Blown Diffuser??

[CMSMJ1]

@ Shaddock

Hmm..

I understand the detail of what you think can happen.

A couple of things, for me, make this unrealistic.

1: The engine is a pump. It sends x amount of gas down the system at a set amount of revs. To get more gas, you need more revs.
2: the throttle has to be fully controlled by the driver in a linear fashion.
3: if the car needs more gases to control the downforce losses then for the system to produce(or sustain) a gas level then the revs not falling when the throttle is lifted is in contravention of 2.

how do you get around that?

[Shaddock]

@ Shaddock

Hmm..

I understand the detail of what you think can happen.

A couple of things, for me, make this unrealistic.

1: The engine is a pump. It sends x amount of gas down the system at a set amount of revs. To get more gas, you need more revs.
2: the throttle has to be fully controlled by the driver in a linear fashion.
3: if the car needs more gases to control the downforce losses then for the system to produce(or sustain) a gas level then the revs not falling when the throttle is lifted is in contravention of 2.

how do you get around that?

When the driver lifts off full throttle at the engine limit 18k and the engine starts to slow down, the amount of gas flowing in the exhaust is reduced dramatically. This isn’t directly proportional to the slight reduction in engine revs, due to the fact that there is no longer the expanding gases from combustion going into the exhaust.

The swept volume of ‘clean’ air in the cylinders isn’t what’s driving the blown diffuser, it’s the expansion of gasses from the fuel combusting that’s the key.

If team can get unburnt fuel into the exhaust chamber then it will ignite and expand and flow down to the exit (diffuser) without affecting the engine rpm and drive to the wheels. In effect the exhaust mani is acting as another combustion chamber, independent of the cylinders, you just need to get fuel into it.

[Pup]

If this were what Red Bull were doing, wouldn't it be plainly audible?

[Just_a_fan]

Heat rises and the push suspension on the McLaren looks vulnerable to tranfering heat to the dampers as well as distorting the floor.
Without such a clean aero rear end as the RB, or low mounted dampers etc, it will be a far bigger problem of heat for Macca when sorting the EBD.
I did predict the heat problem as being more acute on the Ferraris but aside from their driver problems (which could be partly balance problems) it looks to have effected the Macca more.

Carbon fibre has a much lower thermal transfer coefficient than aluminium, steel (or even stainless steel) so for the few moments that the suspension is exposed to undiluted exhaust flow, e.g. in the pits, not much heat will be transfered to the dampers etc. At speed the air flow will help to cool the suspension arms anyway (I'd doubt the localised temps get very high as the cf itself would degrade which is much more of a potential problem than dampers being heated).

Distortion of the floor is the given reason for McLaren having problems (or at least why they decided to pull if off the car). Distortion of the floor leading to suboptimal airflow through the area is probably not a good thing for lap tims...

[Richard]

AFAIK ....

Each team can put their own maps into the SECU. That is then controlled by the driver changing a switch on the steering wheel.

So the suggestion is that RB have a SECU map designed for Q3. Possibly other teams do as well, they all use a high fuel burn that would be unsustainable in normal race conditions.

The detail is that the RB map might include significantly retarded ignition to help with exhaust gas flow.

[Just_a_fan]

If this were what Red Bull were doing, wouldn't it be plainly audible?

I remember hearing the Williams in '96 at Silverstone. On the over run in to Stowe the thing sounded like a shotgun being fired repeatedly. It reminded me of the anti-lag used by rally cars. I think the FW18 had exhausts discharging over the top of the diffuser which might suggest that the noise of a system being suggested hereabouts might not be that easy to hear. Not sure if the current V8s overrun in quite the same way though.

[Shaddock]

If this were what Red Bull were doing, wouldn't it be plainly audible?

Apparently according to my mate in the office who was there on Sunday (who isn't very techie) the RB sounded completely different to the other cars when it was slowing down into the loop. It had a sharper & louder 'cackle' in the exhaust than the other cars on the track

[gcdugas]

AFAIK ....

Each team can put their own maps into the SECU. That is then controlled by the driver changing a switch on the steering wheel.

So the suggestion is that RB have a SECU map designed for Q3. Possibly other teams do as well, they all use a high fuel burn that would be unsustainable in normal race conditions.

The detail is that the RB map might include significantly retarded ignition to help with exhaust gas flow.

I think you are wrong. The whole point of the SECU was to contain costs of teams that were constantly experimenting with different maps etc. I think I remember reading that they had about 11 different maps. What is the point of a SECU if they can create the maps?

[CMSMJ1]

@ Shaddock

Hmm..

I understand the detail of what you think can happen.

A couple of things, for me, make this unrealistic.

1: The engine is a pump. It sends x amount of gas down the system at a set amount of revs. To get more gas, you need more revs.
2: the throttle has to be fully controlled by the driver in a linear fashion.
3: if the car needs more gases to control the downforce losses then for the system to produce(or sustain) a gas level then the revs not falling when the throttle is lifted is in contravention of 2.

how do you get around that?

When the driver lifts off full throttle at the engine limit 18k and the engine starts to slow down, the amount of gas flowing in the exhaust is reduced dramatically. This isn’t directly proportional to the slight reduction in engine revs, due to the fact that there is no longer the expanding gases from combustion going into the exhaust.

The swept volume of ‘clean’ air in the cylinders isn’t what’s driving the blown diffuser, it’s the expansion of gasses from the fuel combusting that’s the key.

If team can get unburnt fuel into the exhaust chamber then it will ignite and expand and flow down to the exit (diffuser) without affecting the engine rpm and drive to the wheels. In effect the exhaust mani is acting as another combustion chamber, independent of the cylinders, you just need to get fuel into it.

I'm still not sold.

The cylinders inhale and exhale 300cc (nominally) per revolution - this is how I see it.

The engine will fire the plug, inject some fuel and exhale very nearly the same amount of gas each revolution.

I cannot see, apart from causing large explosions, how you would attempt to manage, at high speed and revs, the dumping of fuel in the exhaust system - to try and ignite it?

On my motorbike - If you kill ignition at high revs, then restart the unburned fuel in the system causes an almighty bang. if you could actually dump fuel into the system it would be messy!! The system would probably fall to pieces.

Also, it is bad for the valve train to have the excess heat and shockwaves in the system.

All the cars already have popping, banging and booming on the over run - this is normal. I cannot see how you can manage what might be a slim lift, at high speed, with an uncontrolled explosion in your very lightweight and fragile exhaust system?

[gcdugas]

AFAIK ....

Each team can put their own maps into the SECU. That is then controlled by the driver changing a switch on the steering wheel.

So the suggestion is that RB have a SECU map designed for Q3. Possibly other teams do as well, they all use a high fuel burn that would be unsustainable in normal race conditions.

The detail is that the RB map might include significantly retarded ignition to help with exhaust gas flow.

I think you are wrong. The whole point of the SECU was to contain costs of teams that were constantly experimenting with different maps etc. I think I remember reading that they had about 11 different maps. What is the point of a SECU if they can create the maps?

from: clicky

Engine maps
An engine map is much like a ‘sport mode’ in one of those posh German cars – it changes the throttle response and consequently the torque curve you get from your engine through the rev range.

The introduction of the common ECU has cut down on the number of engine maps the teams can use.

There used to be lots of different maps for lots of different occasions, and the drivers could change them whenever they wanted, to get the best useable power from their engine.

Now, though, there is a 90-second period from the moment you get up to speed with one map to when you can change it for another.

This was done to dissuade the drivers using a particular map for the start, which would help them get off the line in a way that might simulate the banned launch control.

The thinking was that no one would want to drive with the start map for the first lap of the race.

But guess what? Everyone is using the start map and just living with the consequences for the first minute and a half. This has contributed to some of the first-lap incidents seen so far this season.

The start map effectively ‘softens up’ the power delivery so it is more controllable. There will still be the same amount of travel in the throttle pedal, but the torque comes in more smoothly at the low revs used at the start.

Then, the fun starts. This start map has a big torque plateau where revs rise but nothing happens, then all the twisting power comes in at the top of the rev range. With no traction control, you can imagine this takes a little getting used to.

They’re all doing it because, sad as it may seem, a driver’s best chance of overtaking someone these days is at the start, and a bad start will wreck your race.

[marcush.]

if at all it might be possible to not put in that much fuel and do the ignition retard...if you have the fuel ignite only in the exhaust I´m pretty sure it will fall to peices ...

So basically you do not cut the fuel off in overrun ,but that is something not unusual isn´t it? flames coming from the exhaust ...we have seen that .

[myurr]

So basically you do not cut the fuel off in overrun ,but that is something not unusual isn´t it? flames coming from the exhaust ...we have seen that .

This is what I don't understand about all those saying it's impossible - there are plenty of other real world examples where similar techniques are employed. Yes it is a huge strain on the system, but don't forget that Red Bull were cracking exhausts in the pre-season testing and had spark plug issues in the first race. They did stress the system to breaking point, why presume they didn't find a way to then scale that back.

[Shaddock]

@ Shaddock

Hmm..

I understand the detail of what you think can happen.

A couple of things, for me, make this unrealistic.

1: The engine is a pump. It sends x amount of gas down the system at a set amount of revs. To get more gas, you need more revs.
2: the throttle has to be fully controlled by the driver in a linear fashion.
3: if the car needs more gases to control the downforce losses then for the system to produce(or sustain) a gas level then the revs not falling when the throttle is lifted is in contravention of 2.

how do you get around that?

When the driver lifts off full throttle at the engine limit 18k and the engine starts to slow down, the amount of gas flowing in the exhaust is reduced dramatically. This isn’t directly proportional to the slight reduction in engine revs, due to the fact that there is no longer the expanding gases from combustion going into the exhaust.

The swept volume of ‘clean’ air in the cylinders isn’t what’s driving the blown diffuser, it’s the expansion of gasses from the fuel combusting that’s the key.

If team can get unburnt fuel into the exhaust chamber then it will ignite and expand and flow down to the exit (diffuser) without affecting the engine rpm and drive to the wheels. In effect the exhaust mani is acting as another combustion chamber, independent of the cylinders, you just need to get fuel into it.

I'm still not sold.

The cylinders inhale and exhale 300cc (nominally) per revolution - this is how I see it.

The engine will fire the plug, inject some fuel and exhale very nearly the same amount of gas each revolution.

I cannot see, apart from causing large explosions, how you would attempt to manage, at high speed and revs, the dumping of fuel in the exhaust system - to try and ignite it?

On my motorbike - If you kill ignition at high revs, then restart the unburned fuel in the system causes an almighty bang. if you could actually dump fuel into the system it would be messy!! The system would probably fall to pieces.

Also, it is bad for the valve train to have the excess heat and shockwaves in the system.

All the cars already have popping, banging and booming on the over run - this is normal. I cannot see how you can manage what might be a slim lift, at high speed, with an uncontrolled explosion in your very lightweight and fragile exhaust system?

[youtube]http://il.youtube.com/watch?v=AePLpM5Sn ... re=related[/youtube]

This is fun, I used to do this at school

[donskar]

Thank God for Newey! =D> He gives us interesting topics to discuss -- even in the MP4/25 thread!

I think the solution discussed above (basically, in non-tech terms, modifying the engine (or its ignition map) so the flow of gas though the exhaust system continues even through corners) is not possible without the active participation of McL (for the ECU) or Renault (for strengthening/modifying components like valves and/or camshafts).

IF Newey/RBR/Renault HAVE achieved what we are guessing at, then more power to them. And, back on topic, I think we can be confident that McL and M-B will soon have a competitive solution.

Finally, a competitive advantage related to the engine! (Since the aero advantage of an exhaust driven diffuser is caused by moving parts -- exhaust stream, valves, etc) is it a priori illegal???

[Agerasia]

@ Shaddock

Hmm..

I understand the detail of what you think can happen.

A couple of things, for me, make this unrealistic.

1: The engine is a pump. It sends x amount of gas down the system at a set amount of revs. To get more gas, you need more revs.
2: the throttle has to be fully controlled by the driver in a linear fashion.
3: if the car needs more gases to control the downforce losses then for the system to produce(or sustain) a gas level then the revs not falling when the throttle is lifted is in contravention of 2.

how do you get around that?

When the driver lifts off full throttle at the engine limit 18k and the engine starts to slow down, the amount of gas flowing in the exhaust is reduced dramatically. This isn’t directly proportional to the slight reduction in engine revs, due to the fact that there is no longer the expanding gases from combustion going into the exhaust.

The swept volume of ‘clean’ air in the cylinders isn’t what’s driving the blown diffuser, it’s the expansion of gasses from the fuel combusting that’s the key.

If team can get unburnt fuel into the exhaust chamber then it will ignite and expand and flow down to the exit (diffuser) without affecting the engine rpm and drive to the wheels. In effect the exhaust mani is acting as another combustion chamber, independent of the cylinders, you just need to get fuel into it.

I'm still not sold.

The cylinders inhale and exhale 300cc (nominally) per revolution - this is how I see it.

The engine will fire the plug, inject some fuel and exhale very nearly the same amount of gas each revolution.

I cannot see, apart from causing large explosions, how you would attempt to manage, at high speed and revs, the dumping of fuel in the exhaust system - to try and ignite it?

On my motorbike - If you kill ignition at high revs, then restart the unburned fuel in the system causes an almighty bang. if you could actually dump fuel into the system it would be messy!! The system would probably fall to pieces.

Also, it is bad for the valve train to have the excess heat and shockwaves in the system.

All the cars already have popping, banging and booming on the over run - this is normal. I cannot see how you can manage what might be a slim lift, at high speed, with an uncontrolled explosion in your very lightweight and fragile exhaust system?

Well, owning a bike you should know how exhausts work on newer models. Like that air is actually sucked from the airbox into to exhaust creating a new supply of oxygen, and burning excess fuel in the exhaust as a result. The fuel actually slightly re-ignites.