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Old 01-25-2016, 02:34 PM   #25 (permalink)
Master EcoModder
Join Date: Apr 2008
Location: Michigan
Posts: 261

Bio Deezler (sold) - '03 Volkswagen Jetta GLS TDI
90 day: 50.78 mpg (US)

The Beast. - '03 GMC Sierra 2500HD SLT
90 day: 12.86 mpg (US)
Thanks: 0
Thanked 36 Times in 22 Posts

Increasing engine efficiency (and power ) is always another modding priority of mine.

My last two daily drivers have been turbocharged, where increasing power is about as easy as cranking up the boost and putting on some bigger intake/exhaust pipes.

But now that I'm in the land of naturally aspirated operation and stoichiometric air fuel ratios... there's not as much easy modding to do.

An air intake upgrade is one legitimate option though. I know this flies in the face of a lot of readers here who would rather sacrifice some power with a warm air intake to help reducing throttling/pumping losses, but, I would like to be able to tow 10,000 lbs with confidence. So a less restrictive intake path can still help reduce pumping losses a bit.

Based upon some independent dyno-testing results on a GM 5.3L, I opted to go the cheaper route and replace only the filter and intake pipe. The factory airbox can already flow plenty of air.

BBP Independent Intake Test Results | Chevy Truck Forum | GMC Truck Forum -

I went with an AEM dryflow filter for it's high flow and washable characteristics.

The stock intake pipe has a funky "sound tube" appendage that surely doesn't help the airflow.

Replacement pipe still had a notch to clear the mechanical fan shroud.... GRRrrr, that fan has to go!

The next mod is not something I would ordinarily pay any extra money for, but, I got suckered in by some discounts and free shipping while buying other things. The only reason I actually bought the plug wire set was an attempt to fix an occasional P0300 "random misfire" code that I have been getting (more on that later).

Fancy red color bling, but no change in performance (duh). Was still getting the P0300 code, mainly at highway speeds. This was actually a huge problem, because any reported misfires cause the ECU to unlock the torque converter. So then you are wasting fuel into transmission heat, and eventually burning up the TC. Not cool.

Internet search to the rescue! Thankfully I have access to a professional grade GM scan-tool here at work (GM Tech II). Turns out all I had to do was a "crank position variation learn" procedure. Just select the function, rev the engine, and boom, done.

The ECU "re-learns" the relationship between the crank and cam angle sensors, and re-adjusts its criteria for determining misfires. So basically I wasn't actually having any misfires, but the ECU thought I was. No more! Hopped on the highway to verify, and had full TC lockup and ~+2 mpg.
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