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Just picked up my 16 yesterday. Boost needle doesn’t move. Sometimes it goes to about 5 psi for a split second. Anyone have this before?
 

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At low speeds/throttle, air goes through the bypass, hence no boost.
 

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Depends. It’s subjective. I would say no, but that’s my interpretation of low throttle angle.


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I had the same issue with my 16 V. Turned out that the Supercharger(LT4) needed replacement. In addition, make sure that you have the Service Tech look into the bypass release value. Early modes were defective from factory. There is a TSB for replacement for the Fuelline on the 16's.
 

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You won’t make boost till you go positive on vacuum. Or in other words you start to force feed the engine more then it can suck in. Lots of variables in when that is.

Just remember boost is a measurement of resistance so you have to be in the throttle enough to overwhelm the natural vacuum of the engine.
 

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The LT4 Supercharger is a Positive Displacement type of mechanism. It's more linear, interns of how the power is rely. Completely different from the last gen V2 Supercharger on the LSA. Look into the items(supercharger, valve, fuelline), discussed above. How I was able to determine the issues were through my own dudelgence, asking 'intelligent ol heads', own & know about how this type of supercharger works. Also, C7 Z06 forum, under THE STICKY'S, maybe helpful.

Good luck, keep us informed.
 

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The LT4 Supercharger is a Positive Displacement type of mechanism. It's more linear, interns of how the power is rely. Completely different from the last gen V2 Supercharger on the LSA. Look into the items(supercharger, valve, fuelline), discussed above. How I was able to determine the issues were through my own dudelgence, asking 'intelligent ol heads', own & know about how this type of supercharger works. Also, C7 Z06 forum, under THE STICKY'S, maybe helpful.

Good luck, keep us informed.
i learn something new all the time , how is the supercharger completely different from the last generation lsa ?
 

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i learn something new all the time , how is the supercharger completely different from the last generation lsa ?
It's not.

They are both PD blowers and the lT4 is actually smaller with a much better intercooler.

No. But even lower speeds/throttle should have boost right?
You will have no boost under "normal" driving conditions. The air is just recirculating inside the supercharger through the bypass valve. Once you move the throttle down enough, the engine loses it's vacuum and the bypass valve is closed by spring pressure and now the air is forced into the engine and your gauge will begin to read boost pressure. Gen III CTS Vs generate 9-10psi from factory.
 

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There are basically just two types of superchargers, positive displacement (Roots/Whipple) and centrifugal. PDs are always driven by the crankshaft. Centrifugal can be driven by the engine or exhaust gas. When driven by exhaust gas, it's called a Turbo supercharger, which everyone just calls a Turbocharger. Positive displacement pumps move the same amount of air per revolution. And since they're driven by the crank, they always produce the same amount of additional air per engine revolution regardless of engine RPM. The BOV stays open, circulating air from the high pressure side of the compressor to the low pressure side (since the air has already been metered by the MAF) until vacuum gets near enough to zero, when it starts to close, so you don't see the boost in normal driving. Centrifugal blowers (I had one on my 02Z06) behave a bit like turbochargers. But a turbo's boost is more a function of to engine load than RPM. Centrifugal blowers produce boost that increases exponentially and is purely a function of engine RPM. Because of this, centrifugal blowers usually don't make any boost below some RPM so that they're not making too much boost at redline (my Vortech on the Z didn't start making any boost until about 3000 RPM, but it was making 6 pounds at 6000 RPM. The blower was geared to make max allowable boost at max engine RPM, so it didn't need a high-pressure limiter like a Turbo does). Turbos work "automagically" and don't always have a BOV (some do, because slamming the throttle closed at boost can cause a compressor stall which delays the recovery of boost when you stomp the gas again a moment later. A BOV lets the excess pressure escape so the turbo keeps spinning). When you open the throttle the exhaust gas temp/pressure goes up and the turbo spins faster and starts to make boost (it's really exhaust heat that drives the Turbo). All turbos have a waste-gate. Because their boost goes up exponentially and there's really nothing mechanical that limits how fast the Turbo will spin, twice the RPM is 4x the boost so the boost can go pretty high pretty quick. So when the boost gets too high the waste-gate opens and exhaust gas bypasses the turbine which keeps the compressor from going any faster. The waste-gate's actuating pressure is set by a spring. In the early days of turbo cars, you could get more boost by installing an aquarium regulator valve in the waste-gate actuator pressure line. Now, boost is computer controlled and the aquarium valve trick doesn't work.

The primary difference between a Roots and Whipple is the shape of the lobes in the compressor stage. If I remember right, Whipple compressors compress the air as it is passing between the lobes, where Roots just push the air from the low pressure side to the high pressure side.
 

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How much throttle are you applying, under regular partial throttle driving you will not see boost. Maybe a little bit when you first accelerate but it quickly drops off
 

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I checked this out today and from a stop to WOT. I only see it get up to 3-4 ... Anyone else having the same ?
 
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