Blown Diffuser??

[CMSMJ1]

That is nothing to do with retarded ignition. Just overfill.

I wonder if you guys actually get what retarding the igntion is all about? It is not magic, all vehicles do it - some mechanically and some via a CDI/ECU.

As the pistons speed up the sparks have to be advanced to make sure the fuel is ignited before the compression does it for you.

retarding that makes me wonder why there is no detonation in the cylinder and how this is managed??

[autogyro]

I would guess by using a very rich mixture.

[ringo]

Did a quick sketch, i think this is how the concept of the RB diffuser works
Flow Lines are a bit messy, but im sure you get the idea

RED= Exhaust
ORANGE= Outside/ Upper floor flow
BLUE= Main diffuser flow
GREEN= Upper Deck diffuser flow

This is a bit better.......

Yes this is happening. I think the trick is how the exhaust energy is distributed amongst the different parts and how it is mixed.

[hollus]

If this is not active aerodynamics controlled by the driver, I'll eat my F-duct in a wheel rim plate.

[speedsense]

I don't think Scarbs has it quite right.
1. He shows the throttle fully closed in the retarded ignition picture.

2. Fuel will only burn when in the stochiometric range - which is quite limited.

The exhaust tube temps are in the 1200-1400F range, ample enough heat to ignite unburnt fuel

3. I expect the throttle is somewhat open so the engine can induct quite a bit of air.

According to the rules, must be driver induced and all that is needed is heated air, don't care whether it contains air or not.....

4. The fuel/air mixture is ignited late so there is no real power (pressure) developed. If power was developed then the driver's foot off throttle command would be completely negated.

Heated air to flow over the diffuser, that the only reason this is being done..don't care how much power is developed in off throttle situations...Open throttle and retarding the timing, yes will lose power, but the gain in cornering must be worth it.... less wheel spin as a benefit.

5. The air then expands 15x due to the temp of ignition. The valve opens during (or before according to Scarbs) the ignition process. Blowing on the diffuser is maintained but the exhaust valve has a much increased heat load.

EXACTLY, more heat the better the diffuser works...

6. By letting more air in with the throttle artificially held partly open while the ignition is retarded there is no increase in power but the exhaust volume is more similar to the full power air flow.

Against the rules, to have the throttle "artifically" partially open, driver induced only. In off throttle, the throttle opening must be 0% percent throttle, nothing else...

[speedsense]

Did a quick sketch, i think this is how the concept of the RB diffuser works
Flow Lines are a bit messy, but im sure you get the idea

RED= Exhaust
ORANGE= Outside/ Upper floor flow
BLUE= Main diffuser flow
GREEN= Upper Deck diffuser flow

This is a bit better.......

Yes this is happening. I think the trick is how the exhaust energy is distributed amongst the different parts and how it is mixed.

A quick note here, where the red lines are, is exactly where the highest energy vortices would be formed and they would be created at the end of the diffuser, further raising the effiency. Excellent drawings, thanks for spending the time..

[autogyro]

So if you are using a promo day to test 'legaly' an EBD you would use a new ignition map that retarded the ignition to allow fuel to be burnt in the exhaust when throttle closed, there bye increasing the exhaust gas volume and improving the flow over and through the diffuser, result more downforce.
However if you were realy clever and extended the retard ECU map over into throttle apply it would sneekily give a reduction of engine torque as the power was applied. Bingo 'traction limiting' and a miss fire sound just after upshifts as the throttel is applied.
Case rests I think!

[CMSMJ1]

NO---don't agree there my gyratory forum brother..

retarding ignition will CAUSE detonation of the mixture.

the ignition needs to be advanced to keep up with the piston speeds. Not advancing it far enough means that the cylinder copression will pre-ignite the fuel. Retarding ignition will cuase issues. You cannot wait long enough to allow the exhaust valves to open and then fire the sparkplug. By that time the high compresion will have detonated the fuel charge.

Is it only me that sees this? Can someone not put me right if I am wrong?

My experience is through ym racing bikes and creating my own maps for ignition and tailoring this to suit compression and fuel octane (knock resistance) so I do feel I know about this...

[autogyro]

NO---don't agree there my gyratory forum brother..

retarding ignition will CAUSE detonation of the mixture.

the ignition needs to be advanced to keep up with the piston speeds. Not advancing it far enough means that the cylinder copression will pre-ignite the fuel. Retarding ignition will cuase issues. You cannot wait long enough to allow the exhaust valves to open and then fire the sparkplug. By that time the high compresion will have detonated the fuel charge.

Is it only me that sees this? Can someone not put me right if I am wrong?

My experience is through ym racing bikes and creating my own maps for ignition and tailoring this to suit compression and fuel octane (knock resistance) so I do feel I know about this...

Compression ignition will not occur if the mixture is made extra rich at the same time as retarding the igniton past exhaust valve opening.
Of course when the throttle is opened the effect would be intemitent firing in the combustion chamber which would sound like a miss fire. Hmmmm.

[mdexion]

In off throttle, the throttle opening must be 0% percent throttle, nothing else...

Wrong. 0% throttle pedal corresponds to the throttle plate at its "nominal idle" position. The engine throttle is always slightly open. No need for "artificially open" conditions.

[cornermarker]

Sorry if this has already been covered, but...
Looking at the positioning of the MP4-25's exhaust, it looks like there was some significant venturi action going on around the back of the car. The exhaust is placed at the back of the side pods, where air from both above and from around the sidepod meet, both would be a little sluggish at this point, threatening to become turbulent and separate.



Hot exhaust gasses at high velocity placed were they are, and directed backward probably have a siphon effect on the sluggish air, exciting it and keeping it moving backward (even better if there's a vortex coming of each pipe). It seems one of the major benefits of this placement is to simply smooth out flow at the back of the car, making it, in effect, more slippery. The cleaned up air exiting over the top of the diffuser then perhaps has a similar kind of siphoning effect on it, helping it work better and create more downforce. I.e., it's an active and dynamic air flow conditioner.

The messier or "chunkier" the sidepods and rear of the car, the more benefit this can bring you. Hence McLaren's suggestion that it could be worth .75s. Some of that 3/4s would likely also come from a higher top speed, having a more aerodynamic package. But all this also means there'll be a much more dramatic difference in air flow (and thus, downforce) between on-throttle and off-throttle air flow at the back of the car and to floor, bridge wings, and diffusers. Perhaps this explains the difficulties the Macca boys experienced when coming off the throttle.

It would be a natural progression in the "cleaning up" of the lower rear of the car by Newey, after introduction of the pull-rod. Wonder what's next...

Kelpster

[speedsense]

In off throttle, the throttle opening must be 0% percent throttle, nothing else...

Wrong. 0% throttle pedal corresponds to the throttle plate at its "nominal idle" position. The engine throttle is always slightly open. No need for "artificially open" conditions.

The ECU is calibrated 0-100% for the throttle, which is recorded for use by the FIA, the throttle pedal and the throttle opening MUST be exactly the same, with 0% on off throttle of the pedal and 0% opening at the FI throttle plates. It cannot be any other number in off throttle.
0% can be an open throttle plate (normal idle) though not all F1 systems have partially open throttle plates at normal idle. Some have normal idle with the plates close. Don't know if F1 FI is this way as it depends on the fuel delivery system.
But the point is the throttle must be 0%, NOT 1,2,3% (according to the ECU readings) and/or varying on reset to off throttle. This would be illegal....
The main reason it is this way is to prevent TC, through "artificially controlling" the throttle opening. IMHO

[autogyro]

If there is normal idle with throttle plate fully closed then there has to be an air bleed somewhere.
So it is not a problem.

[747heavy]

not sure about the throttle actuation system of an F1 engine.
I was under the impression it is pneumatic, but I could be wrong.

To get the conversation away from, if the throttle has to be at 0% in idle or not.

Who says, that the driver in this EBD application, not just maintains a degree of throttle
with his foot.
I don´t think, that the rules specify, that you have to lift completely off the throttle while you are braking.

So if the driver just maintains the throttle in open position (let´s say 30%), and an
input from the brakes is used to define, we are in "overrun" condition to select the redarded ignition map, and whatever may goes with it.

This would solve the TC problem, as you are (normally) not on the brakes why exiting the corner.

Just a thought - not saying that this is how they do it.

The other considerartion is, that why the rule may say 0% on the pedal has to correlate with 0% or idle position on the engine.
Do they say, how long can it take to arrive in the 0%/idle position. There will be allways a delay. Can be 100th of a second at best, or x seconds, but there will be allways a delay. If the time to achieve 0% is not strictly specified, it may just "takes a while" to get there. Finally 0% pedal will correlate with 0% on the engine again.

[marcush.]

not sure about the throttle actuation system of an F1 engine.
I was under the impression it is pneumatic, but I could be wrong.

To get the conversation away from, if the throttle has to be at 0% in idle or not.

Who says, that the driver in this EBD application, not just maintains a degree of throttle
with his foot.
I don´t think, that the rules specify, that you have to lift completely off the throttle why you are braking.

So if the driver just maintains the throttle in open position (let´s say 30%), and an
input from the brakes is used to define, we are in "overrun" condition to select the redarded ignition map, and whatever may goes with it.

This would solve the TC problem, as you are (normally) not on the brakes why exiting the corner.

Just a thought - not saying that this is how they do it.

The other considerartion is, that why the rule may say 0% on the pedal has to correlate with 0% or idle position on the engine.
Do they say, how long can it take to arrive in the 0%/idle position. There will be allways a delay. Can be 100th of a second at best, or x seconds, but there will be allways a delay. If the time to achieve 0% is not strictly specified, it may just "takes a while" to get there. Finally 0% pedal will correlate with 0% on the engine again.

didn´t we hear that Michael schumacher was using too much throttle when braking in certain corners?..

must be hell for the brakes..to have the engine pushing still instead of helping the brakes..will of course not be good for rear end stability as well ...