Start/stop emissions and economy

One thing I am curious about is are any repairs a result of this tech?  The manufacturer is weighing the fuel savings/CAFE penalty vs. the cost of implementation and reliability during the warranty period.  I'm weighing fuel savings vs. the cost of a repair due to this tech at any point during ownership.

To use a different example, think of cylinder deactivation GMs or Hondas which can have absolutely massive problems as a result.  In the Odyssey case, the cylinder deactivation model (ex and above) is rated at 2mpg better on the highway than the LX without it.  And of course it costs significantly more to make in the first place as well.

For the test, it's about 1/2 MPG if I remember- most of it in bag 2 of the test which is a lot of stop and go.  And if you spend significant time in traffic, the benefit can be better than that- this is one of those things that is easily seen in real life, depending on your personal drive cycle.  If you drive 30 miles to work, 90% on the freeway, it won't mean much.  But if you drive 10 miles to work with a few stop lights, you will notice it if you turn it off.

Most engine idle with really retarded spark so that it can control the idle speed really tight, add that to the vacuum that is run- idle is not efficient combustion, let alone, you are not moving.  The useful things that happen at idle is HVAC and charging the battery- and the system will not operate if the cabin is too cold or too hot or if the battery is not charged enough.

There's commonly a claim that start up uses more fuel- but that's only applicable on a "cold" engine- meaning the engine is whatever the ambient temp is and there's no fuel puddle since it evaporated off over the hours it was sitting there.  The hot restart for the test (after a 10 min rest) doesn't use much extra fuel, and the start/stop system barely uses any extra to get going.  So little that the fuel economy benefit is really easy to measure.

WRT emissions, after a little experimenting, the emissions impact is really tiny- so that the SULEV30 and SULEV20 is still possible with start stop operating after every stop on the emissions test.  The catalyst does not cool down at all for start/stop events- nothing is going through it to change the temp- but at the same time, you can go down hill for a long time with the fuel off, and it will still be hot enough when the fuel starts back up.  So....

As for the starter- we are not in the 60's anymore.  While starters to break, they don't very often.  And batteries are a lot better- I'm more concerned about the various  modules that stay on after you shut the car down than the start/stop feature.  Plus the amount of energy it takes to spin a hot engine is not very much- these are not -20F starts.

BTW, for some OEMs, the amount of pressure you put on the brakes will effect if it goes into start/stop.  So if you are on the edge of creeping the car, it won't shut off.

Personally, I dislike the feature for many of the reasons mentioned above.  But combine it with a mild hybrid setup so the A/C can stay on, car can start to move while the engine is starting, etc. and it becomes much better. 

The biggest thing that drives me insane to see is poorly programmed stop/start.  I can't count how often I see a car pull into a parking spot.  Engine stops.  Driver puts the car in park, engine restarts.  Then the driver promptly shuts it off. 

Forgot one thing- with the EV mandate, you will see a LOT of the mild hybrids where there will be an starter-alternator doing the hard work- so after a stop, it will start the engine AND provide some power to the engine as you drive away.

I get there's so much annoyance for it, but at the same time- if you encounter it a LOT in your driving, it will have the biggest benefit.  So if you spend money on some gizmo that disables it, you spend money on the gizmo and the extra fuel you burn.  

Paul_VR6 (Forum Supporter) said:

I have to say implementation is key. Our 23 odyssey is a pita and rough and the 25 vw is smoooth coming back on and off. 

This.  All of the Mercedes-Benz cars I've driven that have this "feature" have been almost undetectable.  Some (I wanna say GM?)  are downright onerous.

I agree that implementation is the key to whether or not it bothers me. I've had rental cars where it's really a pain in the ass and I've turned it off after a few minutes and others where I've truly enjoyed having the feature. No engine noise or vibration from * insert appliance vehicle here * while not moving is very nice. 

I splurged and rented a BMW 4 series last summer while in the LA area to have at least some fun in the canyons and it's start-stop feature was well done except it never lasted the entirety of a red light, let alone being stuck, stuck in LA traffic. No A/C or heat on, just the radio but I wouldn't think the battery was being drained that quickly. 

It also surprises me that this hasn't been figured out for manual transmissions. At least I haven't seen it. I feel like it should be possible to write a program that accurately detects when you're coming to a stop using brake pressure, clutch pedal travel and shifter location to make it function. Disclaimer - I know nothing about programming. I was actually hoping it would be a feature on my GR. 

AxeHealey said:

It also surprises me that this hasn't been figured out for manual transmissions. At least I haven't seen it. I feel like it should be possible to write a program that accurately detects when you're coming to a stop using brake pressure, clutch pedal travel and shifter location to make it function. Disclaimer - I know nothing about programming. I was actually hoping it would be a feature on my GR. 

It works fine with manual transmissions.  My wife's 6MT MINI has it.  IIRC, it fires when you touch the clutch to put it in 1st gear.

mfennell said:

AxeHealey said:

It also surprises me that this hasn't been figured out for manual transmissions. At least I haven't seen it. I feel like it should be possible to write a program that accurately detects when you're coming to a stop using brake pressure, clutch pedal travel and shifter location to make it function. Disclaimer - I know nothing about programming. I was actually hoping it would be a feature on my GR. 

It works fine with manual transmissions.  My wife's 6MT MINI has it.  IIRC, it fires when you touch the clutch to put it in 1st gear.

That seems logical for how to program it.  Clutch released, 0 speed (and ideally a way to sense that the trans is in neutral) and it's good to kill the engine.  Step on the clutch to get ready to move and it restarts. 

ГУЛАГ мальчик УР следующий said:

Speaking with a traffic engineer years ago, emissions were highest at idle and deceleration, so the idea was to keep cars moving. That requires either synchronization of traffic lights or more roads/lanes.

I remember being frustrated at the morons who thought it was bad to have more roads/lanes because there'd be more "traffic".

I wonder that's the benefit is not so much the individual car, but in aggregate. 

That said, I more often than not shut off the car when waiting in drive throughs or similar situations.  

Aside, not related (directly) to the start/stop. I attended a presentation for a big "master planning" type deal my local area DOT put on to show contractors what's on the 2, 5, 10 year horizon for infrastructure projects. The point was made there that it is better to add "miles" and not "lanes". So, give people options on how to get somewhere, not more lanes of the same option. So, more roads is much preferred to more lanes.

Just found it interesting.

The auto-start / stop on my 2019 6.2 high country uses the starter motor.

I turn it off every time because I'm the mechanic and I'd rather put fuel in my truck than change a flex plate.

Spearfishin said:

ГУЛАГ мальчик УР следующий said:

Speaking with a traffic engineer years ago, emissions were highest at idle and deceleration, so the idea was to keep cars moving. That requires either synchronization of traffic lights or more roads/lanes.

I remember being frustrated at the morons who thought it was bad to have more roads/lanes because there'd be more "traffic".

I wonder that's the benefit is not so much the individual car, but in aggregate. 

That said, I more often than not shut off the car when waiting in drive throughs or similar situations.  

Aside, not related (directly) to the start/stop. I attended a presentation for a big "master planning" type deal my local area DOT put on to show contractors what's on the 2, 5, 10 year horizon for infrastructure projects. The point was made there that it is better to add "miles" and not "lanes". So, give people options on how to get somewhere, not more lanes of the same option. So, more roads is much preferred to more lanes.

Just found it interesting.

Understood; the end goal was to keep cars moving not slowing down and stopping.

Lanes are expensive, and if you keep em moving, fewer lanes needed. 

The middle of town in Tucson is pretty restricted, so emphasis for years was that.  Buses stopping caused huge delays during rush hour since the #2 lane was blocked (only two lanes each way on the major thoroughfares), so they made cut outs that the buses pulled in to, traffic flowed.

But, as the city has grown the three major east west roads expanded to three lanes each way.  Lot of eminent domain needed, and some really cool early 20th century structures went by the way side. 

I think the start/stop feature is just a way to keep all those cars from idling at stoplights along everybody's twice a day 20-40 minute commute there and back.

TravisTheHuman said:

One thing that always blows me away is the start/stop doesnt "stop" when I put the engine in neutral or park.

Worse is when I pull into the driveway, the engine stops until I put it in park... and it starts again so that I can turn it off.

AxeHealey said:

It also surprises me that this hasn't been figured out for manual transmissions. At least I haven't seen it. I feel like it should be possible to write a program that accurately detects when you're coming to a stop using brake pressure, clutch pedal travel and shifter location to make it function. Disclaimer - I know nothing about programming. I was actually hoping it would be a feature on my GR. 

It works pretty great in my Jeep. I only disable it in creeping traffic. I did once catch it at a funny time and it shut the engine off at the wrong time and the truck stalled itself.

My wife's car is annoying.(RDX) It feels like the car isn't ready a lot of the time. Sometimes it feels like its watching the light color and reacts quicker than I do. More often It feels like it waits for me to touch the accelerator to start. My car (x5) is pretty consistent. If I'm not in a hurry its ready, but if I'm trying to beat oncoming traffic its a few tenths slow sometimes. I think the worst thing is if you pull forward and are waiting to turn left across traffic and it shuts off. I should just turn it off and see if it makes much difference.

In reply to alfadriver :

So the short form is that it adds approximately 0.5 MPG and minimal improvement to emissions?

ГУЛАГ мальчик УР следующий said:

I remember being frustrated at the morons who thought it was bad to have more roads/lanes because there'd be more "traffic".

Induced demand theory clearly has a lot of big holes in it, otherwise the Wangan would be too busy for street racing and the huge roads leading to empty cities in China would be too busy for the Top Gear cast to play futbol in it.

But one place where it is true is where the bottleneck for traffic is in intersections, as is commonly the case in congested cities. Adding lanes in such a place would at best to nothing or possibly make things worse.

TravisTheHuman said:

One thing that always blows me away is the start/stop doesnt "stop" when I put the engine in neutral or park.

You can say that again!!! Holy crap I don't mind the systems while driving but then I get where I'm going, stop, engine dies, shift to park, engine starts running, then I have to push the stupid start button to shut the engine off. 
 

wtb

ГУЛАГ мальчик УР следующий said:

Speaking with a traffic engineer years ago, emissions were highest at idle and deceleration,

This rattled around my head for a while.  To say that emissions were highest during deceleration is suspicious as fuel injected engines are (usually) in fuel shutoff during overrun (any time that the engine is being turned by the motion of the vehicle).  How can you have emissions without fuel?

GameboyRMH said:

ГУЛАГ мальчик УР следующий said:

I remember being frustrated at the morons who thought it was bad to have more roads/lanes because there'd be more "traffic".

Induced demand theory clearly has a lot of big holes in it, otherwise the Wangan would be too busy for street racing and the huge roads leading to empty cities in China would be too busy for the Top Gear cast to play futbol in it.

But one place where it is true is where the bottleneck for traffic is in intersections, as is commonly the case in congested cities. Adding lanes in such a place would at best to nothing or possibly make things worse.

?.  Since the major east west streets have added the additional lanes, traffic moves better. 

It's got zero to do with "induced demand" and a lot to do with having more people on roads that were over capacity.

triumph7 said:

ГУЛАГ мальчик УР следующий said:

Speaking with a traffic engineer * years * ago, emissions were highest at idle and deceleration,

This rattled around my head for a while.  To say that emissions were highest during deceleration is suspicious as fuel injected engines are (usually) in fuel shutoff during overrun (any time that the engine is being turned by the motion of the vehicle).  How can you have emissions without fuel?

Key part in bold.  I could probably use the word decades at this point. 

The solutions mentioned at the time have been implemented by the manufacturers at this point (decel fuel shut off/start stop at rest). 

What I find interesting is that alfadriver seems to indicate that the emissions effects of start/stop are minimal, I'd like a little more info there (as would duke).

I'd have thought that the effect of start/stop would be somewhat significant for the individual car, for a large aggregate effect.  It may well still be for large urban areas with lots of stop and go.

In reply to Duke :

So did you win the argument?

The first thing I noticed when my son and I were looking at cars was, holy carp that thing has a huge battery for such a small engine. Then I realized why.  I drove his Encore recently and the stop/start was barely noticeable to someone who would really notice something like that. I'm guessing most people don't even know it's happening 

rslifkin said:

mfennell said:

AxeHealey said:

It also surprises me that this hasn't been figured out for manual transmissions. At least I haven't seen it. I feel like it should be possible to write a program that accurately detects when you're coming to a stop using brake pressure, clutch pedal travel and shifter location to make it function. Disclaimer - I know nothing about programming. I was actually hoping it would be a feature on my GR. 

It works fine with manual transmissions.  My wife's 6MT MINI has it.  IIRC, it fires when you touch the clutch to put it in 1st gear.

That seems logical for how to program it.  Clutch released, 0 speed (and ideally a way to sense that the trans is in neutral) and it's good to kill the engine.  Step on the clutch to get ready to move and it restarts. 

I have it on three cars, two are manuals. I have driven stick for almost 40 years, I always come to a stop with the car in first, so I never have the start/stop work. it is great if you F-up and stall, you just push in the clutch and the car starts again. I am always amazed by the amount of people that hate on start/stop. I understand in some cars it can be a pain, but the forums/groups that I am in for the cars I have, I don't see how it bugs people so much. I have a 2019 F150. the start/stop is almost unnoticeable when driving but on the facebook groups you would assume that it made the truck un-driveable. It is fun in the Porsche with an aftermarket exhaust because the restart sounds pretty good. 

Peabody said:

In reply to Duke :

So did you win the argument?

The first thing I noticed when my son and I were looking at cars was, holy carp that thing has a huge battery for such a small engine. Then I realized why.  I drove his Encore recently and the stop/start was barely noticeable to someone who would really notice something like that. I'm guessing most people don't even know it's happening 

The other day I drove some new Merc battleship that had it, it was barely noticeable in how the car drove but my E36 M3box racer sense made me think that the car just had a major failure the first time it shut the engine off.

Sure, auto start/stop will lower emissions and fuel use in the long term.  But once you start adding in extra starter and battery costs to the equation I am going to guess and say it is a wash. And AGM batteries are NOT cheap.

That seems like another area where cars could greatly benefit from supercapacitors, the starter could crank from one that gets charged from the main battery when the engine shuts down for start/stop, and the car could then run off of an ordinary, regular-sized lead-acid battery instead of some giant AGM wallet-crusher.

EVs could use them badly for regen braking too, I've heard of EV drivers disabling regen on track(!) to keep battery temps down, because regen further heats the battery and regular braking lets the batteries cool for a second while the heat goes into the brakes instead, but the result is wasted energy and further reduced range. If they could use regen braking to charge a supercap for a few seconds instead, that energy could be released from the supercap into the powertrain on corner exit and the battery would see little to no recharge and discharge near corners, keeping heat down.