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Discussion Starter #1
So this was a running combination 3.5 years ago, pulled the engine apart to freshen it, changed from brodix track 1's to brodix Dragonslayer heads, and changed turbos to Chinese t3 flange t72, 71 mm. At this point I was running a fitech 1200. Anyway, only had 3 psi boost, on the transbrake at 3 psi you could almost hear something that sounded like a limiter and the motor sounded like it was breaking up a little. So new cap, rotor wires and plugs and coil, along with a pickup in the msd distributor, Same thing. So I figured the fitech was fucked up, so I changed to a holley 4500 super sniper, same problem. At that point figured it was a turbo problem, talked to viren at vs racing, and he didn't think it was the turbos, but sold me a set of t4 flanged 67/66's. It does the same thing, 3 psi. I've pressurized the air side, no leaks. Masking taped the wastegates closed, and didn't burn through the tape, so the gates aren't opening. Checking total timing, 36° total, and set for 20° in boost. Same camshaft as before, old combination made 850 rwhp, at 16 psi. I even went and verified cam timing. Only thing left is the msd box, digital 6 programmable. Any suggestions? Motor runs great, but doesn't rpm like it used to, used to spin 7200 easily, now it struggles to hit 6k, unless that is boost related
 

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Compression and leak down tests done? Valve lash large enough to allow valves to close? No flat cam lobes.? Any smoke? Fuel delivery issue like pump?
 

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Discussion Starter #4
Plugs gapped to.026, same as what I used to run, and br8es plugs. Engine itself runs perfect down low, doesn't use any oil, I've probably got 300 miles on it since the rering. I've checked the valve adjustment several times, runs a bullet solid roller cam.
 

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Discussion Starter #5
Engine itself maybe lazy up top because it's not building boost. Is it possible that the msd box is bad in this way?
 

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Discussion Starter #6
Compression and leak down tests done? Valve lash large enough to allow valves to close? No flat cam lobes.? Any smoke? Fuel delivery issue like pump?
60 psi fuel pressure, doesn't drop at wot, camshaft is fine, when I adjusted the valves I watched all the rockers. Engine has no blowby and runs perfect otherwise.
 

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Leak down and compression test. Camshaft installed the same/correctly? Intake leak?
 

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Discussion Starter #9
Leak down and compression test. Camshaft installed the same/correctly? Intake leak?
I degreed the cam in the old engine combination, and was spot on, basically pulled the shortblock apart and reringed it, and reused the timing chain and all. When I started having this problem, I verified the cam timing in place, put a dial indicator on #1 intake pushrod, cam timing is 10° btdc at .050, I had 8° on the balancer verifying it this way
 

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Discussion Starter #10
You changed a complete efi system because of a boost reading ? Holy fuck.

So exactly how and where are you measuring this 3psi ?
It's measured below the throttle body, guage and the efi have the same numbers. Even checked it at the turbo outlet, Same numbers.
 

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Discussion Starter #11
And data log last nite showed the wideband reading 12.5 at 2.5 psi boost.
 

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It's measured below the throttle body, guage and the efi have the same numbers. Even checked it at the turbo outlet, Same numbers.
So both your gauge and ecu map sensor read from exactly the same place ?

Numbers should not be the same at those different locations, numbers at the turbo should be higher.

Have you applied pressure to these ports manually to verify if they are even capable of reading higher than 3psi on whatever devices you're trying to read ?

And are your wastegate/s verified actually closed ?
 

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Discussion Starter #15
verified timing?
Brought it up to 3k rpm, and 34° on the display, and same number on the balancer. One thing that is weird about this whole thing, I typically run 30° at 16 psi. I had phased the rotor on the original engine build by putting the balancer at 28°, and aligning the rotor tip to it and it ran fine. After the rering, set the timing like I always did, all good, and checked the phasing and it was good. Anyway go to drive the car, and it kept stalling, and the fitech screen would go blank. So at that point I assumed the fitech had gone bad and changed to holley. Same thing would happen. Went through all the wiring, same thing. If I put the rotor in the center position the problem went away. I am now going through the car checking all the grounds, but the only common link in all this is the msd box, everything else has been replaced
 

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Discussion Starter #16
So both your gauge and ecu map sensor read from exactly the same place ?

Numbers should not be the same at those different locations, numbers at the turbo should be higher.

Have you applied pressure to these ports manually to verify if they are even capable of reading higher than 3psi on whatever devices you're trying to read ?

And are your wastegate/s verified actually closed ?
Guage reads from below the throttle body, and the holley efi reads from the throttle body itself.
 

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Discussion Starter #17
Has anyone seen an msd box go bad and cause something like this, where it's misfiring once it starts to build boost and prevents the boost from going higher? Engine is definitely lazy once it gets to 4500-5k.
 

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Exhaust leaks between heads and hot side of turbo?
My car almost dropped to zero boost with some holes in the merge collector.
 

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Discussion Starter #19
Exhaust leaks between heads and hot side of turbo?
My car almost dropped to zero boost with some holes in the merge collector.
I just had the headers off, cut off the t3 flanges, changed to t4, and inspected everything, new gaskets and all and same thing
 

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My holes (cracks) were very hard to see until I put some bubble solution on the collectors where the tubes merge. It blew out bubbles like crazy. Check them good. Hot side needs to be tight. My car runs like crap if it isn't making boost. I fought finding that leak for a long time.

Good luck!
 
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