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Re: Mileage declining - Why?
Compression ratio is neither huge nor primary...
It simply determines the minimum octane rating you can use in an engine. ...And that any octane rating, and therefor cost, above that required is wasted. Simply put higher octane fuel, used in an engine with an appropriate compression ratio, means you extract more energy (to the crankshaft) from the same amount of available energy in the fuel. That's all. Your answer still convinces me you don't understand the inter-relationship of octane rating and compression ratio to power extracted from the fuel. |
Re: Mileage declining - Why?
Originally Posted by Bill Winney
(Post 200023)
Compression ratio is neither huge nor primary...
It simply determines the minimum octane rating you can use in an engine. ...And that any octane rating, and therefor cost, above that required is wasted. Simply put higher octane fuel, used in an engine with an appropriate compression ratio, means you extract more energy (to the crankshaft) from the same amount of available energy in the fuel. That's all. Your answer still convinces me you don't understand the inter-relationship of octane rating and compression ratio to power extracted from the fuel. So, switching fuels causes the computer to fatten the mixture, and mileage suffers. It's the same with other oxygenators. They made sense before lamda sond style closed loop strategies, but now, not so much. |
Re: Mileage declining - Why?
Hmmmm... oxygen...
Methanol combustion is: 2CH3OH + 3O2 → 2CO2 + 4H2O + heat Ethanol combustion is: C2H5OH + 3O2 → 2CO2 + 3H2O + heat Turns out OBD-II computers also measure the oxygen in the exhaust stream and adjust fuel mixtures accordingly. I just don't believe that the programming in these systems don't presume that alcohol may be present in the fuel and account for it. |
Re: Mileage declining - Why?
Originally Posted by Bill Winney
(Post 200039)
Hmmmm... oxygen...
Methanol combustion is: 2CH3OH + 3O2 → 2CO2 + 4H2O + heat Ethanol combustion is: C2H5OH + 3O2 → 2CO2 + 3H2O + heat Turns out OBD-II computers also measure the oxygen in the exhaust stream and adjust fuel mixtures accordingly. I just don't believe that the programming in these systems don't presume that alcohol may be present in the fuel and account for it. Bill: They do account for it, by enriching the fuel mixture to compensate for the increased oxygen. That's the issue with mass air style fuel injection and the addition of oxygenated fuels. The combination causes a drop in mileage. Further, because the adaptive portion of the system uses a moving average of the information stream, changing from fuel with alcohol to fuel without and back causes the system to be temporarily "wrong" at each fill-up where the fuel changes. This is what Gary et. al. are trying to tell you. |
Re: Mileage declining - Why?
The point is the control system does not "enrichen" the mixture. It matches the fuel to the available oxygen and maintains the Oxygen level in the exhaust stream. The fact that it does this by increasing fuel doesn't mean the mixture has been enriched so long as it is matching the air to fuel ratio.
The thermodynamics of the engine mean that the energy is used. The idea that horsepower goes up and the mpg goes down doesn't pass the common sense test. C'mon guys. My objection to alcohol fuel is that there always is some blowby past the rings. The blowby of gasoline residue is a different mix than the residue from alcohol. I feel that adding alcohol is not so good for engine corrosion & lubrication chemistry. So long as we replace cars every 100,000 miles or less it makes little difference. When you start to think in terms of 200,000 or more it does make a difference. My other cars: Suburban 17 years & 377k, Mustang 8 years & 251k. |
Re: Mileage declining - Why?
<<
Originally Posted by Bill Winney
(Post 200194)
The point is the control system does not "enrichen" the mixture. It matches the fuel to the available oxygen and maintains the Oxygen level in the exhaust stream. The fact that it does this by increasing fuel doesn't mean the mixture has been enriched so long as it is matching the air to fuel ratio.>>
So you agree that more fuel is used when alcohol is added to the mix because of the extra available oxygen. Wouldn't this put you in agreement that fuel with added alcohol causes lower mpg? <<The thermodynamics of the engine mean that the energy is used. The idea that horsepower goes up and the mpg goes down doesn't pass the common sense test. C'mon guys.>> I have never seen a situation where horsepower increased and fuel mileage increased at the same time. Can you explain this one? <<My objection to alcohol fuel is that there always is some blowby past the rings. The blowby of gasoline residue is a different mix than the residue from alcohol. I feel that adding alcohol is not so good for engine corrosion & lubrication chemistry. <<So long as we replace cars every 100,000 miles or less it makes little difference. When you start to think in terms of 200,000 or more it does make a difference. My other cars: Suburban 17 years & 377k, Mustang 8 years & 251k. My other cars are an '83 GMC Suburban with about 150k on this motor. It has a 454 crate motor and a 4-speed lockup overdrive from a GNX in it. Gets 17 if I'm gentle. Tranny is a direct bolt in from the turbo 350. My Mustang is an '88 GT Convertible with an Eaton Blower on it. It's got 225,000 or so on the chassis. I welded subframes and a roll bar into it so you can still open the doors when its on jack stands... My '66 Galaxie convertible has about 135,000 on it. It's the stock 390 hypo with the venerable cruise-o-matic. The FEH only has 46,000 miles on it. The Highlander Hybrid has just about 45,000 on it. Mark |
Re: Mileage declining - Why?
Originally Posted by Bill Winney
(Post 200194)
The point is the control system does not "enrichen" the mixture. It matches the fuel to the available oxygen and maintains the Oxygen level in the exhaust stream. The fact that it does this by increasing fuel doesn't mean the mixture has been enriched so long as it is matching the air to fuel ratio.
The thermodynamics of the engine mean that the energy is used. The idea that horsepower goes up and the mpg goes down doesn't pass the common sense test. C'mon guys. My objection to alcohol fuel is that there always is some blowby past the rings. The blowby of gasoline residue is a different mix than the residue from alcohol. I feel that adding alcohol is not so good for engine corrosion & lubrication chemistry. So long as we replace cars every 100,000 miles or less it makes little difference. When you start to think in terms of 200,000 or more it does make a difference. My other cars: Suburban 17 years & 377k, Mustang 8 years & 251k. Mark, my first car was a hand-me-down to get back and forth to high school. My Dad bought this '66 Galaxie 500 convertible from San Jose Ford new back in the days and I ended up rebuilding the 428 and driving it to school. It had 7 Liter emblems and was a 4 speed manual. Fast boat for my first car but I also went the Mustang route with a early original '67 GT 500 built at LAX airport in LA. Sold it in 1980 for 5 X what I paid for it and it's worth 20 - 30 X that now. The movie "Gone In Sixty Seconds" brings back memories to my family and friends. Took a girl for a ride just after I bought it in '73 and we've been married now for 33 years. GaryG |
Re: Mileage declining - Why?
I suppose we should be talking of the merits of water injection. If you look at this you'll find that does improve the combustion process and increases power. Effectively it increases the octane rating.
Does that mean that these systems are "burning" water in the engines??? The Ford Escape Hybrid engineers that lurk on these posts must have been laughing themselves silly. No crate engines in my cars... all are OEM engines! I guess that's my point about maintaining good chemistry inside the engine and that's why I don't like alcohol inside my engines. |
Re: Mileage declining - Why?
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Re: Mileage declining - Why?
Mark, my first car was a hand-me-down to get back and forth to high school. My Dad bought this '66 Galaxie 500 convertible from San Jose Ford new back in the days and I ended up rebuilding the 428 and driving it to school. It had 7 Liter emblems and was a 4 speed manual. Fast boat for my first car but I also went the Mustang route with a early original '67 GT 500 built at LAX airport in LA. Sold it in 1980 for 5 X what I paid for it and it's worth 20 - 30 X that now. The movie "Gone In Sixty Seconds" brings back memories to my family and friends. Took a girl for a ride just after I bought it in '73 and we've been married now for 33 years.
GaryG[/quote] Nice hand-me-down! 428 in the KR too I gather. I had a TR-3a in '72 when I met my wife. Similar story... She came to my 22nd birthday party and never went home again. (Don't tell my kids..<G>) As for the Galaxie, It's nice to take the top down and just putter around once in a while. By the way, those 7-Litre cars are beginning to have some value too. Not like the fastback mustaings though. Mark |
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