View Full Version : Ethanol/E85... question for people who understand turbos

09-15-2006, 12:14 PM
I am posting this question here becuase TR owners understand turbos. Saab has a car availible in Europe that can produce more horsepower and have just as good milage on E85 versus regular gas. This is interesting because Ethanol has less BTU's than gas and if you have a "flex fuel" car or truck you will notice your MPG worse with E85. I think CP did a study and found a Tahoe would get 7 MPG on E85 in the city, the worst economy ever they have ever tested. E85 does however have higher octane.

That said, how can Saab get comparable economy with E85 vs regular gas? Must be with the turbo. If so how? Any ideas?

For those of you who do not know what E85 is, it is 85% ethanol and 15% gasoline. You need a "flex fuel" vehicle to burn this mixture. All cars can burn E10, or 90% gas, 10% ethanol.

I dont want to get into a debate about is Ethanol a good product or not, just some feedback about what saab could be doing with the turbo to make thier car work while burning E85.


09-16-2006, 10:59 PM
Manufacturers aside...

I don't believe any car will get the same MPG on E85 as standard fuel. Period. An alcohol based fuel has less energy, but a higher octane (much higher). Yes, the turbo may make the vehicle more efficient in how it uses it. But E85 will still be a lot less efficient than regular fuel.

There was an expiriment with 5 (?) '87 T's from the Department of Engergy using E85, I believe. They were all modified to have 30 gallon stainless tanks, larger injectors, and some other mods. One was procured at auction by a member of our old mailing list. Ahhh...here it is:

http://www.ajlc.waterloo.on.ca/cgi-bin/SFgate?language=English&verbose=1&listenv=DL&application=gnttype&convert=Mail&converthl=&refinequery=&formintern=&formextern=&transquery=stainless%20and%20tank%20and%20injector s%20and%20auction&_lines=&multiple=0&descriptor=local%2f%2fhome%2fhttpd%2fwais%2fwais-sources%2fgnttype%7c237%7c3313%7cHorace%20Lut%20Re :%20Re:%20Those%20M85%20T-types%20that%20went%20on%20auction.%7cTEXT%7clocal host:0%7c%2fhome%2fhttpd%2fwais%2fwais-sources%2fgnttype%7c0%203313%20%2fhome%2fhttpd%2fW WW%2fgnttype%2f199907%2f1295

Actually, Horace had an ex-M85 car. Not quite exactly the same, but similar.

09-18-2006, 05:32 PM
Thanks for the reply and the link. I do understand that Ethanol has less energy (BTU's) than gasoline. I think it is 135K for gasoline and 77K for ethanol. (I could and am probably wrong). That is why I posted the question in the first place. How would the turbo make it more efficent. maybee it does not get exactly the same, but the % drop-off in Milage is not as big as other cars. From what I have been told it is the turbo. How?