Running a turbo without the intercooler connected

[Tippy]

Reading the webs in its' infinite misinformation cesspool, do you think you can overrev or overspeed a turbo if the intercooler is NOT connected venting to the atmosphere?

99% of the web says 'yes', but I found a turbo engineer who states otherwise. He states there is still resistance of air on the compressor side into the atmosphere and is not a problem as the engine is not producing enough exhaust airflow due to the lower HP output, essentially.

I also have blown off hoses many times under full boogy without grenading a turbo yet.

What are your thoughts?

Why I ask, is I plan on massively revamping the intercooler piping on my custom Treadstone unit on a Carrera 3.4, but I want to continue to drive the car if needed as this may take weeks.

I thought of hooking direct without the IC and not getting into the throttle, but that probably would not be wise.

[mark houghton]

Unless I misunderstand your question, well of course you can't run at all without the intercooler connected to the intake, for CIS anyway, unless you rig up some sort of MacGyver plumbing.
Isn't the issue that if you don't vent out the boost pressure - or recirculate it- when shifting gears, you get all this back pressure against the turbo and it stalls the spin?

[Tippy]

Yeah Mark, I am EFI. Carrera 3.2 with a turbo, so no CIS.

[mark houghton]

Originally Posted by Tippy

Yeah Mark, I am EFI. Carrera 3.2 with a turbo, so no CIS.

Ok, that 'splains that!

[kamaro]

If that was true then I should have replaced every turbo when I had a slipped out hose during a full boost blast. which I did endless times and will still do it.

[Tippy]

Originally Posted by kamaro

If that was true then I should have replaced every turbo when I had a slipped out hose during a full boost blast. which I did endless times and will still do it.

Same. I’d imagine at full tilt, the turbo is spinning its max RPM, then losing a connection would send them to the stratosphere bet it never does.

I think it’s more than likely ok to run them unconnected.

[Speedy Squirrel]

You can and you will overspeed the turbo. You won’t see any particular effect though. The shaft and bearing system is designed to remain relatively stable to at least 150% of design speed. Event that level it may only cause a slight wheel rub.

The turbine wheel burst speed is also very high, and the HCF limit is also very high.

The aluminum compressor wheel burst speed is also at least 150% of the design speed. The problem for the compressor wheel is LCF. You will eat up a bunch of LCF life with a big overspeed, but this is not visible. These old aircooled engines are running at pressure ratios that are not high enough to make LCF a very big problem though. I don’t think it likely that anybody would experience a failure from running a short test without the intercooler.

[Tippy]

Originally Posted by Speedy Squirrel

You can and you will overspeed the turbo. You won’t see any particular effect though. The shaft and bearing system is designed to remain relatively stable to at least 150% of design speed. Event that level it may only cause a slight wheel rub.

The turbine wheel burst speed is also very high, and the HCF limit is also very high.

The aluminum compressor wheel burst speed is also at least 150% of the design speed. The problem for the compressor wheel is LCF. You will eat up a bunch of LCF life with a big overspeed, but this is not visible. These old aircooled engines are running at pressure ratios that are not high enough to make LCF a very big problem though. I don’t think it likely that anybody would experience a failure from running a short test without the intercooler.

I need help on initializations LOL. HCF, LCF, etc