I'm going to assume (usually a bad idea) that you understand the basic theory about how and why the Warm Air Intake works and some understanding about automatic transmissions, more importaintly, the Torque Converter oeprations.
In an effort to get at LEAST 30mpg highway without having to P&G in my tracker I decided to give the WAI a try. I've changed my acceleration to hard ont he gas hovering around 4500 to a shift until I hit 35mph where the TCC locks itself and then continue at a steady speed(in town of course). I removed the tube from my air box that was there to pull fresh air as opposed to the surrounding engine bay air and gave it a whirl.
The engine was noticeably louder under load. If the engine was in a small RWD 5 speed car I would have loved the sound, it was simply incredible, but for a small SUV like this it was nothing but annoying, especially on the freeway where the engine ends up being under heavy load to keep 75 and really sucks on a long trip.
I can honestly say I didn't like it after the engine warmed up. When the engine hadn't fully heated up and the engine bay was still cold it ran like a top but after the radiator and engine both warmed up I ended up with an even bigger dog of a car than I already had. This wasn't too big of an issue I guess seeing as that is how the WAI is supposed to work.
I had gotten an all time freeway high of ~26.5 mpg and even that I only got once, usually it hovers around 23-24mpg @ 75mph (VERY lame). With the WAI I averaged a trip total of 24.3 mpg. Not very outstanding. Since so many people on here rave about the WAI increasing mileage by 6% or even more I started to wonder just what was going on.
Of all of the different things out there that could be options as to why it didn't work like: ECU in a limp mode, ECU doesn't read very hot intake temps well, O2 sensor bad, or even the air wasn't hot enough, I ended up not blaming it on the engine. This is what lead me to my torque converter lock-up mod. I can manually lock the TC any time the transmission is NOT in first gear.
The confirmation of this came this morning when I was on the freeway to work and found myself at around 90mph(don't ask) and, to my astonishment, I was able to look down at the dash and see my green 'torque converter locked' indicator light glowing. It was 51 degrees outside and the engine was running GREAT.
Then I started thinking to myself, "you know, on a hot summer day I can barely keep 70 while pressing the gas little enough to keep that converter locked and here I am doing 90 and it's locked no problem". I pressed the gas down more until it unlocked and I'd say I had a good 15-20 degrees of throttle left before it unlocked.
Basically, the reason the WAI didn't work for me is actually the same reason that it's supposed to work for everyone else. Opening the throttle more to get the same amount of power(reducing pumping losses) ends up putting my throttle position to a point that the converter never locks on the freeway, totally negating any benefit the WAI may have possibly had.
Now that I have my manual TC override I need to take another trip. My only issue, again, is noise from the intake being rather annoying on the freeway. I also have my $20 craptop so I can start datalogging on more than my single channel TI-84+
Maybe now that you have a manual TC override you might want to try letting the engine suck air from the engine bay again? Do you know how hot your intake air was with that setup? I have not noticed any substantial power losses from WAI in The Beast, but then with a 350 V-8 I have some power to spare.
you may have a rare case where you need all the power the engine can supply.
not sure if you have a scangauge but you can monitor percent load. you may be taking away the power that you need. I have noticed that on my car, I only get up to about 40 percent load during norman conditions. I do use more throttle when taking off to get it up to top gear (overdrive) and at that time I will see more of a load.
your may be a worse power to weight ratio than mine which requires more power at times which is where the WAI may be hurting you.
just a theory
also if it is too much to give up, just drive it comfortably and take the hit in MPG. if you aren't comfortable, then what is the point? same thing with windows down (a/c broken) I get better FE with windows up but am not willing to give up that level of comfort (especially on the really hot days).
Be the change you wish to see in the world
Yeah, I'm too cheap to buy a SG. I've been getting throttle position with an analog multimeter and wires running under the hood. According to my TI, I was running ~145 degree air from the engine bay in town and down to 120-127 on the freeway.
Also in case you didn't do the math, 6% of 24MPG is only 1.4MPG or so, so it might be easy to miss, you'll have to watch for a running average across a few tanks.
My truck definately noticed using warm air but I think that's because it may be running right. My old TBI is speed density so I'm not even sure it looks at intake air temp and it certainly doesn't have a MAF. I really need to get a programmable EFI.
Still, you're pulling an average of 18 in that truck which is fantastic. Don't short change yourself - You're doing a great job so far. Your truck is even heavier than mine because I have the 6.5 foot bed, and you have the 8. Add the fact that its 14 years old and 230,000 miles... I think you are doing very well indeed.
Meh, I want to try warming the fuel and tuning the O2 a bit. This thing will squeal tires at any speed and runs like it has 40k on it and it's actually at 242k right now. Not sure if it's original motor or not though, I bought the truck with 210k on it. My first tank at 19 though and that was my highest. Probably a calculation error but I'm really itching for more. 20 is so close.
It might help to have a gauge too, I've almost got the DIY working, just need a laptop with stereo input :/.
Hey just a question... how did you get the manual TC override?
I have been trying to do this for soooo long to get it to lock at much slower speeds like 25mph instead of 42mph (where it locks by itself right now), and to keep it locked under a little more load... ??
The idea is pretty simple. The ecu puts out 12v to a wire going to the transmission to lock the converter. If you want to lock the converter earlier just feed 12v into that wire sooner. I'd recommend at least a rectifier in the circuit to keep 12v out of the ecu(not sure if i'd hurt anything or not.
Mine was a little more complicated, it switched the ecu to a dummy load of 16 ohms whenever the circuit was active and then either connected 12v or disconnected it with an indicator light for when the TC was locked(regardless of wether or not it's in manual or auto mode) and a red light to indicate when the system is active by a half lit red LED and when you hit the brakes with the TC locked with the red led at full brightness.