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Larger exhaust installed, lost a psi of boost pressure. Single turbo 5.0 Coyote on 8psi wastegate spring pressure

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Hey all, so recently I got rid of my full exhaust system on my 2019 Mustang 5.0 with a 76/75 Single turbo. I am running 8psi springs on dual 44mm wastegates and with the full exhaust I was always seeing 8psi on intake manifoldpressure, every once in a while it would spike to 9psi in colder weather. I recently installed a 4" bumper exit exhaust and the highest boost pressure I see is 7psi on the same 8psi springs. Nothing else was changed other than the exhaust. Car still feels just as powerful and the top end actually feels better but I'm confused as to why I am only seeing 7psi max on 8psi wastegate springs

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Hello, it could be possible that there is less back pressure in the exhaust system now, without testing the spring opening pressure your gauge maybe not as acuate as you think or the wastegate is perhaps opening at 7 but it is very normal to see this happen in my many years of experience.

Regards Ross

Don't get hung up on "boost" as the measure of power potential, you really want the lowest "boost" while maintaining the air mass entering the engine, as that would usually give the least pumping losses.

It's probably because you improved the ACTUAL volumetric efficiency of the engine - the freer flowing exhaust would have had an affect upstream of the turbine, too, and so there should be less back-pressure holding the exhaust gases in the cylinder. This means more intake charge can enter the cylinder which would reduce the pressure in the intake as there would be less resistance to flow.

When the engine's efficiency is improved there is alway a slight drop in boost...

Were the gates plumbed into the exhaust? I' suggest more bias to waste gate flow for the same valve lift when not in a shared stream with back-pressure if they were.

Thanks for the replies guys, I'm still learning more and more everyday so turbocharging a naturally aspirated car and how the boost works is still somewhat new to me. Car actually feels more powerful and top end is much better so that's good.

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