Forums/Z31P/z31-performance-upgrade-forums engine-mechanical-aa/Turbo A/R Discussion
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300zxturboftw: (2015-08-12 15:38:38)
Looking at grabbing a 6266 gen 2 precision turbo today or tomorrow. Grabbing a divided housing but not sure which A/R to get. Precision suggested 1.0 or 1.15. Is 1.15 going to be too big? Fully built engine, 280/270 cams, power from probably 3600-7200.
Thoughts, suggestions? Go Bigger? Looking to make low 600's efficiently.
300zxturboftw: (2015-08-12 17:44:10)
Went with a 1.0 A/r 6266 gen 2. Funny enough the Gen 2's are rated better at high boost pressure, but not necessarily as great for lowers vs. gen 1.
G-E: (2015-08-12 20:44:35)
Should be fine
nismo kid: (2015-08-12 21:17:27)
Check out Flawlez build. He's running a .63 A/R 6262. Everyone tried telling him it would choke up top but it doesn't. I'll tell you what his car just pulls and pulls up top. Even near 7k it just wants to freight train.
http://z31performance.com/showthread…-RWHP-540-RWTQ
300zxturboftw: (2015-08-12 22:02:04)
^ Very nice. I'm looking for something that I can use and expand on. Who knows what the turbo might go on other than a VG down the line. Going to see how long this motor holds up - hopefully for a while.
FlawleZ: (2015-08-13 03:56:01)
Highly recommend swapping out that hotside. My .63 has shown 0 signs of choking at 25+ psi 545+ HP. You don't have to rev that high at all to make 600+. Mine broke 530 at 5300 RPM. I think the .68 would be perfect, maybe a .82 or .86 at most.
Also, what do you mean by "low 600s efficiently"?
300zxturboftw: (2015-08-13 14:55:11)
Saying efficiently via turbo choice. I'll give the 1.0 a shot and go from there. They have a .84 divided if I want to switch it down the line. Think I'll be OK. Just want to get the car going already.
ShamWow: (2015-08-13 15:25:32)
im using a GT35R (much older tech I think) with the divided .78 AR housing. This was streetfighters recommendation. haven't been back to the Dyno to see what it does up top, but it really slams headfirst into the rev-limiter.
Several tuner buddies told me the T4 1.06 divided would've been a better choice, but who knows.
300zxturboftw: (2015-08-13 18:56:59)
Whatever the case, it will be a nice upgrade from what I was running.
ozzyrulez: (2015-08-14 04:41:14)
On my PTE 6262 I opted for the .82 housing. Thing spools fast and pulls hard.
PoorMans180SX: (2015-08-18 18:01:55)
Looking at grabbing a 6266 gen 2 precision turbo today or tomorrow. Grabbing a divided housing but not sure which A/R to get. Precision suggested 1.0 or 1.15. Is 1.15 going to be too big? Fully built engine, 280/270 cams, power from probably 3600-7200.
Thoughts, suggestions? Go Bigger? Looking to make low 600's efficiently.
I always suggest running the largest turbine that is going to give you the flow you want, with a smallish turbine housing. The turbine is really what determines the overall response and power output of the charger, the A/R just tweaks it around the rpm range. So I'd suggest the 1.0.
Precision does a decent job of matching their turbines and compressors, but If you haven't already, I'd suggest checking out the new S300SXE lineup that BorgWarner just released. Killer turbos at really awesome prices.
Racinjitter: (2015-08-19 14:08:29)
I am running a 6266 gen two also. I think we have the same ISKY cams, I'm running EPR's 9.2:1 pistons and forged bottom end. I opted for the SS vband .82 housing. The thought process on the turbine housing and size, was if the 2j crowd can get 836rwhp at 29psi with a .82 housing… 600 will be easy to do and not strain the turbo.
300zxturboftw: (2015-08-19 15:07:26)
^ There's someone I haven't seen in a while! Thanks for your guys input. I'll let you know how it turns out once I post dyno graphs in a couple weeks. I think the 1.0 with the twin scroll will do me good as I would most likely go with something .7x-.8x if it was an open/vband.
G-E: (2015-08-20 21:56:59)
Our local turbo expert has been doing clever wheel clipping mods for the rally guys for years, and his contention is that while a/r plays a role, it only affects the spool ramp..
Basically the turbine wheel turns because of the air going into it radially (centrifugal thrust), but most of the power comes from the axial flow out the back
Likewise a turbo manufacturer told me the cross-section area of a divided 1.06 is the same as an undivided .63, give or take a hair… once you add the increase in pulse effect, it generally makes the 1.06 still perform better with less backpressure…
300zxturboftw: (2015-08-20 22:16:06)
FlaweZ are you running a divided or open scroll? From what I've always understood that always plays a part in A/R as G-E discussed above.
I could understand running a .63 open scroll, but wouldn't understand anything lower than .8 on a divided (which is the reason why most don't even make something that small).
z31t: (2015-08-26 14:15:46)
You won't notice a big difference until you try to max the turbo out. When you see these 800+whp cars on 6xmm turbos they have the large a/r housings on the exhaust.
liladair: (2015-09-28 19:00:37)
I have a .65 on my open scroll 60-1 and it spools great. 15 psi spring in the wastegate right now and it holds steady. After I finish the harness for the new management system i will up the boost and see how well she responds at higher boost / power levels. Also changing from ported stock manifolds to tubular manifolds when they are finished. My car always goes thru big changes in a weekend because i drive it everyday lol.
james: (2015-09-29 08:16:47)
i have tried a couple of different turbo combinations and A/R
The GT35 (journal bearing copy) with 0.82 open scroll and log manifolds was lazy until 3500rpm then ran like a demon at 20psi and showed no signs of dropping off, the manifold pressure at 20psi spun the gauge needle right around until it read zero again. Those manifolds then failed, the turbo failed the journal bearing and bent the shaft. It was probably more the cheap turbo but I can see that turbo with perhaps a divided 0.82 would have been a really good match.
can also understand what flawlez is saying about not needing a huge A/R
My car runs Tube headers, Schneider cam and ported heads with a hybrid turbo i built out of leftovers. Its a GT35R compressor wheel on T04S front cover (machined to match) with your typical mild stage 3 turbine wheel and bored out stock housing. You would think its not a great combonation with a massive compressor wheel on the small turbine but this thing really moves.
at 13psi my RB25det heavy duty clutch slips at anything over 5500rpm and it shows no sign of being any less punchy than the old Journal bearing GT35R.
Yes the hot side is probally holding back power and no it hasn't been on the dyno but its a properly matched system all there way through and its breathing very well on a surprisingly small stock turbine housing.
To anybody thinking of experimenting with their turbine housing sizes Setup a manifold pressure guage , wrap a thin copper tube around a pieces of 1" stock a bunch of times and plumb it into the turbine housing and run it to a boost gauge.
Somebody with tube headers and a well matched perhaps a ball bearing turbo should in theory be able to achieve a higher boost pressure than manifold pressure.
FlawleZ: (2016-01-20 17:51:15)
FlaweZ are you running a divided or open scroll? From what I've always understood that always plays a part in A/R as G-E discussed above.
I could understand running a .63 open scroll, but wouldn't understand anything lower than .8 on a divided (which is the reason why most don't even make something that small).
I know this is super late to reply but still helpful for those who may search in the future. My .63 housing is an open. Precision doesn't produce a divided housing on T3 frames. On a T4 I would have opted for something like a .82 divided.