My First 5 Blade Turbo!

Posted by urgirlamy 10/31/2019 0 Comment(s)

Actual Q&A from Nick:

Nick:   I just got a 472/83/1.00 T4 5 Blade...   My question is: 

If I wanted to, could I swap out your 1.00 exhaust housing with another Borg Warner T4 exhaust housing?  Or will I have to do some special machining if I want to change exhaust housings?

I ask because this is my first 5 blade turbo and I assumed nothing is interchangeable on it since it’s a custom turbo. 

Johnny:   On that unit we do use the Borg Warner Exhaust housing for the 83mm turbine wheel. So yes, you can change the T-4 1.0 AR size you have to another size . We have a tremendous amount of R&D data on that particular unit with the 1.0 AR size exhaust housing.  However I caution you against going to a smaller size .90 size. On our 87mm units we do, have a special machined exhaust housing for the 87x80 turbine size that we use.

Nick:  Johnny you read my mind! I was in fact thinking about throwing a .90 housing I have laying on the shelf on this turbo. Primarily for a skosh better spool up.

I’ve read and read and read until my eyes started bleeding and I haven’t been able to get a solid understanding / consensus on the .90 housing. I assumed that suggestion to avoid it was made because the majority of your customers run aggressive fueling and drive aggressively.

Is it (.90) still a bad idea on stock fuel?  I don’t run any fuel mods nor do I plan on it. Nor do I drive my truck hard (WOT runs or even aggressive launches).

Johnny:   A 72/83 unit even on a 6.7 with stock fuel only, is a large of a turbo for 550 to 600 rear wheel horse power.  You will here many different options given freely on the Internet.  My opinion comes from 10 plus years of experience that is directly related to my wallet.

The .90 on a 72/83 unit on Cummins will and can push the turbo operation into the surge line. If your set up has a highly flowed, modified cylinder head & camshaft, it will be it a lessor extent that the surge condition will happen.  Operating a turbo in surge will damage the thrust bearing.

On a 6.7, it’s been our experience that the .90 AR housings will put a turbo at a faster shaft speed than we consider to be good for longevity or for a reliable operation.

Surge ... is to much flow for the engine to ingest at a given RPM / load and operating rate due to the fact that the volumetric efficiency of the motor is incompatible to that air flow volume.

The same turbo sizing on DMax won’t surge under the same operation, although the motors are similar in cubic inch.  It has 8 cylinders with better flowing cylinder heads. 

Slowing down the turbine speed with a large AR exhaust housing helps to mitigate unwanted operation conditions in the lower RPM ranges .

Hope that helps 

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