Re: I have never used ethanol - Saab 900 Bulletin Board - Saabnet.com
NG900 & OG93 |
Vintage Models |
Clubs & SOC |
Other Cars |
Member Photo Galleries |
Member Directory |
*Buddy Registry |
*Mileage Registry |
What's New |
Photo of the Month |
Octane: The research octane of ethanol is 106 vs 90 for gasoline. The (R+M)/2 octane of ethanol is 98. The autoignition temperature is about 200 degrees higher. Ethanol doesn't ping nearly as readily as gasoline, and will tolerate higher compression ratios and stronger and longer boost than will gasoline.
You want to fire ethanol about 5 degrees sooner with ethanol. I've seen no data on what the ideal spark angle should be for C900. Start at 21 and experiment.
Ethanol burns faster than gasoline (faster flame front propagation). Ethanol burns cooler than gasoline, yielding exhaust temps of about 1000 degrees instead of 1400 to 1650 (this is not data from a Saab). It has a higher flash point than gasoline, which makes it harder to start in freezing temperatures.
As for ethanol's energy density, that's not the most interesting property. If you measure energy density by E=MC^2, then ethanol, with its greater mass per gallon, would nuke gasoline. Hmmm. But that's not the kind of energy we want. ;-)
It's popular in the press to compare BTUs, a measure of heating value. Gasoline has about 110,000 BTUs per gallon, ethanol 76,000, and #6 Fuel Oil about 150,000. If you were running a radiant floor heater and had all day, gasoline's 45% higher BTU content would be interesting. But we don't care about BTUs so much because efficiency matters and *time is of the essence*. If BTU was the key property, we would be running Saabs on melted beeswax.
What matters is how efficiently is energy converted to work in the limited time available.
Combusted ethanol produces a greater volume of exhaust gas, at a lower temperaure, than you get with gasoline.
We have some very interesting properties that are nicely suited to an internal combustion engine. It's a stable fuel that doesn't detonate until you tell it to, then it flashes rapidly, it takes compression very well, you can advance the timing giving it a bit more time to combust, leading to more complete combustion, and you get a higher volume of exhaust gas at a cooler temperature. Compared with gasoline, more of the chemical energy is going into expanded gas and into piston motion and less into heat.
I don't have a good handle on how this *really* works. But the possibilities are interesting.
posted by 69.12.207...
Posts in this Thread:
- Do cooler operating temps reduce mechanical losses?, mag , Mon, 13 Jul 2009 02:54:45
- Re: Do cooler operating temps reduce mechanical losses?, Ari, Tue, 14 Jul 2009 04:19:15
- Let's leave the politics aside ..., mag , Mon, 13 Jul 2009 21:41:35
- Re: Do cooler operating temps reduce mechanical losses?, mag , Mon, 13 Jul 2009 13:48:16
- I have never used ethanol,, tibbidoh , Mon, 13 Jul 2009 15:46:26
- Re: I have never used ethanol, mag , Mon, 13 Jul 2009 20:13:08 <-- Viewing This Message
- Re: I have never used ethanol - me either, oldsaab, Mon, 13 Jul 2009 17:09:44
- Re: I have never used ethanol,, Justin VanAbrahams , Mon, 13 Jul 2009 16:35:33
- Re: Do cooler operating temps reduce mechanical losses?, tibbidoh , Mon, 13 Jul 2009 07:00:39
- Re: Do cooler operating temps reduce mechanical losses?, Landjet , Mon, 13 Jul 2009 05:18:29
Post a Followup
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
This is a moderated bulletin board - Posting is a privilege, not a right.
Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY.
Classifieds are to be listed in The Saab Network Classifieds pages.
This is a problem solving forum for over 250,000 Saab owners, so expect to see
problems discussed here even though our cars are generally very reliable. This is not an anything goes
type of forum. Saabnet.com has been a moderated forum since 1988. For usage guidelines, see the
Saabnet.com Mission and Purpose Page. Please remember that you are
not anonymous. Site Contact | Site Donations | Other Sites by SP -
Your address is: 184.108.40.206 - Using CCBot/2.0 (https://commoncrawl.org/faq/) - Logged.
Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all
the Site Membership Benefits!