Before I buy, looking for a little reassurance. Buying twin Comp 6267's, shooting for 1000 whp on E85. Want to keep similar transient response as my current setup. Should i go for .68 A/R or .81A/R?

2010 Grand Sport M6, SBE LS3 with forged rods and pistons. Currently running .82A/R T3 frame PTE 6265's @ 12psi making 800.

What do the masses say? I was going for the .81a/r option but second guessing it now.

 

Quick sanity check...

Did you mean the 64/67 comp turbo? Even then they are only rated for 75 more hp than the 62/65. So what's the point?

The turbos you have now are rated 900 HP each. And you are barely leaning on them with 12psi. Why do you feel you need to upgrade?

So your gonna spend that kinda money to change the exh wheel diameter 2mm?
Then you are considering going down in AR from what you have currently?

If the 65mm exh wheels are tapped out now, a 2mm exh wheel change isn't gonna do much and you def wouldn't want to reduce the exh housing size. If you aren't tapped out, why not just push what you have to 1000? If you are upgrading, upgrade the compressor as well as the exh wheels and do it by a healthy margin.

None of that makes any kind of sense to me. A healthy LS3 should have larger units with a 1000whp goal anyway. Should be looking at S366 or similar sizes.

 

Turn the boost up. Like 15-20 psi kinda up. If you can't make 1000 rwhp on those turbos buying only slightly larger turbos isn't gonna get you there either

 

The new turbos would be the 6267 CTRX which I believe are rated at 1020hp as opposed to the PTE gen 2 6265’s rated at 835hp . The entire turbo kit is getting replaced and the new kit is T4 based instead of the current t3 turbos. I have heard that generally an .82 a/r t3 is similar in size to a .68 a/r t4 but am not sure if that’s the case in this instance.

the motor is currently SBE, so rods and pistons are going in it before I crank up the boost further, so while the old kit is out I want to install the new kit. The kit on the car also does not prioritize the wastegates well, and I don’t think I’ll be able to effectively have a low boost option when I don’t want to run it all out.

I really enjoy the response from the current turbos which is why I’m hoping to keep a similar sized turbo. I hoped the better compressor wheel coupled with a slightly larger turbine would help bump the power without me losing the response.

I hope that all makes a bit more sense now, and I know I can’t always have it all, but don’t want to end up with a setup that is lazier that what I have now or isn’t capable of my goals.

 

The smallest one of those turbos I see is a 64/67, and the smallest housing is a .81 a/r. Do they have a product listing I am not finding?

 

I think so. Huron speed suggested it when I was asking about the 6265 ctrx. I’ve decided to go .81a/r

 

I'm still trying to make sense of the "SBE LS3 with forged rods and pistons". I thought SBE meant stock bottom end as in stock rods, pistons and crank. Not just a stock crank. If you have forged pistons and stronger rods, its not a stock bottom end... is it?

 

Your current setup should do everything that you need. 12psi is barely in their efficiency range. At 20psi they should be good! I would turn it up before making any radical changes like you propose.

 

This thread seems like a troll thread. Throwing perfectly good stuff away without actually knowing what it's capable of is wild work. He's either being fed horrible information or just wants to throw money at it for no real reason

 

The bottom end means the oil pan, right? LOL