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Start/Stop does it really save you gas?

5K views 17 replies 8 participants last post by  GioSailor 
#1 ·
Ok I'm not talking about sitting at the red light for 2min, but when you have to stop at a stop sign for few seconds (for other cars to pass) and the car shuts off, then it starts again constantly one stop sign after another, does that really helps with saving fuel, or every stop/start actually wastes more gas for those short stops?
 
#2 ·
I posted numbers from a published study here somewhere, but I can't find it. The conclusions:

1) No tested condition resulted in increased fuel use. Fuel savings were in the single digit % range for all of the conditions that they tested.
2) Battery life expectancy is an issue. Cars with start-stop have heavier, start-stop specific batteries.
3) Alternator capacity is an issue. Cars with start-stop need a heavier, higher current output battery.
4) Starter capacity is an issue. Cars with start-stop need a heavier, higher duty cycle starter.

I'm going to guess that start-stop costs at least 25 pounds of weight (15 pounds of battery, 5 pounds of alternator, 5 pounds of starter, maybe a larger refrigerant reservoir, maybe heavier starter wires). That extra weight costs some fuel economy to start and stop it, and I do not think it was factored in to the fuel economy study. The energy required to make those heavier, more complex components was also not factored in. The energy required to constantly complain about start-stop on the internet was also not factored in :wink2:

EPA says that they disable start-stop for their MPG tests, so forcing it to default to enable is a AR/Euro thing. Personally I think putting Tecnico wheels, lighter battery, alternator and starter in a Ti would save the same or more fuel for a similar cost while yielding a better to drive vehicle.
 
#3 ·
EPA says that they disable start-stop for their MPG tests, so forcing it to default to enable is a AR/Euro thing.
Start-stop is there because they get carbon credits, which translate to MPG credits under CAFE accounting.
Supposedly there is no EPA test cycle that can effectively measure benefits (maybe nothing with extended stops?)

SAE article on CAFE: http://www.sae.org/misc/pdfs/meeting_cafe_2025.pdf
C&D article: http://www.caranddriver.com/feature...e-of-the-new-fuel-economy-regulations-feature
 
#8 · (Edited)
sorry, its not 33% of the total value of the car its for every dollar over a certain amount

in 2018 a non fuel efficient car valued at say $70,000 attracts 33% for every dollar over $65094 ... that then gets added to the car price obviously

a fuel efficient car the threshold is $75596, so our Veloce comes in under that

https://www.ato.gov.au/rates/luxury-car-tax-rate-and-thresholds/

it is total bullshit,


and yep, a fuel efficient car is 7 litres /100klms and Giulia scrapes in at 6.9L/100klms
https://www.ato.gov.au/business/luxury-car-tax/in-detail/definitions/


(i would have thought a beer truck would have been classed an emergency vehicle, but oh well)
 
#10 ·
We pay by the USA gallon. The highest prices in any metro area of the USA is San Francisco, which I believe is currently at $3.29/gallon or so (it's $3.09 in Silicon Valley currently, while the lowest prices in the country are about $2.39/gallon). Prices are currently inflated because a bunch of refineries in Houston were forced off line by the hurricane. $3.29/gallon (that is for regular/87 octane) works out to $0.869/liter US.

California fuel is refined in California while the oil comes from Alaska and California. So. Cal oil is difficult to produce and poor quality (it is better for paving roads and preserving fossils than powering cars), but it effectively keeps a cap on the local cost of oil (that ~$60/BBL cap hasn't been reached in a while). There was quite the "black gold" rush when the trade price was hovering around $100/BBL quite a while ago. California has large oil reserves that can be extracted by the controversial process of fracking but production has been limited while rules for safely fracking (if it is possible) are being worked out. Farmers don't like it when their well water catches fire or all of their cattle suddenly die; I can't imagine why...

The USA gas guzzler tax starts at $1000 for a "near miss" and ramps up to a max of something like $7000. It is based exclusively on the fuel economy of the vehicle. Trucks are allowed to use more fuel than passenger cars.

I drive very little in town (I ride a bicycle) or in stop and go traffic (I drive late at night), so I am actively seeking any way to permanently disable start-stop and then lighten the car to take advantage of the situation. I find it hard to believe that start-stop is good relative to smog production--the catalytic converter will cool off during the "stop" cycle.
 
#11 ·
For more examples of questionable taxation, look at the Giulia's native country. We've got a wide variety of stuff to choose from.

Extra-steep VAT (38% instead of the ordinary 18%) on cars with engine displacement >2L in the eighties (which is the reason why cars like the Ferrari 208 and the BMW 320iS E30 existed).

Annual registration/road tax surcharge on diesels from the seventies to the nineties.

Another similar surcharge meant to hit off-roaders, except the law defined off-roaders as vehicles with all wheel drive and more than 5 forward gears, so AWD sports sedans with 6-speed gearboxes were classified as off-roaders and subject to that tax.

Car radio tax. LPG tax. Oh boy, we've had it all.

And the current situation isn't much better.

Let's start with purchase. We've got 22% VAT/sales tax, plus IPT, a "provincial transcription tax" that is paid every time the car gets a new owner, whether it's brand new or bought used. IPT is based on engine output power, and varies slightly between provinces. In my province, IPT on a Giulia Quadrifoglio is 1408.92 Euro.

Then we've got regular vehicle taxation (bollo, an annual registration/road tax). While in past decades it was based on engine displacement, in contemporary times it is based on engine power, with no correlation to vehicle value, or CO2 emissions, or anything else. It varies slightly by region. In my region, bollo on a Giulia Quadrifoglio is 1455.50 Euro/year.

But there's more. We've got superbollo, a surcharge on bollo, meant to hit luxury cars. The problem with it is that, like bollo, it's purely based on engine power, with no other considerations. It kicks at over 250hp, and it's very steep. Superbollo on a Giulia Quadrifoglio is 3800 Euro/year in the first 5 years, then goes down in steps every five years, first to 2280 Euro/year, then 1140 Euro/year, then 570 Euro/year, then goes away. All that is always in addition to the base bollo of 1455.50 Euro/year.

Then there's gas, which on average currently costs between 1.50 and 1.60 Euro/litre, the equivalent of over $7/gal. And that's for regular (95 RON, roughly equivalent to US 93 octane). Over half of that price is taxation.
 
#12 ·
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#14 ·
I think single digit percent changes will be very difficult for a single driver with an un-instrumented car to detect. Did you get 20MPG or 20.2MPG? Can you reliably tell the difference given all the variability in traffic, fuel filling, frustration with the engine stopping, etc? The latter should not be underestimated. I don't know about other people but if my car doesn't go when I want it to go I have a tendency to overreact and stomp on the accelerator to "catch up with the traffic", an act which would negate any fuel efficiency advantage of the start-stop and which computer simulated drivers probably do not do.
 
#15 ·
That's a good point. I personally started to turn it off, part of it is because the car shuts it self down almost immediately when it stops, at a stop sign or when trying to make a left turn at a light. Probably would have been ok if you could set a timer like 15sec. auto shut off when you are pushing the brake. So for the car to not shut off I'm rolling the stop signs and riding my brakes.
I'm not an expert of how the engine works in this car, but to me it seems it wastes more fuel every time the car stops/starts 100 times in a stop and go traffic. Your thoughts?
 
#16 ·
That's a good point. I personally started to turn it off, part of it is because the car shuts it self down almost immediately when it stops, at a stop sign or when trying to make a left turn at a light. Probably would have been ok if you could set a timer like 15sec. auto shut off when you are pushing the brake. So for the car to not shut off I'm rolling the stop signs and riding my brakes.
I'm not an expert of how the engine works in this car, but to me it seems it wastes more fuel every time the car stops/starts 100 times in a stop and go traffic. Your thoughts?
The experts (EPA, Euro counterparts, etc) say that when all else remains the same, start-stop saves a little bit of fuel (IIRC typical was 2-3%) during city driving. Who am I to question that statement?

My point 1 is that with start-stop "all else" does not remain the same. People are not robots.

My point 2 is that they measured this on a subset of all cars with start-stop and then passed rules that assume that all cars with start-stop have the same performance. This may be a nod to practicality, but it is non-sense.

My point 3 is that 25lbs of extra HW can be expected to decrease city fuel economy by some amount (around 1%?). Was that factored in? I really doubt it.

My point 4 is that popping the car into neutral when stopping also saves fuel (automatic transmissions), adds no weight, and is not nearly as annoying as start-stop. Was this considered and/or measured?
 
#18 ·
My concern would be long term wear and tear on the various systems, possibly engine as well when not fully at temp, anyway it makes high city driving mileage consideration even worse on a used car buy for a prospective buyer. Just a dumbass idea overall.
 
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