What turbo

[colinx6242]

Good morning all,

I recently bought an E28 524td.

The original turbo was worn and the previous owner rode a water cooled TD04HL-15T. On the internet I see that TD04-15T is being offered for upgrade. But what is the difference between TD04 and TD04HL ??? After some research I have the impression that this means that the exhaust wheel is bigger. Do you have any information? Is the TD04-15T that good? And the HL version even better or worse?

I am not very happy with the result, there is no pressure below 2000tr, from 2200 it starts to rise well and I can get 0.8bar at 2500tr.
The response time is very slow below 2500tr.

I'm not looking for maximum power but rather torque for a pleasant drive without making the engine scream. I would like the boost to start rising under 2000tr already. It's rare when I shoot over 4000tr.

I am going to fit a water cooled intercooler and I would like to increase the pressure to 1.1bar.

The original turbo is a Garret TB0324, I believe it is the equivalent of a td04-11b. The 525td and tds had received turbo TD04-13T, maybe it is a compromise of what I need?

I live in Belgium so my E28 is a European version. Thank you for your reply.

[gadget73]

probably needs to be a relatively small turbo to get it rolling at low rpm. These things don't make any torque without the turbo and introducing significant lag makes an already less than zippy engine really not any fun. Have you tried adjusting the waste gate? The stock turbo on mine was adjusted incorrectly and the gate was partly open. It made no useful power at low rpm. Adjusting the waste gate as tight as it will go without pushing pressure beyond the relief valve made a huge difference in low rpm performance. I also added 1 turn in on the "smoke screw" on top of the boost compensator to improve off-idle acceleration.

I'm sure you know this already, but the stock pressure relief valve opens a little shy of 1 bar. I think its adjustable or can be shimmed, or you can just block it off to add more pressure.

[colinx6242]

Yes the turbo valve is working fine. According to my research this turbo is intended for a Saab turbo gasoline car, therefore an engine that runs faster.
I have already optimized the setting of the LDA and the fuel screw to obtain the maximum power with limited smoke.
I think it remains to find the turbo that will do the best job for my use at 1.1bar and the intercooler on this engine.

[colinx6242]

Here is a large part of the answer to my question:
http://turbolabofamerica.com/tdo4-turbi ... l-9-blade/

Turbine:
TD04 = 40.0mm exducer, 47.0mm inducer
TD04HL = 45.6mm exducer, 52.0mm inducer

My turbine is the largest.