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Old 05-13-2019, 07:22 PM   #1 (permalink)
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How to hypermile v8 with mds?

Hi guys,
does anyone tried hypermiling a v8 mds build in Rams and Chrysler 300s?
Driving my Ram I'm always asking myself if I should accelerate gently do be in 4 cylinder mode, accelerate fast to 20 mph (because thats the point where it begins) to get fast in 4 cylinder mode and then accelerate gently or should i just accelerate fast to my wanted speed (2000 or 3000 u/min?)?

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Old 05-13-2019, 09:49 PM   #2 (permalink)
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Personally I’d just go gently all around... what speeds are you accelerating to?
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Old 05-13-2019, 10:39 PM   #3 (permalink)
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The Honda Insight is a vastly different beast, but I have found accelerating "rapidly" to 15-20 MPH, and then slowly going through the gears up to optimal speed was best for fuel economy.

In my Civic I didn't have the best instrumentation, but it was definitely possible to accelerate too slow in the Civic, as well as too fast. Moderate acceleration seemed to be best. Same was true for the Sienna my family used to have.

The 2nd gen Prius seems to return best fuel economy somewhere between slow and moderate acceleration.

Looking at what I did with those cars, the most fuel efficient acceleration was keeping the car at best BSFC - in the Insight's case, ~2K RPMs at 70%-80% load. The other cars' best BSFC was at higher RPMs (I'm not sure where) so that was where it accelerated most efficiently.

I don't think I'm explaining this very well, probably because I don't fully understand it myself. To my knowledge BSFC is a chart that shows you at what RPMs your engine is running most efficiently at, and then if you accelerate within that range, your acceleration will be more fuel efficient.

You could try testing various accelerations and measuring their fuel economy to compare, although I'm not sure how accurate that would be.
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Old 05-14-2019, 11:03 AM   #4 (permalink)
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For most engines, ideal bsfc comes in below peak torque. Generally 1-400 rpm below the peak torque number.

The idea is to accelerate when the engine is operating in its ideal bsfc rpm range and while at moderate throttle opening to reduce pumping losses.

Beyond that, slow down the cruising speed to keep in 4cyl mode.


Last edited by ksa8907; 05-14-2019 at 11:09 AM..
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