Beto

I don't know if this has been discussed before, but I think I've just solved one of the major issues with my S/C 2002 4runner.

I have the URD 7th injector kit, and I've had trouble trying to "tune out" a ping and lack of power that occurs at between 2000 and 3000 RPM in third gear. After a bit of reading, I discovered that the torque converter lockup clutch is active in both third and overdrive gears, and the ECU for whatever reason is very reluctant to unlock the lock-up clutch when driving in 3rd with O/D off, you can floor it and the L/U stays engaged. I confirmed this by measuring the voltage leaving the ECU on the SL terminal. O/D seems more reasonable, and the L/U kicks out much sooner.

I've got a little more tinkering to do, but I've so far found that giving the ECU 12V on the "STP" terminal (input from the brake switch) forces it to unlock the clutch. I have it wired to unlock the clutch at 50% throttle (VTA signal) and the pinging /lack of power is gone. I'd like to rewire it to use boost as the trigger (when above 0 psi, disable L/U), but a little more work to do on that one.

Is anyone else having this issue? Has there been another way to solve it found?

nothingbetter

maybe not the anwser your looking for, but a manual tranny swap would do the trick. You'll also have less power loss through the drive line and get more power to the ground. Thats my recomendation.

Texas_Ace

You are trying to bandaid the problem instead of fixing it.

With the right tune you should not have any problems with knock, I never had a single issue with knock in any gear under any conditions (towed many a heavy load as well).

Remove more timing is the first place to start. Also do you have the O2 calibrator? That alone might fix it.

Another practically garateed way to fix it is to install a water/meth injection kit. You won't have any issues with knock with that installed and setup properly.

Beto

Thanks for the ideas. I don't have a stand-alone O2 calibrator, but Gadget was adamant that the kit that he sent includes this feature, but the map is pre-set and not user configurable (part throttle boost enrichment). It does tie in to one of the wires from the AFR sensor, so it is possible that it is performing this function.

I've been all over the place with timing adjustments. I even tried adjusting out only the range between 2000 and 3000 RPM at 0 to 7 PSI (retard by 5 to 8 degrees). This section of bad performance cannot be eliminated.

I also took additional fuel injection to some extremes in this zone, and anything short of drowning the engine does not solve the knock either.

I'm out of ideas on this. Are you sure that your lock-up clutch is not kicking out earlier than mine does? It happens when I am driving with O/D off and accelerating with >50% throttle (just over 0 psi, and continues to almost 100% throttle, about 6 psi, until the transmission kicks down).

Texas_Ace

If you have the AFR sensor then it should be included, what does it richen up to when in closed loop boost (aka, ~low boost part throttle)?

Also remove more timing, if you are knocking then you have too much timing and you just need to keep taking it out. I would try -15 degrees in that range and see if things improve.

I had no issues on my truck at any point, I could tow 5000lb in 4th gear @ 2000rpm without an issue (was playing around with it during a long tow to keep my mind active lol).

This brings up another point, have you ran a compression test? Too much compression can be a sign of carbon buld up which will increase compression making you more knock prone. Too little can be a sign of worn rings that will allow oil blowby which will also make you more knock prone. I would run a test and run some seafoam though the motor to clean it out as well. Could try some marvel mystery oil as well, it worked wounders for me. I hav a detailed writeup on this subject on here someplace.

What octane fuel are you running? 93octane? Anything lower will GREATLY increase the knock proneness of the motor. You must run the highest oct you can get (preferably 93oct).

If all of that checks out and doesn't improve anything then next step is a complete tuneup, this should be a given at the install of a supercharger anyways but do an in depth tuneup with colder spark plugs and see if that helps. The combo of all that stuff should at the least greatly lesson the issue.

If it is still a problem then the next step I would take is a water/meth injection system, that will cure the problem, I was running more timing then stock NA with a supercharger and 2.0 pulley.

xxxtreme22r

Converter lockup specs have no bearing on engine ping/pre-ignition. Not sure where that idea came from.

X2 on the colder stepped plugs. That cures alot of issues. My rule of thumb is 1 step colder for every estimated 50 HP gained with forced induction. Running stock heat range plugs just isn't going to cut it. Plug gap may or may not play a part it in as well.

Another thing I would look at is if the stock fuel pump can handle that 7th injector. Pretty sure it can, but it's something I wouldn't overlook.

Beto

The idea (right or wrong) came to me when reading the toyota service training about transmissions and the logic behind the unlock - the converter lockup clutch will not engage under the following conditions:
1) Engine temp low
2) Brake applied
3) Cruise control setpoint > 6mph from actual speed
4) High throttle operation

It seems that any high-torque scenario disengages the lockup (or should). When I measured the signal, the L/U clutch was remaining engaged for way longer than I though it should (almost full throttle in third gear).

I definitely agree that engine knocking shouldn't occur at any RPM/gear/load, like my manual tacoma used to be with the S/C on it. I know the engine is pinging ( I remember the sound from tuning my manual taco) but I think I also have some low frequency grumbling from the transmission when this is happening. Not too sure what would be causing that, or if it's my imagination.

I have the high flow fuel pump that came with the URD kit, and the cooler plugs (can't adjust gap on iridium though).

@ Texas Ace -

I usually run 92, but I've run several tanks of 94 through with the same results. Compression testing is a great idea - I'll be doing that this week and end the speculation on that point. Speaking of speculation, I really wish I had a wideband A/F meter, I'd be able to answer your question about what my mixture is really at during part throttle boost.

Also, 15 degrees of timing retard? Wow. I think it'll stall out as soon as I hit 10, but I'll give it another shot. At one point I had the map starting at nothing a little below 0 psi, ramping to 5 degrees @ 2psi, and then ramping to about 15 by 8 psi. I remember it acted almost as if I had a rev-limiter on it, and wouldn't pass ~3750 rpm until I backed off the throttle.

Texas_Ace

If you are spark knocking then you can still remove timing and need to remove timing. If it is knocking due to some other factor (hot spot ect) then you have bigger things to worry about.

For now runt he tests and see what you find out.

xxxtreme22r

Texas Ace, I am a little confused with the changing timing on this. I'd like to learn a bit more on these engines since I am more of a carb guy. But aren't these electronically advanced? Meaning regardless of distributor positioning it's still going to electronically advance to where the ECU wants the timing set?

Texas_Ace

Yes and no. It will advance it to the same knock level once the knock sensors come online regardless of what you input into the URD box.

The knock sensors don't come online until ~3k though which is why you only have knock issues below that. Below that you do have control over the timing to an extent.

xxxtreme22r

Ok, I get it. Forgot all about those knock sensors. Been awhile since I messed with forced induction.