southchatham

2018 2.7, does anyone know at what RPM the turbo(s) are designed to kick in?
Also, does cold weather effect this?

Not looking for exact science, just in general.

Thanks

dalola

In general, the 2.7 turbos are a "torque demand" system, not rpm based. They are already spinning at idle, and will start to build boost as soon as the ECM sends the signal. Obviously, rpm helps build boost.

Cold weather, per say, has no effect on the principles of operation, but will certainly help to keep things cooler.

Jeff1024

It's not as simple as 2,500RPM = 10psi of boost. The ECU is looking at several variables and open or closes the wastegate to provide the amount of boost needed to make the amount of power the engine needs at a given time.

Boost at 1,750 RPM at 60mph is going to be less than boost at the same RPM and speed with a 7,000lb trailer behind the truck.

Jeff1024

Cold air is more dense than warm air though, so you will notice more power under boost in the early fall. First crisp fall morning was always my favorite time to drive my WRX.

robbieg

Old Grey Mule

Turbos are not dependent upon RPM.

dhmcfadin

I know you said you didn't want anything exact but here is a 0-60 run I did showing Speed, RPM, Boost, and Gear.

https://docs.google.com/spreadsheets...it?usp=sharing

elptxjc

I have a related question, as a turbo newbie, so be gentle. He he. When you get on the throttle of my 3.5EB, you can faintly hear the turbo whistle, as they spool up. As we all know, the turbos are spinning even at idle, so what's exactly happening that makes them audible momentarily only? Are they spinning above a certain threshold (and what rpm would that be?), or is it based on the wastegates being completely closed at the time? Wonder why they only sound momentarily, even as you keep the throttle the same. Finally, what's the max rpm on typical turbos like ours? Thx.

acdii

If you had the ears of a bat you could hear the turbos more. They are tiny in comparison to those on a Diesel, and spin at very high speeds. That initial spin up from idle the blades are making human audible noise, but as they spin faster the pitch increases where we can't hear them, dogs can though! LOL Also the amount of gasses passing over the blades makes noise until the flow equals the rotation, which is partially why you only hear them from idle up to a certain point. Spin a bearing with compressed air, makes a similar noise.

Old Grey Mule

So the most boost a 3.5 stock has is 20 psi ?