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Message: [QUOTE="Charles, post: 57916, member: 103"] Brilliant... That's what this idea is. I'll try to clarify a few points that seem to be circling this discussion. 1. With adequate wastegating the stock charger turbine section would be a non issue in terms of shaft speed and drive pressure control, just like when you guys gate around them with big fuel now. 2. The compressor side of the stock charger setup would not be an issue because.... now don't let your heads pop.... but the CFM flow into the stock chargers would actually [i]decrease[/i] a good bit if you added another compressor stage upstream because you would [i]lower[/i] the PR the stock chargers were acheiving and they would be doing [i]less[/i] work than they did without the additional compressor stage. Giving exact values for CFM flow takes a bit more time, and with 3 stages I just don't feel like it right this second, plus I don't have time right now, but.... showing the dramatic PR swings should make this clear without even really showing the expected CFM flow drop anyway. In terms of PR, if you had a truck running the stock chargers at 40psi, and if both of those compressors were balanced, then each would be operating at a PR of ~2, meaning each would be making ~13-14lbs of boost.... loafing really. Now what if you added say a GT47-88 in front, and you wanted 70psig on the manifold? What would each stage have to make? Well, for simplicity, lets assume they will be balanced stages for the moment, just to get a feel for where we'll be. Well, balanced, with 3 stages making 70psig, each stage would be required to produce a PR of only 1.79... :eek: That's [i]not[/i] a typo! Each compressor would be making ~11-12lbs of boost with 70lbs on the manifold. In other words, with a first stage compressor in the mix, the stock chargers would be working [i]less[/i] at 70psi on the manifold than they were making 40 without help. But truth is, you wouldn't want to run your atmosphere that low, and not take advantage of the bigger turbine, so you would probably make say, 15 to 20lbs with the 47 or 55 and then let the stock chargers just make up the other 21lbs between them. Is the stock setup pretty efficient at 21lbs of boost? Yep... and it would be just as efficient with a big single pumping up the atmosphere running into them. And the required CFM flow through the stock chargers and heads would be reduced, power per power compared to the stock chargers alone given the greater charge air density from allowing the stock chargers to flow a heavier media at a lower pressure with a first stage compressor pumping up the density upstream. Three-stage compression with two of the stages already in place...... I like it.... a lot.... [/QUOTE]