My new Modified CT12b Turbo’s are Installed! by Stu Hagen

By diyauto
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8 minute(s) of a 11 minute read


My new Modified CT12b Turbo’s are Installed!

Compliments of Stu Hagen @


NEW MODIFIED TURBO'S HAVE BEEN INSTALLED 5/06 (sorry for this as being a long post)


4th Gear is at 22psi and the 5th Gear is at 24psi

4TH GEAR PULL GRAPH "Blue is the newer run" Uncorrected"

5TH GEAR PULL GRAPH "Red is the newer run" "Uncorrected"

4TH GEAR PULL GRAPH "Blue is the newer run" "SAE Corrected"

5TH GEAR PULL GRAPH "Blue is the newer run" "SAE Corrected"


DYNO DYNAMIC-Chart from Vancouver, BC Supra meet Sept-2006

After years of research I have finally found a source for modified CT12b USDM turbo's. This source is another Supra member who has 2 Supra's and is an engineer back East. The modification is minor in the overall scheme of things. All we did is add a larger T3-60 Trim Compressor wheel. The Turbine and OEM shaft are all still USDM specs. (not the larger JDM spec) This larger Compressor wheel is about 7.5 mm larger with an additional 2 blades (12).. In essence it is now a T3-60 Trim. After I "Beta" test these, we may upgrade. Our goal is to eventually test out a set that will have the larger JDM turbine.This is a greater challange due to the different hosuing set up in the JDM versions. 

The installation didn't take as long as I expected. Myself and another Supra owner friend (toyotafan) started at around 11:00am and was test driving it at 9:00pm. Although the night before I took out the radiator and all of the turbo piping to get a jump start. We actually just removed the turbo's from the exhaust housings. We weren't sure how it was going to go just taking the turbo's off only. We did have to take off the EBV bypass tube, but not the DP off. The biggest struggle was getting the #2 turbo oil and water lines off. The way the bolts are aligned, it is difficult to get a lock on the nuts. We think we can shave off at least an hour if we do it again. We also took real caution on installing new gaskets on real cleaned up surfaces. The "delicate" issue was actually tapping off the compressor housings off the exhaust housings. A little PB blaster and constant tapping and they finally broke loose. From there, we were home free.No leaks wanted, so we wanted to do it right the first time. It paid off, not a single drop of any fluids after the test run

The overall efficiency is greater by about 20%. These new turbos will run at a much lower compressor rpm. There maximum efficiency range will be 22psi. When they are running at 24psi, then they will be close to an OEM CT12b running at 18psi. There is definitely a small lag over stock. Not too noticeable, maybe 100 rpms. They also continue to rise in HP at redline. You could definitatley take advantage of this by raising the rev limit, or tune your cams to monopolies on this. 

You can "beat" on them as I did at the dyno. I actually hit 27psi on one 5th gear pull. Anything above 22psi I saw about a 2psi drop at redline. Any boost levels 22psi or below, it held boost to redline. I also had to install an adjustable spring on the wastegate to be able to go to higher boost levels. Basically this is a spring on the wastegate actuator arm that I rigged a bolt and wing nut so I could add, or delete, tension. All this did was extend the range of boost. I have mine set where 17-18psi is my least boost, and 24psi is my max boost. 

In regards to the dyno shots below, I had one problem that I didn't notice until we were all done. When I went back to install the turbo's I forgot to re-adjust the #1 turbo controller. So all of the sequential runs look goofy because I was stuck at 10psi until 3800rpm transition. I will eventually go back and re-dyno so I can see the higher HP/Torque lower down. So basically, with the small additional lag, and no raised boost, it almost looks like I am loosing HP down low. You can actually see the "pulsating" of the EBV trying to "hold" the boost to around 10psi. In my new set-up, I feel that having it set at 16psi is optimal, and safer on the #2 turbo. But for now, it looks like severe lag. This is not present now because I have re-adjusted it, but won't be seen until I re-dyno.

The basic "gain" in HP and Torque is from 4800 to 6800+rpm range..My estimate gain is around 40HP for whatever set-up your car has. The best HP I previously had was 493HP 537TQ (with Electric fans). My best now is about 530HP and 560TQ SAE. So assuming W/O electric fans I would have been at 490HP I have gained 40HP. I did a 3rd gear pull in the beginning to tune for fuel, and that run was 503HP and 472TQ at 22psi. This 530HP run I actually hit about 25psi. So consideration needs to be taken at this boost level. My estimate for "street" use at around 20psi would be 470ishHP. I have NO worries running these between 18-20psi on pump gas since they will be running at 123,000rpm compressor speed. On a stock CT12b running at 123,000rpm compressor speed I would be at about 16psi. We all know how Density Ratio and "heat" above this level isn't efficient. 

OEM CT12b 

Upgraded Turbo2 

Upgraded Turbo1




Compressor Wheels

Compressor Map for a OEM CT12b

Compressor Map of the new T3-60

2JZ Flow Chart OEM 

2JZ Flow Chart my car (Stage 1 head, 264 cams, and turbo components porting everywhere) 

A/F Curve + Boost curve 

Wastegate Spring 

**Note: on the 2 excel sheets above, the 1st one is based on 6 cylnders, so you need to divide by half for each turbo. Where the other one is already per turbo)

Overlay Dyno----This one dyno composite graph shows my car prior to any Head work and Cams. It is also before I installed my #1 MBC. It is a good comparrison for anyone that is BPU+++, and still in sequential. Although these 2 runs don't really show a good spool up under 3500rpms. This is from having OEM #1 boost at 10psi then jumping to like 20-22psi. Another reason why I feel the #1 turbo MBC is a good mod. 

I wasn't pleased with the results overlayed from my last year's 493hp run. The only thing different then and now (other than the turbo's) was I removed my AAP Electric fans. Not thinking this matters, but maybe a couple of HP maybe. I REALLY need to go back and re-dyno with my raised #1 turbo boost. The area under the curve looks terrible compared to last years dyno. The good news is the way these new turbo's continue to climb in HP, not dropping off at all. Once I fix the low end a little, I think the curve will come back and show higher levels accross the board. I will also try to dyno at lower boost to try to simulate more "stock" form. My particlular car has many modifications in the "Flow" end of things, so that may be harder to compare to people with cat-back exhuasts and no extra engine work. You would definitely see higher trap speeds due to climbing HP at redline, and the ability to hold a higher boost. Maybe 3mph+ I would guess. The "GOOD" news is there is a 10% gain in HP and Torque. Even better is that when you open the hood, it will look STOCK~!

Many thanks to "toyotafan" my best friend for helping me through all of this with his time and efforts. (he is next in line for these upgrages (

A complete copy of this post is on my webpage; on the index page.