel-specific AFR, and avoid comparing gasoline-scale AFR numbers across different fuels.
Turbocharger fundamentals
Boost Gauge PSI vs. Compressor Pressure Ratio
Convert gauge boost to absolute compressor pressure ratio and see why inlet pressure and pressure loss belong in the equation.
Fitment engineering
Tire Size Math vs. Measured Diameter: Why the Numbers Differ
Learn what a sidewall tire size can calculate, why the mounted tire may measure differently, and which number belongs in each fitment decision.
Worked examples
Latest guides
Everyday fuel tracking
How to Calculate Gas Mileage Accurately
Use the full-tank method, handle partial fills, calculate weighted MPG and L/100km, and avoid misleading averages.
Worked tire comparison
225/45R17 vs 245/40R18: Diameter, Speedometer Error, and Fitment
A worked comparison of 225/45R17 and 245/40R18 tire sizes, including diameter, sidewall, circumference, speedometer error, and the checks the numbers cannot answer.
Worked ethanol blend
How Much E85 Do You Need to Make E30?
Calculate an E30 fuel blend from the fuel already in the tank, the actual ethanol content of pump E85, and the target tank volume.
Wheel fitment geometry
Wheel Offset Explained: Calculate Poke and Inner Clearance
Understand positive wheel offset and calculate how a width and offset change moves a wheel toward the fender and suspension.
Datalog workflow
How to Read a Turbo Datalog Without Chasing One Channel
A practical workflow for comparing boost, timing, lambda, fuel pressure, trims, throttle, RPM, and temperature in a turbocharged-engine datalog.
Fuel-system planning
Injector Sizing for E85: A Worked Horsepower Example
Size port injectors from horsepower, BSFC, injector count, and duty cycle, then understand why pressure and ethanol content still matter.
Dyno comparison
SAE vs STD Dyno Correction: Why the Numbers Differ
Understand SAE, STD, and uncorrected dyno numbers, how weather normalization works, and how to make a defensible before-and-after comparison.
Power math
Why Horsepower and Torque Cross at 5,252 RPM
Derive the familiar horsepower equation from torque, rotational speed, and the horsepower unit instead of treating 5,252 as engine magic.
AWD tire planning
AWD Tire Circumference Mismatch: Why One Universal Limit Is Wrong
Calculate front-to-rear tire circumference mismatch and understand why the vehicle manufacturer—not a universal internet percentage—sets the final limit.
Compressor-map math
Turbo Pressure Ratio at Altitude: Why 20 PSI Is Not Always the Same Work
Calculate compressor pressure ratio from gauge boost and atmospheric pressure, then see why the same boost target is harder at altitude.
Vehicle identification
VIN Decoder vs Build Sheet: What Each Can Actually Tell You
Understand what NHTSA VIN data can identify, what requires a manufacturer build sheet, and why recalls and enthusiast codes are separate layers.
Garage references
Chassis and engine indexes
BMW reference
BMW chassis codes
Look up E, F, G, and U-series chassis families by generation and body style.
BMW reference
BMW engine codes
Match common BMW engine families with their layouts, induction, and applications.
Porsche reference
Porsche chassis codes
Decode familiar internal model numbers across modern Porsche generations.
Useful before searchable
Every guide begins with a real decision, shows the equation or evaluation process, and states what the result cannot prove. Articles cite primary or manufacturer sources where a formal definition or platform behavior matters.
Use these pages to understand the assumptions, then open the connected calculator to work with your own vehicle.