What Turbo to upgrade to, mild S4 TII build
 

Well me oem S4 turbo has decided its seen better days.

My current build is minor, Rtec 1.7 ecm with 720 secondaries and 550 primaries. A 81mm corksport Dp, and a cone filter.
Putting in a fidenza light weight AL flywheel and a Spec 2 clutch. I am also deleting the omp, and and the emissions crap. Upgrading to a better fuel pump and removing the resistor pack. I do plan to custom fab up an air to water intercooler system at some point. No specific hp goal, but want it to be a fun weekend car, and to run smoothly.

The Turbos Im looking at are the BNR hybrids, any one of the staged ones look good, but unsure which will just be too much for my current fuel supply. I want a staged one for the wicked s4 ported wg that they do now.

I also have been in talks with a local guy that has a full stainless manifold, down pipe and WG turbo kit with a couple choices for turbos. One is a small t4 journal bearing t60-1 size or 67mm dbb. Small turbo good for 300-350. Big turbo 350-450.hp.

Do those # make any sense to you guys? Im not completely on the game of turbo specs. He is getting more info and pics for me once he's back from Vacation.

Are there better/ other options to go with? If these flow too much can I not just run with a lower psi with a more efficient turbo?

ok... well that's going to degrade your idle quality if you're not careful. Lightweight flywheel + more aggressive clutch + removal of fast idle and BAC valve can mean lots of stalling.

you will need a way to control a low temperature cooling circuit, all sorts of stuff like a water pump and extra radiator. sounds like it's not a near term goal.
Get a stage 1 or 2. And don't delete the twin scroll control.

that's a whole different animal there, and costs will greatly increase due to needing custom piping for everything and a more expensive fuel system.

what's your budget?

Bac is staying operational, not all blockoffs are going to be used.

I understand there is more to a air to water than just the cooler, rad, overflow, pump, control cct water lines etc. Its more than likely going to be pieced together over time. Since it really wont be a daily driver, I would plan to run the pump, cooling fan at 100% duty.

Well the kit the local guy has is put together to be bolted on, piping and downpipe is included. Said it can work with the stock tmic, but didn't recommend it. This setup from him will be roughly $1300, more if I want his lager turbo, but I would stay with the smaller of the two. Where as the BNR turbo would probably be near the $1000 range after shipping etc. Does a guy need to specify to BNR to keep the twin scroll operational?

I don't plan to have it wrapped up this fall, but am planning to get it on the road again before the snow melts next spring.

how much power do you want? if the stock turbo was fine, then the BNR stage 1 should be a great choice, you'd get more power, and it should handle 10-12psi with more reliability than the stock turbo offers*


*we found that the stock turbo spins 130k rpm, which is already really fast, so when we try to run MORE boost, it just wears faster. the larger compressor of the BNR type will move the same air as stock, at fewer shaft rpm. or put it the other way, if you're running 10psi, the BNR stage 1 will be about what the stock turbo does at 6.5psi, give or take

Honestly I don't have a number that I want to get to. But I don't want to just replace the oem turbo with another direct oem when I can upgrade to something more efficient. I don't want to outrun my current fuel system and ecm's limits, but I also dont want to limit myself later down the road. Im fine with using a larger turbo (within reason) at a lower psi now that is still in its efficiency range. I may be asking for to much.

Is the BNR Stage 3 just too much for it to worth my while getting now? From the website saying they are all basically the same $, it seems wrong to not get it. But if its too much its too much.

$ is the same, but you choose between different compressor wheels. the bigger the compressor the more power you make, but the longer it will take to spool up.

i've been looking at compressor maps (i'm not far away for needing a turbo for the same reason!), and i am really liking the instant boost that the stock turbo gives, and its fast enough, so i would probably do the stage 1.

the stage 2 has an H3 wheel, which will make something around 310hp at 12psi, but it won't hit 12psi until after 3000rpm, whereas the stage 1 should spool ~2500? sometimes spooling a little later can be easier to drive, ymmv!