Porsche's idea for a six-stroke internal combustion engine
Porsche’s patent for a six‑stroke internal combustion engine — effectively adding a second compression–power sequence to the traditional four‑stroke cycle — is sparking debate over whether such complexity meaningfully boosts efficiency or just extracts more performance. Commenters dig into how the design might reburn exhaust gases, manage knock, and borrow ideas from Miller and Atkinson cycles, while questioning long‑term reliability and cost. The conversation also widens into whether investing in advanced ICE technology still makes sense as electric vehicles gain ground, especially for sports cars where driving feel and mechanical engagement remain central.
Engine concept & combustion strategy
- Many try to infer how the six-stroke works: intake → compression → power → compression → power → exhaust, with two different TDC/BDC positions via an eccentric crank “ring.”
- Hypotheses for the second power stroke:
- First burn is very lean, leaving oxygen and partially burnt products to be recompressed and reburned.
- Extra air (and possibly fuel) is introduced through scavenging ports between the two BDCs, making the second phase like a mini uniflow 2‑stroke.
- Alternative idea: inject water into hot exhaust for an extra expansion stroke (referencing older six‑stroke concepts), though that’s not clearly what Porsche is doing.
- One commenter reads the patent and lays out the exact six strokes, confirming: first power stroke uses a longer expansion path; second compression uses a higher effective compression ratio.
- Overall goal is seen as Atkinson/Miller‑like: greater expansion than compression to extract more energy from a charge.
Efficiency vs power and Porsche’s priorities
- Repeated debate: does “efficiency” here mean more power from same fuel, or less fuel for same power?
- Several argue Porsche historically uses efficiency gains to make higher‑performance cars, not economy cars, though they do care about fuel use as a constraint (emissions, range, marketing).
- Discussion of Cayenne/Macan: disagreement over whether base models are just luxury family SUVs or fundamentally high‑performance, overengineered platforms repurposed as family cars.
Mechanical complexity and feasibility
- Multiple notes that modern ICEs already have very complex valvetrains (variable timing/lift, multiple cams).
- Porsche engines are seen as especially complex and expensive to rebuild; this six‑stroke crank mechanism adds yet more high‑precision loaded parts.
- Concern that such complexity limits down‑market adoption, but Porsche’s clientele is less sensitive.
ICE vs EV and market trajectory
- Some see investing in advanced ICE as like optimizing OS/2 in the Windows era; others argue ICE will persist for decades (long‑distance, racing, aviation, rural use).
- European data cited showing EV sales slowing, blamed mostly on price and infrastructure.
- Counter‑arguments: battery tech and charging will improve; majority of people could use EVs within a few years, though a minority will remain ICE‑dependent.
Driving experience and enthusiast culture
- Strong theme: sports‑car enthusiasts value light weight, handling, manual gearboxes, and engine sound more than 0–60 times.
- EVs praised for straight‑line performance and some Nürburgring times, but criticized for weight and “sterile” feel.
- Others claim attitude is shifting and electric or hybrid supercars are increasingly accepted, though many report ICE still dominates enthusiast meets.
Alternative engine ideas referenced
- Mentions of Miller/Budack, Atkinson, variable compression (Nissan), free‑piston generators, camless valves, rotary/vaned engines, and earlier six‑stroke concepts (Crower water‑injection, Ilmor/“5‑stroke”).