FFV vehicles if optimized for higher octane of E85 get mileage just

[JohnWxy]

as good as gasoline powered cars.. Ethanol has an octane rating of 105, while premium grade gasoline is 92 -93. Ethanol can be run at higher compression ratios than gasoline yielding higher performance resulting in just as good as mileage as running on gasoline at lower compression ratios.

But lets consider FFV vehicles without taking advantage of the higher octane of ethanol - they get 15% - 25% less mileage. So what does ethanol 85 sell for - about $2.06 per gallon compared to $2.35-$2.55 a gallon for mid and premium grade ($2.55) on average. So being that much cheaper even if it gets lower miles per gallon it balances out.

NOw, if American manufacturers wanted to optimize for ethanol's higher octane as does Saab (Saab 9-5 BioPower: Alternative Fuel with Performance Benefits) they can use variable valve timing andor turbo-charging or super-charging to effectively raise the compression ratio and the performance of the engine. All these can be computer controlled to lower compression ratio when operating on pure gas or ethanol 15 so you can use regular pump gas (92-93 octane).

What's interesting about Saab's 9-5 BioPower concept is that it offsets this disadvantage by providing more power. E85 has a 104 octane rating, compared to the usual 91 or 92 rating for premium gas. Without getting too technical, this higher octane allowed Saab engineers to add more boost to the 9-5's turbocharged 4-cylinder engine. The result is 310 hp instead of the usual 260.

Saab is currently selling a production 9-5 Bio -power that is turbocharged and gets 260 horsepower from E85 and delivers comparable mileage to gasoline powered cars. It's all a matter if you want to provide the extra horsepower E85 allows (if you turbo charging or use variable valve timing to take advantage of the higher octane of E85).

See??

AND LET'S NOT FORGET YOU CAN BUY A FFV VEHICLE FOR NOT A PENNY MORE THAN A REGULAR CAR! AND NO EXPENSIVE BATTERIES TO REPLACE IN 8 YRS! WOW! AND A FFV VEHICLE WILL RUN ON ANY MIXTURE OF ETHANOL AND GASOLINE FRO E15 ALL THE WAY UP TO PURE GASOLINE.

[Boo Boo]

1. Variable valve timing does not "effectively raise the compression ratio"

All it does is vary the valve timing. Variable valve timing optimizes fuel/air delivery across a range of engine speeds (RPMs). Turbo charging does not raise the compression ratio either. What Turbo charging does is cram more fuel/air into the combustion chamber, but the ratio of compression remains exactly the same since the ratio is a fixed value. So with turbo charging you would be getting even worse gas mileage because you are compensating for a loss of performance (with E85) by burning more gas.

Compression ratio is a standard specification that has one meaning: it refers to how much the fuel/air mixture is compressed by the piston at the very top of its stroke, just before the mixture is ignited. So, for an equal amount of fuel/air mixture, the engine with a higher compression ratio produces more power because it is sqeezing the mixture into a smaller space prior to ignition.

Raising the compression ratio is usually accomplished by replacing the pistons. How much compression can be used depends on (among other things) the octane of the fuel. High octane fuels can withstand higher chamber pressures without detonating (exploding before being ignited).

[JohnWxy]

3. NOtice the use of the word "EFFECTIVELY"

You can't put out a car with high compression ratio engine if you may need to put low octane gas in it.

To use your words "What Turbo charging does is cram more fuel/air into the combustion chamber" - and by cramming more air-fuel mixture into the combustion chamber you - in effect - by gettting more air+fuel into the combustion chamber than you would with a naturally aspirated car - get much the same effect as if you had a higher compression ratio.

Of course the compression ratio is fixed, until you swap out pistons or connecting rods. That's why I said "effectively".


Anyway , the point is that you can optimize an engine to take advantage of the higher octane rating of the ethanol fuel. (by the way thanks for explaining that how higher octane rated fuel can handle higher compression ratios - I believe I stated that in my post - but thanks anyway - LOL)

This is what SAAB did and it could be done by American manufacturers too.

Oh, and by the way, while the valves are open longer, what do you think the pistons are doing? Perhaps traveling farther before the valves close and thus gaining extra stroke (resulting greater compression)?

[Boo Boo]

2. RE: Turbocharging

This obviously works to increase power output with E85 (or any other fuel for that matter). And, you could still run on lower octane fuel by reducing the boost pressure with ordinary gas. I suspect that Saab is also taking advantage of the higher octane of E85 to allow leaner fuel/air mixtures, otherwise turbocharging would further increase fuel consumption for a given engine displacement using a given fuel.

OTOH, turbocharging is not really needed to get good power from E85. One could just crank the compression ratio up (way up) and that would compensate for the fuel's lower energy density. BUT, I'm pretty sure that the required compression ratio would mean that you couldn't run the car on ordinary gas. It would be an E85-only vehical, not an FFV.

Saab's trick seems to be that they've produced an FFV that makes big power and gets (comparably) good mileage. Although, they don't really seem to be doing anything new here. This is all looks like previously existing technology (turbos, variable valve timing, etc.) that is already used in production automobiles. Volkswagen/Audi, for instance, offers direct injected, turbocharged engines with variable valve timing. It would appear that nothing has been stopping auto makers from doing this earlier except previously low fuel prices, and production costs.

[JohnWxy]

4. You are right this is NOT any new Technology here.

Both GM and Ford have sold supercharged and turbo-charged engines in the past and currently. What's needed is a willingness to do it. You definitely can't put out an engine with an actual high compression ratio because you have to be able to run low octane gas in it. Supercharging and turbocharging allows you to adapt to the fuel you are running (with sensors and computer controls).

[DemSigns]

5. Saab is part of GM

Saab is part of GM. They should start making those engines over here now. Some smaller lower horsepower ones would be good too. I am not a turbo fan due to the added complexity and no real increase in efficiency that I know of, but this would be great to see more widespread. I have used a lot of E85 in my Grand Voyager. E85 does drop my mileage from 18 to 14, but at 169.9/gallon it is worth it. I would rather see the mileage increase with E85.

[JohnWxy]

6. DID YOU SAY $1.699 A GALLON??? I HAVE BEEN SEEING AN AVERAGE PRICE

Quoted on the web of $2.10. This makes the cost advantage even greater!!

By the way, Super-charging is a more low-tech way of achieving the same result and no high cost alloys for impellors - super-chargers are belt driven and have been around for years. GM sells a number of models right now (e.g Cobalt, Pontiac) that have supercharged engines as options.

[NickB79]

7. Here in Minnesota the few E85 stations I've seen sell it for $1.59

That was a week ago, and at that time regular unleaded was $2.10 or so.

BTW, all regular gasoline sold in MN has to have 10% ethanol blended by law. It reduces mpg a bit, but cars run fine on it with no modification.

While making all cars E85 capable is a nice dream, I think our time would be better spent first making it a federal law that all gasoline sold in the US uses 10% ethanol. After that, if we can produce enough ethanol sustainably from crops and waste, start increasing the mixture used towards E85.

[DemSigns]

8. $169.9 last few times I filled up.

Even when regular is in the $2.30s. This is the only way it gets economical for me. I may have to look into a supercharger??