Precision Billet Turbo discussion

Hey John,

Any chance you could post up a compressor map of your new turbo? what kind of dyno are you going to run on? are we going to be talking about corrected or uncorrected numbers? I might have a guess if you're interested… Thanks Man :-D

John

[quote]FCvg30et wrote: The VG30 and VG33 cams die off after 5500 rpms. The 33's are a little worse up top.

So what is the best place to buy a billet wheel precision turbo. I was thinking of a t67 or t72

I dont have a compressor map for my comp turbo 62mm, but I imagine its close to similar 62mm turbos. With this T4 turbine housing, I pull real hard to 6000rpm on stock cams, and it still pulls very well up to 6500rpm, at least better than my HX35 did. This is most likely because of the larger T4 turbine housing and wheel versus the HX35 turbine setup.

I will be running on a DynoJet 248 Model Inertia Dyno. I am just shooting for corrected numbers since most people on this forum ALWAYS post up corrected numbers, except for SATAN. I want 450rwhp+ corrected.

I am wondering what a set of aftermarket cams and springs on stock heads will give me??? Is there only a minimal gain due to not porting and polishing? I would like to do JUST cams, leave stock springs in, quick and simple. My springs are very low mileage, around 25-30K miles OEM new from nissan. Think they will float? Who has actually heard of someone on this forum floating valves from running stock springs with aftermarket cams and actually causing valve and/or piston damage?

Z31t: So your going to do aftermarket cams on stock head castings and stock valve springs? This is what I want to do. Are you worried about valve float? Ever plan on porting the heads?

If it's pulling hard up to 6500, how much higher do you want go?

During the middle of the 09 season I did a little test on my 4g63. At that time I was running 2.5" IC piping, stock TB, stock IM, unported head with HKS 272's and BC Ti springs and retainers. The turbo was a mitsu bolt-on BEP A/R .55 S259 with a 2.5" exit. Up until the test the best pass I had was a 11.10 at 133. The test basically consisted of checking the exhaust manifold pressure and comparing to the intake pressure. Last year I switched over to a A/R .70 T-3 manifold with the same turbo and a 3" exit, that's all I changed besides adding a little more fuel up top. I ended up running a 10.75 at 140 last year. I know I'm talking exhaust and not cams, but the way I look at it, it's all kind of the same thing-sort of. Get to your target RPM and boost level, then check your back pressure on the exhaust manifold and then determine if larger IC piping, IM, port & polish head or cams would benefit you or not.

What device did you use to check exhaust manifold pressure? Never seen a pressure gauage that can handle that type of heat....although I have never really looked either

IIRC, a brass 1/8" NPT fitting with a barbed end and about 18" of soft copper waterline into some hose that was hooked up to a spare boost gauge. I've got most of the pieces in the garage or basement somewhere… I'm sure you know that I didn't leave it on for very long either. I also came up with the fittings and a gauge to check the oil pressure at the turbo just to be sure on that one too.

Now that this thread has had a chance to sit and ferment a bit while more people got on the Precision band wagon....

Has anyone had a chance to try out the billet Precision BB turbos in comparison to the journal bearing ones?

Is the difference really worth the $500 or so difference?

Yes, if you are willing to pay it.

The journal bearing ones don't like 35psi for too long…ask me how I know.

Sounds like the voice of experience.

35psi is quite a load on the turbine side I would think. Do you know if that side failed first?

Good point. I plan to run 20psi fairly often. Not near what you run, but over the long haul a factor.

I'm old school so I'm still a bit uncomfortable with air cooled center section. I wish Precision offered a WC center section for those left behind in the 80's like me.

It didnt completely fail yet but I have questionable back and forth shaft play. When I called precision they told me about how much stronger the ball bearing was when it comes to thrust load (I forget the actual number). If your going to run lower boost Id say 22psi and below Journal bearing will be fine, I mean mines going back on as is but I hopefully won't have to be as aggressive on boost with this next setup.

did you change platforms? LSX ? I get confused who's doing what.

Just for comparison, I can tell you that I have a OEM Garrett T3 that was rebuilt about 50-60K miles ago.
It currently has ZERO hand detectable lateral or longitudinal free play. Of course, it has and never will see the stresses you put on yours 8)

I ran 23psi on my pt5857 journal for 800 miles and it is tighter than a factory BB unit. We'll see what it can do this summer hopefully.

My ebay turbo was run on my car at 30psi and now its on the 1jcar with almost no shaft play. The precision has no movement side to side but its pretty noticeable front to back. It saw heavy heavy abuse though at 30psi for around 4the months and then I cranked it to 35.