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Turbo Size Recommendation

19K views 20 replies 6 participants last post by  bozo4 
#1 ·
Can you help me size a new turbo?
I have had my turbo build on road for about 10k miles.
My current turbo is too hard to drive normally. Light throttle boost, makes this daily driver a handful. Its too small. Its a T-4 housing and a 76 mm compressor wheel.
My car is a 05 Magnum with Rear mount plumbing. I am looking to cut out spare tire well to give more room for a T6. Like a Borg Warner S480? 80mm
Any suggestions on a nice single turbo.

Here is a little about my build.
engine is an Arrington build.
5.7 forged, 6.4.

Cam Duration @ .050 lift - Intake 225 / Exhaust 235
Lobe Lift - Intake .360 / Exhaust .365
Lobe separation 116 - Intake center-line Degreed to 115 - Lift @ TDC = .043

Compression 9.46:1
Heads are Mopar Performance that have been ported by Arrington.
valves, 2.055 intake, 1.600 Exhaust

3200 stall converter
06 SRT PCM
80lb injectors
Meth injection
Some limiters are no intercooler yet.
Stock 5.7 intake manifold

With this build and T-76 turbo and 7psi
I pulled 550 whp and 630 wtq on a mustang dyno.
But only 11.7 @ 120 with 1.9 60' on street radials.

Car is in shop now to get a
scat pack rear cradle with 3.09 LSD
Trans reworked.
 
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#3 ·
The turbine is a 75mm with .96 ar
At full throttle the exhaust pressure forces waste-gate open not allowing more than 7psi. On the flip side, I will pull 12 at light throttle. Very hard to tune.
I am getting a new turbo and waste-gate. Looking for great street manners.


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#6 ·
From what it sounds like you have a 12lb setup on the wastegate but the backpressure from the long plumbing is forcing the gate open at at 7 lbs. I’m thinking you need two larger wastegate and tune the part throttle boost better. Just keyboard theory here though.


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#7 ·
650-700 whp. or 10.50s is the goal.

I used a Cxracing T76 0.96 A/R Q Trim turbo to get started...
I am ready to get serious now.
the turbo "kit" i used was really designed for a stock engine and the turbo placement at the axle has serious size limits. the T76 was pushing the limits in physical size.
I am now cutting out the spare tire well.
We are thinking about this turbo; BorgWarner S400SX4 Turbocharger 80mm
 
#10 · (Edited)
What you have now should hit your goal but if you want to step up then might as well do it now.
Hard to beat the S480

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Agreed, what you have will make that power, what's the wastegate info on the set up now? I'd bet it's too small and it prob doesn't measure what it's claimed if it's a cheap knockoff version. Add a second and try again with your current turbo.

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#12 ·
Both turbo and wastegate were lets say "economical" parts of the original build.
I like the rear placement as it doesnt interfere or overheat whats underhood.

Ill keep you posted.
 
#14 ·
The important pieces that the knockoffs have not perfected yet are the blow off valve and the wastegates. They just cut too many corners and use too inferior materials and have too far lesser machining tolerances. And these are the pieces that usually cause trouble. Bovs won’t stay closed wastegates won’t stay closed, inaccurate spring rates leaks, burrs in the metal causing hanging.

The budget turbos themselves are pretty decent, I would fully disassemble them make sure there is no manufacturing flaws or leftover materials, clean and lube and reassemble, just for my piece of mind. Also don’t follow any of the instructions for oiling. The knockoffs never get it right. No restrictor for journal bearings and the biggest drain you can make. For ball bearing you’d need the appropriate restrictor for your oil pressure.


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#16 ·
If it were me, I'd get my WG and spring to the point where I could control the boost down to the 3-5psi range. I was never really happy on the street until I did that, then it was fun to drive again. Something like dbldwn is suggesting would probably be better, but at the relatively low boost you are running, the turbo you have is workable. However you've got to have enough WG and the lightest springs you can get a way with so you're not always pushing all that exhaust through the turbo. I only made 3.5 on the spring and then used a boost controller from there.
 
#19 ·
Another problem with my mid mount was the turbo sits a bit low and would scrub every now and again.
I am going with a twin hellion kit.


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