Originally Posted by Boosted Performance

There are a lot of guys with built engines, they just don't brag about it. This engine is 6 years old now, and warranty periods are long gone for most, so built engines will become a lot more common.

As for efficiency, the 6266, 6466 and the 6766 will all work well and will get you the same HP across the board on pump gas (knock limiting). I have customers with all those turbos, as well as a couple with 7675 turbos. On pump gas, same tuner, same dyno there are all within 5hp. So in theory the 6266 would be the best fit, because it does have the lightest rotating assembly.

So, for stock block applications a BB 6266 with a T4 turbine 1.15 a/r turbo will be the most efficient, because most of the tuners are comfortable pushing these engines to no more than 550whp on pump gas. For E85 applications and stock block for up to 620whp, I would keep the 6266, but go with the 1.32 a/r housing. Of course, most tuners will be hesitant to push the stock block to that power level.

I should also mention that I would not hesitate for a second in putting this new 6870 on a stock block with a 1.0 a/r turbine housing. THAT, would also be a very efficient set-up, especially where these engines like to operate...in the higher RPM range. Spool difference would be negligible, and exhaust back pressure would be very low, which means very high efficiency.

They key to all these turbos on a VHR engine is turbine housing. Based on all the testing I have done, a T4 housing is optimal. A lot of guys are concerned about spool, when really, flow should be the primary factor when choosing a turbo (turbine).