Single Turbo Selection for 1UZFE

I am in the process of building a single turbo for the Lexus LS400 and I have been doing lots of research on turbo unit and trying to get the proper turbo size for the my application.  I have experience with Twin Turbo and Supercharging my Lexus LS400.  Now I would like to create a single turbo for the LS400 and possible SC400.  When I was running my Twin Turbo with Twin T3 (.48 A/R from the Skyline).  I maxed out at around 14.5 psi and that is not enough for my application.  If you are doing Twin, I would go T3/4 would great.  However, we are talking Single Turbo in this article.  Only two person have do this modification so information of single turbo 1uzfe is very limited.  Jaime in our forum uses Garrett GT40 and the other member uses GT42.  However, I have been studying the Supra MKIV turbo dyno with a mid-size turbo specifically Precision or Sound Performance T67GTQ.  I think Sound Performance (SP) turbo is the same as the Precision GTQ turbo.  From what I have reading, the Precision GTQ turbo is just as same as the Garrett GT turbos.  Precision buy the GT wheels from Garrett and put in their in-house cast turbo housing.  Therefore, the Precision GTQ turbo is basically same as Garrett GT turbo.  I was originally leaning toward the Garrett GT turbo, but the GT40 (700 bhp) is little too small and GT 42 is too big (1000 bhp).  The T67GTQ is rated at 800 bhp.  Here are my performance goals for the daily driver:

Power: 550 RWHP
Application: Street- low end with power at full band
Full Boost: 3.5-5,000 rpm

Second factor would the physical dimension of the turbo.  Since I will using the battery location for the single turbo, there physically large turbo would not work in this case.  Here is an email I got from Induction Motorsports:
we don't have the 67GTQ in stock, but it should not take too long to get... precision is currently out of the .68 p-trim housings, but we have received several of the 67GTQ .82's lately without a significant delay...he compressor is an "S" cover standard, but it can be optionally upgraded to the "H" or "HPS" cover... the "S" is the 4" in, 2.5" out and the "H" is the 4" in and 3" out... the "HPS" is an "H" in size, but adds a ported shroud (anti-surge) inlet...  the H and HPS are the same cost, both are an extra $150... on the 67 we have not had any problems with surge, but the HPS cover does offer slightly more power potential and it creates a wicked "whistling" noise that the normal covers do not.  The H and HPS will offer a slight amount of extra lag over the S 'm not sure what you and Shane had talked about as far as wastegate selection, but we should be able to supply you with any components and flanges that you need.  I Feel free to always email either of us, it's usually easier to keep track of emails than PM's anyway.

So lets do some calculation comparing the 3.0 to the 4.0 liter.  The 4.0 1UZFE is 25% larger in cubic inch.  Therefore, it should have 25% greater spool up time and 25% greater power at a give pressure level.
Engine Size A/R A/R divided By Liter
3.0 .68 .2267
  .82 .273
4.0 .68 .17


.82 .205

If the 4.0 1UZFE uses .68 A/R than the factor is .17 and that would be too restrictive.  In order for the 1UZFE to have the same spool up time and rpm, the A/R for the 4.0 1UZFE would be .904 (.2267 factor time 4).  However, if I use T67GTQ with .82 A/R (factor .205), this setup would spool up much quicker than Supra 3.0 with .68 A/R.  The example  #1 below, I would take the Supra 3.0 18.5 psi to produce 544 rwhp.  At the similar rwhp, it would take about 15 psi on the 4.0 liter motor.  In another word, the 4.0 will require lower boost level to produce similar horsepower than the 3.0 motor.  The following dyno charts are obtained from Andi Baritchi Supra Dyno

Example # 1:
Supra 3.0 = 544 rwhp @18.5 psi .68 A/R, GTQ trim (CTC67H)
                  RWHP per PSI: 29.41 rwhp
1UZFE 4.0 = 680 rwhp @ 18.5 psi .68 A/R GTQ trim (CTC67H) -Calculated HP)
                  RWHP per PSI: 36.75 rwhp
                  - The theoretical line is in green with 4.0 1UZFE
                  - The thin red line is my goal for 15 psi on a 4.0 liters

Example # 2:
Supra 3.0 = 591 rwhp @21.3 psi .68 A/R, GTQ trim (CTC67H)
                  RWHP per PSI: 27.74 rwhp
1UZFE 4.0 = 738.75 rwhp @ 21.3 psi .68 A/R GTQ trim (CTC67H) -Calculated HP)
                  RWHP per PSI: 34.68 rwhp
                  - The theoretical line is in green with 4.0 1UZFE

Example # 3:
Supra 3.0 = 631 rwhp @24.1 psi .68 A/R, GTQ trim (CTC67H)
                  RWHP per PSI: 26.18 rwhp
1UZFE 4.0 = 788 rwhp @ 24.1 psi .68 A/R GTQ trim (CTC67H) -Calculated HP)
                  RWHP per PSI: 32.69 rwhp
                  - The theoretical line is in green with 4.0 1UZFE

This might not be fair to the 2JZGTE in comparison.  However, there are too many variables that will alter the final dyno numbers on 1UZFE, especially with the head (s) flow rate between the two engines.  Like people say two heads are better than one.  The are too many factors involved.  In this article we just look at the big picture, comparing cubic inches between the two great engines.  My goal is to run 15 psi on my 4.0 motor with 91 octane.  From the above calculation.  I should achieve around 550 rwhp (15 psi time 36.75 rwhp per psi in example # 1) with proper tuning.  I want to thank Andi Barithci for the wonderful dyno numbers.  Now its time for the 1UZFE owners to prove this theory on the V8.

Thanks for reading!