Engine Calc

{
  "asOf": "2026-10-11T14:38:36.873Z",
  "boreMm": 86,
  "boreStrokeRatio": 1,
  "compressionRatio": 11.01,
  "compressionRatioText": "11.01:1",
  "cylinders": 4,
  "degraded": false,
  "design": "square",
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "displacementCc": 1998.23,
  "displacementCubicInches": 121.94,
  "displacementLitres": 1.998,
  "displacementPerCylinderCc": 499.557,
  "meanPistonSpeedFtMin": 3386,
  "meanPistonSpeedMs": 17.2,
  "notChecked": [
    "the actual compression the engine makes: the static ratio ignores valve timing, boost and head-gasket thickness unless you include them in the chamber volume",
    "knock limits and fuel octane for a given ratio",
    "…2 more"
  ],
  "reasons": [
    "Displacement = pi / 4 x bore^2 x stroke x cylinders. Compression ratio = (swept volume + clearance volume) / clearance volume. Mean piston speed = 2 x stroke x RPM / 60.",
    "1 cubic inch = 16.387064 cc."
  ],
  "source": "computed locally",
  "strokeMm": 86,
  "summary": "4 cylinders of 86 x 86 mm displace 1998 cc (2 L, 122 cubic inches); square. Compression ratio 11.01:1. Mean piston speed at 6000 RPM is 17.2 m/s.",
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://automotive-calc.x402tookit.com/engine-calc?bore=86&clearanceVolumeCc=49.9&cylinders=4&rpm=6000&stroke=86&unit=mm'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://automotive-calc.x402tookit.com/engine-calc?bore=86&clearanceVolumeCc=49.9&cylinders=4&rpm=6000&stroke=86&unit=mm' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fautomotive-calc.x402tookit.com%2Fengine-calc
const res = await pay("https://automotive-calc.x402tookit.com/engine-calc?bore=86&clearanceVolumeCc=49.9&cylinders=4&rpm=6000&stroke=86&unit=mm");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://automotive-calc.x402tookit.com/engine-calc?bore=86&clearanceVolumeCc=49.9&cylinders=4&rpm=6000&stroke=86&unit=mm")
    print(res.status_code, res.text)