DDD vs EBD

[Javert]

There was more performance in (the first part of) last year non-blown DDD or in this year modernly blown single deck diffusers?

The DDD itself helped car to gain 1s-1.5s (or more?) than a non-blown single deck diffuser

But the use of exhaust gases this year helped cars to have downforce: MP4-26 for example gained 1s immediately after mounting EBD, and more has come during the year.

So if you can choose to mount a non-blown DDD or a single deck EBD, which one would you choose?

[shelly]

I would go or EBD (beyod all obvious issues of such a choice not being precisely evaluable).

EBD this year has shown its great performance potential, which at the beginning of this year was underestimated by a lot of posters here, and by some teams too.

[Pierce89]

I would go or EBD (beyod all obvious issues of such a choice not being precisely evaluable).

EBD this year has shown its great performance potential, which at the beginning of this year was underestimated by a lot of posters here, and by some teams too.

I think the mass flow through the more extreme DDD's would produce more DF than a 2011 EBD. I believe if we had very mature DDD's but no EBD in 2011 lap times would be close to 1 second quicker through the field.

[shelly]

I agree with you Pierce on that the DDD can process a bigger mass flow rate, but I think the effect of added momentum and vortex enhancement of the EBD overshadow this. I think that if 2011 cars had fully developed DDD but no EBD they would not be as quick as they are.

[Pierce89]

I agree with you Pierce on that the DDD can process a bigger mass flow rate, but I think the effect of added momentum and vortex enhancement of the EBD overshadow this. I think that if 2011 cars had fully developed DDD but no EBD they would not be as quick as they are.

I don't think you're thinking about just how powerful the DDD could be made. The way the loophole was interpreted the DDD had virtually no geometric restrictions other than needing volume for something else. If allowed to fully mature the DDD would've had a massive diffuser volume which would produce massive DF. We would've ended up in a sort of "mini ground effect" era. I've also read an article where Willem Toet(ex BMW-Sauber head of aero)said the DDD gave 2010 cars the best L/D ratio he saw in his career. If you consider that quote and the fact that the DDD doesn't really reduce drag then you have the DDD adding ALOT of DF. IMHO.

[raymondu999]

McLaren had a massive DDD though; and that didn't end up to well did it? There was speculation (that never died until the end of the year) that they couldn't afford to go above certain ride heights as the diffuser stalled.

[wesley123]

And I think everyone suffered from that more or less, of course the teams with bigger opneings more then others, and I think the ones who had slits in their floor(McLaren, Renault and Ferrari) suffered more from ride height change. The DDD imo has more potential, but it is much more sensitive to ride height change, for example an higher ride height causes starvation, the EBD has this problem much less

[shelly]

@perce: being the flat floor leading edge rule limited, I think that also the potential downforce from DDD is limited (you can see it as a bottleneck at the front of the flow). A for Toet quote, it is about 2010 vs the past, whereas here we are discussing 2010 vs 2011, so it is not relevant.

[Javert]

For a better understanding of what a blown diffuser make gain over a non-blown diffuser (single deck), I suggest watching these: it's RB5 vs RB7 in China, the fuel weight can't explain it all considering that Bridgestone could be used "faster" than Pirelli.

[youtube]http://www.youtube.com/watch?v=uvNdYG6sFRw[/youtube]

[youtube]http://www.youtube.com/watch?v=GVI4QAfzvTE[/youtube]

You can watch only the final 2 corners, the braking in the penultimate is much more late in RB7 (even if it was going faster due to DRS) and the way the cars make into the last corner is visibly different.

Interesting also Istanbul 2009 vs 2011: embrional double deck (?) vs exhaust blown diffuser

[youtube]http://www.youtube.com/watch?v=i9Cv_JqN ... re=related[/youtube]

[youtube]http://www.youtube.com/watch?v=aBBv9L9CAP4[/youtube]

The first sector is taken much, much better thanks to EBD

[raymondu999]

The Pirellis would cloud the situation would they not? I mean, do we have any basis of real comparison of how much mech grip the Pirellis give vs the old bridgestones?

[Javert]

The Pirellis would cloud the situation would they not? I mean, do we have any basis of real comparison of how much mech grip the Pirellis give vs the old bridgestones?

The Pirelli soft compound was meant to be harder (even if degradable) compound than Bridgestones of last year, which were meant to be harder than the soft compound of 2009
So the performance of the tyre should be worse

[horse]

I think this is a great question, by the way, although I think it will be almost impossible to answer. My first thought was to compare this years RB7 lap time at Australia to last years MP4-25 fastest qualifying lap. Now I compare these two because the MP4-25 had a non-blown second-gen double diffuser and (importantly) the f-duct which could be seen as equivalent to DRS (for qualifying). The RB7 is the best example of an EDB car in 2011. So the results

RB7 (2011): 1:23.529
MP4-25 (2010): 1:24.675

Note, also, that the blown DDD of the RB6 set a lap time in 2010 of 1:23.919 for pole.

Also interesting is that this years EDB cars are faster than last years DDD non-blown and blown cars. The caveat to that is that you'd probably expect (with static rules) that the cars would gain a second a lap over a years development. So you could argue that the DDD MP4-25 would have set a 1.23.5 (ish) in Australia after a years development.

Then chuck the new tyres into the equation and who knows!!!

[Lycoming]

DRS is substantially more effective than F-duct. and not to mention, 2011 cars weigh more and are running KERS. and dont forget the different tyres. There are too many unknowns to draw any reasonable conclusions about any single aspect of the car.

[Pierce89]

@perce: being the flat floor leading edge rule limited, I think that also the potential downforce from DDD is limited (you can see it as a bottleneck at the front of the flow). A for Toet quote, it is about 2010 vs the past, whereas here we are discussing 2010 vs 2011, so it is not relevant.

I just personally believe that the DDD has more ultimate potential than a 2011 style single deck EBD. The teams gain around 2 seconds a season purely in development so lap time comparisons are worthless. I'm just basing it off my limited aero knowledge(starting 3rd year of a 5 year Mech engineering and aeronautics program. So far the only aero class I've had was totally theory and math based with virtually ZERO practical application. But I'll get there.) I'm not really comparing 2010 to 2011. I'm just comparing the overall concepts and I feel the DDD to be more powerful ultimately.

[MIKEY_!]

This is incredibly difficult to compare. Each car is optimized for the current set of rules. Different tires get in the way, different car designs and wings optimized for DRS cause trouble too. And then some teams just seem to get it right with one particular design and others do not.