F1technical.net

I often wondered when looking at the 2009/2010 diffusers, why didnt they use the full area they could use for diffuser area which is 1000mm across rather than the 750mm used in the picture below. What are the advantages/ disadvantages of not using the full area?

so why use this:


Over this:

The Monza and Silversone pics you show are actually DDD.

It isnt build to full width to reduce the influence the tires have on the diffuser with air flowing in etc.

This was also done on the LMP's from 2000-2005 until rules forced a largely standard diffuser.

timbo wrote:The Monza and Silversone pics you show are actually DDD.

I know but why loose the extra downforce you could have by extending across to near the tyres

wesley123 wrote:

wesley123 wrote:It isnt build to full width to reduce the influence the tires have on the diffuser with air flowing in etc.

This was also done on the LMP's from 2000-2005 until rules forced a largely standard diffuser.

but I would think outright downforce from the floor is better than clean flow exiting from the diffuser

It is not when you have air from the tire flowing in and killing the whole low pressure in this area

wesley123 wrote:It is not when you have air from the tire flowing in and killing the whole low pressure in this area

if there is that advantage then why don't they do that now?

They still do the same thing as then, only with a smaller diffuser

The blown diffusers apparently have a big effect on the tyre squirt, allowing them to run much more (lateral) expansion.

They can also reduce the effect with fences and other clever geometries in that area.

I'm slightly confused by the question.

In my mind all those diffusers exploit the full 1000mm width. However the double deck on top was limited to 750mm by the normal bodywork rules (green image below) which is why we get those stepped top surfaces, but the width at the reference plane is always 1000mm (red in image below).

From Autosport http://www.autosport.com/news/report.php/id/73083


From f1.com http://www.formula1.com/news/technical/2009/0/



Here is Scarbs' succinct summary from 2009, there are some good pics at the start of that thread too ... viewtopic.php?p=91928#p91928

scarbs wrote:To feed the upper part of the double deck diffuser, the middle 750mm of the lower diffuser doesn't reach the kick line where the flat floor meets the diffuser (i.e. the rear axle line). This leaves a window for the flow either side of the stepped floor to flow up into the upper deck.

The upper deck is permitted to be 25mm higher than the lower diffuser, which creates a 25 x 750 exit window, quite a gain in addition to the 175 x 1000 everyone else has.

Also:
http://www.f1technical.net/news/11521
http://scarbsf1.com/blog1/2011/03/22/fl ... explained/

What I'm saying is, for the double diffusers, why not make the lower deck full width, and the upper deck at the width they had normally,

here is a diagram:

N12ck wrote:

timbo wrote:The Monza and Silversone pics you show are actually DDD.

I know but why loose the extra downforce you could have by extending across to near the tyres

That is because the air near the edge of the floor just infront of the diffuser is not a good quality. You have the leading edge of the tyre there, and also the trailing egdge of the cut out of the floor. So you stand to loose by making the diffuser too wide.

n smikle wrote:

N12ck wrote:

timbo wrote:The Monza and Silversone pics you show are actually DDD.

I know but why loose the extra downforce you could have by extending across to near the tyres

That is because the air near the edge of the floor just infront of the diffuser is not a good quality. You have the leading edge of the tyre there, and also the trailing egdge of the cut out of the floor. So you stand to loose by making the diffuser too wide.

so why not use this same trick now with non DDD's ?

They are using the same trick now, but to lesser extent. Why? it's because of this;

One thing that was pretty clear with the new rules was a much smaller diffuser, which started and ended much further back. Where in previous years the diffuser was further forward and the tire had effect on a smaller part, now the tire had effect on a large part of the floor. This was in some way similar to the LMP diffusers from 2000-2005. In LMP they learned that they could make a less wide diffuser which was much more efficient since it wasnt affected by tire squirt.

So as for the f1 cars it was a logical step to apply these lessons learned. To enhance low pressure however the diffusers sweep outward to full width, this was applied differently over the different teams, McLaren choosing to use a larger footplate in that area and the possibility for a larger gurney. An additional gain was made by these outward sweeps was that low pressure airflow was directed into the wake of the rear tire.

On the other side of the new rules, Red Bull decided to take a different route, they decided to lower the rear wing end plate all the way down to the step plane, this reduced exit area but gains were made by the diffuser which was sealed off. Red Bull was also the first who found out that by injecting high pressure flow in the area between the diffuser and tire they could manage the tire squirt and the effect the tire has on the diffuser. The route of injecting high pressure flow into this area was followed by the rest of the teams, some already in 2009, but more in 2010.

In 2010 this solution was taken more to the extreme, with red bull having the diffuser remote from the floor itself, from the front it was fully open, by this they could inject the exhaust gasses and high pressure flow in the whole diffuser, making huge gains in this area, possibly by the fully open diffuser the could make a larger kink without the flow detaching.

Anyway, the diffuser isnt full width at the kink to reduce the effect tire squirt has on the diffuser itself.