custom 68

iTrader: (9)

Hey all I wont be doing my own tuning (yet) but have transplanted a 5.3 into my truck. The vin indicates it is a Flex fuel vehicle. I understand the injectors are larger for tihs option. Now to tune for "gas" does my tuner need to be aware of this? I assume there is some changes to be made to compensate for the larger injectors. I have had the truck mail order tuned and it runs and starts great but I think it is running rich. I will scan it with autotap but dont know what this will tell me? my fuel mileage is lower than expected.
also are the injectors marked differently so I can confirm this?
thanks
Dave

hondo

iTrader: (2)

The flexy fuel injectors ARE larger, they should have a different PN and a little chatting with the GM parts counter guy should get you the info you want.
I believe they are Denso injectors(gas would be delphi's).

Then I'm sure there are tables in the pcm to deal with the different levels of ethanol in the fuel, theres a sensor that measures that.The tuner just really needs to know the LB/HR rating of the injectors, so they can get the Injector Flow Rate table right. If the tuner just sent you a tuned PCM for a 5.3 truck without knowing you can be sure its setup for the gas only injectors.


If the PCM is set up for 5.3 gas only injectors(19 LBS/HR?) it will be rich everywhere with the larger flex ones installed.

MSURacing

iTrader: (1)

Stock 5.3L injectors are 28lb/hr, flex fuels are 33 lb/hr. These are aka as the LS2 injector. They should have a different connector on them. The stock 5.3L connector will not engage with the flex fuel injectors.

custom 68

iTrader: (9)

ok thanks guys for the info. I am still on the quest to make sure what I have. I thought after I decoded the VIN I was given from the yard indicated it is a flex fuel but I bought an aftermarket harness and they pluged into it so that makes me think they are the "stock" ones.

I will do some scanning and get a better idea. It runs great I just wanted to verify what I have.
Dave

horist

the harness should be the same regardless (doesn't matter injector size, they all use the same plug)

I believe flex fuel vehicles have an extra sensor that determines the type of fuel... I could be wrong... but I thought this was how they worked... and this is what let them switch between fueling tables.

custom 68

iTrader: (9)

Mike I think you are correct, however I dont believe I have this on my conversion? so I assume they will only work on in "gas" mode. I will do some more digging and figure out what injectors I have. During scanning can my narrow band o2 sensors get accurate enough to determine if I am running rich or not. I will be using Autotap.
Dave

horist

The narrobands can give you a ballpark... part throttle you should see them switching high low high low (after warmup)

WOT high 800s to 930 or lower is probably ok... higher you are probably running rich, lower and probably lean ... but hard to get exact ranges w/out a wideband, so you have to just ballpark it

Busterandnitro

Hey do you still have that tune? I just put a 5.3 in my jeep. I bought a LM7 but they sent me a L59 Flex Fuel. So i have the same situation with my injectors and it running rich. Any info on the tune would be helpful.
thanks

kbracing96

iTrader: (25)

Do you realize this thread is over 2 1/2 years old?? What software do you have? We can probable help you find a stock tune that will work with your FF motor.

Busterandnitro

Yes i know its an old post but i was hoping someone like you would respond and be able to help me......So my plan worked

Anyway, My buddy has an HP tuner. I don't know what changes he needs to make to the fuel table, or anything else for that matter, to make this thing run better. I want to set it up to run standard 87 or 89 octane. The computer i'm using is from a 99 silverado 5.3

Any recommendations?