I did a search but was unable to find what I was looking for. Can you talk more about this?
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The G1 Insight is a special interest car to me, and as such I follow developments on it pretty closely. On Insight Central, people have discussed options for making it a full efficiency EV. One challenge to reusing any of the existing drivetrain components is that the factory electric motor is connected directly to the crankshaft - they're a single rotating assembly. The motor cannot spin without spinning the crank, and vice versa. To put a clutch between the crankshaft and the motor would require putting a spacer between the two, which then moves everything around in the engine bay. The engine doesn't have much room to slide (looking at it from the front) left, and if it does, your exhaust and possibly some coolant lines won't mate to it anymore. If the transmission slides right, your axles don't fit anymore. These are relatively trivial issues, but on the face of it, for the gains being sought, it appears to be more effort than it's worth, considering what other options exist.
What does appear to be mechanically simple and straightforward - the G1 Insight engine and transmission mount positions, and the bell housing, are identical between every hybrid 1.0, 1.3L and 1.5L from 2000 through to today (2025). Which is to say, you could bolt the CVT from a CR-Z to the engine, and mechanically, everything lines up. Or, you can use the 3rd gen Fit/Jazz hybrid DCT, which has an EV mode. Or, you can use the G3 Insight / 11th gen Civic Hybrid / Clarity / 4th gen Fit / Jazz hybrid "gearbox" and use that. The axles slide into the transmission, the transmission bolts to the engine, and the mounts bolt to the chassis. The challenge becomes electrical.
But then, the stock Insight motor is only 14hp. The Clarity gearbox, for comparison, has a 200hp electric motor, and a clutch that allows disengaging the engine for EV-only operation.
Similarly, the 41% thermally efficient 1.5L in a 2025 Honda bolts directly to the Insight gearbox. Or, any other gearbox in the series.
Any combination of engine and gearbox can be (mechanically) used, and all options other than the manuals and old CVTs have provision for efficient EV-only operation. The "eHEV" gearboxes (if they can be called that) appear on the surface to be the most straightforward. In these, you just have an EV drivetrain, but also with an input shaft and clutch that allows an engine to add power to the system as desired. Turn the engine on and drive clutch to the wheels 1:1 in parallel to the 200hp electric motor. Or, toggle the engine on and off whenever to spin the generator and fill the batteries.
Honda is not unique in this implementation. It's the classic "series hybrid". Nissan uses something similar in nearly all of their hybrids, but they do away with the clutch and engine connection entirely. You have what is essentially a Leaf drivetrain, but there also happens to be a combustion engine and generator somewhere in the chassis that can add to the battery.