So, I've read a bit about the popular mods for the H3 (PCMforless tune, e-fan conversion, etc.), but I can't really understand from their website what this stuff actually does.

I've done some mods to my current sports car and previous cars I've owned, but I've never replaced a fan or heard of such a thing having significant power gains? What is this thing, what is it replacing, and why is it better than stock?

What does the tuning change?

Why is a cat back so worthless on the I-5?

I'm sure these have been answered at some points in the past, but my search keywords aren't turning up the layman's terms answers I need.

TIA!

 

Most cars have used electric fans since the 90s, for trucks that has been a slow transition, GM started with them OEM in 2009 FS trucks. The H3 has a mechanical clutch fan driven by the serpentine belt off the crank pulley. It basically is on all the time even when the clutch is disengaged and it weighs about 6#s.


The Efan does no produce power, rather it frees up some that is being used to spin it. The Efan conversion is a solid 1 MPG boost and 5-10 HP.

The PCM (Power Control Module) is the flash computer program that runs your power train. Think of it this way, the factory sets it for Grandmas and Soccer Moms, and leave a bunch of performance on the table because John Q consumer doesn't want or care about firm quick shifts, keeping the motor in the peak power band while mashing the skinny pedal, higher RPM down shifts, advance spark curve or increased fuel trim tables. The PCM tune is the biggest bang for the performance buck you will likely ever see.

You can order the tune to match your other mods, like an intake, PP TB, Cat back, tire size, fuel octane...etc. In fact, the PCM controls the Efan in 2008+ H3s, the 06/07 are controlled through a temp sensor placed in the lower radiator hose.

 

Wow, awesome write-up and pics! Thank you very much!

I have an '06; is there any difference in the benefits offered by the tune (and the difficulty of the swap) considering the fan is controlled by that temp sensor instead of the PCM?

 

Doc knows his stuff. I don't know if there's been an improvement since I heard about the electric fan a few years ago, but the electric fan made a lot more noise than the stock fan. I remember seeing a video of someone driving in the woods and someone commented that he was wondering who was running the leaf blower in the background. Maybe there's a quieter version now. Definitely a good mod if it frees up that much HP.

 

Not really, to drain the radiator in a 3 you disconnect the lower radiator hose. While it is disconnected, you cut it where you want to mount the sensor.
Here is a good look at mine.