Auto start/stop, do you leave it on or disable it?

I have had a message pop up on the small display saying the engine stop is disabled because of "battery charging". That was in -20 (-5F) weather. I think it's only the one 12v Battery on the non-hybrid.

 

That actually sounds fairly useful and user friendly. Around here there are some horrible intersections with absurd wait times if you catch the cycle wrong. That would be a good time to shut 'er down.

 

Somebody in the 2.5 gen side of the forum did an mpg test while idling with information from the CAN bus. The fuel usage was significant.

 

And I guess this stop/start system is another reason they have an electric circulator for turbo cooling. Otherwise these hot stops would coke the oil in there.

 

so about 2.3 mpg in city driving with small displacement in line 4 cylinder.

although surprising result it isn’t meaningful unless you drove everyday in stop and go traffic and gas was $5/ gallon.

the inline engine configuration is known to be mechanically more efficient so the proportional argument wouldn’t hold for a v8 engine ( with additional mechanical design aspects that would make starting fuel consumption larger).

lastly bearing design doesn’t assume a stop start cycle that is 500% higher frequency.

 

I believe this is disabled when your running AC.

 

connecting rod, main bearings, cam bearings are designed to support the loads placed on them from weight and combustion cycles and rotor dynamic forces.

This requires an assumption of oil flow being constant ( or at least proportional) to engine rpm.

when engine is off there is no hydrodynamic oil film supporting the different bearings.

when cranking the engine into a full start there is a brief period where oil hasn’t reached its full hydrodynamic film thickness at all the bearing surfaces. This means the bearing surfaces are relying on the shear strength of the fluid film between them for anti friction function.

this is a weak film relative to the hydrodynamic film. Slight incidental contact between the rotor and the bearing occurs. Over time this will degrade the bearing. Throw in thermal issues from shutting off the oil flow and your bearing life will degrade faster.

 

My neighbor who we refer to as "Princess" drives her children 100 yards from there house to the corner bus stop. Virtually every day Hot-Cold-Rain-Snow. I walked everyday to Grade school a mile from home.

I find the feature annoying and disable it by activating applicable button. Problem solved.

 

Let's do the math! I drive in town 3 - 4 times a week. If start/stop activates on those trips, I'm probably saving maybe a 1/10 of a gallon of gas a week. Take that times 52 weeks equals 5.2 gallons of gas. Take that times $3.15 a gallon equals a whopping $16.00 a year. Now let's examine the cost. More moving parts, increased wear and tear, and then the inevitable repair after 6 to 8 years of use. I would bet that the repair would significantly exceed the $96 to $120 I have saved in gas. But think of all that extra carbon I've prevented from going into the atmosphere. Wait... if this requires a repair, that would require me to spew more carbon into the air as I drive to my dealership, more carbon to manufacture the part and ship to the dealer, and consider the carbon emitted by the tech as he drives to work, and then exhales his breath in exasperation as he swears at the stupidity of mandating the installation of this stop/start feature in order to save us all from dinosaur like extinction. Maybe this attempt to increase mileage at all costs has some unintended consequences. I feel better now that I've had my rant.

 

I got anxiety just reading about this feature.

 

Not necessarily, it’ll shut off unless the AC load is really high. A message does pop up that says the HVAC is inhibiting the engine shutting down though. AC/heater demand will also force an early restart to maintain the desired cabin temperature. There’s a setting in the instrument panel options to extend the time the engine is off and it can get toasty in the car on a warmer day.

 

How long does it take to start? Does the oil pressure come up completely before you mash the gas pedal? When your vehicle is warming up, do you really want endless cold starts... which is where most engine wear occurs.

 

We’re assuming here that the manufacturers didn’t consider this in their engine design though. Honestly, I’m not worried about this kind of wear especially when hot.

Most vehicles won’t shut the engine off until a certain operating temperature is reached. I’ve also seen the feature disabled on really hot days over 100 F. Typically the engine restarts in less than a sec so unless you’re driving two-footed, the engine will be running by the time you’re on the accel pedal. The oil pump probably starts to provide oil pressure by the time the engine starts cranking.

 

bearing design or system design hasn’t changed in such a way to mitigate the tribological concerns.

the bearings are still plain journal style bearings. We aren’t talking about 9 pad tilt pad bearings here.

https://www.researchgate.net/public...performance_evolution_of_engine_main_bearings

just reading the abstract you can get an idea that bearing damage is related to starts and stops.

edit: victor shepherd didn’t get to a million miles driving in the city turning his truck off every 10 seconds.

 

exactly my point: there is a transient situation. The oil pump like all pumps require a certain rpm range to make their rated performance of pressure and flow. Below this rpm the flow is unstable.

and at lower flow rates the longer the flow path ( to rear bearings) means the longer period of time without adequate flow.

 

To me, the most annoying part is that it turns the engine off when you put in park and turns back on when you take your foot off the brake

 

I get what you’re saying. I agree there will be a chance for increased wear on bearing surfaces but knowing Toyota, I’m sure they considered this. I mean look at this 300k mile Prius engine: https://youtu.be/ujEJDDB7pBU
Bearings look pretty good and this engine shuts off a lot more than the Tundra’s would.

At any rate, you’re probably not going to get a million miles driving the truck in city traffic anyway.

Finally, the good thing Toyota did was allow the driver to control engine shut down by brake pressure. Stop normally and engine stays on, stop harder or press the brake a little harder after stopping, engine shuts off. No need to press the stop/start off button every time any more.

 

This feature is such garbage. The only time it turns my engine off is when I put it in park. Then it restarts right when im turning the truck off. I haven’t been able to get into the habit of turning it off. Most of my drives are really short. Anyone figure out the permanent delete yet? Lol

 

Just checked Operator manual last night on this stating override with AC. It also will not auto stop if battery charging, and vehicle has not fully cycled through warm-up to standard operating temperatures. Warm Day? Pretty cold here in PA with multiple mornings at single digits near zero. So, pretty sure it takes about 20 miles before the engine reaching standard operating temps.

Another observation especially when cold after first start the Turbo Lag is very pronounced. I am watching this and note after a few miles it goes away as vehicle starts warming up. Once reach normal temps the lag barely noticeable. My gauge is other fun car tha is Supercharged with linear throttle response - very predictable with boast.

 

Had a couple of days in the mid 70s in SoCal… usually run Auto 68 on the AC and the engine shuts off no problem. It only overrides if AC compressor demand is really high. There are a ton of criteria for stop/start. There are a bunch of criteria that disallows the engine to shut off like ambient temps, vehicle temps, battery charge, electrical loads, etc.

I also think I know what you mean about sluggish acceleration. I went up to Mammoth last week and lows were in the single digits. It seemed to me like the transmission takes awhile to heat up. Less crisp shifts and slower take off acceleration. Even if the engine was warmed up for 15~20 minutes, I felt some delay.

 

Good point on the transmission. Other car is six Manual. Wifes is Rav4 TRD Sport garaged where it's not exposed to outside cold. Tundra is parked outside

 

Had my Tundra for a few days and it has never done the auto stop/start. Not once. Probably because of a few things: 1) I don't push the brake pedal hard, 2) the heat is on 3) sometimes it gives me a notification that auto s/s is disabled due to battery charging.

I agree this is an annoying feature to think and rant about, but while actually driving the truck it is virtually nonexistant to me. I forgot it even has this feature. It's more like the truck doesn't do it unless you choose to, as opposed to the truck forcing it upon the driver.

 

Interesting video and I'll admit the bearings were surprisingly in good shape given the oil condition.

Hybrid systems though are much easier on engine bearings than the start/stop systems that use AGM battery and starter. For example hybrid systems typically don't start the engine until an oil pressure 'permissive' is reached and instead is moving car forward under battery power. This reduces the load on the bearings by not subjecting it to the power cycles of the engine. With this arrangement the boundary film lubrication (just base oil shear strength between two surfaces) is likely enough to neutralize wear.

it also seems that hybrid systems may also not cycle start/stop as much as the non-hybrid start stop systems.

 

I hate auto-off, as well as lane assist.

 

Whaaat?

Putting it in park is a great reason to have the engine shut off. So you put the brake on, engine off, shift into park, engine still off, take your foot off the brake, engine back on?

Could that be a programming/software mistake?

 

That’s not what I’ve observed. The engine in a hybrid shuts off frequently. Basically when the car is stopped or coasting the engine will shut down and the power necessary to accelerate or maintain higher speeds requires the engine to be on. So a hybrid engine will be at a minimum off just as many times as a non-hybrid engine such stop/start.
Also I’m not sure what you mean about “permissive oil pressure”. The engine still has a mechanical oil pump so no oil pressure if the engine is off. Maybe the one benefit is that hybrid engines start very quickly due to the high electric motor torque and the engine seems to provide power instantaneously after starting to drive the car forward.

 

the hybrid motor will spin the engine prior to starting.

 

Not if your putting it in park to Shut the engine off. Put it in park engine shuts off for half a second and then it kicks back on then you push the start button and it shuts off. How is that a good thing?

the only time I put my truck in park is to shut it off and it’s the only time it auto shuts off.

 

So does the starter though…