depends...some of these guys ARE pushing close to 30 psi on racing fuel (I knew one guy doing 45 psi). However the are usually running electronic boost controllers so they can run pump gas at lower boost levels the rest of the week. Depending what series engine you are running you can typically run about 15 psi on pump gas with proper tuning. Some more, some less. Of course ALL of those are intercooled. The stock benz is pushing the limits non-intercooled stock due to intake charge heating. But there are numerous other threads dedicated to discussing that topic. This one was how to to control a variable vane turbo in a different application. My idea was how to control the turbo for a rapid and smooth spool up rather than an on or off type control which would be less smooth spoolup , and potientially cost less than $200 to build excluding the turbo, assuming some computer skills.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche