Why doesn't everyone have a 'blown diffuser'

[browney]

I was suprised to see that this was one of the things that Red Bull had on the other teams. This is not a new or innovative thing, we were tought about doing this a couple of years ago when I was at university and I had assumed that Formula 1 teams would all send some of their exhaust into the diffuser.

If it has been known about for a while, why would only one team do it? I can't see a lot of dissadvantages other than perhaps packaging/less freedom with how you tune your exhaust.

[ECW Dan Selby]

Yeh I think the main disadvantage is interruption in air flow, and possible overheating issues.

Selby

[Tim the Grey]

I remember this being BANNED in the Ground Effect days. Seeing as if you lifted mid corner, the downforce went, and you exited Stage Left, rapidly...

So howcome it's legal now? Same issue, surely.

[zac510]

These things tend to come and go in trends really. But trends have influences that start them and it could be that the double diffuser works well (ie less sensitive compared to 80s style) with this design. Thus it could have been the opening up of that section of the rules, together with something like advances in CFD (modelling exhaust flow) that have collaborated to bring them back.

[1200Datto27]

IIRC, the older blown diffusers had the total exhaust volume dumped into the diffuser's main tunnel, causing the handling variances when the diffuser suddenly had around 900cfm of air removed from it's flow. Whereas the RBR seems to energise the flow through the diffuser by running the airflow across the top of the diffuser and creating a lower pressure region there that pulls extra volume through.