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Discussion Starter #1
I've heard it gives you better throttle response, like that of a gasser. But how and why does it do that?

Is FICM tuning completely separate from a tune like looney or SPD through an SCT?
 

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Yes, completely separate tune. A FICM tune modifies the programming in the FICM, whereas the other tunes modify the PCM programming.

Exactly how it does it is a closely guarded secret. If everyone knew exactly how it was done, companies all over would be duplicating the process. However, basically what they do is change the timing of the injections, the length of the injections, and the number of injections per stroke. Here is an exaggeration of one possible change....

In an old engine you might get 1 injection per stroke. The injection occurred 45 degrees BTDC, lasted 36ns, and it injected 2CCs of fuel. (please remember, I'm making this crap up...I have no idea what real figures would be, but I do have the general concept down) With this process you have too much fuel in the cylinder at one time which results in unburnt fuel washing down your cylinder walls and coming out of your exhaust, and/or partially burnt fuel pouring out the exhaust as black smoke. Everything runs, but it's rough as hell and there's not a lot of power. Modern engines have changed things to give two or three injections per stroke. It starts with a little one somewhere around the same point as stock, lasts only 10 ns, and injects 2/3CC. The second is somewhere around the point of ignition. The third is after ignition, but still during the flame-front phase. The same amount of fuel gets injected, the injection duration is a little less with different timing, but nearly all of it gets consumed resulting in less waste, more power, and better MPG.

This is the same concept with the FICM tuners, but they have added more injection cycles and tweaked the timing. You inject less fuel more often, at more appropriate times, and get an increase in power, reduction in fuel used, and a smoother running engine.
 

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i've hear the "less fuel per injection with more injections per stroke" before as well! ^^^

a couple interesting side effects is that (1) FICM tunes seem to increase exhaust temps, rather, the ones that increase power. the economy ones don't really i don't think. not sure though...
and (2) cylinder pressures aren't jacked up way high like pcm tuning usually does.

so there's some tradeoffs to think about based on how the vehicle is used and what state of health the truck is in.

Ed at ficmrepair.com explained that to me, and he made more sense then i just did lol! he'd be more than happy to answer that better for you, just call the number on their webpage
 

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Discussion Starter #4
Ah I see, that makes sense. So does the FICM break up the PCM commands into X amount of injections per stroke?

I've read up on pulse width which I understand to be how many seconds total an injector is open per stroke. Would the PCM command, say, 20 NS of pulse width and the FICM would break that into 3 injections of like 6 or 7 NS each?

Interesting how it all works. I would have thought the PCM would have commanded how many injections per stroke for how long from the very beginning.
 

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That's a good question...and probably another one of those trade secrets! lol

Turd's right about some of the trade offs. On the 80 I saw a little increase in EGT and with the 100 I saw a bunch more. However, after installing a 5 inch turbo back exhaust with CAT delete, my EGTs may as well be stock. Even pulling a trailer they're WELL within comfortable limits on the 40 and 80...though the 80 does get higher than the 40 with the trailer. And as for less pressure, with the economy and 40 tunes they (PHP) say this is true. My ex is running their 40 on a 2003 with 230,000 on the ticker with only an EGR delete done (still on factory head bolts!) and she often tows an 8,000 lb trailer, and no head gasket issues. (knock on wood)

Oh...and just because I have to brag. lol Driving my 8,000 lb Excursion down the interstate at 82 MPH for a 4 hour trip, I got 18.5 MPG running the 100 HP tune. Not too shabby! This was on summer fuel. I doubt I would have broken 15 with this winter grade crap. lol
 
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