35 MPG

yatdave · 07-17-2006, 04:53 PM

Yep. I'm getting 35mpg in the city. I must clarify: I'm getting 60+mpg on the highway, and 58+mpg driving around nice flat Palo Alto. But when I get home to San Francisco? 35mpg. The hills and the stop signs/lights at every corner are killing my fuel efficiency. And while I'd certainly expect it to take it hit in those conditions, I must point out I was getting 29 mpg in my del Sol, so the Insight's doing only marginally better. In this city, the hybrid system basically seems mostly ineffective.

One thing I notice that drives me nuts is that in SF, regenerative braking is pretty much useless. The car uses plenty of assist going uphill, as it should. But it regains little to no charge on the downhill. I coast downhill with my foot on the brake just light enough to show a full charge meter. But at the slightest bump in the road (a patched pothole, for example,) the regenerative braking just quits, the car surges forward, and I lose all that potential energy from the downhill. It's really pretty annoying, frankly.

I'm driving a new 2006 M/T Insight with 3300 miles on it. (Yes, a manual in SF. And I wouldn't have it any other way.

) Has anyone noticed similar behavior with the regen braking? Does anyone have any tips for increasing the mileage in the San Francisco hills? Or for any other city with a stop light at every corner? I'm really loving the Insight in all other respects...

Billy · 07-17-2006, 07:27 PM

Hi Yatdave; It's all driver technique. First suggestion: leave 5 minutes earlier, and plan on driving just a bit slower. With that in mind, you should be able to get 52+ mpg in your situation, if you try these tips:

Inflate tires to maximum pressure (44 psi or more) Speed up gently just prior to the next hill. While ascending, allow the car to slow down, and try NOT to use any assist, or very little (keep the bars showing close to fully charged) Have patience and crest the hill at a slower speed that normal. On descent, if the hill is steep and short, just keep it in 2nd gear and let compression slow you. Try to minimize the use of brakes. Look way ahead to the next stop light and get OFF the gas pedal when it turns yellow. Always look for chances to save monentum.

If descending a long hill, use the FAS technique described in other threads. (shut the engine off) So bottom line is, try not to use electric assist or brakes, and slow down a little. Practice, practice.......

Dougie · 07-17-2006, 07:35 PM

Quote:

Originally Posted by yatdave

The car uses plenty of assist going uphill, as it should.

Try staying out of assist. Converting energy back and forth between kinetic energy and chemical potential energy is wasteful...

yatdave · 07-17-2006, 08:47 PM

Thanks for the responses.

I still need to try inflating my tires more. Thanks for the reminder.

I do try accelerating before the base of the hill when possible. But during the morning commute - and most other times, for that matter - a good segment of the driving is stop-and-go on the hill. There's a line of cars stopped at the stop sign at the top of the hill and you just have to inch your way up, car length by car length. So I'm starting from a dead stop while I'm already on the hill. <sigh>

As for regaining that energy on the short steep downhills, I'll try going down in 2nd and see how much the compression slows me. With these hills, though, I'm hoping it will be enough. I'll try tonight and see.

jtmco · 07-17-2006, 10:42 PM

I suspect that the regen quitting when you hit a bump is the same kind of issue others (including me) have with the ABS being very sensitive so that the brakes "jump" when you hit a pothole. The other question is "how fast are you going when this occurs?" I believe that the regen will quit below a certain speed. That might be a good time to push in the clutch and see if you get autostop since you aren't getting any regen any more.

One more simple question - what is the climate control set on? If the a/c compressor is running (Auto, Econ with A/C, defrost) you are going to take a bit hit on mileage.

Good luck.

Jim

P.S. - I had a 70 mpg tank going (very good for me), but today it hit 99 deg. F and I had to run the a/c. Plus, it went to the shop for the state inspection and that always lowers the mileage.

Scott · 07-18-2006, 09:58 AM

I believe it is normal to lose regen while braking when hitting small bumps or uneven road surfaces. Mine does this all the time regardless of speed. I use the regen (just touching brake pedal) more to help slow down than to charge batteries. My CVT SOC has never been down more than 3 bars and is mostly either fully charged or 1 bar down. The reason you lose regen while braking over bumps, seems to be similar to why the ABS "chatters" when hitting bumps.

Rick · 07-19-2006, 02:07 AM

A quick blip on the gas will make regen come back if you hit a bump and ABS kills regen.

**IamIan** · 07-19-2006, 09:29 AM

I first must say I am sorry to hear you have so much stop and go traffic on hills... that is always a bear...

Agree with other posts about trying to reduce speed .....use less assist.... econ AC ... Don't race accelerate to the next red light and stoped cars you see ahead of you .... drive at or bellow the poste3d speed limit .... etc...etc... but in your situation getting past 50MPG in the city will be hard....

If you are not getting AutoStop regularly when doing the stop and go up the hill it woudl be very worth while to install a FAS.

I would still say though the way I look at the Insight is improvement over other cars.... While I have my doubts that the de sol was getting 29MPG in the stop and go traffic ... more likely this was the average over the whole gas tank of driving which will include the highway, and it would be lucky to get 20 MPG under the same driveing conditions the insight gets 35 in .... but even if you got 30 MPG in the de sol and only 35 in the Insight that is only 5 MPG ... but it is a 15% improvement.... that is one of the hardest things about FE improvement at the lower end.... it might take allot to get that SUV from 15 to 20 MPG and most people would not think that 5mpg improvement is much at all but it is a 30% improvement in FE... The other problem is that in stop and go traffic on hills like that you will never get to the highway cruising MPG .... The whole way Hybrids work is to undersize the ICE for better FE as you only need the power for acceleration and then it is wasted... so in Hybrids you use the Electric motor to help with acceleration.... if you never get to the point where you can take advantage of the efficiency of the smaller ICE of the Hybrid and always trying to use the hard acceleration .... you will have a hard time seeing large MPG.

Best of luck.... I would hate that driving myself.

james · 07-19-2006, 11:35 PM

The regen does quit, not at a certain speed, but at a certain engine RPM. If you're in 5th, it quits at maybe 30 mph. In 2nd with light braking, regen stays on down to 15 mph or less. So downshift on the hills, and see if that helps.

cindyao · 08-13-2006, 04:31 PM

Yatdave, you're my alterego. I googled specifically looking for anyone else with my car, driving in San Francisco, who can't exceed mpg in the mid-30s. This is so frustrating. My overall driving, since most of it is spent in SF, is mid-40s. True, for the past 4 1/2 years with my 2002 Insight I've been fighting some bad Type A driving habits. But I've been way more B than A for quite awhile now. All of the posts since yours have been from non-SF drivers so I wonder whether they have an accurate sense of the steepness of our hills and their very inevitability (which I do love, by the way). In any event, it was comforting to know I'm not alone in my Insight's mpg deficiencies. Thank you.