Hey all,

what kinda of boost pressures do you see out of a stocker/s400 MPI set of twins. I am thinking longer term I need to address my trans first but after that I think I will do a set of MPI twins. Thanks in advance...

 

bump bump bump

 

no body???

 

I would think like most sets of twins its all in fueling and wastegate setting, drive pressure will be more important.

 

Yeah I was thinking that too, I was just trying to get a ball park. I think I will get a set of MPI twins once I get my transmission rebuilt and upgraded. I will definitely do a drive pressure gauge to keep an eye on that.

 

Good idea on the drive pressure gauge. That stock turbo exhaust housing is by far the weakest link in the "stocker over s400" set up. It's just too restrictive for good top end flow and drive pressures soar. That said, I know a few folks with that setup that top out at about 55psi with their fueling. No idea what the DP is.

 

Nathan has run a few tests with his twins setup measuring drive pressure in relation to boost. Its not nearly as bad as you would think!

Maxed out his numbers were 67 psi for boost and 77 psi drive without an external wastegate.

With an external wastegate the results were 67 psi for boost and 73 psi drive.

They are higher than the boost but certainly not soaring. I'm sure the drive/boost ratio is much lower using the stocker with twins than it is on its own.

 

Yep, those are the numbers he gave me as well.

Drive pressure becomes an issue with the stocker when the WG is disabled. In a twins setup the WG is still used and it's actually set much lower than stock.

With the stocker/S400 setup my typical max boost in OD is ~54psi. It has hit up to 64psi in really cold weather though.

 

Wow. Those are great numbers! You are right those drive pressures seem much more manageable then I thought they would be. Ok, I am sold...now I just need a good transmission....and a lot of money. Thanks a lot guys!

Oh JRussell, great run in the sig. I am not much of a smoke guy either.