Hey guys, sorry about writing another book with this post, but I would like to share some information I hope will be useful to those of you who are interested in getting more control and adjustability over the electronic fuel injection system that governs our little 2.5l engines. I wanted to let anyone know who might be interested know that I have successfully built my first MAP sensor adjustor per the instructions I got through a thread on this board and the Google research I did on the subject. I changed the design a little to suit my tastes, and to offer a few features the original design didn't offer. Now I will admit that I have a lot more electronic theory and circuit design/creation experience than most people I know, so this was very easy and quite enjoyable a project for me, but it's easy enough that a simple one can be made by someone with only very basic electronic skills (I think one of the designs that was offered didn't even need soldering, it relied instead on connecting all the components with a screw-down type terminal strip). My design relocates the circuit to the passenger compartment. I added a second adjustable voltage regulator circuit to run in parallel with, but independent of, the single regulator circuit the original design called for. I added a second switch as well. The end result is I have a nice little box on my dash that has 2 presets that are selectable with the flick of a switch. One switch selects between the stock signal and the new, modified signal. The second switch selects between the two adjustable regulator circuits. This allows you to tune one circuit for maximum fuel efficiency, and tune the other circuit for a more aggressive setting and select between these two settings instantly. You can also re-adjust these settings anytime you like from the comfort of your driver's seat! No need to climb under the hood to fumble around with the adjustor pot's anymore!
I also have located and modified a circuit for a Air/Fuel ratio gauge. I'm going to build this right into the MAP sensor adjustor box I built so I can monitor and adjust my fuel ratio without having to get out of my seat, all in one little box!
If anyone is interested in this stuff, I will be happy to provide information and I am debating producing a few of these MAP/Air-Fuel ratio boxes like the one I have, for a modest contribution cost (I need to recover the cost of materials and time that goes into building and testing one of these babies! It will be ridiculously cheaper than anything else you can buy, and offers a lot more adjustability and better features than any commercial units I've seen yet. Just to give an idea, I think the MAP adjuster-Air/Fuel ratio meter combo box can be built and shipped for less than you can get a cheap Air/Fuel ratio gauge from AutoZone, or anywhere else for that matter-probably less than, or about $50 for the whole she-bang including all the wiring you'll need to install it and nicely detailed install instructions). I will ONLY extend this offer to members of this board, if I do decide to build a few extras, and this will ONLY come after I fully test these things and am completely satisfied in their operation. So far, it bench tests PERFECTLY! I get total adjustment of my MAP sensor reference signal from ~0vdc to 6.55vdc. The original reference signal is 5.0vdc. This is more than enough adjustment to compensate for the 4.0l Throttle Body upgrade and other future mods.
I would SERIOUSLY suggest using an Air/Fuel meter if you want to try and make one of these MAP adjusters on your own. Setting this thing is just a guess if you don't have any type of real-time feed back from your engine. My Air/Fuel ratio meter I'm making building (as with most commercial units) can share the stock O2 sensor's signal with the ECM, or you can have your favorite exhaust shop weld in a bung for a second O2 sensor somewhere near the exhaust manifold. Install a single wire sensor in this new position and wire up your gauge to that if you'd like to keep the gauge separate from the ECM's O2 sensor, whatever you want. I'm cheap right now, so I'm double dutying my O2 sensor. The draw back, though, is if my single O2 sensor starts to go bad due to old age, I won't have a separate sensor's signal to compare it to, so it might take a little longer to realize your sensor is taking a crap on you. That's not a big deal though; eventually you'll figure it out when your A/F ratio gauge consistently gives weird readings all of the sudden and the classic dead O2 sensor symptoms emerge.
