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API · /engine-api

Engine Displacement API

healthy 4,398 Subscribers

Internal-combustion engine maths as an API, computed locally and deterministically. The displacement endpoint computes an engine's swept volume from the bore, the stroke and the number of cylinders, V = (π/4)·bore²·stroke per cylinder, in cubic centimetres, litres and cubic inches, and classifies the bore-to-stroke geometry as oversquare, square or undersquare. The compression endpoint relates the compression ratio and the clearance volume, CR = (swept + clearance)/clearance — give the clearance to get the ratio or the ratio to get the clearance — and, with a boost pressure, estimates the effective compression ratio of a forced-induction engine. The power-to-weight endpoint computes the power-to-weight ratio in horsepower per tonne, kilowatts per tonne and watts per kilogram, the weight per horsepower, and, with a displacement, the specific output in horsepower per litre. Bore and stroke are in millimetres, volumes in cc, weight in kilograms and power in horsepower or kilowatts. Everything is computed locally and deterministically, so it is instant and private. Ideal for automotive, motorsport, motorcycle and engine-builder app developers, build-spec and tuning tools, and mechanical education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is engine geometry and tuning; for EPA fuel-economy data use a fuel-economy API and for tyre sizes a tyre-calculator API.

#engine #automotive #displacement #compression-ratio #motorsport #developer-tools
api.oanor.com/engine-api
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Machine-readable spec so AI agents can integrate this API.

/api/engine-api/openapi.json
/api/engine-api/llms.txt

Discovery: GET /api/index.json lists every API.

Engine Displacement API — live data on the oanor API marketplace

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
81 ms
Server probes · 24h
Subscribers
4,398
active
Total calls
76
last 7 days
status Full status page → · 12 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 2,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • Displacement from bore, stroke and cylinder count
  • Deterministic local compute, no upstream latency
  • 2 requests/sec for prototyping
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Starter

€9.00 /month

  • 25,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • All engine-geometry endpoints (displacement, compression ratio)
  • Metric and imperial bore/stroke units
  • 25k monthly calls for small tools
  • Email support
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Pro

€24.00 /month

  • 150,000 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • Full motorsport math suite incl. compression ratio
  • Batch multi-cylinder configurations
  • 150k monthly calls for production apps
  • 20 req/sec burst headroom
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Mega

€74.00 /month

  • 764,000 calls / month
  • 60 requests / second
  • Hard cap (429 above quota, no overage)
  • Unlimited engine-geometry computations
  • High-throughput 60 req/sec for fleet/dyno tooling
  • 750k monthly calls for high-volume integrations
  • Priority support and uptime SLA
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Turbocharger and boost engineering maths as an API, computed locally and deterministically — the pressure-ratio, charge-air and airflow numbers a tuner, engine builder or motorsport engineer sizes forced induction with. The pressure-ratio endpoint gives the compressor pressure ratio = absolute manifold pressure ÷ ambient = (atmospheric + boost) ÷ atmospheric, so 10 psi at sea level is a 1.68 ratio — the x-axis of every compressor map, which climbs at altitude where ambient pressure is lower. The charge-air endpoint shows why an intercooler matters: compressing air heats it (T₂ = T₁ × (1 + (PR^0.2857 − 1)/efficiency)), and hot air is less dense, so the real gain is the charge density ratio = pressure ratio × (T₁/T_charge), not the pressure ratio alone — 10 psi at 70 % compressor efficiency makes ~93 °C and a 1.37 density ratio with no intercooler, rising toward 1.6 once an intercooler claws back the heat, and the estimated power gain tracks the density. The airflow endpoint gives the engine mass airflow ≈ displacement × (rpm/2) × volumetric efficiency × charge density, in lb/min — the y-axis of the compressor map you plot against the pressure ratio to land in the efficient island and avoid surge or choke. Everything is computed locally and deterministically, so it is instant and private. Ideal for engine-tuning and turbo-sizing tools, dyno and data-logging apps, and motorsport calculators. Pure local computation — no key, no third-party service, instant. Sizing estimates — verify on a dyno. 3 compute endpoints. For engine displacement and compression use an engine API; for shop compressed air a compressor API.

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Air-Fuel Ratio API

Air-fuel ratio and lambda maths for engine tuning as an API, computed locally and deterministically — the lambda, AFR and mixture numbers a tuner, ECU developer or motorsport engineer dials fuelling in with. The lambda endpoint turns a measured air-fuel ratio into lambda (the AFR divided by the fuel's stoichiometric AFR — 14.7 for gasoline) and the equivalence ratio φ = 1/lambda, classifying the mix as rich, stoichiometric or lean: a gasoline AFR of 13.0 is lambda 0.88, an 11.6 % rich mixture, the sort used at wide-open throttle for power and a cooler, safer burn. The afr endpoint runs it the other way — pick a target lambda and it gives the AFR the wideband should read — and because the AFR number is fuel-specific (E85's stoichiometric AFR is about 9.8, not 14.7) it always works from the right fuel, which is why pros tune in lambda when switching fuels. The mixture endpoint links the air the engine breathes to the fuel the injectors must add: give an air mass and a target lambda and it returns the fuel mass (or vice-versa), the heart of how an ECU sizes fuelling from measured airflow. Built-in stoichiometric ratios for gasoline, E10, E85, ethanol, methanol, diesel, LPG, propane, methane/CNG and hydrogen, or pass your own. Everything is computed locally and deterministically, so it is instant and private. Ideal for engine-tuning and dyno tools, ECU and standalone-management apps, motorsport and data-logging utilities. Pure local computation — no key, no third-party service, instant. 3 compute endpoints. For engine displacement and power use an engine API; for chemical reaction stoichiometry a stoichiometry API.

api.oanor.com/airfuel-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Engine Displacement API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Engine Displacement API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Engine Displacement API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Engine Displacement API cost?
Engine Displacement API has a free tier with 100 calls / month. Paid plans start at €9.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Engine Displacement API GDPR-compliant?
All requests to Engine Displacement API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/engine-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/engine-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/engine-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/engine-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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