Hybrid Tech Question

[trikkonceptz]

It's seems obvious to me, but in order to begin raising MPG's in your line of cars, (Insert Brand Here), why not implement and engine cut off like the hybrids do when idling?

I have to imagine that a change like that alone can have a significant impact on the MPG's of any vehicle. Now to go along with that some design changes would have to be made like an electric a/c system, but that already exists, so what am I missing?

I think if all the cars at an intersection were to shut off and sit silently while we wait for lights to change the impact would be incredible .. not to mention automakers could boast about a bump in MPG's to stay ahead of government regulations.

[user removed]

13% of fuel consumed by cars in the US is wasted idling.

My Insight will go 40 MPH on the same fuel a V8 consumes idling.

regards
Mech

[Bicycle Bob]

When one of the car magazines got serious about getting 100 MPG by driving technique, they found that the car used a shot of rich mix to start, equal to about 30 seconds of idling. It takes a strong starter, and usually some fancy mixture control to come out ahead on this. Measures to keep the oil pressure up are also needed to avoid a false economy.

[Grant-53]

This is where route selection comes into play. Also, if you are stopped at a light with a sensor loop in the pavement and have room, back up a car length and pull forward again. You sometimes can make the system register another vehicle in the queue and the signal may change sooner.

[SVOboy]

I believe 3 main things need to be done:

Electric accessories with sufficient battery capacity to run things like A/C during stops.
Electric safety stuff, like brake vacuum etc
Some sort of electric motor that could turn over and start the car from a stop when the gas was pressed (something a starter traditionally is not used for.

[RobertSmalls]

http://ecomodder.com/forum/showthrea...snt-11623.html

The technology is out there and easy to implement, but it adds a few hundred dollars to the price of the car, and it's hard to explain the benefit of it to new car buyers. Some of them would actually be annoyed by the engine cutting out when they stop and lurching back to life when they lift off the brakes. So the cars would cost more, get the same EPA rating, and annoy a few customers. Where's the benefit to the automaker?

[Olympiadis]

Originally Posted by trikkonceptz

It's seems obvious to me, but in order to begin raising MPG's in your line of cars, (Insert Brand Here), why not implement and engine cut off like the hybrids do when idling?

I have to imagine that a change like that alone can have a significant impact on the MPG's of any vehicle. Now to go along with that some design changes would have to be made like an electric a/c system, but that already exists, so what am I missing?

I think if all the cars at an intersection were to shut off and sit silently while we wait for lights to change the impact would be incredible .. not to mention automakers could boast about a bump in MPG's to stay ahead of government regulations.

I'm sure it would have been implemented earlier if not for several important factors.
Pre-OBD2 cranking strategy involves quite a bit of extra fuel.
First, I think if some of you saw the "Cranking Fuel" table you would probably have a cow. Some of them are factory calibrated to go 40% richer or more, depending on the coolant temperature.
Once cranked, there is something called "After-Start Fuel" or "Time-Out Fuel" which can start you out at an 11.0:1 AFR, and ramp you up to stoich over a period of seconds or minutes, depending again on temperature. This time period is called the "Time Out". After that there is often "Warm-Up Enrichment" or sometimes called "AFR vs LD vs ECT" which is just a name for a 3-D fueling table that adjusts the AFR based on coolant temp and load.
There was often a significant "time-out" period for going into closed-loop mode after certain other qualifications were met by the sensor feed back.

In my experience, the larger the engine, the larger the % of cranking fuel is skewed to the richer AFR. It's not proportional to the engine size.

When I tune an OBD1 system I reduce these fuel enrichment tables drastically until I find the limit of operation. Engines with aluminum heads, cold-air intakes, unrestricted exhaust and/or headers, low static compression, or the use of fuel diluted with alcohol, will all require some extra cranking fuel, and after-start fuel.

Newer OBD2 strategy still uses some of this extra fueling on some models, though it is much less than before, and the system goes into closed-loop mode very quickly in comparison.
There is still going to be a trade-off there, and if you kill the engine while sitting at a stop for less than 20 or 30 seconds, then you'll probably come out on the losing end of the equation.

As far as non-hybrid cars go, if everyone was killing their engines at stop-lights there would probably be a multitude of other problems created along with increased traffic congestion, which could easily negate the fuel savings IMO. The way I see it, there are already way too many people with delayed reactions when taking off from stoplights, due to distractions like texting, or just plain being oblivious to their surroundings. If you end up having to sit through two or more lights because of the delays, you will still have to start your vehicle to move up in the line.

Using electric mode for these short stop-n-go's is the ideal way to deal with the situation, at least IMO.

I don't have electric, so my preferred way is to go into the calibration (tune) and lower the idle speed, especially the "Idle in P/N" (park/neutral), and when possible use open-loop idle when available. In open-loop you can command a leaner AFR. You can get away with extremely lean AFR when in park or neutral.

Also, since you mentioned government regulation, how about we just get rid of at least 60% of the traffic lights out there? More and more go up every day.

[Dean in Milwaukee]

Its interesting that mazda was mentioned as they have what may be the coolest restart system ever devised.

It works by having a mechanical device that stops the motor in the same position every time, on a cylinder that has the intake valve open. The injecter for this cylinder fires followed by the spark plug causing the motor to turn backwards up against compression, then firing the other injectors and plugs, starting the motor instantly and flawlessly every time. The only extra part is the mechanical motor stop indexing thingy and some some extra computer code, and it doesnt use the starter motor or place a load on the battery.

I am familier with the spin it backwards to start forwards drill with some of my model airplane motors. They can be a bear to start if you flip the prop in the right direction, often spitting back and running backwards, but if you flip the prop the wrong way, it bounces back against compression and starts up nice and easy.

Dean in Milwaukee

[user removed]

Rolls Royce engines before 1910 were built to such close tolerances that they could sit overnight and hold compression.

Next day when the ignition was turned on the engine would start as long as the piston was just past TDC.

This was before the invention of the electric starter.

CS Rolls was the second licensed pilot in Britian, and he died in a plane crash.

Royce carried on.

regards
Mech

[Nevyn]

Originally Posted by Bicycle Bob

When one of the car magazines got serious about getting 100 MPG by driving technique, they found that the car used a shot of rich mix to start, equal to about 30 seconds of idling. It takes a strong starter, and usually some fancy mixture control to come out ahead on this. Measures to keep the oil pressure up are also needed to avoid a false economy.

There's another study out there that says 7 seconds.

Here's one link, there's a bigger/more detailed article somewhere else - but I can find it now.

IWillTry.org How many seconds of idling is equivalent to starting your engine