gearheadE30 said:@Curtis - all of the warmup modifiers, from the factory, are out by 155-165F depending on the table. That was one of the first things I checked, and logging confirms it never falls back into warmup. If I'm not in warmup, is there still benefit to running higher thermostat temperatures? I had always heard there was for carbureted/TBI stuff, but once you get into dry manifolds and port injection, that the evaporation impact didn't matter so much, but that's all secondhand "knowledge" or worse.
One way to find out. My next step would be to stab in a factory stat and watch injector pulsewidth after entering closed loop... all the way from 160 up to 205F and see how much it changes. It's probably less than an all-iron LT1, but I promise that pulsewidth will get shorter as the incoming air continues to get hotter. Less air and the O2 closed loop injects less fuel. The ECM isn't modifying it, physics is.
Much of what makes a "cold air intake" help is two things: Keeps the intake air colder which allows for the ECM to add fuel (power) and removes restriction. Adding a cold air intake would likely help you make more power with cooler air and thereby need less right foot to maintain the same speed, (probably a wash) but it won't do much (I'm told) for removing restriction, and therefore might not help you much. A lot of these trucks have massive filter elements and big boxes that don't restrict much. I was itching to do a CAI on my Express van until I pulled out the filter. Dear god you could probably feed three 5.3L engines with that thing.
The big killer I'm told is that factory muffler. Not only is it huge, but it makes the exhaust flow the whole way down, back forward, and down again. I ditched mine for a Magnaflow. Sounds great, but check the intarwebs for drone feedback and always take it with a grain of salt. The Magnaflow I put on, every Express van owner said "no, no drone, it's quiet inside." They all lied because they were embarrassed they spent that much money on a premium muffler only to ruin their driving experience. I'll be adding some change to try and shut mine up.