need to lean out my m112 ranger..with SCT | Ford Explorer Forums - Serious Explorations

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need to lean out my m112 ranger..with SCT

hey...soo i just barely got the eaton m112 running on my 4.0 ranger, and it is running very rich, like mad black smoke rich....ummm i had the engine tuned at "quintin brothers" local shop here....they tuned it when it had the m90 on it with 24 lbs injectors....

i then 2 months later (yesterday) put the m112 and 42lbs racing injectors in...soo the thought is that it is getting almost twice the fuel it should? going from 24lbs to 42lbs injectors on the same tune...??

sooo when i got it tuned, they gave me the SCT x3 tuner, and im wondering how to do the datalogging and tuning to lean this sucker out alittle...cause its sooo rich that it like bogs down.....

The tune has to be changed for the 42 lb injectors. You need either the Pro Racer Package or go back to the shop and pay them to change the tune. The tune will still need to be changed more after datalogging A/F ratio with a wideband to get it right.

42 lb injector values should be something close to this:

.0112 High Slope
.01375 Low Slope

.0000166 Fuel Injector Breakpoint
.00040 Fuel Injector Minimum Pulse Width

Just to give you an idea of what's going on here.

The Pulse width is how long the injector stays open. This is different for your 42s vs the 24s you had.

"Fuel injectors have four main characteristics, and all of them vary with fuel rail pressure.
Injector behavior; it's important to note that an injector has nonlinear behavior and that it takes time to open!
The first is the offset. This is how long the fuel injector takes to open when the ECU asks it to do so.
The second is low slope. This is how fast fuel exits the injector when it first opens.
The third is the breakpoint, which is how long the low slope phenomenon lasts.
The final parameter is the high slope, which determines the overall rate of flow of the injector.
There are constants and functions in the ECU that are designed to model these phenomena. I had loaded the correct values for the slopes and breakpoint, but the offset was wrong. The offset value stored in the computer was for my stock 21 lb/hr injectors, and my new injectors opened in about half the time! As a result, I was injecting more fuel than expected because the EEC didn't "understand" how quickly the injectors would open after it sent the signal. I'd leaned out the MAF transfer function to compensate, and the load calculation was off by ~20% at idle."