E85Forum.com

jdorff · Joined: 01 Aug 2006 Posts: 25 Location: RTP NC USA

Hello,

I've been weaning my BMW with richer and richer mixtures of E85 and unleaded. I've found E40 seems fine, but E50 causes a CEL. The car is designed for high octane premium fuel and seems to run fine on E40 (E85 and 87 octane blend). I haven't driven enough to get firm numbers on fuel economy, but using the car's computer it seems to be slightly less on E40 vs premium gas.

I'm considering full E-85 conversion using the Full Flex product described here: http://www.beutilityfree.com/still_home_page/flextek_homep.html . My primary motavations are political and environmental rather than cost savings.

Any comments or suggestions ?

hotrod · Joined: 19 Apr 2005 Posts: 872 Location: Colorado

Your experience appears to be pretty typical as most modern cars seem to tolerate around 30% or better mixtures of ethanol.

Your conversion could take on several forms, either an all or nothing conversion where you install larger injectors or increase base fuel pressure (or a bit of both) to get enough fuel flow to allow higher blends of E85.

If you car has some performance tuning options that allow you to have full control over fueling then you should (assuming no incompatibility issues) be good to go on a full or high ethanol blend conversion.

Larry

jdorff · Joined: 01 Aug 2006 Posts: 25 Location: RTP NC USA

Can you educate me on the details of larger injectors. I can find "hi-flow injectors" for my engine.. often from folks selling supercharger kits. How do larger injectors interact with the ECU ? Do larger injectors supply more fuel than normal injectors with the same ECU pulse ? What effect would "hi-flow" injectors have w/o changing the ECU ?

GripperDon · Joined: 26 Aug 2006 Posts: 5 Location: Scottsdale

that the engine Electronic Control unit would.

Listen for Knock (pinging) and adjust the timing as advances as possible to maximize power and efficiency, More ethanol more advance

Second the oxygen sensor ( lamba unit) would adjust the fuel quanity by changing the pulse width to the injectors to keep the A/F ration at close to 1 as possible.

If the systems is Mapped ( has a memory that says a certain Air fuel ration lamba input is to be given a certain pulse width in relation to the oxygen sensors output then the system is not 100% Closed lop but has inputs that cause it to go to a certain value of output as governed by as lookup table.

Then in this case a unit like the flextex is providing a streached or increased pulse width to the injector to increase the amount of fuel provided to the engine in response to the percentage of ethanol in the fuel.

It should not be required to use higher flow ( larger orifice) or increased fuel line pressure to accomidate the Ethanol content when a longer pulse width can do the same thing.

Confused