differences between 603.96 and 603.971 turbos
 

I have semi apart Garrett turbos from a 603.96 (I don't remember if this is a 124 or 126 turbo) and the turbo that came with the 93 SD.

The intake sides are visually different because the .971 doesn't have ARV. The .971 doesn't have a fitting for a boost signal to the wastegate since the wastegate is actuated by a vacuum signal modulated by an ECU (I'd sooner keep the EGR hooked up). ARV makes the compressor housing ~95mm deep for the .96 vs ~64mm deep for the .971 compressor housing. The compressor wheels and contour of the business surface of the compressor housings are different but I can't quantify the difference. What I can measure is the base diameter of the wheels = both are ~60mm, and the tip diameter of the wheels = .96 is ~42mm, .971 is ~44mm. The pics show how the .971 wheel drops into the .971 housing but interferes with the .96 housing.

Maybe someone like Brian, Dave or ForcedInduction can explain the technical and flow differences in the compressor wheel and contour of the compressor housing. No hablo turbo tech.

The exhaust sides look pretty much identical. The key difference is the .96 wastegate housing is ~51.5mm thick while the .971 wastegate housing is ~23.5mm thick. The actuators are positioned differently. It's hard to say why but probably because the .96 has that funky trap oxidizer manifold while the .971 has the sleeker Euro manifold (it is a sight to behold). I'm hoping to fit the pressure actuator to the .971 turbo. That might require some modifications since the .96 wastegate flap arm is ~21mm long while the .971 wastegate flap arm is ~40mm long (see pics).

Finally, the .96 shaft has a LH thread at the compressor end while the .971 shaft has a more common RH thread. The nut at the turbine end of the .96 shaft is an assymetrical hex (if it's even a hex after I got done with it) while the nut at the turbine end of the .971 shaft is a more common hex that fits nicely in a 14mm socket.

Sixto
93 300SD

Here's the pics.

Sixto
93 300SD

The turbo from the 3.0L 603 has a 50 trim compressor wheel and the 3.5L 603's turbo has a 55 trim compressor wheel.

In other words, the one from the 93 will move more air. The compressor wheel, housing and back plate have to stay together because of the wheel differences. The center sections, and turbine sides should be identical.

I was afraid you'd say something I wouldn't understand and my fears are realized :) What does trim mean (of course I'll look it up)?

Thanks,
Sixto
93 300SD

Trim just means the ratio between the smaller diameter and the larger diameter of the wheel. The larger the trim, the more air it will flow.

I would think either unit would do the job on the 603.971. While the proper unit may flow more and provide air at a slightly lower temperature relative to it's boost level, the difference is probably insignificant. The wastegate is going to limit boost in both cases.

Use the one in the best condition.........everything else being equal.

Your better off using the 55 trim wheel with your 93 SD. It needs to breath more air.

How much do you want for the .96 compressor housing?

Does anyone have airflow maps to compare the 50 and 55 trim turbos? I'm curious to know if the 50 trim builds airflow more quickly. I'll gladly take more air at 2000 engine rpm at the cost of less air at 4000 rpm.

www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html

What's it all mean???

Thanks,
Sixto
93 300SD

Nobody seems to have a map for the 55 trim compressor except Garrett and they don't seem to want to share. This is probabally because its very good and they don't want others to reverse engineer it.

I would think that the 50 trim compressor wheel would build boost at a lower rpm than the 55 trim compressor wheel, however where boost starts building between the 45 trim and 50 trim wheels is negligible. If you have both turbos and a boost gauge try it and see.

I'll buy the 55 trim compressor wheel, compressor housing, and back plate if you don't want those either.

Don't forget a lot of spare time :)

I'd either do it with both turbos and a logging map sensor or both turbos and a dragstrip.

Sixto
93 300SD

I was under the impression that the 3.5L just used a larger cold side with a same hot side...