I am currently running a Garrett gt3582r with a 1.03 a/r on my single turbo 350z and it is rather laggy. Its a momentum single kit. I was planning on selling the current turbo and downsizing to a gtx3076 with .82 a/r for quicker spool and a bit less horsepower. Car is currently making 430 wheel on 110 octane and 14psi. Looking to go down to around 375 on pump gas. Would I be better off with the turbo downsize or simply replacing my housing to a .63 a/r or .82 a/r on the 3582r?

 

I would vote for a .82 A/R

 

I had a .82 housing, upgraded to a 1.06 housing to reduce exhaust back pressure, etc.; didn't really notice a significant difference in spool.

 

Bam! listen to thatv35guy.... Back pressure is not good.

 

Im thinking .82 might be my best of both worlds solution, since I'm not looking to push a ton of power.

 

IMO, I don’t think the extra spool is worth the time and money…

 

I have the 1.06, it doesn't seem too laggy to me.

 

Im also currently not utilizing a boost controller. From what I've been researching, the combination of the smaller a/r and a controller can make a pretty big difference?

 

Smaller A/R won't bring you that much difference in spool, if any. But definitely will backpressure problem.

Instead, look into boost and exhaust leaks and use boost controller. Boosting with WG spring only is the slowest possible boost building.

 

If you have not , should get your tuner to pull in the cam phasing.
On my MTM set up , was able to improve spool by a few 100 RPM by doing so.

Also on an ST setup where the hot pipes are longer. It is much more important to have your hot pipes ceramic coated to minimize heat loss. I also have the hot side Tial housing coated. You will also a notice a bigger difference in spool depending upon how warmed up thodr pipes are. This is less noticeable than on a twin setup.

 

define "pull in cam phasing"

thanks!

 

move the intake cam to exhaust cam phasing to minimize overlap in the early mid range.

OEM slope sets the phasing to improve mid range emissions via overlap (ie the EGR effect). That effect aids emission but slows turbo spool. Uprev now supports cam phase tuning and that is one tool I used to improve my ST spool. It was more important ot me , sicne I recently swapped in hotter JWT C2 cams.

 

since you add C2's which have a ton more overlap and duration, you must have had to add a lot more advance to reduce it back to stock levels.

 

Not totally back to stock spool levels , since I run 9:1 CR .

With C2s , adding some timing and moving the intake cam phasing , the spool delay was minimized to only ~200RPM over stock cams.
My idle is smooth as stock and picked up ~40 rwhp at same PSI with the C2s. Overall a great improvement in driveability. Smoothed out Torque spiking , which allowed more timing advance to be rolled in early

The intake CAM re-phasing made the most difference in spool improvement
.A good tool that should be pursued by those looking for spool time improvement.

 

there have been studies on intake manifold pressure : exhaust manifold pressure.
for the street the rule of thumb is 1:2 which will give you boost earlier
for racing its a balance of that up to 1 : .5 (indycars etc)

when going with a smaller AR make sure your wastegate is large enough to handle the extra exhaust you will be venting.