Prius engine surge problem

I'm wondering whether you had a chance to look at the traction battery state-of-charge gauge? My guess is that the SOC was quite low so the engine was trying to power the vehicle while recharging the battery, and did not have sufficient power to do both.

The US EPA mileage estimate is 46 combined mpg so your mileage is not that far off, depending upon your mix of highway/city driving, whether you routinely have lots of hills to climb, etc.

If you want to improve your realized mpg there are a few things you can do to the car, like increase tire pressure, ensure that wheel alignment is correct, make sure that there's no rear brake drag, etc. This may also require modification to the way that you drive; if you are interested there are numerous posts on the subject.

 

Having driven my car several times up to Tahoe and high elevation, my guess is also that the SOC (state of charge) of the battery was low after climbing to the summit. The car responds by trying to charge the battery and provide more power simultaneously. I have had the same thing happen under similar circumstances. Its not an elevation issue, its a battery low SOC issue.

 

The gas engine is fairly low horsepower, so the Prius uses the electric motor to boost power on uphill climbs. Once the battery is exhausted, it uses the gas engine entirely, so the engine will race and you'll have less power.

 

You aren't hurting the car (the ECU will only allow the SOC to get down to 40%) but you are seeing the effect of the car's programming to only allow the SOC to get to 40%. If you slow down, you won't drain the battery as quickly on the steeper parts.

BTW, I have also seen this behavior when I took my car in for an alignment and the tech wanted to leave the car in N while it was on the rack for about an hour. The battery cannot charge with the transaxle in N, so with the other electrical loads, the battery was drained down to the purple bars (about 40%) on the MFD. Same high revving behavior and lack of power for a few minutes after I left the alignment shop.

 

It's completely normal. The engine revs up to provide the required power after the battery is (temporarily) used up. Do not be afraid to floor the gas pedal: the engine will roar but, again, that is completely normal. The computers will not allow the engine to redline. No, you don't have to do anything special to recharge the battery, it manages itself. Yes, there are hills which a Prius cannot climb at 80 MPH :_>

The one thing you might need to do on the way down is, if you find yourself riding the brake, shift to "B". This is only to avoid the possibility of overheating the brakes, it has nothing to do with managing the battery. "B" will reduce MPGs in normal driving, so don't forget to shift back to "D" at the bottom of the hill. If there is no need to ride the brake then just stay in "D".

There's a zillion other threads on improving MPGs.

 

I've driven down from Donner Summit to the valley (right past the turnoff for Lincoln) and I didn't bother using "B" mode. I have used B mode less than a half dozen times in 26k+ miles.

The downhill parts are where you get the best mileage. Here is what I got from Echo Summit to Kyburz on US 50:

 

Others here have explained what happened and why it happened. Let me confirm that it had absolutely nothing to do with altitude, so the statement by the service manager is just smoke. I have frequently driven my Prius at altitudes higher than 9000 feet with no difficulty at all.

 

Well, it had to do with altitude to the extent that climbing a hill requires much more power than proceeding on flat terrain. But I agree that if the battery SOC is at an acceptable level, then the Prius works fine at high altitudes. I've also driven my 2004 at 9,000 ft. elevation without difficulty.

 

The change of altitude and rate-of-change of altitude are relevant, because they can affect the state of charge of the battery (because they affect how much power is required). The absolute altitude, not much.

 

Possibly not, because engines are most efficient near full load. While just ticking over a larger fraction of their output is needed to overcome frictional losses.

 

Hi All,

The Prius engine has good efficiency from about 1900 to 2300 RPM. If your battery SOC is about 60 % then an accelleration without battery will occur in a warmed-up Prius at about 2000 rpm. Going higher than that and the car will use progressively more battery to assist.

So, I tend to accellerate around 2000 RPM, which is olive drab green to orange on my add-on dashboard. This is an accelleration sometimes faster, sometimes slower than other cars.

 

Aha: if it's happening in an '09, it's not a software issue in
the earlier NHW20s. I detailed this same problem I had when heading
for Denver last summer, also on a couple of steady climbs over the
big passes. It's fine to say "the car works fine AT higher altitudes",
but we need to consider what happens in the process of getting TO
higher altitudes particularly at [attempted] rates that are going to
make it draw down the battery faster than the already-gasping-for-air
engine can replenish *while* also hauling the car uphill.
.
Not only does thinner air make the engine have to work harder and
rev higher for a given production of kilowatts, there may also be
some pressure effects on the NiMH battery cells that reduces their
amp-hour capacity somewhat.
.
None of this means there's anything wrong with the car, and this is
a good opportunity to go back and educate those dealer techs about
what anyone should *EXPECT* from the system under these conditions.
.
And anyone that simply floors it up the big hills shouldn't expect
anything like good fuel economy, in any vehicle. There's no harm in
choosing to climb more slowly, it's just a tradeoff.
.
_H*

 

Do you have a picture going up?

 

I seem to have misplaced that one.