I am Confused!!!!

The questions you are asking here are all good ones, and to be perfectly honest, 99% of the people here (myself included) do not fully understand the workings of a supercharged engine like this. I will try to explain the basics as best I can. If someone else with a degree & experience with mech engineerings wants to chime in, by all means...

So, to start from scratch: A smaller pulley drives the SC faster. Faster = more air pushed = more horsepower, right? Not really. The supercharger has an optimal operating range, and if you drive it outside that range (ie too fast), then it will NOT flow any more air. All it will do is heat the air up more.

This is the heat we're talking about. It's the temperature of the air being pushed into the engine (called the intake charge). A supercharger dramatically increases the temperature of the intake charge. This causes higher temperatures inside the engine, which is very bad, because if the temperatures get too hot, you start to experience a condition known as knock, detonation, or "pinging". Essentially, knock is when the charge is so hot that the fuel ignites on its own (ie, not ignited by the spark plug), and burns very rapidly and in an uncontrolled manner. It's called pinging because the intense pressures that build up actually cause the surface of the piston to distort, which makes a metallic "pinging" sound. That's the sound of a hole about to be blown in your piston.

The engine computer can detect knocking when it starts to occur, and it will retard the ignition spark to compensate. Retarding the spark lowers the combustion pressures, which protects the engine from damage. It also reduces performance. Significantly. So in other words, if you take the same engine, same supercharger & boost, and heat up the air being pushed into the engine, all you will do is hurt performance. This is the danger of smaller pulleys. There's a fine balance between a smaller pulley that moves more air and therefore makes more power, and one that puts the supercharger outside its efficiency zone, and just makes excess heat.

Now, to try to answer your questions:

Intakes and exhausts both relieve restrictions. Less restriction = less resistance to flow = less heat. Basically, you're allowing the engine to breate easier, which lessens pumping losses and heat. You don't have to have a header to get a smaller pulley, but you will almost certainly get better performance if you do. It's like trying to blow really hard through a tiny straw. Not easy.

Here's the problem with talking about max boost: Boost is pressure. Pressure is a measure of restriction. That's a bad thing. If you're registering 12PSI, that means the supercharger is pushing really hard, so hard that 12psi of pressure has built up, but the engine can't inhale anymore!! What I'm trying to say here is that to assume more boost = better is not true. What you want is more airflow. Here's a really good link that explains it in more detail; I'll save myself from retyping it: http://gcoast.com/turbo/technical.html

I have not actually taken the time to sit down and calculate it out. In general, however, it appears that the M62 used in this motor is fairly close to its efficiency ceiling. In other words, it may not be able to flow a lot more air before it starts to drop off. This needs more investigation; hopefully all the companies getting involved can shed some light.

As to the engine internals, it's more about safety than absolute power. I would be willing to bet that the internals can hold down 400+hp if it's done safely! My point here is that, again, you can't say that it'll handle X psi of boost. It depends on the power level, and the state/tune of the engine. There will be some hack who puts on a smaller pulley, disables his knock sensor, and shreds a piston while pushing only 13psi and 220hp. Conversely, there will be someone who, with a proper tune, can pull off 400hp without really hurting the motor.

Hope this helps some. If I confused you any more on some points, feel free to ask.

Edit: as to swapping your pulley, the best advice I can give you is this; unless you're an engineer or mechanic or have experience with this stuff, do not be the first one to do it. Let performance shops or other 'pioneers' experiement first, and benefit from their learnings. PSI-FI is supposed to have a kit out shortly, they no doubt have some experience, but they seem to be being rather tight-lipped about it. Others will come along as well. Your best bet is to keep watching these forums, and in 3-4 months, you'll probably be able to get much clearer answers about the specifics of this motor, which is what's really important. Going and buying a pulley right now without experience with the LSJ is a pretty risky and not terribly intelligent move, IMO.

No prob man.

If the only thing you take away from all that is that more boost does not equal more power, then, frankly, you're ahead of most people. Most people just say stupid stuff like "my RSX is running 45psi, I r0x0rz!". Ugh. Best example is this; consider your stock SS. It makes 205hp, and pushes about 12psi boost. If you took your car, did nothing else, but swapped the cylinder head for a better one (more free flowing, bigger valves), you would notice that the boost would actually DROP. Say to 10psi. Yet a dyno would show you to be making more than 205hp. In other words, 10psi+freer flowing made more power than 12psi. This is a perfect example of why you can't use boost to measure power.

Good call on the header and intake. On a supercharged engine, any kind of mod that improves breathing is usually beneficial. And it will only be more beneficial if you do go to a smaller pulley at some point.

Yep, that's exactly right. The SS does have an intercooler, however it's sort of cast into the intake manifold. Ie, it's all one piece, and from what people who have been into the engine thus far are saying, it looks like it's going to be very difficult to upgrade it. Which is too bad, because, yes, an upgraded intercooler with more capacity to cool the intake charge would help significantly.

(the supercharged 3800 GM uses in Grand Prix GTPs, for example, doesn't come with an intercooler. It only makes about 7psi stock. GTP owners have found that if you add an intercooler to cool the charge down, you can run a much smaller pulley and make a lot more power. Pretty good for the price of a $500 intercooler. Unfortunately because of the way the LSJ is designed, it doesn't look like intercooler upgrades are going to be that easy for us. )

DanM said:

Yep, that's exactly right. The SS does have an intercooler, however it's sort of cast into the intake manifold. Ie, it's all one piece, and from what people who have been into the engine thus far are saying, it looks like it's going to be very difficult to upgrade it. Which is too bad, because, yes, an upgraded intercooler with more capacity to cool the intake charge would help significantly.

(the supercharged 3800 GM uses in Grand Prix GTPs, for example, doesn't come with an intercooler. It only makes about 7psi stock. GTP owners have found that if you add an intercooler to cool the charge down, you can run a much smaller pulley and make a lot more power. Pretty good for the price of a $500 intercooler. Unfortunately because of the way the LSJ is designed, it doesn't look like intercooler upgrades are going to be that easy for us. )

Click to expand...

Dan, you are correct on Intercooling is the best way to increase boost and performance on any Pontiac GTP / L67 Supercharged Engine, but there is other ways of improving the performance and of course run higher levels of boost, like my 97 GTP that has been doing since day one I bought it. To my 97 Pontiac GTP does produce 12 lbs. of boost on the street, without an Intercoooler and and "0" on any Knock Retard at all.

Also for a good Intercooler System for any GTP will run you approximately $1000 to $1500 , depending on it's volumetric efficiency of not only the Intercooler core itself, but also the Heat Exchanger the kit comes with.

As for the 2.0 SC Engine in the Cobalt SS as well as the Ion Redline vehicles , you will no doubt see someone come out with a more efficient Heat Exhanger kit for it , just like we have for the Pontiac GTP's, Ford Cobra's, Lightning/Harley Supercharged Engines.

Thermal properties are very important to any and all Forced Air Induction Engines and the necessary precautionary measures need to be addressed , before trying to build more supercharger boost over the stock factory configuration, as many of us supercharger owners have done exactly that, even without the use of an Intercooler unit installed upon our L67 SC engines.

Hope this helps