I'm currently upgrading my S5 Turbo 2 motor, and I need a little bit of input on what type of porting I should go with. The engine is being outfitted with a To4 60-1 compressor and an exhaust housing with a .96 A/R,. The engine is going into a street car, but I'm not too concerned with sacrificing low-end as long as I can make it up in the upper revs, as this car will be more of a toy than daily transportation. Is anything beyond a small street port going be usable with this combination? Also, are the Racing Beat templates well designed? I'd like to handle the porting myself. BTW, while I am keeping the stock tranny, I was planning on switching the rear end ratio to something more in line with the new power curve. Any input would be welcome.

 

The racing beat templates are pretty good, maybe a little on the conservative side.
You could do a 1/2 bridgeport on your engine with excellent results (as long as your turbocharger is sized accordingly). But then, you may be making more power than you can handle with the stock rear, so be sure to put in a high quality limited slip when you change gear ratios.

 

Thanks Spongebob. I know the general rules for sizing a turbocharger based on engine displacement and speed, but how should I aply those rules when changing port sizes? Should I just calculate a higher redline depending on which port arrangement I go with(maybe 8500 w/ 1/2 bridge and some internal work)?