Ok, here's the deal. I am not going to modify my LS1 tank's sending unit, and I want to use my stock gauge. Eventually going to do an LSx swap. But, I'd like to go ahead and get the tank in now. So I made up a schematic (attached as an image) of something that according to the simulation should work. But, it seems kind of complicated and will require very specific resistances (probably need to use variable resistors for exact calibration.) So, I guess what I am wondering is: Is there any simpler or more forgiving way (with regards to the resistances) to achieve the same goal? The goal being to make a device that will manipulate the current flow through the gauge coils in the same manner as a 0-90 ohm sending unit, while using a 40-240 ohm sender. Or, is what I have basically it? I considered a microcontroller + digital potentiometer setup, but they don't make digi-pots with 0 resistance, and the ones they have can't handle much over 10mA of current anyway. The schem. is attached as an image. Ignore the resistance values of the individual resistors. They are non-standard and I have just been messing with them to ballpark what I need to acheive good range and linearity from the current changes. Also the gauge coils are represented by the 85 and 100 ohm resistors in the gauge. After all that I wonder if it will make sense to anyone what I'm trying to do... EDIT: On second thought, it's pretty simple already, I guess. It's just the resistances that have to be so perfect. Even a little bit off screws everything. And, I wonder what supply voltage variances will do to it. I would probably have to add a voltage regulator... I guess I'm just looking for some feedback from anyone out there who is more experienced with this sort of electronics stuff. I mean I know my way around it (a little), but I'm not officially educated in the field...

well from your avatar it looks like your doing a 6.0 swap down the road, and that (i think)is good news. see, if your useing a 6.0 truck computer, the signal from the gas tank sender actually runs through the ecm. now i havent messed with it yet because my mustang is an ls1 not a 6.0 . but i did see that you can change the program values for the sender.

this is what i have been thinking about doing in my mustang because i have camaro gauges. and the sender is diff than the camaro (cuz its a stang). so i wonder if this can be used in some way to adjust for your gauges too.

or you could just hook it up and know that around a little less than half tank your on E!.

Hmm, I think you're right, but here's what I found on my demo version of EFILive. This is with regards to a 2002 Corvette LS1 (one of the sample files). Anyway, here's what it says under "Fuel Gauge Calibration:"

Looks like the certain PCMs can be setup to emit a PWM signal to directly drive a fuel gauge. Normally the LS1 fuel gauge is controlled by the "serial data bus" mentioned above. According to this, it looks like it might be possible to use this PWM signal... Although it doesn't give any sort of wiring diagram or directly explan the gauge he is using, so some more thought would have to be put in to see how it might work on one of our gauges. And, more research into the characteristics of the PWM driver in the PCM.

However, when I do the 6.0L swap, I'm planning to use an LS1 gauge cluster anyway. So, when I do get to that point I will just run the gauges like normal in an LS1 f-body.

But, you definitely reminded me that the LS1 sender does still emit a usable range for half of the stock third-gen gauge. I did know that, I promise, I guess I just let it slip my mind cause I got all side tracked on this little electronics project. Which is ok I guess because I enjoy this kind of stuff.

So, with that said, I think I will just do that... Hook it up and go, keeping in mind, and maybe making a subtle mark where the "new" empty will be.

If anyone has any interest in this "adapter" thing, just let me know, I'll be glad to offer any help I can. I might even make a prototype anyway, if I can find the parts around here and not have to order them.