I just read through the whole thread in A-specs section on the GT3574, but there is not a lot of information regarding spool. If you have their kit, and a stock or lightly ported engine, what kind of spool are you seeing for 1 bar?

 

We had one local car here run the GT3574 on a stock motor running a SMIC and a open exhaust car was rerouted too I believe I will see if I can find a dyno for it. Car did roughly 380whp@13psi.

While I'm not a customer so I'm sure it can seem biased, my honest opinion of driving the car was that from a standstill it felt very similar to a 35R car. Driving around the transient response was off a bit compared to a 35R car. It came on softer, if that makes sense. Those that have drove a non BB unit versus a GT series turbo will probably know what I mean as they tend to come on harder.

We are offering them in BB versions now as well.

Hope that helps a bit.

 

Personally, I run (well, soon to be "ran") the 3574 and its a great setup.

Had great response for a non-BB unit and on the build I'm basing that on, my engine was only a mild streetport.

As my turbo currently sits, its eaten a number of apex seals and the chipped turbine is hurting boost response badly. I'm sure A-spec would like to smack me for running it like that - but hey I'm small game in a big ocean I'll likely ship it back to them for a new wheel/balance/check over in the winter time, but overall I'm *VERY* pleased with the kit for the price, and A-spec gives great service/support so you can't go wrong.

Oh, my numbers on the DAMAGED turbo at the time were 350@15psi, basically stock ports, on a Greddy cast manifold (not aspec's!!!) with fuel pressure issues, incomplete tune, horrible response from the damaged turbine and only revving to 6K rpm due to a trigger issue on the Haltech....................but the thing is still tickin'

EDIT: Before the turbo ate any seals, punching the throttle at 3500rpm would net 10psi almost instantly, if the EBC was set for 15psi, it would ramp up to it by 4K (was still also on the greddy cast manifold at the time) that's with a 10psi spring in the WG. Setting for 19-20psi were never reached before the turbine met mazda seals, so I can't comment on the response of it on higher settings, but when damaged it didn't have trouble with 25psi, so I can only say it must be better with no damage at those pressures

But bear in mind, X boost at Y RPM has a *MONSTROUS* number of variables, and this is only my experience.