First Mile mpg

gazz · 01-03-2008, 08:09 AM

A recent post in which Bob Wilson stated that using "N" during the very initial warm up phase as beneficial to cold start mpg got me thinking. So the last two mornings I have used this method, what I can do is accelerate from a cold start to 30mph and then drop it straight into "N" and glide to the junction at the end of my road. What I noticed is that normally I get about 20mpg while driving very carefully during this period, but in "N" it gets 40-50mpg, and my first 5 mins nearly matched my summer mpg.

Out of all the things I've tried during cold driving this has made the biggest difference.

Any thoughts.

JimboK · 01-03-2008, 08:43 AM

I do the same thing, terrain allowing, until I get to S2 and can force shutoff with the EV button.

I moved a couple of months ago, and the road through my new development is ideal for this: a gradual downhill for about 1/3 mile. It's lightly traveled, so I accelerate only to about 20 MPH before putting it N. That's normally enough for momentum to carry me to the stop sign.

It's especially helpful given that I can't plug in the block heater at my new place.

gazz · 01-03-2008, 08:54 AM

Quote:

Originally Posted by JimboK

I do the same thing, terrain allowing, until I get to S2 and can force shutoff with the EV button.

I moved a couple of months ago, and the road through my new development is ideal for this: a gradual downhill for about 1/3 mile. It's lightly traveled, so I accelerate only to about 20 MPH before putting it N. That's normally enough for momentum to carry me to the stop sign.

It's especially helpful given that I can't plug in the block heater at my new place.

Yes I use a block heater to. Only need to coast a few hundred yards but seems to get you into S2 and the engine will shut off on its own.

You state you use the EV button to force a shutdown, will it not shutdown on its own once that initial stage has taken place. (ign no longer negative).

JimboK · 01-03-2008, 09:13 AM

Quote:

Originally Posted by gazz

You state you use the EV button to force a shutdown, will it not shutdown on its own once that initial stage has taken place. (ign no longer negative).

It will if the car's at idle, but not while trying to glide until S3/S4 (ICE temp 70C) is reached.

bstanier · 01-03-2008, 04:07 PM

My feeling is that using N in this way delays recharging the HV battery while the ICE is operating at low efficiency. This will have to be done later, and then the ICE may be operating more efficiently so perhaps there is an overall gain. But don't take too much notice of the first 5 minute bar. Its the long term figure that matters.

JimboK · 01-03-2008, 05:32 PM

Quote:

Originally Posted by bstanier

My feeling is that using N in this way delays recharging the HV battery while the ICE is operating at low efficiency.

There is no recharging of the battery during S1 anyway. The electric motor propels the car while the ICE's total focus is on warming itself and the catalytic converter. So running in neutral during this stage is to minimize battery discharge.

gazz · 01-04-2008, 06:21 AM

Quote:

Originally Posted by JimboK

It will if the car's at idle, but not while trying to glide until S3/S4 (ICE temp 70C) is reached.

I wounder if that is a difference in UK spec, I can glide with engine off at S2, as soon as ign goes positive about 1/2 mile normally about 40C but I think it is more time based. Over 70C I have to go over about 35mph unless it goes into S4.

JimboK · 01-04-2008, 09:54 AM

Quote:

Originally Posted by gazz

I wounder if that is a difference in UK spec,

Hmm, could be. In fact, it must be, if that's how yours behaves. Seems odd that while an S3 glide from speeds <35 MPH is prevented (same as the US version), yours allows it in S2. Another of the great engineering mysteries of the car.

gazz · 01-04-2008, 10:38 AM

Quote:

Originally Posted by JimboK

Hmm, could be. In fact, it must be, if that's how yours behaves. Seems odd that while an S3 glide from speeds <35 MPH is prevented (same as the US version), yours allows it in S2. Another of the great engineering mysteries of the car.

Must make it interesting for you in the cold, with temp down to freezing if I use my heater it can take miles to reach 70C but luckily I can still ICE off glide. One option is in fact is to use the heater to keep it below 70C but above 60C and it will ICE off at any speed. (not easy but in low speed situation can be of benefit)

JimboK · 01-04-2008, 02:37 PM

Quote:

Originally Posted by gazz

Must make it interesting for you in the cold, with temp down to freezing if I use my heater it can take miles to reach 70C but luckily I can still ICE off glide. One option is in fact is to use the heater to keep it below 70C but above 60C and it will ICE off at any speed. (not easy but in low speed situation can be of benefit)

Yep, that's why I use the EV switch pretty frequently during warmup in this cold weather. And I keep the heater off as much as I can tolerate so I get it up to full operating temp ASAP.

You Brits sure do things wacky!

01-03-2008, 08:09 AM	#1
gazz Senior Member Join Date: Mar 2007 Location: Coventry, UK Posts: 173 My Car: 2007 Prius Package: T4 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	First Mile mpg A recent post in which Bob Wilson stated that using "N" during the very initial warm up phase as beneficial to cold start mpg got me thinking. So the last two mornings I have used this method, what I can do is accelerate from a cold start to 30mph and then drop it straight into "N" and glide to the junction at the end of my road. What I noticed is that normally I get about 20mpg while driving very carefully during this period, but in "N" it gets 40-50mpg, and my first 5 mins nearly matched my summer mpg. Out of all the things I've tried during cold driving this has made the biggest difference. Any thoughts. __________________

01-03-2008, 08:43 AM	#2
JimboK One owner, low mileage Join Date: May 2006 Location: Chesterfield, VA Posts: 2,058 My Car: 2005 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 3	Re: First Mile mpg I do the same thing, terrain allowing, until I get to S2 and can force shutoff with the EV button. I moved a couple of months ago, and the road through my new development is ideal for this: a gradual downhill for about 1/3 mile. It's lightly traveled, so I accelerate only to about 20 MPH before putting it N. That's normally enough for momentum to carry me to the stop sign. It's especially helpful given that I can't plug in the block heater at my new place. Last edited by JimboK; 01-03-2008 at 08:47 AM.

01-03-2008, 04:07 PM	#5
bstanier Junior Member Join Date: Oct 2005 Posts: 7 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: First Mile mpg My feeling is that using N in this way delays recharging the HV battery while the ICE is operating at low efficiency. This will have to be done later, and then the ICE may be operating more efficiently so perhaps there is an overall gain. But don't take too much notice of the first 5 minute bar. Its the long term figure that matters.