Hey, seems these questions may be a dime a dozen but just trying to get educated a bit more on spec'ing a turbo and hoping I can get some help here.
How would one determine what is good size for turbine wheel size and a/r?

I've currently got an lq9 with mild ported 241 heads and about 10.8:1 c/r, spinning up to 6900rpm with a comp xr281 cam, fast lsxr/nw DBC 102, 3600 converter/3.73 gear in a 4wd rcsb. Considering this winter going to a low-boost front mount setup. My truck really falls off on the long end of the quarter, or in most higher mph roll races (I know I'm fighting up hill with a truck), but hoping boost can help me out without altering much else on my setup ( fuel system will change and considering changing to e85 capability).


So, say I choose to go with an 80mm turbo (looking at BW S480 t4), well then how would I go about selecting which turbine wheel size? Looks like options range from 83, 87, and 92mm.
What effects would the smaller vs. larger have?

Then, what about a/r selection?
Looks like options are .90, 1.00, 1.10, and 1.25.
Again, just looking to get educated on what effects this choice has on the overall setup.


...then on top of that looks like choice of Billet wheel, and race cover. Seems race cover is popular on ls1tech, and people still run it with cast wheel, but never billet wheel with reg. cover... I don't think I'll be swinging the cash for a billet wheel. Possibly race cover though.


Any help or informative tips are much appreciated!
Thanks,
Dave

 

Oh yeah, almost forgot...
What about choosing Wastegate size?
And BOV size?

 

Turbine wheel and AR will effect spool time and how much power you hae on the top end. If your AR is too small you will run out on the top end. For your build a 87mm/AR1.10 should work well. I think the 50mm WG and BOVs from JGS are nice on a budget. I don't think a race cover or billet wheel are needed, but some people swear by them. The difference isn't big enough to justify the cost IMO.

 

Thanks for the reply.
Have any idea how independently each, turbine size and a/r, effect spool time and top-end separately?

 

Turbine size depends on engine size and helps lower back pressure on high rpm and big boost for top end. Small turbine on big engine sometime spool faster but looses top end faster too at certain boost. Usually on smaller boost #'s this is unnoticeable because they are not pushing the turbo much.

A/R is more of and final adjustment on how early or late you want it to spool.

So depends on whats you want, finding the medium is best in my opinion.

Play areound with BW tool to get an Idea.

Turbodriven.com