Blown Diffuser??

[raymondu999]

I read somewhere though that Newey designed the exhaust feeding to the diffuser to feed through some sort of bodywork so that the downforce was not RPM dependent, as this had previously caused problems in another design. I can't recall where I read this at the moment though.

[JohnsonsEvilTwin]

I read somewhere though that Newey designed the exhaust feeding to the diffuser to feed through some sort of bodywork so that the downforce was not RPM dependent, as this had previously caused problems in another design. I can't recall where I read this at the moment though.

Yes I think there is somthing helping them there, we know this because this is an "exhaust driven diffuser" that doesnt suffer the drawbacks. Newey knows this inside out from his McLaren years, so it would surprise me if he refined it to where it is now.
I think its an area giving them huge benefits

[doopie2you]

Hi guys, i know that there are allot of threads about the blown diffuser. But they all say that the exhaust gasses flow near the diffuser causing it to suck more air out of it and this way create more downforce. But the thing i want to know is: What causes the sucketion. Is it the chemical gasses in the exhaust fumes or is it because the temprature of the gasses is higher then the temprature of the air around the car?

[siskue2005]

Guys i have a doubt

Is the exhaust driven diffuser illegal next year?
Or is it simply not possible to adopt that next year

So why did the teams ditch their previous exhaust driven diffuser incarnation in the 1998 to 2000 era?

And why is it revisited again?

Can the team have exhaust under the car like before for 2011 and beyond?

And what happened to all those talk about Exhaust driven Diffusor car is highly unstable?

[mike]

EDD works because it reduces drag per downforce generated, even with out DDD it can still work to the lesser extend.

EDD was previously used by mclaren, but since downforce is the function of rpm it was hard to control, but newer gen EDD placed the exhaust more upstream so the affect of rpm is reduced, it works more down on the heat of the air and the change in pressure, which is more stable

[speedsense]

EDD works because it reduces drag per downforce generated, even with out DDD it can still work to the lesser extend.

EDD was previously used by mclaren, but since downforce is the function of rpm it was hard to control, but newer gen EDD placed the exhaust more upstream so the affect of rpm is reduced, it works more down on the heat of the air and the change in pressure, which is more stable

According to Autosport, Mclaren will return to EDD at Silverstone....

Just out of interest,, was the last time EDD was used at Mclaren, during Newey's time?

[sknguy]

A while back I inquired at a web site (can't remember where & wish I could) about where the center of force would be for a flat bottom car with a diffuser. Like on an F1 car. After some discussion by several posters someone posted an illustration of LeMans car with a graphic below the car indicating where there were changes in the pressure gradients of a flat bottom car with a diffuser. The illustration was similar to the following:



The downward spikes indicated where the pressure was greatest (or I should say least) under the car. The large spike at the leading edge of the the flat bottom was much greater than at the diffuser end.

I'm very much a novice at aerodynamics. But I'm curious as to whether an increase in efficiency in the diffuser would have an effect on the Center of Force? Or would the effect simply be an increase in the efficiency of the whole system (flat bottom + diffuser) and not effect the location of the center of the downforce?

In the illustration that was shared at that web site it seemed to indicate that the force's center of the system would be a lot more forward from center. For example, in the above image somewhere in the area of the fuel tanks.

So... I'm under the impression now that efficiencies in the diffuser don't only effect downforce at the rear wheels, but rather over an area closer to the center of gravity (center of the car). I know that things can't be that simple but, is this reasonably correct?

Also, if you stall a diffuser wouldn't the ride height increase too? Would thins be RB's adjustable ride height system? Just curious and thanks for your responses.

[xpensive]

Interesting curve skinnyguy, it seems most credible as the pressure should be related to the square of the air-speed under the car. I would find it logical that said speed is highest (lowest static pressure) at the entry at the front edge of the sidepods like in the pic, while it tapers off further back as outside air finds its way under the car from the sides, reducing air-speed.

That could xplain why the sidepods begin at the centerpoint of the car, but I don't understand the peak at the diffuser-xit however?

[marcush.]

Interesting curve skinnyguy, it seems most credible as the pressure should be related to the square of the air-speed under the car. I would find it logical that said speed is highest (lowest static pressure) at the entry at the front edge of the sidepods like in the pic, while it tapers off further back as outside air finds its way under the car from the sides, reducing air-speed.

That could xplain why the sidepods begin at the centerpoint of the car, but I don't understand the peak at the diffuser-xit however?

maybe it is just the fact that an upward slope of the diffuser creates a wedge type
upper surface ,which of course creates downforce?

[FW17]

A very basic question,


A couple of years back it was easy to follow the exit of the air from the radiators which were either done with a slot on the engine cover or with a chimney just ahead of the wheels. Where are these exits in this years cars? are they also used to acclerate the air thro the diffuser?

[wesley123]

they just exit out of the back of the engine cover and sidepods

[pascaljackson]

maybe i didnt get it, but can someone clear it.
is a blown diffuser allowed next year?

and would it make sense to blow it right under the floor, kinda there where these big holes for the ddd at the ferrari, renault or redbull are.

doing my 2011er car so i would like to know it

[wesley123]

No, it wont be allowed, there aren't any holes allowed in that area. Also it would be a bad idea to blow it in the diffuser, it will cause an Throttle sensitive rear end. On my car i simply decided to keep a really low exhaust exiting out of the sidepod as soon as possible. it allows lower CofG and keeps space at the back and removes a heat source from there

[PlatinumZealot]

maybe i didnt get it, but can someone clear it.
is a blown diffuser allowed next year?

and would it make sense to blow it right under the floor, kinda there where these big holes for the ddd at the ferrari, renault or redbull are.

doing my 2011er car so i would like to know it

a James Allen article said it is allowed.

No, it wont be allowed, there aren't any holes allowed in that area. Also it would be a bad idea to blow it in the diffuser, it will cause an Throttle sensitive rear end. On my car i simply decided to keep a really low exhaust exiting out of the sidepod as soon as possible. it allows lower CofG and keeps space at the back and removes a heat source from there

The Ferrari, Ranault and Mercedez diffusers have no holes for the exhaust they simply blow on top of the diffuser. So this type arrangement can be used.

[ringo]

A while back I inquired at a web site (can't remember where & wish I could) about where the center of force would be for a flat bottom car with a diffuser. Like on an F1 car. After some discussion by several posters someone posted an illustration of LeMans car with a graphic below the car indicating where there were changes in the pressure gradients of a flat bottom car with a diffuser. The illustration was similar to the following:



The downward spikes indicated where the pressure was greatest (or I should say least) under the car. The large spike at the leading edge of the the flat bottom was much greater than at the diffuser end.

I'm very much a novice at aerodynamics. But I'm curious as to whether an increase in efficiency in the diffuser would have an effect on the Center of Force? Or would the effect simply be an increase in the efficiency of the whole system (flat bottom + diffuser) and not effect the location of the center of the downforce?

In the illustration that was shared at that web site it seemed to indicate that the force's center of the system would be a lot more forward from center. For example, in the above image somewhere in the area of the fuel tanks.

So... I'm under the impression now that efficiencies in the diffuser don't only effect downforce at the rear wheels, but rather over an area closer to the center of gravity (center of the car). I know that things can't be that simple but, is this reasonably correct?

Also, if you stall a diffuser wouldn't the ride height increase too? Would thins be RB's adjustable ride height system? Just curious and thanks for your responses.

a little off topic of exhausts but...

here's a little exercise i did with a flat bottom evolution.

the diffuser starts at the rear wheel centre line.
The y axis is inverted. The more negative the coefficient of pressure the more suction on that surface.
The diffuser pulls the suction for the whole floor, the peak mainly in the middle of the car depending on the rake. (pink line)
The belly of the pink curve is because of leakage to the sides.
What clears up some misconceptions about diffusers is that the diffuser throat is where the downforce is at, ie by the wheel centre line (peak at 0.. The rest of the floor has a nice flat distribution of pressure; which should be flatter with skirts on the car.

The top surface is more erratic, and this is what most people overlook. The top surface takes away a lot from the net downforce if it's not designed carefully. This is why i always say the redbull has a better body; the top surface is most smooth and it has as little pressure drops as possible. The roof needs to be the opposite of the floor, as much pressure recovery as possible.
My roof fails here, but that's the downfall of enclosed cars.