high octane gas in MN
Jun 25, 2003, 09:14 PM
#16
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Does anyone know how much, if any, ethanol is in Texaco's 92 octane, or any other gasoline in the Twin Cities?
After some googling, according to my calculations based on the relative energy content of the two fuels, a 90-10 gas-ethanol mixture (the lowest ratio allowable and what I'll assume Holiday is running) would have 96.2 percent the energy of pure gasoline. (E.g., 3.8% less power ~ 10 bhp!). Note: This is just a theoretical number and I am not a chemist!--I have read elsewhere that the difference in power/economy is actually 1-2 percent. Pure MBTE has 82% the energy content of gasoline, although I think it takes less MBTE than ethanol to boost the octane the same amount. It's hard to find information on the web that isn't obviously biased pro- or anti- ethanol (some sites claim ethanol improves mileage--the only way this makes sense is if they're comparing 87 gas to 91 gasahol where the car is auto-adjusting timing)
I've been running 93 from Holiday since I bought the car, as I'm not near any place that sells 100 gas. I haven't found any reliable information that it would be worse on the car, just perhaps slightly less power. (Texaco ran some engines on gas, some on ethanol, tore them all apart, and supposedly the ethanol ones were "cleaner") Also, I wonder if going to 93, even with "gasahol" would be enough to keep the ECU from pulling the timing, which could easily be worth 10 hp according to Shiv's 91 graphs.
I had a weird experience this morning--I was on a two-lane, and pulled out to pass some cars, and it felt like I hit a wall around 6000 RPM--the acceleration dropped really suddenly, felt like it lost 100 horsepower. Not a good feeling! I had the defroster on, which I believe runs the AC as well, so I turned it off later and tried another run-up, and the same thing happened. It was raining both times--I wonder if that was affecting it? I tried again this evening after it had stopped raining and it seemed to pull more normally to redline... I am curious if the ECU was pulling the timing more because of detonation, or it was freaking out from the rain or what.
I am getting very tempted to go for a Vishnu stage zero with a 91 octane map for daily driving and a 100 map for track usage, since it's pretty far out of the way to fill up in Plymouth every time, but I could imagine filling up with race gas for a track day. I hope he comes out with a plug&play connector soon, I'm guessing that would fit better than XEDE + a home-spliced extension harness all shoved above the glovebox, plus those wiring extensions are pretty expensive and I'm not cutting my stock harness...
After some googling, according to my calculations based on the relative energy content of the two fuels, a 90-10 gas-ethanol mixture (the lowest ratio allowable and what I'll assume Holiday is running) would have 96.2 percent the energy of pure gasoline. (E.g., 3.8% less power ~ 10 bhp!). Note: This is just a theoretical number and I am not a chemist!--I have read elsewhere that the difference in power/economy is actually 1-2 percent. Pure MBTE has 82% the energy content of gasoline, although I think it takes less MBTE than ethanol to boost the octane the same amount. It's hard to find information on the web that isn't obviously biased pro- or anti- ethanol (some sites claim ethanol improves mileage--the only way this makes sense is if they're comparing 87 gas to 91 gasahol where the car is auto-adjusting timing)
I've been running 93 from Holiday since I bought the car, as I'm not near any place that sells 100 gas. I haven't found any reliable information that it would be worse on the car, just perhaps slightly less power. (Texaco ran some engines on gas, some on ethanol, tore them all apart, and supposedly the ethanol ones were "cleaner") Also, I wonder if going to 93, even with "gasahol" would be enough to keep the ECU from pulling the timing, which could easily be worth 10 hp according to Shiv's 91 graphs.
I had a weird experience this morning--I was on a two-lane, and pulled out to pass some cars, and it felt like I hit a wall around 6000 RPM--the acceleration dropped really suddenly, felt like it lost 100 horsepower. Not a good feeling! I had the defroster on, which I believe runs the AC as well, so I turned it off later and tried another run-up, and the same thing happened. It was raining both times--I wonder if that was affecting it? I tried again this evening after it had stopped raining and it seemed to pull more normally to redline... I am curious if the ECU was pulling the timing more because of detonation, or it was freaking out from the rain or what.
I am getting very tempted to go for a Vishnu stage zero with a 91 octane map for daily driving and a 100 map for track usage, since it's pretty far out of the way to fill up in Plymouth every time, but I could imagine filling up with race gas for a track day. I hope he comes out with a plug&play connector soon, I'm guessing that would fit better than XEDE + a home-spliced extension harness all shoved above the glovebox, plus those wiring extensions are pretty expensive and I'm not cutting my stock harness...
Jun 25, 2003, 09:24 PM
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Correction, just found this:
"Ethanol and ethanol blends of gasoline conduct electricity. In contrast, unblended gasoline is an electrical insulator. For this reason, pure ethanol is more corrosive than gasoline and materials-compatibility must be considered when designing large-volume, bulk-ethanol storage tanks."
"Ethanol and ethanol blends of gasoline conduct electricity. In contrast, unblended gasoline is an electrical insulator. For this reason, pure ethanol is more corrosive than gasoline and materials-compatibility must be considered when designing large-volume, bulk-ethanol storage tanks."
Jun 25, 2003, 09:36 PM
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Last post--I promise!
Another factor I hadn't considered is that ethanol has a stoichometric rate of only 1:9, compared to about 1:15, and since we know our evos run rich, this may help offset the power loss since more of that extra fuel is actually being burned instead of depositing on our tailpipes.
I also read about an effect where blended ethanol will dissolve out into water--I wonder if that is somehow involved with my weird rain experience. Maybe someone who knows some actual chemistry can help out!
Another factor I hadn't considered is that ethanol has a stoichometric rate of only 1:9, compared to about 1:15, and since we know our evos run rich, this may help offset the power loss since more of that extra fuel is actually being burned instead of depositing on our tailpipes.
I also read about an effect where blended ethanol will dissolve out into water--I wonder if that is somehow involved with my weird rain experience. Maybe someone who knows some actual chemistry can help out!
Jun 27, 2003, 11:49 AM
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I don't see what stoichiometry has to do with combustion. Stoichiometry is used to figure out mole ratio of reactants vs reaction products in a reaction. Ethanol is blended into gasoline by volume and there are no reactions. You burn 10% of ethanol and 90% of gasoline. ie You get less bang for the buck 'cause that 10% of ethanol gives less energy then equivalent volume of gasoline when ignited - that's it, fairly simple.
Ethanol is quite miscible in water - ever drink vodka? As such, any water in the gas tank will actually be "picked up" by ethanol in the blended gasoline and "carried" to the combustion chamber - causing bogging 'cause now you'll get even less bang... Did you fill up just before the storm and inadvertently get a "bad" tank o'gas?
Ethanol is quite miscible in water - ever drink vodka? As such, any water in the gas tank will actually be "picked up" by ethanol in the blended gasoline and "carried" to the combustion chamber - causing bogging 'cause now you'll get even less bang... Did you fill up just before the storm and inadvertently get a "bad" tank o'gas?
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