Replacing CT20A's with CT12A's question

**kemicalx** · 07-02-2011, 02:32 PM

Hi all,

I've just purchased what look to be some reasonable condition CT12A's (just the turbos) off eBay to replace the worn CT20A's on the 2J in my soarer, while I understand the differences and inherent limitations between the two turbos. What i'm not sure on, is if there are any differences in the stud pattern or shape of the turbine inlets and outlets? Will the 12A's be a direct bolt in replacement for my 20A's?

I've attached the TSRM picture for reference sake.

Cheers everyone.

**kemicalx** · 07-02-2011, 11:19 PM

no one has done the swap here? I might ask on supraforums

**Mole** · 08-02-2011, 12:49 AM

AFAIK they are actually the same turbo.

**kemicalx** · 08-02-2011, 05:55 AM

ahh my bad, i meant CT12A's the euro/us spec steel wheeled, smaller diameter shaft turbos. I thought the CT12B's were the same.

I've edited the original post accordingly.

**slipway** · 08-02-2011, 12:06 PM

think you had it right at first,ct12a is 1jz, i believe the ct12b's are the steel wheel ones

**kemicalx** · 08-02-2011, 02:34 PM

Cheers, I was aware that 1jzgtes had CT12As. I just seem to be getting conflicting information.

From wikipedia -

The export version of the 2JZ-GTE achieved its higher power output with the use of newer stainless steel turbochargers (ceramic for Japanese models), revised camshafts, and larger injectors (550 cc/min for export, 440 cc/min for Japanese). The mechanical similarities between the Japanese-specification CT20 turbine and export-specification CT12B turbine allow interchangeability of the exhaust-side propeller shaft. Additionally, the export-exclusive CT12B turbine received more durable turbine housings and stainless steel turbine and impeller fins. Multiple variants of the Japanese CT20 turbine exist discretely, which are identified with the B, R, and A part number suffixes (eg.: CT20A).

**kemicalx** · 08-02-2011, 08:04 PM

Ok i've found all the info I need to know,

theres a good read here - http://www.scribd.com/doc/3977379/2JZGTE-HiFlo-Summary

In summary

CT20A (Ceramic)
Turbine Size: 60mm/48mm (inducer/exducer)
Compressor Size: 62mm/39mm (inducer/exducer)
Turbine material: Ceramic
Scroll area (mm^2): 600
A/R ratio: 0.42
Shaft Diameter: 9.96mm

CT12B (Steel)
Turbine Size: 52mm/44mm (inducer/exducer)
Compressor Size: 58mm/39mm (inducer/exducer)
Turbine material: Steel
Scroll area (mm^2):740
A/R ratio: 0.53
Shaft Diameter: 7.48mm

And finally CT12Bs require different manifolds and dump pipe for installation, a bit annoying.