Rain Sucks

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DougWantsALeaf

Well-known member
Joined
May 10, 2013
Messages
3,797
Location
Chicago North Side
So when returning from Iowa City to northern Suburbs, we were drenched. I had not yet driven in Plus in heavy rain on the highway before, certainly not for extended periods of time.

I have done this trip a couple times now, so usually, on the 225 miles, I can average low 4's at around 65 mph average (I did punch it on the way out, and at 70 for good distances ended up with 4.0 miles per kWh). Now I do stay with set set of traffic, and will go a bit slower if by myself as the wind resistance will quickly eat into my efficiency.

So in the heavy rain (even in medium rain), the impact of rain was significant. In the heaviest of rains, due to visibility, I was only going about 40 mph and was only getting about 3.5 miles per kilowatt. I had not anticipated getting such a large impact to efficiency.

We were lucky in the end, as between Dekalb and Aurora the rain lightened giving back a bit of efficiency, We were going to stop at the EA charger off of 355, but then the rain stopped and efficiency improved again.

As we moved on to 294, because weather patterns were moving quickly north and east, we had an unbelievable tail wind. I sometimes feel like driving an electric car is more like flying a plane then driving a car. I had never seen such amazing efficiency on the highway, for the 18 miles, between the end of 88 and 294 we averaged over 5.3, at 60 mph... It was truly unreal to get that type of efficiency. (maybe normal for Tesla 3's, but crazy good for us Leaf drivers when not driving downhill).

I ended up rolling up with 5 kilowatts left on Leafspy which was much less close then I thought due to the amazing tail wind. It never even hit very low battery (though very close). 1% showing on the dash for the last 6 miles. I sometimes think Nissan made a mistake by leaving so much range under 1%, as the car reviewing places tend to discount it. I think i had close to 6 kilowatts or 10 percent when dash went to 1%. In the few videos I have seen, it seems Tesla only leaves a couple miles of spare at the bottom of gauge. While I know this prevents getting stranded (in fact has anyone heard of anyone getting stranded in a plus), it gives a more negative perception of overall range.

Battery temp was about 87 F when we left and about 94 F when we pulled into the garage. Ambient temps were between 73 and 76 F. Temp was flat at around 91 for much of the trip until the battery was very low, and crept up the the last few degrees only in the last 15 minutes. I am guessing the rain with slower speeds for the mid section kept temps in check. Usually it creeps up a bit more during these 4 hour drives on a charge.

The good news is the Michelin Defenders did really well in the rain, even at 44PSI ,and traction on the roads, even when driving through mounting water was very good.

I think it was Olympia Dave that said rain is your biggest impedance to efficiency, and I would have to agree after this run. 25-30% impact to range in the downpour. When you consider even at 40-45 i was only in the mid 3's.
 
Heavy snow is the biggest impediment, but heavy rain is more likely to be encountered. Did you try "rain drafting" or letting other vehicles clear some of the standing water from your path?
 
The SV plus comes with Michelin Energy Savers 235/50 17”. It’s the same type of tire as the SR+.

One of my other gripes is that the tires are sidewall rated at 44psi, but most reviews keep them at 36psi, like the door reads. I believe the S comes with ecopia tires.
 
Typo above? Stock tire size is 215/50R17.

And I thought you said you had Michelin Defenders, not the Energy Savers.

Anyway, surprised heavy rain can make such a difference. Interesting.

Not a common occurrence here. But good to know.
 
One of my other gripes is that the tires are sidewall rated at 44psi, but most reviews keep them at 36psi, like the door reads.

It is not good practice to inflate tires to the sidewall max for everyday use - some EV situations excepted. What would make sense would be for Nissan to raise the recommended pressure to at least 38psi - preferably 40. (I inflate mine to 42 and let them get down to 38.) But hey, this is Nissan...
 
I’m impressed with the efficiency you get. With my SL+ I normally only get 3.6-3.9 at 65 mph. Tires at 38 psi, AC set to 73 deg (OAT ~90 deg) and about 500 lbs in cabin between driver, passenger, dog and baggage.

I routinely do a 125 mile trip on sea level flat land between house and cabin across Florida. When I arrive after 125 miles I have about 80-90 miles of range remaining on the GOM and LeafSpy.
 
I would be at that efficiency if I didn’t ride with a block of traffic. Even mild slipstream help can push you up a few tenths. If you drive 135 miles and have 85 left on the dash, you likely have another 20-30 in reserve which is pretty close to what I am seeing range wise.

I really want to find a weekend to try to replicate the 500km and 1000 challenges seen with next move and bjorn as I believe they can be done substantially faster if planned well and some luck with the EA chargers.
 
There seems to be some discrepancy with the Leaf reported air pressure and my digital gauges (plural). My gauges all report 40 psi on all tires. Car reports 36.

I trust my gauges. Particularly because they’re all consistent with each other as well as with my old school pen type gauge.

I’m not inclined to sweat a couple of pounds either way as long as I’m not running low. I routinely run 10% over car sticker on all of our vehicles because we have such large temp swings between daily high and low. That alone can trigger a 3# psi difference.

As always YMMV.
 
I think the TPMS reports absolute pressure while a tire gauge will report relative pressure. Or something like that :?: I remember reading about the difference and it made sense at the time but I can't remember enough details to know if this could be the cause the discrepancy you are seeing.

My digital gauge is about 1 PSI off from the TPMS readings which I find to be acceptable error. The pressure varies quite a bit with temperature as well but I'm sure you know that.
 
webeleafowners said:
Are the tires on the Eplus SL the same as the tires on the Eplus SV?

Yes, unfortunately they are Michelin Energy Saver A/S 215/50 R17 tires like my 2015 SL came with. I will be replacing them with much better tires as soon as they wear out. They actually seem to grip better in the rain than the one that came on the 2015, but they are still marginal at best. Tire pressure dash display in 2019 and reported by Leaf Spy for 2015 and 2011 have always matched my gauges (digital, dial, pencil, and outlet gauges on compressors). I generally run 44 psi cold on the OEM tires with 44 psi maximum shown on sidewalls. I tried up to 51 psi in the Continentals (sidewall maximum) I had on the 2015, but found that a bit harsh and settled on 48. I ran 46 psi in the Ecopia + tires which replaced the Continentals (215/55 R17 with 51 psi maximum pressure rating).
 
goldbrick said:
I think the TPMS reports absolute pressure while a tire gauge will report relative pressure. Or something like that :?: I remember reading about the difference and it made sense at the time but I can't remember enough details to know if this could be the cause the discrepancy you are seeing.


Highly unlikely. The difference between psia (lbs. square inch absolute) and psig (lbs square inch gauge) is 14.7 PSI or one atmosphere. The gauge ignores that 14.7 psi, which is the pressure of the atmosphere at sea level, and only looks at the difference between that and the air pressure inside the tire.
 
I honestly don't know the details and actually I don't really care that much although I am a bit curious, but this article seems to indicate that the TPMS system takes the atmospheric pressure into account.

https://www.quora.com/What-type-of-pressure-is-tire-pressure-Is-it-gauge-pressure-absolute-pressure-or-differential-pressure

This all assumes that the TPMS is using direct measurement. Apparently some systems measure the rotation speed of the tires somehow and use that to calculate the air pressure while some use a direct (absolute) pressure measurement.

https://en.wikipedia.org/wiki/Tire-pressure_monitoring_system
 
Some vehicles look at wheel rotational speed differences by using the ABS sensors to detect a tire going flat. Those vehicles will not indicate low tires due to temperature or altitude changes since all four tires will be soft, but still rotate at the same speed.

The LEAFs (at least all cars intended for USA market--2011 and 2012 made in Japan and 2013 through 2019 assembled in Smyrna) have a sensor in each wheel that directly measures pressure and periodically transmits data which includes sensor ID and pressure to a receiver in the car. I don't know if the sensors measure gauge pressure or absolute pressure (difference is 14.7 psi at sea level), but suspect they measure absolute pressure. If sensors measure absolute pressure, the car must somehow convert the readings to gauge pressure because the dash display on 2018 and 2019 (and CAN Bus data displayed by LEAF Spy on earlier models) is approximately equal to gauge pressure. If the conversion is simply to subtract 14.7 psi, then the displayed pressures will be lower than true gauge pressure at higher altitudes.
 
^^^What GerryAZ said. The tire pressure placard inside the door is in PSIG, so even if the TPMS measures absolute pressure it has to convert that to gauge, which is the difference between the ambient air and the air inside the tire, and is what a tire gauge measures. Otherwise, using a tire pressure gauge makes no sense at all, as you would have a reading varying by 14.7 PSI +- a bit depending on local air pressure.
 
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