Recent car owner: hypermiling (p&g) for diesel?
 

Hi guys

I’m new here and I recently got a Renault Megane 110 dci.

I’m generally a light foot and my average over the last 3 months has been between 40-48 mpg.

I don’t really know all the jargon so I hope for some clarity.

My engine specs show
Max power 110 HP @ 4000rpm
260NM @ 1750rpm

Published consumption
Fuel Consumption - Economy - Combined: 3.7 L/100km
76 mpg UK / 64 mpg US
Fuel Consumption - Economy - Extra Urban: 3.4 L/100km
83 mpg UK / 69 mpg US
Fuel Consumption - Economy - City: 4.2 L/100km
67 mpg UK / 56 mpg US


If I could get to the advertised consumption, I’d be quite happy.

It’s a 6 speed auto as well.


Hope to know how best to adopt p&g (some day not useful for diesel autos?) or other hypermiling techniques.

Thanks everybody

Hi Slowth-

Someone more knowledgeable than me should respond, but my understanding was that diesel engines don't benefit as greatly from pulse and glide because they don't suffer the same pumping losses from restricting the throttle like a gasoline engine.

I see your engine is turbocharged, but I'm not sure how that changes the equation.

My recommendation would be to check tire pressure and wheel alignment, and consider running a little extra tire pressure based on what you're comfortable with.

If you're making short trips, that might explain why you aren't hitting the published numbers.

You'll generally want to be in the highest gear you can get away with (reduce engine RPM), but you don't want to lug the engine to the point the turbo doesn't provide adequate air (avoid black smoke).

Warming up the engine is the biggie with the diesels.

Thanks!

Would it help a little?

My tire pressures are already on “eco” with another 0.3 bar because I cannot pump them cold.

Anything about keeping to max torque 1750rpm I should look into?

I also read that I don’t need to warm engine on idle just go easy till temp builds up naturally.

My experience with diesel is limited to my truck, which takes about 10 miles to reach operating temperature for the engine. The transmission might take even longer.

People in cold climates use engine and transmission heaters to preheat their vehicle. My truck has a block heater that I've plugged in during the winter to assist with warmup.

That's probably among the best things you could do, but I'm not sure your climate justifies installing this, or if you even have access to electrical outlets to preheat your engine.

Max torque might be at 1750 RPM, but only if you mash the accelerator. I've heard it said that sticking to peak torque is efficient, but my guess is that reducing RPM is more important.

I run tire pressure as high as I can tolerate as far as road noise and ride harshness is concerned, which ends up being about 20% over the recommended cold tire pressure.

Well I live in Singapore. My Ambient temp is already at 90 deg F

A thread from a few years ago.....

https://ecomodder.com/forum/showthre...cle-15801.html

I'm driving a Dacia Duster with (probably) the same diesel engine and 6-speed auto as your Megane.

Published consumption, combined:
Manual: 4.4 L/100 km (53.4 mpgUS)
Auto: 4.5 L/100 km (52.2 mpgUS)

My result, lifetime: 5.7 L/100 km (41 mpgUS)

-which sucks, but I'm still #2 on Spritmonitor for this vehicle. (#1 looks weird, I think I'm actually #1.) Hilly terrain + lots of highway @ 110 km/h (68 mph) + auto trans is probably why my fuel consumption is so high.

A few weeks ago I raised tire pressure from 30 psi to 45 psi (warm) (max sidewall: 51 psi). First tank indicates a tiny improvement, perhaps 1 mpgUS. Time will tell.

Diesels (newer ones especially) give worse results when you P&G.

They run lean under light loads and any attempt to accelerate even moderately results in much richer fueling.

Put your car in ECO and and press the accelerator to the throttle stop - that give about 80% load at most speeds and I've found is the best way to accelerate in a diesel Renault.

The only trick I have to share is once you're up to speed, lift off completely (wait for 0.0l/100km on the display) and then use the accelerator gently to maintain desired speed. This forces the ECU into lean cruise mixtures faster than if driven normally.

Mine has a switch under the throttle. Pressing up to that is ok. If it clicks then car downshifts.

Does your car already get idle shut-off?