Also known as: dm-i, dmi, dm-p, dual mode
DM-i is a badge, not an engine — BYD's name for its plug-in hybrid system, where DM is Dual Mode and the -i denotes the efficiency-focused version.
And what it names is a system in which the engine mostly does not drive the wheels. Like Honda's e:HEV, a DM-i car is electric at almost all speeds with the engine acting as a generator, and a clutch connects the engine directly only at steady high speed.
So the symptom that alarms new owners is normal: engine speed that does not track road speed at all, rising and holding under acceleration, and an engine that starts and stops with no relation to the accelerator. There is no transmission searching for a ratio — there is barely a transmission.
The combustion side is a naturally aspirated Atkinson-cycle petrol four designed for thermal efficiency rather than output, and its faults are ordinary. The interesting failures are electrical: the motor, the power electronics and their coolant loop, which is separate from the engine's.
DM-p is the performance version of the same idea with more motor and a different balance; the letter is the only place the difference is written.
Cars fitted with this engine
5 generations, across 1 make. From the authored catalogue — an absent car means the catalogue has not reached it, not that the engine was never fitted.
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Posted about this engine
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Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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