What will be better choice for a 6262 a .63 or a .82? it will be for a drag racing application. Would the .63 A/R turbine be a restriction? On a 1.8

 

Do you really need to ask what ar rear for drag racing?

 

It seems you don't fully understand A/R

Do you want fast or slow boost?

 

If it was for the spool i would had gone with the .63. I wonder at what point does the .63 turbine housing begins to be a restriction in flow and top end power.

 

neither one, best A/R size for 1.8 engine is a .48

The trick is using an external wastegate for your drag race setup

 

probably a long time after you realize the cams are the limiting factor.

 

I tuned a 6262 .63 AR on a 2.3L mazdaspeed3 ... i have a feeling you will hate that turbo on this car. Maybe i am premature in saying that, but even with .5L more displacement, and VVT i had a hard time getting that thing to spool in a reasonable amount of time. That being said, we went on to make 530 whp without having to try too terribly hard, so you'll by no means be limiting it with a 1.8L at .63 A/r.

Not to mention that turbo was an absolute dog around town. We had DBW, so luckily i could ramp up the throttle tables at a super aggressive rate, which helped offset some of the sluggish feeling (25% throttle position was closer to 40% throttle opening), but on a throttle cable car like the miata you'll just have to stomp the gas. Maybe i dont understand how well bigger turbos work on this platform yet, but i just wouldnt go anywhere near that big. There's no point, we were seeing power levels in line with much smaller turbos until we reached the beginning of the efficiency range around 30-31 psi.

 

I have a Precision 4828 in my car. IMO, the .64AR turbine housing is perfectly fine (with EBC). In retrospect I wish I would have stuck with a standard GT2560 though, because by the time I built my engine I could have had several years of better spool.