This is just a follow-up post for things I've learned. The summary is that I could not get a slightly smaller S/C pulley to work despite living at a higher altitude (thinner air) and having Gadget's fuel kit upgrade.

Here's the details: My 2000 4Runner is now at 130K miles. I've had the S/C since about 8K and overhauled the S/C at around 115K or so. I installed Gadget's entire fuel upgrade kit, including the larger fuel injectors, Split Second FTC1, different fuel pump, spark plugs, wide band O2 sensor and gauge, etc. Other mods I have that also affect this are: ceramic coated TRD headers, 4.88 diff gears, almost 33" tires, Amsoil air filter, IPT auto valve body mod, etc. I have Iridium spark plugs that I think are 1 step cooler than stock.

Only because I live at 5300 ft altitude and I usually go higher to play, I tried the next smaller supercharger pulley. My original pulley was the TRD 2.4", which actually measures 2.35" where the belt contacts. I tried Gadget's URD 2.2" pulley (aluminum, red, holes in the side, innovative design, looks cool, etc). It measured exactly what it should be -- 2.2". So it was only 0.15" smaller, or about 6.4% smaller. That was the next smaller size pulley readily available. I definitely noticed an increase in torque available at lower and moderate rpms. No matter what I did with tuning the air/fuel ratio at full throttle (14.7 or either rich or lean), I couldn't get rid of retard and misfires at full throttle or the last bit of the pedal. So it felt like torque would reach a plateau or even drop off as I pushed more on the pedal. Cylinder misfires were typically on cylinders 2 and 5 and once in a while also on cylinder 3. I even changed out the coil for 2 and 5 but that didn't make a difference. I changed out all the spark plug wires but that didn't make a difference. All spark plugs look great. When I installed the FTC1, I very carefully soldered the wires so I know connections are good.

I recently went to Moab, Utah, (4200 feet) and noticed significant pinging at only 3 psi of boost. Well, that won't work for me, cause I'm not planning to add other things like water injection to avoid problems. So I changed back to the stock 2.4" pulley and gave up on this attempt. I get none of those misfire problems or retard or pinging with the "stock" TRD pulley at full throttle. Fuel ratio is great. As far as I'm concerned, there's nothing wrong with the URD fuel upgrade kit. It works well. I'm glad it's not lean at full throttle so the kit did what it was supposed to do, especially on rare occasions when I go to sea level. I'm just saying I wasn't able to push the S/C pulley any smaller. I installed the wideband O2 gauge at the same time as the rest of the kit, so I don't know how lean it was at full throttle at this altitude prior to the kit install. I could previously just feel acceleration flatten out at full throttle and I very definitely noticed it at 1000 feet altitude, so I know it was just on the verge of being lean or slightly lean at this altitude before the kit.

If URD had a similar pulley that's 2.3", I might consider it, but I'm not convinced that I could avoid problems even with that.