Problem holding boost at 20psi
 

VQ35DE
8.8 Wisco pistons
Eagle rods
ACL bearings
ARP L19 studs
Cometic head gasket
JW valve springs, otherwise factory heads
MD plenum spacer
Powerlabs single turbo kit (first version)
Garrett GT3582R turbo, new CHRA
Tial MV-R 44mm WG, 17lb spring combo brand new springs
HKS EVC-S controller
Uprev GT MAF
equal length headers, 3" turbo back, Tomei Expreme Ti
Tuned on Uprev

484hp/475ft lbs on 93 octane
515hp/505ft lbs on 110/93 mix

I am at 20psi by 3700 RPM, but around 4700 it will steadily drop to 16-17psi. We have leak tested to 22psi and everything held, no leaks and no lift. WG diaphragm is good, no exhaust leaks. Originally tuned on manual controller and when the boost would drop it would get very choppy and fluctuate, so we went with the HKS controller. This smoothed it out, but it will still drop. Because of this drop we get fight detonation at high RPM.

My questions are these:

I'm told the GT3582R should be big enough to achieve 600hp on this motor. I'm currently ~500rwhp, could the turbo be getting maxed already? I'm seeing conflicting information on this turbo and the capabilities. If so I'm looking to change to Precision 6266. I've tried to do all the calculations on what I need for a turbo but that ish goes right over my head, or I'm just thinking too hard about it.

The WG is right off the passenger side header, would moving it downstream closer to the turbo help? Possibly need a new WG? The diaphragm looks good.

You sure you don't wanna just argue about oil or wheels? That's kinda what this site is for.

I know its a long shot asking something technical here :cool:

Detonation at high rpm is likely not causing your dropping boost pressure. In fact, it's a good thing you are dropping boost to reduce cylinder pressures. Sort out the detonation first if that is really happening. A little race gas and you can test that.

The most likely reason for not being able to maintain boost is too much exhaust pressure in the manifold. Increase your A/R on the turbine side or move to a larger turbo housing (T4). Or be happy with what you've got (I recommend this). If you want more power, look for a Boosted Performance twin scroll kit. Good luck.

Its detonating after the boost drop, starts around 56-5700 RPM. We did try race fuel as well, made more power, but same problem.

I did wonder if it was a small A/R on turbine and might need to go larger. I did end up find another thread here that someone was having a similar problem and swapped to the 1.02 housing and made more power, but was only able to get another 50ish hp. I'd like to see 550 on pump but also don't want to be running the turbo at its limits, so will be looking into different setups.

Thanks for the help!

H
 

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How in the world did you find/choose this thread to post your completely unrelated question?

appreciate this post