kary4th

Sunoco stations around here all have 15% ethanol stickers on them. It's a pretty standard thing to boost octane levels with it since MTBE and every other old additive has been condemned as a terrible thing.

Daniel Dudley

Pano did an article a while back. They seem to think 15 % was a fair upper limit for older cars.

Been running 10 % here for years no problems , but you want to keep the tank full to prevent condensation while sitting. Wierd emulsions and separation can happen I hear.

EC928NC

Actually this is totally wrong.... an increase of greenhouse gases (carbon) in the atmosphere is exactly what will make a rain forest thrive - trees breathe carbon and exhale oxygen... Now the ice sheets are another story. Let's not get our global catastrophys mixed up.

But lets get back on topic - A healthier rain forest means MORE rubber trees, thus negating the effects of ethanol on rubber fuel lines. Problem solved.

marton

They cut down the rain forest to create more space to grow the corn (or whatever) they use to make ethanol. The corn absorbs less CO2 than the rain forest did.
Plus the CO2 generation by the tree cutters equipment & the subsequent wood burning.

All in favour of more rubber trees

Marton

LightStriker

Actually... It's a bit false. On the day, trees breath CO² and release O²...

However, at night it's the other way around as trees don't have light to do the photosynthesis, it goes O² --> CO²

The ammount of O² trees create is small in overall.

However, the oceans is another deal. A metric ton of phytoplancton create much more O² than any tree will ever do.

So the big deal is to save the ocean.

Meh.

Larry Velk

If you have a 'motorbike' (as our transocean friends say) on the edge of a tune, you can feel differences in fuel. So-called oxygenates cause a surge in my bike at lower speed cruise. The fuels are quite obviously different. We've had one of our cars for 18 + years and my records have tracked the comings and goings of winter fuel, MTBE (used here for several years), ethanol, etc. Ethanol gives lower per gallon results, period. As stated, a BTU issue. Why people don't understand the science involved here is maddening. If it were cheaper or obtained more easily - as stated by our Lotus poster - then it would be a wash. The arguements are not complex, but a lack of actual knowledge involving the principles junks things up. Our 928 I'm sure has many odd issues which come and go like sticking injectors that are more important than the ethanol, but the ethanol helps nothing, even if it hurts little - that's the issue for me.

VehiGAZ

Now THIS statement is untrue (for the time being, anyway). Click here for a map of what grades of gas are legally required around the country. You will see that most of the country enjoys conventional gas (little or no ethanol), unlike on the coasts, which are the main users of ethanol-oxygenated gas (to reduce emissions, ostensibly). As for octane, ethanol has a high octane rating, and may be used to boost the octane rating of gas slightly, but think about it - how much can you boost the octane of a blend of only 10% 129-octane ethanol? Not that much - certainly not to 108.

By the way, the complexity of that map is one of the reasons for high gas prices in this country. If we didn't have these ridiculous county-by-county variations, the supply chain would be much more flexible.

Wikipedia has a good write-up on gasoline and additives like ethanol. Note that just because the pump has a "up to 15% ethanol" sticker on it doesn't necessarily mean it has ethanol in it. In VT, they run conventional gas, which can contain some ethanol (see wiki link), and so they have the stickers on the pumps, but that doesn't mean they are using the dreaded 10% ethanol blend.

Ethanol in gas is hygroscopic, so our primary concern should be to avoid letting gas sit in the tank too long because it will absorb moisture from the air (or use a stabilizer additive if you let gas sit in your shark for more than a few weeks). This should be a far more pressing concern than the effect of low concentrations of ethanol on gas hoses over 10 years.

The worst part of this ethanol-oxygenated fuel fiasco is that once your state's politicians start mandating ethanol, they will never stop because of the boost in tax revenues... As noted above, your mileage will decrease running ethanol-oxygenated fuel (my Isuzu gets a full 20% better mileage on conventional gas versus Connecticut's ethanol-oxygenated gas). But you are still driving the same distances on a weekly basis, right? Well, if it now takes you let's say 12 ethanol-oxygenated gallons of gas to get you where you need to go in a week instead of 10 conventional gas gallons, your state gov't just increased its gas tax revenue by 20%! (They are charging you per gallon of fuel sold, not per gallon of the gas component of the fuel.) They will NEVER stop suckling that teat...

BC

As I have said time and time again in these threads, I don't give a **** about the political or environmental issues with ethanol production or distribution. Oil from the ground to the pump is no saint either, and the amount of power you can get out of a high boost engine with ethanol is staggering because of its characteristics. It also burns cleaner, without the nitrogen and benzene chemicals, etc. It has no soot to speak of, and as long as the engine is built for it (high compression), and the fuel lines are not normal rubber, or uncoated metals, its fine, and the water issue is a non-starter.

Bill51sdr

That being said, you WILL see a noticeable decrease in MPG. That is a well known fact.

928ntslow

Bill...probably one of the best avatars I have ever seen. No doubt I have driven that road.

Anyway, I like the idea of a bit of Ethyl in my cars. This stuff was around I think before most of us were born. Cars seem to have run fine for years. I would say before anyone starts to make accusations as to the ill effects of this latest fuel addition, we should get some history behind us with it.

I will GLADLY destroy my rubber bits over the course of several years in gas savings knowing that I will have saved more than enough money to buy a nice supply of what I will need for future maintenance.

Do the math!

Bill51sdr

Thanks Keith, but George Suennen must get credit for that one. It was taken durning the 2006 Devek Days fun drive. We're a few miles south of Half Moon Bay in that shot. That is an '87 930 Slantnose running in fear from my sHark . Tarek (owner) came away from that event with a renewed respect for 928's.

jcorenman

Brendan, I agree completely-- ethanol is a great fuel for engines which are built to take advantage of its characteristics. But you need higher compression and appropriately calibrated fuel delivery, and my question was with respect to ordinary 928 engines tuned for conventional gasoline.

It is certainly true that the energy per unit volume (BTU per gallon or whatever) is lower for ethanol, which translates into more fuel burned to travel the same 100 miles down the road (the no-free-lunch rule of thermondynamics). In other words, a bit more throttle opening is required over the 100 miles to achieve the same average speed. And it is also correct that mileage is relative, and only relevant with respect to overall cost and size of the fuel tank-- i.e. how often you need to stop for gas (which in our family is completely irrelevant, the car can go a lot farther between pit-stops than the people can).

But what about horsepower? If we follow that same argument then isn't it also true that adding ethanol to the fuel mix (without changing anything else) reduces max horsepower? It seems like this has to be true because of the no-free-lunch rule: at WOT at a given RPM, the injectors are going to be squirting the same amount of fuel whatever it is, and less energy per volume fuel means less horsepower. Of course we can raise the compression (octane permitting) and re-tune the injection to squirt more fuel and get the horsepower back, as Brendan suggested. But without changing anything it seems like we wind up with less available horsepower at WOT. Has anyone checked this on a dyno?

Cheers, Jim

BC

I think you may be confusing the issue a bit. Take a 2.0L engine. 11:1 compression or around there. Add 15psi of boost.

Regular high octane gas will not suffice. It doesn't have enough knock resistance. So you would reduce timing, and reduce boost, and make less power.

The Etahnol, because of its characteristics, allows the engine to become more efficient in its own parameters. Advancing timing, raising compression (through physical engine dimensions, or through the addition of boost).

The efficiency issue is more complex - because its a a unit measurement - say one gallon. Well, the one gallon of Ethanol has way more oxygen than the one gallon of gasoline. So the AF ratios are more like 9:1 and 7:1 instead of the 13:1 for regular gas.

But thats only only because each gallon of ethanol has oxygen taking up more space.

This has nothing to do with just filling up a 928 tank with Ethanol and thinking it will work great - it won't. Put injectors that are larger in, and maybe the computer would be able to run the car well enough - but without a specific tune, it won't work as well.

That said, I have run E85 in the honda for weeks now. It doesn't idle well, and its running lean pretty much everywhere, but its a dollar less a gallon here. I could put some larger injectors in there and it would probably run better than stock.

BC

If you put about half E85 (maybe a bit less) and half 91 octane in the tank, it would sure as hell run better - because it won't have to retard timing because there will nearly be no knock. Thats when the Honda runs best - half and half - because the injectors aren't maxed out trying to get to the 8:1 afr equivalent.

marton

Brendan posted
Yes but there is no such thing as a free lunch.
It may be a buck per gallon cheaper but that is because it is subsidised using your tax dollar.
Plus your food prices have increased.
Overall you end up paying more; which you are probably happy to do for your 11:1 compression high revving 2 litre but there is no benefit for your 928 which is the point of this thread?

Marton