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Q: Wondering about upgrading car

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I was wondering, is it safe to up the boost of my turbos on my 2007 BMW 335i twin turbo to 16psi on stock internals? Also, is it worth it to buy a boost controller to control and change the boost whenever I want too? How much horsepower gain would I be seeing if I put aftermarket downpipes on the car and turned the turbos up an extra 8 psi to 16psi from 8?

My car has 157000 miles.
My car has a manual transmission.

A: Hi there, thanks for your question. I’d be ...

Hi there, thanks for your question. I’d be happy to offer my insight.

I would not recommend pushing the stock 335i motor to 16psi under any circumstances. The stock internals may possibly take 16psi for certain spikes in horsepower, but this is definitely not sustainable boost without causing some major damage. The stock turbos on the 335i model are simply not designed to withstand this kind of boost and would likely create enough heat very quickly to send the car into limp mode.

In terms of horsepower gain, based upon adding the down tubes, this is difficult to measure without testing an tuning as there are several factors that come into play such as fuel pressure, mixture, air temperature, air density, injector flow. You may want to consider looking at the Dinan performance packages as there are several options that will offer considerable horsepower upgrades that are lot safer given the stock build of your motor.

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