What we do
We build diagnostic tooling and publish technical writing for professionals who use 5-gas exhaust analyzers. Our focus is the interpretation layer: the techniques, formulas and pattern-matching logic that turn raw gas concentrations into a confirmed diagnosis.
The 4D Petrol Diagnostic Engine
The 4D engine — available at 5-gasanalyzermot.com — matches measured gas concentrations against a library of 52 known fault signatures and cross-checks each hypothesis against calculated lambda (Bretschneider), OBD fuel trims, and the Holy Grail lambda-vs-RPM graph. It was built because we kept reaching for the same reasoning every time we sat in front of an analyzer, and decided a tool should do it for us.
Who writes this site
The editorial team is a small group of MOT testers, diagnostic technicians and emissions engineers based in the UK and EU. Every article published here is drafted against live vehicles and peer-reviewed against manufacturer service information before release. We do not publish speculative content.
Editorial principles
- Primary sources first. Manufacturer service data, SAE papers, and testable hypotheses — not forum folklore.
- One claim, one test. Every diagnostic assertion is paired with a confirmation procedure a reader can run.
- No affiliate-driven recommendations. If we name a tool it's because we use it; we don't take commission to recommend parts or equipment.
- Corrections visible. When we get something wrong we edit in place and note the change.
Contact
Editorial queries, corrections, guest submissions, and commercial enquiries: 5gasdiagnostic@gmail.com. Response within 24–48 hours.