Has anyone done their own conversion from twin turbo to single turbo and would like to create a guide with their own recommendations?
I've done it myself...many times in fact. Here are the steps (from memory - forgive me if I've forgotten any small items):
0.1) First and foremost, figure out how you're going to supplement the octane
of the fuel that you're running. Most likely you'll need to blend in an appropriate ratio of race fuel or run methanol injection. If you don't you'll ruin your engine 100% for certain. No exaggeration - I'm not trying to scare you for no good reason here!!! You need to match the 'net octane' of your fuel with your max boost level. If you do not, the air:fuel mixture will *detonate* (instead of burn), which will tear up the pistons and head (even expensive aftermarket pistons). "There's no such thing as a free lunch" - so a 3L engine can't put out 1000hp *unless* you take care of octane. Plain and simple.
0.2) Take care of your single turbo's increased fuel volume
requirements. Usually this means bigger fuel injectors (matched to the turbo's max hp) and a fuel controller or 'standalone' ecu.
0.3) Lay out your turbo kit and mentally go through all of the instructions below to ensure the turbo kit has everything you need. Also ensure you have all of the proper tools.
0.4) Compression test (and/or leakdown test) your 2jz-gte to ensure it's healthy enough to handle a single turbo. A brand-new 2jz-gte compression-tests over 170psi per cylinder. If any of your cylinders read less than 150psi, or there is more than a 5psi difference between your max and min cylinders...well, you probably shouldn't put a single turbo on until you fix this first (eg. with new pistons&rings or a new shortblock).
0.5) Prep the rest of your car for the new HP levels. For example, width of the oem rear rims can't put wide enough rubber on the ground to handle more than about 350rwhp or so. If your single turbo puts out more rwhp than that, you'll need wider rear rims. Eg. 11.5" wide rear rims and 315 width z-rated or r-rated rubber is fine for up to about 650rwhp or so. If auto, your oem tranny won't handle more than about 525rwhp for very long. If 6spd, your oem clutch won't handle more than about 375rwhp for very long. Etc.
NOW, ON TO THE INSTALL ITSELF
1) Purchase/borrow/rent/steal/beg/etc. a copy of the TSRM (Toyota Supra Repair manual) - "Engine"
2) Follow the TSRM steps to take off the oem twins.
->Note: there's one nut that's extremely hard to remove. You encounter it when you're removing the assembly that the primary oem cat bolts onto (the top-side nut). You need a six-point 14mm box-end wrench (i.e. not a 12-point). After you obtain that rare beast, you should be able to rig up an assembly that will allow you to get enough leverage on it - you may need two people (one from above the shock tower to apply the strength, and the other on the bottom to hold the wrench square on the nut). PB Blaster will help too.
2a) Block off the two vacuum hoses going to the oem pressure canister (only used for twin-turbo operation). Secure electrical connectors that used to control the oem twin turbo VSVs (these will no longer be needed).
3) Install the oil drain assembly* & hose from the single turbo kit*.
4) Install the oil feed hose from the single turbo kit*.
5) If the single turbo is water cooled, install the upper and lower water lines from the single turbo kit
5a) If the single turbo is not water cooled, block off the oem water lines that went to the oem twins
6) Install the lower intercooler piping* for the single turbo's compressor outlet.
7) Put the single turbo header on using a brand-new oem gasket for the exhaust ports. Be sure to use the instructions in the TSRM for installing the exhaust manifold (eg. exact ft-lbs of torque spec for each nut).
8) Install the new downpipe from the single turbo kit.
9) Install the wastegate on the single turbo header. Route the wastegate exhaust pipe from the wastegate to below the car (or back into the exhaust/downpipe, whichever is appropriate).
10) Install the single turbo onto the single turbo header (with appropriate gasket), connecting up the oil drain line, the oil feed line, the water lines (if water cooled), the lower intercooler piping, and the downpipe.
11) Install the new intake pipe and air filter to the turbo intake
12) Connect the wastegate to your boost controller. Be sure all vacuum lines are far away from any heat sources. You may want to add insulation to the hoses as an additional measure.
13) Go through the TSRM (twin) turbo instructions to ensure everything has been re-attached that you removed/disconnected during the disassembly.
14) Check all fluid levels (oil, coolant, etc.) and fill as appropriate
15) Put the race fuel in your gas tank or install your meth injection system
16) Fire it up and get it dyno-tuned with the new injectors and/or meth kit, slowly working up from very low boost to max.
17) Go kick some butt (only on a race-track of course).
*Special fittings/parts/pipes/etc. are required, which must be supplied in the single turbo kit. If your single turbo kit doesn't include everything you need, send it back and get a decent one. Any name-brand kit from HKS, GReddy, Blitz, Sound Performance, etc. will include *everything* you need.
P.S. What kind of recommendations are you looking for?