hiroichi1515

iTrader: (17)

I have a s4 6 port engine that is turbocharged using S4 TII components such as intake manifold, turbo etc... My question is mainly dealing with the lower intake manifold. I did not port it out to match the block and this has felt great on the stock turbo. Half of the aux ports are blocked off by the lim and the car seems very responsive in the lower rpms. I ran it at 10lbs for the longest time. I have now upgraded to a hybrid turbo and the car just feels sluggish when full throttle until 4800. I'm wondering if I may need a stronger wastegate actuator for the big 38mm internal wastegsate or if possibly the lim manifold is becoming a restriction. The reason I did not port the manifold is because I thought it would increase the rate in which the air was being fed into the motor. As in the smaller port opening should increase velocity. Also, in an N/a the aux ports are normally closed at lower rpms, so having half of the port covered would be a middle ground (maybe a dumb idea). Like I said before this has been great with the stock turbo, but now with the hybrid is just seems so laggy. Its not to the point where its unbearable but it really makes me think that something is wrong or could use improvement. Once my injectors come in I will be running 15 psi but as of now I am at 11 psi and depending on the gear it doesn't reach full boost until 4500 - 4700. Is this normal with a hybrid or should that be a bit lower?

My setup is
s4 6 port block
TO4B V trim compressor and 60ar housing with BNR modified Turbine housing, stock CHRA
550cc pri, 720cc sec
Apexi AVCR
Greddy Throttle body inlet
FMIC with very short pipng (intercooler is where stock radiator mounts)
2.25 inch downpipe and midpipe to 3 inch corksport catback

Also, I think my turbine wheel may have been clipped but i'm not 100% sure. There was some small damage to the blades and when I took the turbo to be balanced the wheel looked brand new. I'm not sure how much material they took off when they did that, and I'm not sure how much material is taken off when a wheel is normally clipped.

Aaron Cake

iTrader: (1)

Regardless of whether the actual port is half open or open on the manifold side, the aux ports are still wide open as far as the rotor is concerned so you still get the extremely late closing and inefficient filling at low RPM. That's a huge reason for your sluggish fleeing now that the larger turbo takes longer to build boost.

Clipped turbine wheels suck and are just a band aid to reduce backpressure on too small a turbine.

What are you using for fuel management? Could be way rich at low boost (common).

Without question, port the TII lower to match the 6 port block.

HAILERS2

Still have your outter set of secondary throttle plates? If so then rig a vacuum line to the double throttle diaphram with no check valve in the line and that Will help on low end torque.

hiroichi1515

iTrader: (17)

I understand. I will go ahead and port it out the next time I have everything off. Will there be any noticeable improvements? I was also thinking of changing out my 2.5 inch exhaust pieces to 3 inch.

I am using rtek 2.1 for fuel management and the afrs are in the 11's after about 5 psi.

My fuel injectors came in today so I will be going up to 15 psi soon. I will see at what point it hits full boost and go from there. What would a reasonable spot be for full boost to be reached?

Thanks,