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Fluid Combustion Chamber

fluid_combustion_chamber

The Fluid Combustion Chamber (ccpe:fluid_combustion_chamber) attaches to an Engine Core and burns fluid fuels from other mods — each chamber contributes 8192 SU (× the fuel's stress multiplier). This is the "economy management" half of the engine system: fuel cost and temperature are tuned through the mixture, the throttle and the cooling duct shutter.

Placement

  • Right-click the chamber against any face of an engine core (the chamber attaches to the face it is placed against). A placement ghost previews the attachment.
  • Attach as many chambers as you like around the row of cores; each chamber is a separate input module.
  • Fluid and steam chambers are mutually exclusive on one engine — the two types cannot be mixed (placement is blocked; the controller arbitrates by majority).

Fuel

  • Fuel comes from datapacks: data/<namespace>/engine_fuel/*.json (hot-reloaded with /reload). No need for a specific fuel source block — the engine drains the fluid from any fluid tank in the engine's neighbourhood via its capability (zero internal fluid cache, e.g. the Quick-Fill Fluid Tank works).

Supported fuels

The mod ships the following fuels in data/ccpe/engine_fuel/*.json (you need the corresponding mod installed for its fluids to exist; see the notes):

Fuel Source mod consumption (mb/s per chamber) heat stress
Diesel Create: Diesel Generators (createdieselgenerators:diesel) 1.0 ×1.25 ×1.25
Biodiesel Create: Diesel Generators (createdieselgenerators:biodiesel) 1.0 ×1.0 ×1.0
Gasoline Create: Diesel Generators (createdieselgenerators:gasoline) 1.0 ×1.0 ×1.0
Ethanol Create: Diesel Generators (createdieselgenerators:ethanol) 1.0 ×0.5 ×0.5
Plant Oil Create: Diesel Generators (createdieselgenerators:plant_oil) 1.0 ×0.5 ×0.5
Coral Create Propulsion: Simulated (createpropulsion:coral) 1.0 ×1.25 ×1.25
Turpentine Create Propulsion: Simulated (createpropulsion:turpentine) 1.5 ×1.0 ×1.0
Levitite Blend Aeronautics (aeronautics:levitite_blend) 1.25 ×0.75 ×1.0
Chocolate
"Not the most stylish way to travel space, but certainly the tastiest."		 Create (create:chocolate) 1.25 ×1.25 ×1.0

How the multipliers matter:

  • stress scales the chamber's 8192 SU base — Diesel / Coral produce 10240 SU per chamber, while Ethanol / Plant Oil produce only 4096 SU.
  • heat scales the heat generated into the temperature model (see Temperature & Cooling Model) — Diesel / Coral run hotter, Ethanol / Plant Oil run cooler.
  • consumption is the burn rate per chamber (mb/s) — Turpentine burns 1.5 mb/s (faster consumption at the same power), all others 1.0.
  • One fuel at a time: the engine picks the first usable fuel in its source scan order — with several tanks around, the scan order decides which one burns.
  • These are only the bundled entries — the engine accepts any engine_fuel/*.json in any datapack, so other mods' fluids can be added the same way.

Output & consumption model

  • Stress capacity = running chambers × 8192 × fuel stress × throttle.
  • Fuel burn = lever × economy factor × cold penalty (see below), × fuel consumption.
  • Heat = running chambers × fuel heat × heatFactor(actual mixture) × throttle.

Mixture

setMixture(0.6..1.4) (default 1.0) only affects fuel cost and temperature — never stress or speed:

  • Single linear heat factor for both sides: heatFactor = 1 − (m−1) (i.e. 2 − m), slope −1, no convex curve, no floor clamp.
  • Lean (< 1.0) = fuel saving, but hotter. Heat factor rises linearly: m=0.8 → ×1.20.
  • Rich (> 1.0) = spend fuel to cool. Heat factor falls linearly: m=1.2 → ×0.80, m=1.4 → ×0.60 (no floor).
  • Altitude auto-rich/lean: the carburettor meters by intake air volume — thinner air at altitude naturally enriches (up to ×1.25), high pressure below sea level naturally leans (down to ×0.75) — the actual mixture is lever × autoRichness(pressure), where autoRichness = 1 + 0.45×(1−pressure) clamped to [0.75, 1.25]. Auto-rich/lean only affects heat (×0.75 heat at full auto-rich), it never costs fuel. At Y≈260 the auto-rich is ≈×1.25, so pulling the lever to ≈0.8 gives an actual mixture of ≈1.0 (altitude compensation, see economy).

Economy factor

The economy factor is an AND-gated, time-unlocked discount (0.75–1.0):

  • Requires both |T − 155°C| ≤ 10 and 0.8 ≤ actual mixture ≤ 1.1 (flat-bottom window).
  • Staying inside the window for 15 s ramps the factor in to ×0.75 (25% fuel saving); leaving it decays back in 6 s. Holding the conditions is what matters — briefly passing through earns nothing.
  • If the mixture is wrong there is no penalty, just no reward.
  • The economy factor multiplies consumption only — it never feeds back into heat.

Temperature & cooling

For the full heat-generation and dissipation equations, altitude → temperature and altitude → pressure curves, see Temperature & Cooling Model.

  • Newton cooling model: heat generated minus heat dissipated (ambient + core + cooling ducts, scaled by ram air at speed and air pressure at altitude), integrated against thermal mass.
  • Environment temperature varies by height in the overworld (sea level 20°C → clouds 0°C → world top −40°C); the Nether is a constant 155°C at all heights, the End a constant 0°C.
  • Ram air cooling: 1.0 below 10 m/s, ramping linearly to ×2.0 at 30 m/s — flying fast cools the engine for free.
  • Overcooling penalty (cold): below 100°C the fuel cost rises: cold = 1 + max(0, 100−T)/100 (≈×1.8 at 20°C). Warm up at low throttle before pushing it — this is the "small-throttle warm-up" gameplay.
  • Overheat: T ≥ 220°C hard-stops the engine (no fuel burned); it resumes at T ≤ 200°C (hysteresis). Overheating is the only thing that shuts a fluid engine down besides throttle 0 / no fuel.

Status display

Hover the chamber with goggles (full engine status):

Engine Status
Status: Stopped / Cold / Normal / Efficient / Getting hot / Overheated
Temperature: XX.X°C
Throttle: 50%
Fuel: ×0.60
Heat Factor: ×1.08
Temperature Status Colour
— (not running) Stopped (throttle 0 / no fuel / no water) grey
< ~97°C Cold (fuel penalty active) blue
97 ~ 145°C Normal green
145 ~ 165°C Efficient (economy band |T−155|≤10) cyan
165 ~ 200°C Normal green
200 ~ <220°C Getting hot gold
≥ 220°C Overheated (resumes at 200°C) red

The Fuel line shows the final fuel-cost multiplier = lever × economy × cold; Heat Factor = heatFactor(lever × altitude auto-rich).

Overheating thresholds are fixed by the engine design

155°C economy target / 100°C overcooling threshold / 220°C overheat are engine constants — they do not change with fuel or throttle (like a real engine's design point / thermostat).