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.

I have a 2" pulley on mine currently with most of the URD kit minus the FTC1 (Using an SAFC instead). I am running about 10-11 psi and i only get ping when in 4th and 5th gears below 3000 RPM (which i believe is when the knock sensors kick in) Did you ever reset the computer after installing the new pulley and retuning? Sometime it helps to have the truck relearn the maps when making a big change like that... but not a must. Do you still have the "free FMU" setup connected or did you disconnect that once you did the fuel upgrade kit?

Thanks for replying. That's amazing you're using the 2" pulley.


Yes, many many times. Sometimes I disconnected the battery completely. Other times I would remove both EFI fuses and wait 30 seconds before putting them back in and starting it.


Yes. The "free FMU" is the routing that makes sense to me. Should it still be connected that way?

My original intention was to have about a 6-7% smaller pulley to make it seem the same at this altitude as a supercharged 4Runner at sea level with a URD kit. The max psi I've seen on the TRD boost gauge was 8-9 psi with the 2.3" pulley, versus about 6-7 psi with the 2.4" pulley. (Just for interest sake, I can only get to 4 psi at 14,000 feet).

Do you have any ideas why I'd be getting misfires at full throttle despite an air/fuel ratio of 14.7? What possible things should I look at?

Not that I have ANY clue about how to tune the S/C....but I read a pretty interesting article a while back about how the problems with the S/C were related to the spead limiter on the 3.4L ECU.

The article was talking about how the speed limiter works by leaning out the fuel when the intake volume was at a certain level. suposedly some guy "fixed" the problem by stripping out the speed limiter in the ECU. There is a company out there that will do it....not sure what the name of the place is. and the author was pretty sure all the 7th injector and high pressure fuel pump stuff was now un-needed.

Like I said.....I know really nothing about the S/C...but the article was interesting

Jeff,
If your wideband is showing 14.7:1 at a high throttle angle/WOT, then something is wrong. The ECU should drop into open loop and ideally should be somewhere no leaner than 12.5:1 at roughly 70%+ throttle. I tune for 11.8:1 just to have an extra margin of safety. You should only run 14.7:1 at idle and cruise and you'll run 16:1 and leaner upon deceleration. You may want to start by making sure your wideband is displaying properly and check your throttle position sensor and MAF as these provide the load tables for the ECU to switch to open loop.

Do you have an OBD-II code reader like the BR-3? You can use the software to determine whether the ECU is in open or closed loop.

Ken

Yes, it's definitely going into open loop during the last bit of the pedal, like it should. I was experimenting with tuning it to different air/fuel ratios, including 14.7 to see if I could get that pulley to work for me. A majority of the time I tried it, I had it on the rich side, around 12 to 12.5 since that's what's in the FAQ at the Split Second web site. But I can't get away from misfires with that pulley.

Yes, I have the Auto Enginuity OBDII reader. I can watch the line graph bounce around 14.7 during typical closed loop driving and the wideband O2 sensor bounces around the same numbers, so I know it's right.

Just to mention it, I've always used premium fuel with the supercharger. At this altitude the highest octane available is 91.

I'll clean the MAF again. It's been a while.

I noticed some others mention concerns about the throttle position sensor on other supercharger posts - that is, that sensor very briefly outputs a voltage of zero in between correct voltages, but the error can only be seen on an oscilloscope. Maybe I should check into that.

Make sure to keep it much richer than 14.7:1 under boost or you run the risk of melting the pistons on an extended high boost pull. Shoot for somewhere in the 11.8-12.3 range in open loop. The ECU will do everything it can to keep the A/F ratio at 14.7:1 in closed loop.

You say you were able to get the A/F ratio down to 12:1; did it still ping?

Sounds like good advice.. <img src="/forums/images/graemlins/kewl.gif" alt="" /> That agrees with everything I've been able to dig out of the documentation on OBDII system open loop/closed loop operation.

Yes, I had the air/fuel ratio somewhere in the 12's at WOT when I went to Moab a week ago (about 4000 feet). That was when I experienced pinging the worst.

With this whole effort I was trying to approximate the air going into the engine at sea level, although I don't have as high an octane gas available here. Maybe that's part of it. It just seems there's something else wrong since others have been able to go beyond what I'm attempting.

The wideband is a great tool for any boosted application. It has shown that open loop is triggered by more than just a high throttle angle via the TPS. I can climb a high elevation pass at 25% throttle and yet as the boost climbs past about 8 psi the airflow alone through the MAF will trigger open loop. It's great, the ECU is far smarter than what I could have programmed into a standalone EFI.

Jeff--if it's pinging at 3 psi you might check the gap on the sparkplugs. I wonder if the gap is too loose and causing spark blowout under boost.

Keep it rich man, don't ever let it see that much boost without a 12.5:1 or richer A/F.