Bench testing a turbo engine. Does it work?

[paulmanchester]

Does a turbo require resistance to work or would it be possible to test with wheels off (and well strapped down!)

[billj]

The turbo won't do much without a load. All that will happen with no load is that the engine will generate the tiny bit of power required to reach the rev limiter, then go no further.

I suppose it depends what you're trying to test but if you're looking to generate some boost, I'm afraid you do need a substantial load on the engine.

You could try gently (and briefly) applying the brakes but don't expect to test to anywhere near full boost.

[paulmanchester]

Thanks Bill - it was to check the boost when I get my uprated actuator - would have made it easier to set etc.

[billj]

To be honest, I don't think that would have made it easier anyway. You'd still have to wait for the exhaust system to cool down after every measurement before you can adjust it, which makes it a drawn-out process anyway. Simply take it for a drive with the APC valve disconnected and boost gauge connected. Take it up a hill in 3rd gear, accelerating to 3000rpm then hold that RPM with the brakes while still giving it quite a bit of welly. Read the pressure off the gauge at this point.

And that way, you don't have to take the wheels off or brace the car.

[paulmanchester]

Good point Bill!
What should the base boost be on a carly?

[billj]

As far as I know, the same as other 2.3 Turbos equipped with the T25: 0.37-0.43 bar or 5.5-6.5psi.

If you're fitting an uprated actuator, you might want to adjust it to the top end of the range (or even a tad higher, say 7psi) for quicker response.

[mark e]

From experience, you don't want your actuator spring to be anything less than 1PSI below your base boost- you do need some preload to ensure the wastegate stays shut.

Also, I've heard that making the base boost too high, unless you have custom software designed for it, will tend to decrease your max boost.