Re: 2008 minivans: Honda Odyssey vs Toyota Sienna

/all/ modern fuel injected cars turn of /all/ cylinders when coasting.

it's /some/ cars that turn off cylinders when /cruising/.

Reply to
jim beam
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My Sienna gets 25-28 on a trip. It may be hard for people to believe, but not for me as I own and drive one and have checked it on more than one trip. That is the way it is.

Reply to
dbu

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Mind explaining what you mean? By coasting do you mean rolling with the gear shift in neutral? If that is what you mean is engine cut out in this condition a requirement of North American autos as it certainly isn't so for European vehicles. In Europe it is becoming increasingly common for modern vehicles to stop the engine when at rest and for the engine to restart when the gas pedal (accelerator) is depressed.

Reply to
Edward W. Thompson

no, coasting is when the momentum of the vehicle pushes against the engine and turns it even when you have your foot off the gas, like descending a hill or slowing to a stop.

no, it's for all electronic fuel injection vehicles, globally. the forward energy of the vehicle is rotating the engine - there's no point injecting gas when the motor's just pumping air coasting.

that's not coasting.

Reply to
jim beam

Uh boy, another topic introduced! ;-)

Re: the regular/super debate - here in NJ, we have regular (87), plus (89) and super (91/93). My Audi A4 turbo requires "super" - 91 octane

- although I have run it with no issues on 89. My wife actually filled it with regular (87) once and it definitely was down on power. Don't recall the gas mileage (although I have it in my log). I can imagine some small towns (which is where I assume dbu lives) which don't carry all 3 grades. I've seen that in Maine, but if they have 87 and 89, it's still labeled 'regular' and 'plus', not 'super' for 89. And who uses 'Super' for their lawnmowers, etc?? I use the cheapest crap I can find, just like for the Odyssey. ;-) I filled it up yesterday for $3.83 (full serve, too, which is all we have in NJ).

Dan D Central NJ USA

Reply to
Dano58

Actually, I was in Colorado a couple of weeks ago, and all the gas there seemed to be a couple of points lower in octane than what I'm used to in Texas. I don't know why -- something to do with the altitude, maybe? Alas, I have no photos to support my assertion.

Reply to
Paul

I read through this thread with amusement and I believe dbu. There is a Sunoco gas station here in Baltimore County, MD. It was on York Road, by Seminary Avenue in an area called Lutherville. They sell Premium at the same cost as mid grade. It used to be a Mobile station before they changed maybe over a year ago, but apparently same owner since they were doing this when they were a Mobile station. They have mechanics bays and a very small convenience section.

Why do they do this? Don't know - maybe to get people to buy gas, get to know them and maybe have their car worked on by the mechanic? I don't ask, but used to buy gas there in my previous car when I used premium. Also had the car worked on by the mechanic before. He's a decent mechanic. If you're ever in the area and want to see for yourself, swing by. They've been doing this at least for the past 5 years. And no, I'm not going to take a picture - not worth the time, but it is a brand name gas.

-Dave

Reply to
Dave L

"Dave L" ...

Back when I was in HS and College I worked at a Shell station in Middletown NJ. This was at the time gas was about 50 cents per gallon. Whenever we ran out of regular [and it happened many times] we were instructed to lower the price of premium down to the regular price so the customers wer not pissed off that we had none of their gas. They were always really happy about this. This was when the price was regular, 2 cent more for midgrade and 4 cent more for premium. Tomes

Reply to
Tomes

I'm well aware of that.

Re coasting: the definition is simply forward motion due to force of gravity, I think you have added the bit concerning engagement of engine with drive train.

With respect to the engine cutting out (either by gas cutoff or ignition cutoff or both) when the torque is reversed (vehicle driving engine), this is something new to me and I am pretty sure that doesn't occur in my Civic (2005) or in any other fuel injected vehicle I have driven worldwide. I take your point that there is no gain by injecting fuel under these circumstances. How does the engine detect 'torque reversal' to cutoff fuel and ignition? Does this occur each time you brake as braking is a 'coasting' event the way you define it.

Incidentally what is 'electronic fuel injection' the converse of which is, I assume, 'mechanical fuel injection'. If you mean a carburetor in my 'parlance' a carburetor is an induction system not an injection system :-) re Collins English Dictionary 'induction'.

Reply to
Edward W. Thompson

why gravity? coasting is coasting - taking your foot off the gas while you're moving.

i did.

you can cut off ignition, but i'm not aware of anyone who does - what's important is shutting off gas.

it absolutely does. the point is, when you're coasting, you're primarily pumping air. not point injecting gas in that situation.

rpm and throttle position.

yes.

modern computer controlled electronically activated fuel injection.

if i'd meant carburetor, i'd have said carburetor.

Reply to
jim beam

Yup, I remember when the spread between regular and premium was much smaller than now. When did gas stations start coming out with mid-grade? I thought it was more recent than the gas being 50 cents.

-Dave

Reply to
Dave L

"Dave L" ...

Now I am trying to remember better (ouch). I think that the mid-grade was the unleaded right when unleaded came out, and the regular and premium were leaded. This was 1975-8ish. Tomes

Reply to
Tomes

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explains that lower octaneworks OK in high altitude.

-- Ron

Reply to
Ron Peterson

OK, then restating my previous question, what is the converse to electronic fuel injection in a gasoline engine. Mechanical fuel injection is the normal system for diesel engines but not, AFAIK, used for gas engines.

As I understand it you are saying that during the period when 'coasting' to stop no fuel is being admitted to the engine. If this correct at some point fuel must be readmitted to allow the engine to idle when the vehicle is at stop. The question is how does the 'system' determine when fuel is to be readmitted during the coasting event to prevent the engine from 'stopping' when at rest?

Incidentally rpm and throttle position does not indicate torque reversal (coasting) as you have implied.

Reply to
Edward W. Thompson

the old bosch systems were pretty much mechanical. remember the ones with the braided line that ran to each cylinder?

the computer monitors rpm's and starts re-injecting below a base threshold. older systems, that's about 1500rpm. according to tegger, more modern systems cut it to as low as 750rpm.

then you need to think this situation through one more time - there's no situation under which you can have high rpm's and a closed throttle unless you're coasting.

Reply to
jim beam

Let me get this straight. I think you are claiming that the engine uses

*NO FUEL* during coasting...., right? So, let's think of an example.... If I was coming down a large mountain, on the Interstate, at 65mph, and was to *COAST* for 20 miles (entirely realistic in some places), you are saying that I would not use ANY FUEL? Right?

My take on that is that it's absolutely wrong. The engine is still running, even if it's not doing any real "work". It is using fuel.

Reply to
Dan C

nope. the engine is turning because it's in gear and the weight of the vehicle is pushing it down hill. in this situation, the computer will inject zero fuel. not one drop. [unless you put your foot on the gas again of course.]

go to megasquirt.info, dig through until you find the source code, read it, and there you will see an example of the shut-off, and the parameters the computer uses to do it.

Reply to
jim beam

Ya got me there. I can't remember what the pumps were that far back. I wasn't even hear driving yet!

-Dave

Reply to
Dave L

Your take on that is completely wrong. In this case, the engine is being driven by the transmission. No combustion is taking place. The engine runs on the energy of the downhill glide until your RPM's get low enough that the fuel needs to be injected again to keep the engine running.

Reply to
Joe

OK. Makes sense I guess.

Reply to
Dan C

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