Is it possable to upgarde the secondary turbo to a bigger one while still using the stock housing?

 

You can have a bigger compresser wheel put in one or both turbos alot of turbo shops do it ,

 

You can't put in a totaly new and bigger compressor housing? similar to the M2 TT upgrade?

 

the m2s are hollowed out stock snails to fit the maximum size wheels possible...

they are not different housings...they are just machined out to fit the larger garret gt30 wheels


j

 

can you buy the j-spec twins? i hear they add more HP,this true?

 

The j-spec twins only produce another 5-8 hp over the stock twins but are more efficient. Tim Benton said his spool about 200 rpm later but don't provide any noticeable power difference. Some good size comressor wheels can fit in that stock housing, especially if is machined out like the M2s. BNR has a Stage 1 upgrade where he puts in a larger compressor wheel in the secondary turbo but leaves the primary stock - his stage 2 he upgrades both turbos. Nice option for those who want some extra power but don't want to spend the extra $400 to have the second turbo upgraded.

 

I agree with Barry, the jspec spool about 200 rpms earlier but with the same initial rough tuning I've done with both the stock and 99 j spec, I've only been able to gain about 6 to 8 rwhp across the board at the same 12 psi. I'd imagine the 99 j spec would produce more HP at 15 psi than the stockers, and it would be more than the 6 to 8 rwhp at 12, but I'd think it would be no more than 15 to 20 at best more to the wheels (due mainly to the more efficient design of the housing and cooler charge air coming out). Once I get off my lazy *** and get my T-O bearing replaced, I plan on getting it wide band tuned. If I make more than 380 rwhp at 15 psi, I'd be surprised, thinking more likt 365 to 370 (stock engine, bunch of bolt ons
Bryan's work at BNR is damn best work I've seen on turning the stocker into higher flowing units. He does a great job on them and would recommend them for people wanting to upgrade but not planning on going single

Tim