How much gas will you save turning off a 5.7L HEMI when stopped in city driving? (e-Torque)

[MetroMPG]

The Hemi saves 1.7 oz. (50 ml) of fuel every 90 seconds during a shutdown, Ram 1500 chief engineer Mike Raymond says.

The Chrysler engineer was answering questions about the RAM 1500's new 48 volt stop/start and e-assist system, which is now available on its newest trucks.


They call it "e-Torque", and it boosts EPA ratings:


The Hemi saves 1.7 oz. (50 ml) of fuel every 90 seconds during a shutdown, Ram 1500 chief engineer Mike Raymond says.

• 2-mpg gain (EPA city rating) in the 5.7L Hemi
• 3-mpg gain for the V-6
• 2WD trucks, the e-Torque V8 is rated at 17/23 mpg city/highway, while the V-6 achieves 20/25 mpg
• 4WD trucks 17/22 mpg for the eTorque Hemi, 19/24 mpg for the eTorque Pentastar.

The eTorque system is on sale as an option on the Hemi V-8, but is standard on all Pentastar V-6-equipped trucks.

Interestingly, the V6 version is liquid cooled, while the V8 version is air-cooled.

I wonder if liquid cooling explains why the city MPG benefit is greater for the V6 version. Maybe they can run the electric motor/generator at a higher load/more frequently.

Full article: https://www.wardsauto.com/test-drive...pain-ram-gains

[hayden55]

I'm honestly impressed they only burn 0.53 gpm in a Hemi at idle. My prius burns more than that when cold (0.70 gpm) and still burns 0.25 gpm when warm and the engine is idling. Whoa...
1.8L vs 5.7L

[cRiPpLe_rOoStEr]

Originally Posted by MetroMPG

Interestingly, the V6 version is liquid cooled, while the V8 version is air-cooled.

I wonder if liquid cooling explains why the city MPG benefit is greater for the V6 version. Maybe they can run the electric motor/generator at a higher load/more frequently.

A more efficient thermal management might lead to the more effective result for the V6.

But anyway, I'd like to see what it could do to the EcoDiesel V6.

[Ecky]

Originally Posted by hayden55

I'm honestly impressed they only burn 0.53 gpm in a Hemi at idle. My prius burns more than that when cold and still burns 0.25 gpm when warm and the engine is idling. Whoa...
1.8L vs 5.7L

Pretty sure part of it is due to lower idle RPM. Want to say these trucks idle at 5-600rpm, Prius engine idles at 1000rpm. My Insight burns about 0.2 gph with its 3 cylinder, which needs to idle at 900rpm minimum to not rattle your teeth out - and without the hybrid system smoothing out it's still a very rough idle.

Twice the cylinders and marginally larger cylinders, but half the RPM, still twice the fuel consumption.

[hayden55]

Originally Posted by Ecky

Pretty sure part of it is due to lower idle RPM. Want to say these trucks idle at 5-600rpm, Prius engine idles at 1000rpm. My Insight burns about 0.2 gph with its 3 cylinder, which needs to idle at 900rpm minimum to not rattle your teeth out - and without the hybrid system smoothing out it's still a very rough idle.

Twice the cylinders and marginally larger cylinders, but half the RPM, still twice the fuel consumption.

Makes sense. I've almost forgot how smooth my mustang was at idle (around 750) compared to my Prius. On the bright side the cvt and start stop make it a smooth ride.