.48 a/r turbine. Had a 40mm compressor. Now has a 60mm compressor.
Does that add turbo lag?

 

It can. Think of it like reciprocating mass. The 60mm wheel doesn’t weigh the same amount as the 40mm wheel. So it’ll take a little more to drive it. How much? It’s hard to say. Every setup is different. But it “can” add spool time.

 

Yes, especially when you make such a large change on a small wheel. Depending on the size of the turbine wheel, it may struggle to even drive the larger compressor efficiently. I see you referring to a .48 turbine in many of your posts.... you can't compare turbines by just the a/r alone, you must first know the size or trim of the wheel. gt25, gt28, t3 stg 3, P trim, Q trim...ect. The a/r only comes into play once you know the wheel.

 

Finally found it. The exact turbo i modified is a Garrett gt1446 : https://blaast-turbo-factory.myshop...ett-gt1446-glszm-dodge-dart-1-4l-turbocharger

One reason i'm asking is because when it was unmodified it would scream and you could really tell it was doing work. But when i put on the bigger 50mm compressor it wasn't loud anymore.

The turbine wheel has to be in the 30 mm's . It's pretty small. Unfortunately i cant remove the turbine to get to the wheel.

 

So many variables . Spool or threshold is just part of whole system . Wheel trim etc . If it’s screening ? Chances are turbo is small ! I went to larger trim on exhaust . Spool was the same but didn’t hit so hard and kept making power . I went to larger exhaust system also .

 

If you installed a larger compressor with the same turbine it may be that you are not producing enough torque on the turbine side to spin the compressor. Garrett did the same thing on their gt3076 turbo , when they upgraded it to a larger turbine to the turbo (gt3576) it performed pretty good.

 

Every turbo I have had upgraded to a larger compressor wheel made a minor difference in spool. Went from 75 to 85 on one and from 76 to 91 on another it made enough difference to notice it slightly when street driving.

The two aspects to consider is 1. The larger compressor is heavier, and 2. It can physically "grab" more air than a smaller wheel which also makes it more difficult to turn.

 

[QUOTE ="Bad Medicine Racing, post: 2024493, member: 44008"]Every turbo I have had upgraded to a larger compressor wheel made a minor difference in spool. Went from 75 to 85 on one and from 76 to 91 on another it made enough difference to notice it slightly when street driving.

The two aspects to consider is 1. The larger compressor is heavier, and 2. It can physically "grab" more air than a smaller wheel which also makes it more difficult to turn.[/QUOTE]


Very well said.