does somebody know, what are the circles on the front of these cars🤔

Pardon me for sounding like an idiot, but i have never seen things like e. They look like turboes, but it would make no sense to be mounted right up front. I would guess they are air ducts, so somebody please write it down below what that is. They are not fourth gen and neither subarus, but the second one is a second gen impreza. omg thanks. Edited February 26, 2020 by darthqwo
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Those are velocity stacks for the turbos directly behind them. They are essentially fancy intake scoops.

https://en.wikipedia.org/wiki/Bell_mouth

 

Use them in test cells all the time. Meant to deliver consistent, minimally distorted airflow to the compressor face as efficiently as possible.

omg thanks

omg thanks

 

i want to put one in the passenger fog light and then route silicone tubing up to the airbox but wonder if that would defeat the purpose of efficiency

 

do i have it wrong, or does the compressor face need air separately from the air inlet on turbo

Edited February 26, 2020 by darthqwo

I think it's purely cosmetic on any factory-type Subaru setup. All the bends between the bellmouth and the turbo (not to mention the airbox itself) would introduce plenty of distortion to the charge flow, defeating the purpose. They're meant to work when they're close coupled to the inlet (directly attached to the throttle body or turbo, in this case)

but outside test cells there would need to be an air filter and nonetheless a maf between the belmouth and turbo?

No purpose of routing that through the fog light. Good luck filtering out debris and water. Most people remove the headlight housing completely and replace it with this kind of setup.

Not always. Outside test cells I've run in have been set up such that the entire ingestion zone in front of the bellmouth is clear - care is taken to make sure there's no debris that could be sucked in. In the cases where some filter is installed, it's typically a pretty coarse wire screen, which is uniform across the intake to minimize distortion.

 

Airflow measurements are sometimes taken upstream of the bellmouth, but in those cases the probe is small enough not to meaningfully disturb the flow. Otherwise, in something like an automotive turbo, you'd probably be better off measuring flow on the discharge of the compressor instead.

 

 

...either way, I think there's a world of difference between a controlled test cell environment and running a bunch of piping from a bellmouth to the turbo sitting way back in the engine bay. It'll be all the sharp bends in the tubing and all the internal features in the airbox etc that defeat the purpose.

 

My .02

Edited February 26, 2020 by awfulwaffle

The other thing to factor in is that they probably aren't working for longevity.

Replacement engines and turbos are likely a regular thing for them.

 

If I remember correctly, a speed density tune doesn't need a MAF and would likely be used in these scenarios.