I am currently shopping around for a centrifugal supercharger. One well known company says they have over 30K combined miles on C6 z06's that they have supercharged with 7 psi with no issues What do you guys think?
As having gone through the money pit with my C5 Z06 for boost there is no way I would do it with my C6 Z06.
If the LS7 was suited for long term use of any forms of boost GM would have saved millions of dollars in designing LS3/LSA/LS9.
Our stock engines were not made to support boost long term and with LS7 not having any real cylinder walls and weak ringlands says 7 PSI is a time bomb if leaving bottom end stock.
Compare the amount of head bolts per cylinder ( and their size) of the LS7 and LT4 and guess which has head lift with boost and how often head gaskets blowout or cylinders 7 and 8 get fried
Sure your can get 30K miles with a supercharger installed, just drive it 99% of the time in part throttle but then why add the boost in the first place?
Does the ZR-1 have different internals then to be able the boost?
Yes, the internals are different for the the ZR1. But I think the main point is that it does not use the LS7 block, but rather the LS3 block. I could be wrong though.
Does the ZR-1 have different internals then to be able the boost?
Remember, the ZR1 does not have a blown LS7, it is essentially a blown LS3 (in other words, it is not a bored and sleeved 427).
Not saying I totally agree with with racingvette. I think the LS7 can hold up just fine and dandy with a Procharger at 4.5 to 6 lbs boost. But he does make a valid point that bored, sleeved cylinder walls and 11:1 CR are not the ideal setup you're looking for when you add boost of any kind.
Please forgive the ignorance but I am new to corvettes and am eager to learn. What are key differences between the ls3 block and the ls7? Does the non-z c6 have a ls7 w a differnt compresiion ratio or is the ls7 unique to the z06?
From all that I'm reading it does not appear to be of significant worth to add any form of boost to the c6z especially if u are primarily looking to add low end torque and are not willing to invest in the bottm end.
Please forgive the ignorance but I am new to corvettes and am eager to learn. What are key differences between the ls3 block and the ls7? Does the non-z c6 have a ls7 w a differnt compresiion ratio or is the ls7 unique to the z06?
From all that I'm reading it does not appear to be of significant worth to add any form of boost to the c6z especially if u are primarily looking to add low end torque and are not willing to invest in the bottm end.
Not sure I will explain this correctly but I'll give it a shot...
A 427ci engine is typically a big block engine.
On the LS7, it is basically a Gen IV small block (some variations) with a 4.125 bore and a 4.00 stroke with sleeved pistons to create the 427ci. The bore spacing has been retained and that requires pressed in cylinder liners. What that boils down to is the cylinder walls are a bit thinner than lets say an LS2, LS3 or an LS6 block.
The LS3 engine, by comparison, has a 4.06 bore (not sure about the stroke) and does not require sleeved pistons.
As far as I know, the only vehicles that use the LS7 is the C6 Z06, the Corvette Racing Team (using an LS7R variation) and I think some Holden cars in Australia have the LS7 as well.
A blower on an LS7 engine at only about 4.5lbs of boost will produce almost 150 additional rwhp so don't think you won't feel a very substantial difference in power at low, mid and high rpm's. If your skeptical, just ride in one and you'll see the difference immediately (I have).
Not trying to convince you to add a supercharger or anything. Everyone who adds a blower does so at their own risk. I'm just saying I don't think the risk at low boost is substantial and the power gain is very dramatic.
I think when my Z is off warranty I am going to add a centrifugal supercharger and run 4-6 psi, redo the top end i.e valve springs, rockers etc and give it a good tune. Should blow my socks off.
if my goal is to enhance low end torque (power) then would you advise a roots blower instead of a centerfugal? Another novice question is at low rpm and/or speed will adding rwhp enhance acceleration? I thought acceleration at a low rpm or speed was a function of torque rather than hp?
I also have a few question after reading through the outstanding summary of the differenes between turbo and superchargers found at the top of this section.
"..........(centrifugal) the volume of air that's moved is proportional to the *square* of the compressor's RPM (as dictated by the V^2/r equation). This characteristic presents design challenges that don't exist for a Roots type. Because boost builds with the square of RPM, the design has to take in to account the maximum acceptable boost level (which will occur at the maximum expected operating RPM). Unlike a Roots type, this often means the (centrifugal) compressor makes little or no boost at lower operating RPMs."
THIS IS WHY I AM THINKING THAT A ROOTS TYPE IS BEST FOR ME
"The fact that Centrifugals don’t make boost at lower RPMs also means they don’t place as significant a parasitic load on the engine (though many Roots types include low-RPM bypass valves to help address this discrepancy). As a result, Centrifugals can be more “drivable” than Roots, and might also have less of a negative effect on highway-cruise MPG."
WHAT DOES THE AUTHOR MEAN BY A PARASITIC LOAD? IS THIS IN REFERENCE TO A POTENTIALLY HARMFUL LOAD ON THE ENGINE AT LOW RPM? IF A ROOTS SYSTEM HAS A LOW RPM BYPASS WOULDN'T THAT DEFEAT THE PURPOSE OF TRYING TO INCREASE LOW RPM POWER?
"Besides the advantages Turbos have over Superchargers with respect to operating efficiency, they also have another huge advantage. Turbos are "load sensitive". The boost they generate is proportional to the engine’s load and NOT the engine RPM. This means that a Turbo will generally be able to produce good boost at low RPMs like a Roots, even though it's a centrifugal type compressor. You need exhaust heat, and not so much exhaust volume."
THIS IS CONTRARY TO WHAT I HAVE ALWAYS THOUGHT ABOUT TURBOCHARGERS AS FAR AS THERE USE AT LOW RPM. IN FACT I THOUGHT THE OPPOSITE IF THIS IS TRUE AND THATS WHY TURBO LAG EXISITS. THE WAY IT SOUNDS HERE A TURBOCHARGER WOULD BE A BETTER OPTION FOR ME (LOW END TORQUE BEING THE GOAL)
"Note though, there isn’t a huge mechanical force to be had from the engine’s exhaust gas. Turbo’s have to be small to minimize inertia or they take forever to spin up (AKA “Turbo Lag”). Smaller compressors have lower operating limits, they have to spin faster to move a given volume of air and they can’t move as much air (max out sooner). Larger displacement Turbo applications almost always need to use two or more Turbos. In contrast, a centrifugal Supercharger compressor can be quite a bit larger than its Turbo brethren because it’s got the power of the entire engine to get it spinning. So while V8s like ours can get by just fine with a single centrifugal Supercharger, they always require two Turbos to achieve acceptable operating performance."
HERE THE AUTHOR MENTIONS TURBO LAG SO IT SEEMS THE WHOLE LOW END BOOST WOULD NOT EXIST. IS IT POSSIBLE TO ELIMINATE LAG BY HAVING TWO SEQUENTIAL TURBOS?
Turbochargers have something called a Waste Gate (though they can also make use of BOVs). The WG is a valve that sits in the exhaust flow between the engine’s exhaust manifold and the Turbo's turbine. The valve is pressure-actuated off of the high pressure side of the Turbo. When the boost coming out of the turbo exceeds a given level (set by a spring inside the waste gate diaphragm/actuator), the pressure operates the actuator to open the waste gate valve allowing engine exhaust to bypass the Turbo’s turbine. The turbine slows and since it’s coupled to the compressor, the compressor slows and boost levels quickly drop. Waste Gates make a Turbo self regulating. Even if it's capable of spinning fast enough to deliver 100Lbs of boost pressure, the Turbo will never boost more than the waste gate allows. And since the compressor speed can be regulated independent of the engine RPM, a Turbo system can be designed to produce better boost at lower loads (which are also generally lower RPMs) and not blow the top off the motor at high loads/RPMs.
"An Electronic Boost Controller allows boost level to be set arbitrarily (rather than by adjusting a spring). EBCs insert an electronically operated control valve between the Waste Gate actuator and the high-pressure side of the Turbo. The valve is normally kept closed, so the WG never sees any "boost" pressure at all. This prevents the WG from opening unless the EBC wants it to be open. The boost pressure is monitored by a pressure sensor connected to the EBC. When the EBC measures a boost level greater than the currently selected limit, it opens that valve allowing pressure to reach the WG actuator, opening the WG. An EBC is able to regulate boost pressure to any level it wants across the Turbo’s entire operating range. This allows a Turbo design to produce higher boosts at lower RPMs (load, actually) without having to worry that the Turbo will produce too much boost at higher RPMs (load, actually)."
AGAIN THIS IS AGAINST POPULAR BELIEF AT LEAST OF THE PRINCIPLE THAT TURBO HAVE CONSIDERABLE LAG AND THEREFORE NOT HELPFUL AT LOW RPM. ARE THESE STATEMENTS CORRECT? IF SO WHY DO SO MANY CARS THAT TURBOS HAVE LAG? IS IT BECUASE THE TURBOS ARE TOO BIG?
"Bottom line: Turbos are often the more efficient and capable systems, and deliver higher levels of performance, but they are mechanically more complex, harder to install, more expensive, and can be less reliable/durable than Superchargers."
Last edited by mominayal : 02-04-2010 at 03:44 PM.
I didn't read that whole thing but I think you would prefer roots style? The only reason I wouldn't get one is because I am pretty sure you have to buy an aftermarket hood. I like my stock hood. Is there a set up that fits?
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