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I need to pause for a second here to say that I am in no way trying to do anything here but put out what I believe to be factual information based on research that I have done and what I have been able to observe/read about with respect to turbo performance (kind of like an independent party if you will).

Ok so I did some digging and due to the dimensions posted by Adrian of his turbos and the fact that they are made by Garrett, I went and looked the compressor maps and plotted where these boost numbers were falling out at. The stock turbo is a GT3782 compressor and based off my calculations (derived from the formulas in the Garrett Tech articles), I find the stock turbo to actually be flowing between 40 and 45lb/min of air at 30psi of boost. The Stage 1 turbo is based off the GT3788 compressor (same one as the Powermax) and at 28-29psi of boost (this was the highest that I ever saw with my truck) I find that turbo to be flowing appromximately 60lb/min of air. Lastly, the Stage 2 (while on my truck made 26-28psi) only seems to produce 24-26psi. At 24psi, the Stage 2 (according to the GT4088 compressor map) flows approximately 65lb/min of air.

Now of course one can make the argument that these are only calculations and that I don't have any basis for saying that these turbos are actually performing when in fact I do have real world experience that can be vouched for. Both Matt and Chris of the GPDA have nearly identical trucks when it comes to performance enhancing mods and both trucks even run 35in tires. Both trucks were ran on the same day with the same dyno, using different ECM tunes but the same FICM tune and had the stock turbo and dyno'd 451rwhp (Matt) and 454rwhp (Chris). Then they went and dyno'd on a hotter day a few month's later (again on the same day), this time, Chris with the Stage 1 turbo and Matt with the Stage 2 turbo (before it went on Bill's truck for a while). This time Chris dynos in for a best run of 473rwhp with the Stage 1 and Matt dynos a best of 485rwhp with the Stage 2.

I know folks want tend to want to ignore the math and the calculations and the graphs and charts and just go bolt stuff onto their truck (I know because I am one of those guys), but I really think folks need to learn about this stuff so they can know for themselves of what to expect from a certain product before they buy it. I wish we had more data and could do more runs like the guys at GPDA did here but the bottom line is that the math works. I know no one wanted to believe that 600-640hp with 190s was possible with a single VGT turbo, but I know Adrian did the math and the math said it was and low and behold it was true.

One last correlation of data here. I went to Turbo Engineering Corp's (TEC) website and looked at the data that they are claiming for their turbos (as they use some similar wheel sizes to the MTW Turbos) and their claimed numbers fall right in line with the same results being produced by the MTW turbos.

Based on the GT4088 compressor map, I really think that the max boost that should be ran with this turbo is about 32psi as there just isn't any more of a gain in airflow with that boost pressure and at that pressure, there is about a 5lb/min increase in airflow to what is currently being produced by the Stage 2 which I think might just be what a truck with a healthy set of stock injectors, fuel system, and the right tuning might be able to use to hit that ever elusive 500hp mark for stock injectors.

If nothing else comes of this thread, I hope it spurs some good discussion and encourages more folks to research and understand how they can develop an idea of what to expect from the product they choose to buy.