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Message: <blockquote data-quote="Hellion94" data-source="post: 681447" data-attributes="member: 8471">Re: In Response to Javi's Post....Well, they aren't lying, as the boost may not drop off, but the efficiency will decline. Boost is just a measurement of the amount of air that backs up in the intake tract as the engine rotates, or positive manifold pressure. Boost isn't what makes power. Boost is just the measure of pressure in the intake tract. This is why a 60mm turbo that generates 20 psi of pressure on a 300 cubic inch engine will make the same, or less power than a 80mm turbo that makes 6 psi on that same engine. It's also why you could put an S-trim on a stock 5.0L and make 10 psi and 350 hp, and then put an H/C/I package on that motor and make 8 psi and 450 hp. Boost isn't what determines the power level, it's the efficiency of the compressor in relation to the engine,or the combination of both.Basically, any compressor will hit an efficiency wall at some point, and just not be able to make any more power. The way that the positive displacement blowers compress air tends to generate more heat than a compressor that uses an impeller. This just hampers their high-rpm power, as least on the street-sized blowers. An interesting example of the boost doesn't equal power concept:When Urist used to run a turbo combination, he had a 91mm that made great power at 24 psi. We thought we'd turn it up at a race (WFC I think) and cranked the controller to 28 psi. The car went 1/10th slower than it had the previous run. Basically, we had found the sweet spot for the compressor, and there just wasn't anything to gain by trying to spin it harder.</blockquote>