ADDITIONAL OPTIONS ARE SHOWN AT THE BOTTOM OF THE PAGE!
This is an optional upgrade kit for the STU USDM GT28 Hyrbrid Stock Twin Turbo Kit (shown here: http://www.speedforsale.com/supraparts/speed-for-sale-stu-usdm-gt28-hybrid-stock-twin-turbo-upgrade-550rwhp-p-553.html)
This kit, which we call THUK for short (Transition/Horsepower Upgrade Kit), makes the #1 turbocharger produce more boost and torque at low RPM, and also reduces the transition lag time and boost drop between the #1 and #2 turbochargers when the #2 turbo comes online. It is intended to increase power and response of the STU USDM GT28 turbo kit below ~4500 RPM. We have updated the STU USDM GT28 turbo instruction manual to includes notes regarding how to install these THUK package items, which you can find BY CLICKING HERE! Also, at the bottom of this page, you can see a comparison of the stock EBV tube and housings versus the THUK EBV tube and ported housings.
Here is feedback from one of the BETA testers of this THUK package named 'Lurker' on SupraForums: "Hi guys, I had the privilege to beta-test the T.H.U.K. package for Jeremy, and, in short, they're an extremely worthwhile addition to the hybrid twins kit. I went directly from stock twins to the hybrids plus the transition-improvement-kit. I just finished installation last week... So, I don't have any dyno charts. But on the road, the car feels very smooth and powerful. No flat spots whatsoever at 4k rpm when the sequential transition is happening. I wou.d say that the transition feels even quicker than stock. I do have the EBV mod (installed many years ago) so I can adjust the #1 turbo boost level and also the prespool amount. As a whole, this GT28 hybrid kit is an extremely well designed upgrade from the stock CT26 in term of sheer power increase and how smooth the powerband is."
There are THREE THINGS needed to make this kit work, as shown below. Please read the details below carefully before making your purchase, as only the first item below is included for the price shown, and the other items are shown at the bottom as additional items!
FIRST THING: As shown in the primary image for this product, the larger EBV tube, custom oval port EBV gaskets, EBV spacers/studs/washers, and head shield spacers/studs/washers are included for the base price. These are included with every order of the THUK package.
SECOND THING: The second thing needed for the THUK package is ported EBV housings. While this can be done by your machine shop (or yourself if you have good porting tools/bits), we HIGHLY recommend letting us do the work to ensure it is done correctly. Not only must you port match the ports at the gasket surface, you must also do a lot of porting down inside the casting to ensure that the oval hole is 1.5" or larger so that there is no flow restriction from the larger 1.5" EBV tube and custom gaskets which are included with the kit. Please choose the EBV porting method below, and be aware that if you port them you do so at your own risk! As noted, we offer a core service to provide you with ported housings up front, with a portion of the fee refundable upon your return of good condition used stock cores.
THIRD THING: You will need either a SPRUNG OEM wastegate actuator or the optional HEAVY DUTY wastegate actuator to allow the THUK package to function properly.
If you purchased your STU USDM GT28 kit AFTER February 1, 2012, then you do NOT need ANY extra wastegate parts, as we now include them standard in the kit upon initial purchase.
If you purchased your STU USDM GT28 turbo kit BEFORE February 1, 2012, then please take note of these two options you have regarding the wastegate:
OPTION 1: If you selected the optional heavy duty wastegate actuator when you purchased your STU USDM GT28 kit, then it will work correctly with the THUK package and you do not need anything else.
OPTION 2: If you selected the standard OEM wastegate actuator when you purchased your STU USDM GT28 kit, THEN YOU WILL NEED THE OPTIONAL ITEM BELOW CALLED 'SPRING MOD PARTS ONLY. FOR USE WITH OEM ACTUATOR'!
EBV Housing Porting Work:
Wastegate Actuator Type: