Flex fuel

freedomfueler · July 13, 2005

I have a 2002 Sierra Z71. They offered a flex fuel version of this truck in 2002. Are the fuel system components, other than the ECU and fuel composition sensor, the same for all models for this year, as well as the current models? It seems that the nature of assembly line fabrication would warrant using the same fuel pump, lines, fuel rails, injectors, etc. If this is the case, can an ECU from a flex fuel version be installed into a truck along with a composition sensor to run E85? Or better still, could a custom programmer like the Diablo Predator be used to open up fuel flow and increase timing to simulate the flex ECU?

Chris

GM-Tech · July 13, 2005

No, the fuel system components are not the same. Ethanol in those high concentrations are corrosive to the fuel system and this is not a simple changeover.

Besides, most people I know who have a flex fuel truck and have tried it are not at all happy with the results. The fuel may be a bit cheaper, but consumption goes WAY up and performance is also affected.

I wouldn't waste my time or money trying to convert to something that has little advantage, unless you have a real thing for reducing petroleum usage.

freedomfueler · July 15, 2005

No, the fuel system components are not the same. Ethanol in those high concentrations are corrosive to the fuel system and this is not a simple changeover.

Besides, most people I know who have a flex fuel truck and have tried it are not at all happy with the results. The fuel may be a bit cheaper, but consumption goes WAY up and performance is also affected.

I wouldn't waste my time or money trying to convert to something that has little advantage, unless you have a real thing for reducing petroleum usage.

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I definately would like to see a a reduction in petroleum usage - I guess I'm tired of letting some desert prince get rich off of the manipulation of our econmy. Just my $0.02 worth.

Which components of the fuel system are different on the flex-fuel models? Know any part numbers or references that can be found online? I notice that the shop manuals available from Autozone do not include information on the flex models. Calls to the dealership get me nowhere, either...what seems to be the big secret? Is there a reason that dealers are not forthcoming with this information? I would be interested to see the parts manuals on the non-flex vs. the flex models to compare what is so different about them. In the 70's, people started running ethanol in their cars with only minor changes to the carb. jetting. They just pulled the manual chokes out to increase the amount of fuel. I've read accounts of many of these simply modified cars and trucks running years on end with no noticable negative effects. If the alcohol is so corrosive, and these vehicles didn't just give up the ghost immediately(even with rubber fuel lines and other "non-alcohol tolerant" components,) how long would our modern vehicles hold out before noticable problems developed? Aren't the high pressure systems for fuel injection already made of materials that are more durable than those from the carb. days?

I definately don't want to go screwing up a pricey vehicle, but really, wouldn't I only be looking at eventual replacement of things like the fuel pump, lines and maybe injectors- it seems that if the vehicle would function , then it would be a matter of just accelerated degredation of these components and replacing a pump, or fuel line or rail, etc as it wore out, and that would be a lot less costly on the front end as a complete system changeover.

GM-Tech · July 15, 2005

Calls to the dealership get me nowhere, either...what seems to be the big secret? Is there a reason that dealers are not forthcoming with this information?

There's no secret. We don't do modifications in the dealership, nor does GM support this sort of change over. Why would we have that information?

We know specs that are needed to fix the vehicle and supply the parts that were designed for that specific vehicle. We don't know how a fuel tank/line is made/designed, or what their metallurgic composition is or what makes them resistent or not resistent to E85, nor do we really care. GM doesn't supply us with that information because we have no need for it.

No, no one is purposely trying to hide this information from you.

.

willieboy · July 15, 2005

IIRC, the fuel system seals, the injectors and fuel rails, the fuel tank, and the programming in the PCM are different. The fuel tank actaully has sensors that can determine the amount of EtOH in the fuel and adjust the timing/fuel mixture accordingly...

So, no matter, it is going to be expensive to convert a non-E85 vehicle to run E85. Your best bet would be to find an wrecked '02 with the L59 engine code.

Oh yeah, the LM7 5.3L typically had more HP than the L59 5.3L. For 2005 the specs are:

LM7

Horsepower 310 @ 5200 rpm

Torque 335 @ 4000 rpm

L59

Horsepower 295 @ 5200 rpm

Torque 335 @ 4000 rpm

I am not sure what the 2002 spec are.