[AT] GM Flex Fuel vehicles

[Henry Miller]

I wasn't home for a couple weeks, so I'm late, sorry.   (I work 100 miles from 
home)  A few minor corrections need to be made though, because I'm an 
engineer who hates to see mistakes.

On Monday 31 July 2006 21:18, Steve W. wrote:
> Charlie,
>   There are three major differences in them. One is the gas cap itself.
> Besides being Yellow it has a different vent valve in it because alcohol
> is hygroscopic so the venting is set up to only vent pressure. The
> second is the fuel line assembly. There is a 700.00 flex fuel sensor in
> the line that tells the computer what the mix in the tank is. The sensor
> is the same for all the flex fuel vehicles made from 2002 and up. The
> line itself is also made of a different material.

Maybe, maybe not.   Not all flex fuel cars have the sensor - some cars can 
figure things out without the sensor.   The main difference is the air/fuel 
ratio, and you can get a good clue about this ratio by reading the oxygen 
sensor that is already there.  All cars need to be able to adjust between E10 
and straight gas (often one of the many different types that each city 
mandates), this is just an extension.  

The fuel line being made from a different material can be an important factor.  
(but only when they don't change all cars of that type over to avoidproblems 
where the lines puts the wrong line on a car)   Most people who experiment 
(illegally) have not seen a problem with the wrong line though.

> The last change is in 
> the injectors. Since alcohol has less energy than gasoline they
> increased the flow rate for the flex vehicles to accommodate the higher
> rate of fuel flow.

WRONG!    Yes the injectors are bigger, but it is not because ethanol has less 
energy (though it does).  Injectors are bigger because ethanol needs to run 
richer than gasoline.   Gas needs an air/fuel ratio of about 14:1, while 
ethanol is about 9:1.   Without the bigger injectors your engine runs too 
lean.   Over time (thousands of miles, one tank of E85 is not problem) this 
can burn a hole in your pistons.

> Now for the REAL problem. It is Illegal to convert any unleaded fueled
> vehicle to a different fuel unless you have the DOT do a test on the
> entire vehicle and can prove that it meets or exceeds the emissions
> standards for that vehicle type. That test is about 10,000.00 to have
> done. There are NO approved kits or methods out there to convert a
> vehicle to E-85 or other fuel. Get caught driving a converted vehicle
> and you get to pay a BIG fine for tampering with the emissions system of
> the vehicle.

Yep, but if you seearch you will find conversion kits.  The state of MN is 
considering getting involved in certifying these kits, so you might want to 
revisit this issue in a couple years.   In MN E85 is about $2.59/gallon, so 
there is money to be saved if you can use it.   (MN has more Ethanol than we 
use, and we are not able to transport enough to other states that have a 
shortage, thus there is a large spread in ethanol prices depending on where 
you live)