I am in the process of tuning right now, and it was doing just fine. It had plenty of pulls on low boost (10psi), and was about to turn it up to 15psi. All of a sudden on the last low boost pull the the A/F goes straight to 10:1 at 7000rpm.

Ok maybe it was a fluke so I made another pull. Same thing....the boost gauge went right ten for a second or so and then fell back off to about 5-6psi with the A/F off the chart (10:1). This started at 6000rpm this time

Oooook maybe its hot. Let it cool for a bit and make another pull. Same thing but this time it just touched 10psi and then fell to 4ish psi. This started at 5000 rpm this time.

Hmm, couplings ok? Check
Wastegate on and tight? Check
Vaccum ok? Check, soild at 22"
Fuel pressure ok? Check
What the hell is going on then *scratches head*

The boost keep getting lower and it would drop sooner and sooner the more pulls I made.

The motor is fresh (like 20-30 runs on the dyno...some were the break in):
ERL 84mm sleeves-GSR block and crank
JE pistons
Crower rods
Brand new type R head (crower turbo cams, springs, blah blah blah)
Cam gears/pulleys
Radiator
Full race prostreet manifold w/3"exhaust
JG intake manifold
HKS SSQV
Turbonetics E50 (it's a T3/T4 thats has a custom blade pitch for quicker spools)
Turbonetics Evolution wastegate w/turbo xs MBC
MSD Digital 6/blaster/wires/ ngk bkr7e's
AEM fuel w/660 injectors
quaife lsd
....you get the picture, the customer hasn't really cheaped out on stuff haha nor has he left anything out.


Any advice is appreciated. This car has been fighting us since day one and I am sick and ******* tired of seeing this thing in the shop.

--> If you want dyno charts just let me know and I will post them up. <--

 

got to be a hose clamp

 

its that mbc, weather changes, inconsistant boost pressures, that's why i bought a sbc-id and never looked back

 

I have to believe its a clamp....I mean I made alot of pulls on the dyno tonight and it happened out of no where.

Maybe the cat is plugged or something (which would make no sense since the entire setup is brand freaking new). The back pressure might explain why the turbo isn't able to breathe at higher rpms. I did hear a loud pop which I thought was a back fire but it wasn't. After inspecting the exhaust it looked as though a gasket by the cat had a chunk missing. I am not 100% on that as I didn't feel like getting up underneath the car at that point. But a clogged cat would explain the gasket blowing (the pop) and possibly the boost issues.

Anyways, my brain was hurting earlier and I didn't want to deal with it anymore haha. I'll guess we'll try and take a fresh look at it tomorrow.