Motivation for double decker diffusers

[sinspawn1024]

So although they were only around for the 2009 racing season, I'm curious to the motivation behind the double (and in Toyota's case, triple) decker diffusers. Obviously the design increases downforce, but I'm curious to know whether the design allows more downforce than a traditional diffuser of the same volume, or if it is simply a way of working around technical regulations.

In other words, if the FIA removed all regulations on diffusers, would teams continue to use multi-deck designs or would the cars simply use larger conventional diffusers?

[WhiteBlue]

Diffusor height was limited to 175 mm and DDDs havre increased that considerably. The DDDs also influence the depth of the diffusor and collect the air forward from the position where the floor has still to be flat. But I'm confident that teams would have used higher diffusors than 175 mm if they had been legal. A good indication for this is the reduction of the legal diffusor height to 125 mm next year. The objective is a further reduction of downforce. So if reducing the diffusor height from 175 mm to 125 mm reduces downforce one would be safe to assume increasing it beyond 175 mm will increase downforce.

[Edis]

Double diffusers are still around. They are meant to go around the regulation that limits the height of the diffuser.

On the picture below you can see the air inlet for the double diffuser on the current Red Bull car.

[jian]

Hi Edis, I don't get it, where is the air inlet u mean on the picture?

[l4mbch0ps]

It's on either side of the rearmost portion of the plank. Only visible on one side of the car from this angle.

[piast9]

I am digging up an old thread but I have a question in that topic.

Why did double decker diffusers appear in 2009? The loophole which allowed them was introduced with technical regulations for 2009 or it was present earlier but was noticed in 2009?

[raymondu999]

I believe that if there is a diffuser, vs a double diffuser, with equal volumes, the standard diffuser would create more downforce, no?

[BreezyRacer]

I believe that if there is a diffuser, vs a double diffuser, with equal volumes, the standard diffuser would create more down force, no?

There is much more to the story than volume. One of the prime advantages of the DD diffuser is that the diffuser was able to start much earlier in the chassis.

IMO it's much to difficult to just say a normal diffuser with similar characteristics is always better .. a prime concept of a DD diffuser is that you can plan entrances and exits to take advantage of maximum efficiencies so rather than having one single entrance and exit you can take advantage of a wide range of stepped entrances and exits.

In a world without rules I believe they would have gravitated to tunnels that are highly intermixed with the wings, but then in a world without rules why not just use more wings, which are highly tunable and easy (relatively) to add and remove. And why not make them movable? So you can see it's always all about the rules.

[Sayshina]

I am digging up an old thread but I have a question in that topic.

Why did double decker diffusers appear in 2009? The loophole which allowed them was introduced with technical regulations for 2009 or it was present earlier but was noticed in 2009?

They changed the rules for '09 drastically reducing the area of the diffuser. Newey has said as soon as he saw the rules he asked Charlie Whiting about a double diffuser idea and was told it wouldn't be allowed, and Ross Brawn has said when he saw the rule in the working group he proposed a different wording that would have closed that loophole, and was shot down.

So clearly this was never some new tech, but rather the exploitation of yet another poorly written FIA rule. The reason you never saw something like it before is because in a world where you were allowed to make a nice big diffuser without any goofy crap you did exactly that.

Breezy is right, though, it's not just as simple as bigger is better. We've seen vertical fences in diffusers for years, because while they add drag and reduce volume they also help prevent the flow from stalling. If you could guarantee your flow was going to stay attached without them you'd get rid of them. Oh, and Breezy, the '08 and before diffusers also started quite a bit earlier in the chassis.

But why on earth would you go to big wings? They have terrible drag. You'd much rather have full ground effect, with physically sealed side skirts. You'll always have a front and rear wing, because they've become far too important to the teams sponsorship plans to let them go away.