Clocking the SR T25 Turbo

C

The turbo found on the SR20DET motor is an upgrade that virtually every CA18DET owner has run at one point or another. Where the CA18DET T25 turbo is good to about 12psi and looses boost towards redline, the SR20DET T25 can run around 14psi and will hold steady till redline with the .80 exhaust housing. Additionally, there are tons of SR guys swapping out their factory turbo so finding SR T25’s in good condition and at a good price is easy. To make the SR T25 compatible with the CA manifold, the compressor housing on the turbo must be clocked about 5 degrees clockwise. Clocking a T25 turbo means to rotate the compressor housing while keeping the exhaust housing and center cartridge in the same position. The following documents the process of clocking the T25.

Labelled T25 turbo off of a SR20DET

#1 is the compressor housing and #2 is the exhaust housing. In between lies the cartridge. (fullsize)

First, remove the wastegate actuator by removing the small c-clip from the wastegate and then remove the 2 x 10mm bolts holding the actuator to the housing. (The c-clip is very easy to loose so put it in a safe place. If you loose it anyway, they can be found at your local parts store.) Next, remove the exhaust housing using a 13mm wrench on the 4 bolts holding the housing to the cartridge. If the exhaust housing won’t slide off of the cartridge, give it a light tap downward while holding the compressor housing and it will pop off. Remove any oil and water lines that are still attached to the center to make accessing the compressor side’s c-ring easier.

Image showing the retaining clup on the compressor side of the SR20DET trubo.

This image shows the c-ring (retaining ring) on the compressor housing.

Locate the c-ring that holds the cartridge in the compressor housing. (pictured above) Using a pair of needle nose pliers, hold the compressor housing and then compress the ring with the pliers. Once the ring is compressed, grab the center cartridge at the base and rotate it five degrees clockwise. Oops, you need three hands for that don’t you. For those of you like myself who posses mad monkey skills, sit on the floor and hold the compressor housing with your feet. For everyone else, use a table mounted clamp and lightly clamp the housing to hold it in place.

(Note: The turbo pictured above is clocked for use on a top mount manifold. Make sure that when reassembling your turbo that the oil drain faces downward.)

The SR20DET turbo clocked for use on the CA18DET manifold.

The new relation between the exhaust housing inlet flange and the compressor housing.

With the compressor housing rotated, loosely reinstall the exhaust housing using the two brackets and the 4 bolts. Test fit the clocked turbo to your factory manifold before tightening everything back down. make sure that the oil drain faces downwards and then tighten the exhaust housing down by first snugging the bolts and then turning them one more turn. Now spin the turbo blades and make sure nothing is rubbing. Finally, reinstall the wastegate actuator. It is ok if the actuator arm is slightly slanted. Just make sure the arm does not contact the metal of the actuator base.

By 240am

Chris Simmons is a race car driver, instructor, business owner and all around gearhead. His passion for motorsport started in the drifting community over 10 years ago and progressed into wheel to wheel racing of all kinds. When off track Chris can be found training and working on a myriad of projects. After a hiatus from writing, he is back to share his passion, knowledge and experience in regard to motorsports on and off the track.

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