I've been thinking about switching to a more responsive, less top end power turbo (currently have a 3574 with large hot side). I would be fine with a turbo that can make 375 rwhp at 16 psi, and can reach full boost before 3500 RPMs.

Naturally the rx6 is my first choice, but they are expensive, harder to find, and rarely show up for sale used.

What other turbos compare to the RX6 in their responsiveness and power?

Thanks

 

You should be at full boost below 3500rpms with that turbo, even with as big as a 1.15.

The apexi Rx6 is very similar to a GT35R in a .82 housing.

 

I thought they advertised that turbo as being able to spool "almost" as well as a 35r. My 35r w/1.06 makes 10psi at 2800rpm, I would look into your tune and do a boost leak test before swapping turbos. What turbine housing is on it? I would think you should have no problem hitting that goal with your current turbo. What is your full boost and what rpm are you currently seeing it?

 

Thanks, are you referring to a T3 or T4 35R?

I currently hit 15 lbs by 4100+ RPMs. The dyno plots I've seen with this turbo seem to have similar spool time.

 

There is no difference between t3 and t4 turbine housings on a Gt35R, its just the turbine housing flange.

 

Turbo manifold setup and everything post turbo can have big impact. Wastegate spring rate can also have influence, and so does boost control and whole tune during spool up.
I think that target boost setting has more influence than some people would think. For example Eliots TD61 on stock engine reaching 24 psi by 3400 rpms.

 

Engine condition in my experience has the biggest impact. I also always run tubular manifolds, better coils/cdi etc, 3.5"+ size exhaust systems and boost leak check the cars we build.

That car that did 24psi by 3400rpms was even on a collected turbo manifold !

Manifold tubing size also plays a role...

 

Does runner length impact spool time? I have the older style aspec long runner manifold, it definitely has a healthy runner length compared to most other street set ups.

I'm still not convinced I have a problem though, like I said, every dyno of a 3574 I've seen shows full boost at around 4100-4200 RPMs. Maybe another member who has this turbo can comment.

 

I have a T3 GT35R stock ports and i dont see boost untill 4K+ which is annoying as hell.

 

You dont see any positive pressure till 4k? If thats the case something must be off in your setup, it should be about 1000rpm sooner I would think. Are you running a cast manifold and a huge fmic or something terribly inefficient like that?

 

my experiance with the 3574 is that I start seeing positive pressure around 2500rpm but the turbo doesnt come on strong untill 4000ish rpm, i run a large hotside, wastegate spring, and 3" exhaust with 2 mufflers that all hurt spool time.

I lost my local long track so Im in the same boat of wanting a smaller snappier turbo. Not being familiar with the apexi turbo I cant compare directly but im likely going to switch to a borg warner S256, its a step smaller all around than the 3574 but i think should be a solid ~350-375whp turbo with a real strong bottom end shouldnt choke up top. For reference I only run 12psi @ 335whp (dyno dynamics) and Im wanting to expand my powerband not make a specific number.

 

Ported engine? If you are interested in this part of powerband, its best to keep porting stock, otherwise you canīt change engines natural torque peak and range where it is going strong

Nice turbo choose. Will be interesting to see some numbers from these smaller frame BWs.

 

Motor is an early opening nearly stock closing street port, it has an ok low end but I'm betting the little bw is going to wake up around 1000 sooner but still carry on to 7500rpm, at least at the moderate power levels I'm looking at.

My 3574 has developed some bearing play so it needs replacement anyways, I'm sure I can post results when I get them

 

Thanks, its good to see someone else getting similar boost patterns as me. What are the specs on the S256?