Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Orange4boy's Rescue and Revival of a 2003 Prius

bwilson4web · 11-27-2009, 02:54 AM

Hi,

The A/C compressor is belt driven on the NHW11. Although it tries to cycle the engine off at a stop, almost any use of A/C tends to run the engine. To keep the engine on constantly, use "MAX AC." Defrost is a known mileage killer to the extent I've even experimented with chemical defoggers inside the car (not very successfully.) They tend to cause more problems with internal glass vision than they cure.

When the engine is cold, for the first 30-40 seconds, the car moves on traction battery power while letting the ICE spin at about 1,200-1,300 rpm with gentle accelerator use. You'll hear the engine rev up once this initial warm-up (lighting the catalytic converter) is done. My strategy is to gently accelerate to the highest speed during this 30-40 seconds and then gently sustain or let the speed bleed off. A brief but obscure mileage trick that works if I can pull from my work parking spot onto a 60-65 km/hr street.

During the rest of warm-up, the car goes into a rich mixture mode that is pretty fuel inefficient. For the first 3 km, I try to keep the speed as low as practical, at or under 40 km/hr, by cutting through the neighborhood and using "N" whenever possible. For example, at a stoplight, I'll shift into "N" and you'll notice the fuel burn is a little lower. This continues until the engine coolant reaches 70C.

Ken@Japan has documented the warm-up stages but the last and final, Stage-4, happens when the car has come to a stop and the engine auto-shuts down. Thereafter, the car hybrid control laws work including shutting off the engine when it can. The car really has to be stopped and I've even pulled into a parking lot to stop just to trigger the Stage-4 transition.

Any speed above 67 km/hr (42 mph), the engine has to run. But I prefer to keep a 'guard band', below 62 km/hr or above 72 km/hr, to avoid transiting this critical speed and triggering inadvertent engine operation.

Your plan to install block and pan heaters has a lot of merit. I find it saves about a minute of the initial 5 minutes of warm-up. Any block heater, warm-up interval of 30-60 minutes works great but then comes the problem of what to do when there is no power outlet. You may want to look at this temperature hack inspired by the work of Clive Burk of the UK.

If you can keep your maximum speed at or under 105 km/hr, you'll get excellent highway MPG. This chart shows what I've found to be the mph vs MPG curve (sorry, I don't have a metric version):

During warm-up when stopped at an intersection, sometimes the engine can be trigger to auto-stop by shifting into "R" and with the brakes held, briefly stab the accelerator. It doesn't always work, mostly in the first 1-2 minutes, but if you are stuck at long light and the engine coolant isn't warm enough, engine off is better than even idle in "N."

For the most part, I run my tires at maximum sidewall pressure. The ride is slightly rougher but it improves the ability to take turns at higher speeds. When you get the alignment done, this might help with doing a four-wheel alignment.

The steering has neutral stability. I found that switching to a slightly larger diameter tire seemed to marginally help. But the car can take turns at high speed like nobody's business.

When approaching home or work, I try to find a route that for the last 3-5 km I can keep the speed at or under 50 km/hr. This relatively slow speed maximizes hybrid operation and use of the traction battery. The NiMH batteries have a self-discharge characteristic so I prefer to use the charge and save the gas.

After 70,000 miles (112,000 km,) my lifetime mileage continue to run just over 52 MPG (4.52 L/100km). The car now has over 123,000 miles, nearly 200,000 km. You and your wife are in for a treat.

Bob Wilson

11-27-2009, 02:54 AM	#74 (permalink)
bwilson4web Engineering first Join Date: Mar 2009 Location: Huntsville, AL Posts: 843 17 i3-REx - '14 BMW i3-REx Last 3: 45.67 mpg (US) Blue Bob's - '19 Tesla Std Rng Plus Thanks: 94 Thanked 248 Times in 157 Posts	Hi, The A/C compressor is belt driven on the NHW11. Although it tries to cycle the engine off at a stop, almost any use of A/C tends to run the engine. To keep the engine on constantly, use "MAX AC." Defrost is a known mileage killer to the extent I've even experimented with chemical defoggers inside the car (not very successfully.) They tend to cause more problems with internal glass vision than they cure. When the engine is cold, for the first 30-40 seconds, the car moves on traction battery power while letting the ICE spin at about 1,200-1,300 rpm with gentle accelerator use. You'll hear the engine rev up once this initial warm-up (lighting the catalytic converter) is done. My strategy is to gently accelerate to the highest speed during this 30-40 seconds and then gently sustain or let the speed bleed off. A brief but obscure mileage trick that works if I can pull from my work parking spot onto a 60-65 km/hr street. During the rest of warm-up, the car goes into a rich mixture mode that is pretty fuel inefficient. For the first 3 km, I try to keep the speed as low as practical, at or under 40 km/hr, by cutting through the neighborhood and using "N" whenever possible. For example, at a stoplight, I'll shift into "N" and you'll notice the fuel burn is a little lower. This continues until the engine coolant reaches 70C. Ken@Japan has documented the warm-up stages but the last and final, Stage-4, happens when the car has come to a stop and the engine auto-shuts down. Thereafter, the car hybrid control laws work including shutting off the engine when it can. The car really has to be stopped and I've even pulled into a parking lot to stop just to trigger the Stage-4 transition. Any speed above 67 km/hr (42 mph), the engine has to run. But I prefer to keep a 'guard band', below 62 km/hr or above 72 km/hr, to avoid transiting this critical speed and triggering inadvertent engine operation. Your plan to install block and pan heaters has a lot of merit. I find it saves about a minute of the initial 5 minutes of warm-up. Any block heater, warm-up interval of 30-60 minutes works great but then comes the problem of what to do when there is no power outlet. You may want to look at this temperature hack inspired by the work of Clive Burk of the UK. If you can keep your maximum speed at or under 105 km/hr, you'll get excellent highway MPG. This chart shows what I've found to be the mph vs MPG curve (sorry, I don't have a metric version): During warm-up when stopped at an intersection, sometimes the engine can be trigger to auto-stop by shifting into "R" and with the brakes held, briefly stab the accelerator. It doesn't always work, mostly in the first 1-2 minutes, but if you are stuck at long light and the engine coolant isn't warm enough, engine off is better than even idle in "N." For the most part, I run my tires at maximum sidewall pressure. The ride is slightly rougher but it improves the ability to take turns at higher speeds. When you get the alignment done, this might help with doing a four-wheel alignment. The steering has neutral stability. I found that switching to a slightly larger diameter tire seemed to marginally help. But the car can take turns at high speed like nobody's business. When approaching home or work, I try to find a route that for the last 3-5 km I can keep the speed at or under 50 km/hr. This relatively slow speed maximizes hybrid operation and use of the traction battery. The NiMH batteries have a self-discharge characteristic so I prefer to use the charge and save the gas. After 70,000 miles (112,000 km,) my lifetime mileage continue to run just over 52 MPG (4.52 L/100km). The car now has over 123,000 miles, nearly 200,000 km. You and your wife are in for a treat. Bob Wilson __________________ 2019 Tesla Model 3 Std. Range Plus - 215 mi EV 2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade Retired engineer, Huntsville, AL Last edited by bwilson4web; 11-27-2009 at 03:39 PM..