There’s been confusion about why Ram put big 3.6 liter V6 as a range extender on the 2025 Ramcahrger. Surely that is terribly inefficient?
No, it’s not.
Ram states following specs: 92kWh battery pack, 145 miles of electric range and 690 miles of total range, 27 gallon gas tank.
Electric range of 145 miles with 92 kWh means electricity consumption of 63 kWh/100 miles. Full tank contains 920 kWh of energy and gives 545 miles of range. That is consumption of 168 kWh/100 miles. The electric energy needed for 545 miles is 343 kWh, so the efficiency of the range extender is 37%. The generator and electronics have some energy loss so the efficiency of the V6 engine is closer to 40%. That’s crazy efficient for a gas engine.
Why is it so high? Why not use smaller engine?
Engine efficiency is highest at relatively slow speed and nearly full load. That big V6 can produce the required power at low RPM but needs to work hard. That’s very efficient. Smaller engine would need to run very fast which decreases efficiency.
In summary the V6 is very efficient at this particular application which suits it very well.
If looks like they’ll be using the 3.6 liter Pentastar engine for the generator. That engine has an amazingly flat torque curve, and starts making power at very low RPMs. If I remember right, something like 90% of its torque is available at <1400 RPMs in most vehicles it was put in (tuning varies a bit between an old Dodge Journey vs a Challenger.) Tuned for outright efficiency in a narrow RPM range, this engine should do great for this application.
I’m surprised we don’t see diesel being used instead, it wipes the floor with petrol/gasoline when used as a generator
The extra cost and weight of a diesel is wasted as the engine isn’t running most of the time. I don’t need efficiency on something I rarely use, I just need effectiveness.
Atkinson cycle thermal efficiency gets pretty close to small turbodiesel. And is much cheaper. If they were really focused on efficiency they’d mechanically link the ICE to the wheels instead of choosing a pure series system.
People focus on regen braking as the big gain for hybrids but it’s really keeping the load and rpm in the sweet spot to get over 40% thermal efficiency.
Regen is better for marketing, it’s easier to understand and lends itself to gamification. Everyone loves to see 100% energy recovery on their dash but it’s fiction as there are heat losses.
It should be trivially easy to make this an Atkinson cycle engine - just modify the cam.
Agree regen is the easier marketing pitch. It does help in cities, of course. But Camry Hybrid’s 50+ MPG highway rating doesn’t come from regen!
I read something about this 130 kW V6 having a special 190 kW mode. Maybe for uphill towing. That says variable valve timing to me, which unfortunately does increase complexity over a simple set of Atkinson cams.