How the build score works

The core idea: every build has a weakest link

A performance build is a chain: engine internals, fueling, induction, driveline, cooling, brakes, tires. Power flows through all of them, and the first component past its limit defines the whole car, usually expensively. Most build mistakes aren't bad parts; they're good parts in the wrong order. The analyzer's job is to find the link that breaks first and tell you before the car does.

Step 1: estimating output

Each platform carries its stock crank horsepower and aspiration. Every mod you select adds a typical percentage gain for that aspiration type; a Stage 2 tune moves a turbo car far more than a naturally aspirated one. The sum is capped by the induction ceiling: a stock turbo, supercharger or NA airflow limit only flows so much, no matter what the tune promises. The result is the current estimate, deliberately conservative, in crank hp.

Step 2: checking every subsystem

Six subsystems are checked against that estimate and your goal:

• Engine internals. The documented power stock rods, pistons and head gaskets reliably survive. A built engine raises it.
• Fueling. What stock injectors and pumps can feed. Exceeding it doesn't cut power; it leans out and breaks engines, which is why it's scored critically.
• Drivetrain. Clutch or transmission torque capacity, depending on your gearbox.
• Cooling. Sustained-power capacity weighted by usage. A track lap demands more cooling than the same power on the street.
• Brakes. A package score (base platform + pads/fluid + big brake kit + tire grip) against what your usage requires.
• Traction. How much power the chassis layout and tires can actually deploy. FWD, RWD and AWD get very different ceilings.

Step 3: risks and severity

Mismatches become risks at three severities. Critical means engine-ending or safety-ending: fueling maxed out, power beyond internals, E85 without the fuel system to feed it, no brakes at track pace. Warning means expensive or reliability-eating: clutch slip, cooling under-spec, hardware without calibration. Advisory is the stuff experienced builders fix before it matters: monitoring, harnesses, diffs, traction. On top of that, each platform carries intel: its documented failure patterns (EJ257 ringlands, S54/S65 rod bearings, the B58's HPFP wall, RB26 ceramic turbines) triggered by your power level and usage.

Step 4: the score

The build starts at 100 and loses points per risk (critical −16, warning −8, advisory −3, platform intel −5/−2). A balanced build earns a small bonus. Two hard rules keep the grade honest: any critical risk caps the score at 60, any warning caps it at 84. A build with an open critical can never grade A, no matter how much was spent on it. In the report, green means pass, amber means caution, red means fail.

Score	Grade	Meaning
90–100	S	Dialed. Every subsystem covers the power, for this usage.
78–89	A	Strong build, minor gaps to button up.
64–77	B	Solid base with a few real weak points.
50–63	C	Power ahead of support.
36–49	D	Serious weak links; fix before adding anything.
15–35	F	Critical mismatches stacked on critical mismatches.

The extra numbers

Wheel horsepower assumes ~15% driveline loss (20% AWD). Power-to-weight uses the platform's curb weight, minus 150 lb if you selected weight reduction. The ¼-mile estimate uses the Fox/Huntington power-to-weight relationships (ET ≈ 6.269 × (W/P)^⅓), which track remarkably well for street cars with traction. The report flags when your build is traction-limited and will run slower than the math.

What this tool is not

It is not a dyno, not a tuner, and not a promise. Individual engines vary with age, climate, fuel and, more than anything, tune quality. Use the score to order your spending and find the weak link; use a professional tuner with a wideband and a knock ear to find your actual numbers. When the two disagree, trust the tuner.