New tailpipe regulations (exit holes and loopholes)

[turbof1]

I bumped into a nice tweet from Scarbs today: https://twitter.com/ScarbsF1/status/654585835283722240 The duct from the exhaust/wastegates to the rear wing has to be placed outside the final 150mm of the exhaust pipe. This is quite doable, as Toro Rosso demonstrated earlier this year:
http://www.f1technical.net/development/469

I can't see the utility of wastegate-derived downforce, because any implementation thereof would be unavoidably inconsistent, and that's why the first generation of exhaust-blown diffusers were abandoned.

Well not entirely necessary. The opening and closing of the wastegate is electronically controlled, by the ECU. It might be entirely possible to design maps to control when the wastegate opens. It'll require a lot of syncing and studying of the idea to see if it's ultimately viable, especially because the wastegate still has to activate a fluid duct. But at the base of the design, there are electronics at work.

Also, this is not about adding downforce, but removing drag (along with the downforce). While turbo blowing the diffuser will have created issues with aero stability, the instability will be less of an issue in a straight line. What you have to make sure is that the fluid switch doesn't get activated when turning. Perfectly viable with 2 wastegates: 1 to open it at high speed, the other to keep it closed during low speed.

What's even more is that the turbo speed is electronically controlled through the mgu-h and ecu. Effectively, you are staying in control when the wastegate and subsequently when the fluid switch is activated.

[PlatinumZealot]

I can't see the utility of wastegate-derived downforce, because any implementation thereof would be unavoidably inconsistent, and that's why the first generation of exhaust-blown diffusers were abandoned.

http://i.imgur.com/qUMEXAW.jpg

It was found that cars were both quicker and easier to drive if peak downforce wasn't predicated on throttle position. The later advent of off-throttle blowing is what made the solution truly viable.

Well Bhall.. Those EDB had a different function than the modern day ones. Those were directed at increasing diffuser throat speed by directly routing the exhaust after the throat. That can be disruspted under many circumstances. The Newey EDB of the 2010's were very different. The aim then was to seal the sides of the diffuser using a strong vortex. The downforce was more consistent because the vortex was not in the path of the air stream nor disrupting it.

With that said, you have given us another Idea. The Two waste gate pipes can be used to generate strong vortices if they can be somehow directed over vortex generator of some sort. What to do with those vortices? The floor is open. haha

[PlatinumZealot]

OK.. I want everybody to get something straight. The Waste gate pipes, by regulation, are basically in the same area of the main exhaust pipe... Let that sink in for a few minutes.

This implies that what ever effects that the wastegate can do, the exhaust will be creating that similar effect ALL THE TIME. Whatever you want to do with the wastegate, the main exhaust could have done it in 2014/2015 excepting there was no switching control of it. A lot of engineering has to go into aerodynamically insulating the effect of the main exhaust when you wish to use the wastegate exhaust for aero benefits. It won't be easy to PROVE that it can be done.

[turbof1]

OK.. I want everybody to get something straight. The Waste gate pipes, by regulation, are basically in the same area of the main exhaust pipe... Let that sink in for a few minutes.

This implies that what ever effects that the wastegate can do, the exhaust will be creating that similar effect ALL THE TIME. Whatever you want to do with the wastegate, the main exhaust could have done it in 2014/2015 excepting there was no switching control of it. A lot of engineering has to go into aerodynamically insulating the effect of the main exhaust when you wish to use the wastegate exhaust for aero benefits. It won't be easy to PROVE that it can be done.

PZ, only the final 150mm of the wastegates is the same regulated as the exhaust. Before that, you can do whatever you wish with bodywork and positioning of the wastegates.

I also believe that with the previous set up with having wastegate and normal exhaust being in the same pipe, you had too many variations on exhaust flow to create a controlled environment to reliably activate/deactivate the fluid switch.

[PlatinumZealot]

You could have one wastegate tailpipe end flush with an anular duct wrapped around it. When the wastegate opens via the ECU at high speed, the resulting exhaust flow entrains flow out of the duct creating low pressure. This could be linked to fluid switch to send a stalling airflow up under the rear wing.
Similar in execution to the Lotus passive F-Duct but using the wastegate flow as a signal. The other wastegate tailpipe would be used at low speed so as not to switch the F-Duct.

There is a way you have to make this duct to make it useful. A regular annular duct by itself won't entrain much air. You have to create and area of low pressure. Then Slotted wings are not allowed any more so some more engineering will have to go into making the fluidic swtich. Where will the driving air be sourced, and where will it be diverted.

The "Monkey staller"TM addresses these questions...

is on it's way...

I would appreciate a little competition. someone try come up with a wing staller faster than I can!

As my solution uses a fluid switch as an amplifier the anular duct doesn't need to create a lot of low pressure, just enough to trigger the switch. Secondly as with the Lotus, no wing slot is needed; just the under wing duct exit blowing onto the wing surface.
More reliable and quick to stall and unstall the wing, than relying on the monkey seat cascading a stalling effect to the top rear wing.
Simple...

To entrain air you need a lower pressure fluid stream. Not a lot you say, not a lot is subjective I know. Well the F-duct worked by creating a near vacuum. In the Mclaren car, the driver blocks off a hole cutting off all entrained air flow that was coming from the cabin. This dropped the pressure even more in the "X" shaped junction in the system ducts: The main stream duct, the switching duct, the wing blowing duct and the "vent" duct, thus creating an momentum change diverting the main stream of air away from the duct leading to the Rear wing, stalling it.

With that said, you can see the challenge you will face using the waste gate exhaust to do this without creating a low enough pressure. I am at work but maybe I can do a quick sketch.. or maybe I can do it tomorrow.

[PlatinumZealot]

OK.. I want everybody to get something straight. The Waste gate pipes, by regulation, are basically in the same area of the main exhaust pipe... Let that sink in for a few minutes.

This implies that what ever effects that the wastegate can do, the exhaust will be creating that similar effect ALL THE TIME. Whatever you want to do with the wastegate, the main exhaust could have done it in 2014/2015 excepting there was no switching control of it. A lot of engineering has to go into aerodynamically insulating the effect of the main exhaust when you wish to use the wastegate exhaust for aero benefits. It won't be easy to PROVE that it can be done.

PZ, only the final 150mm of the wastegates is the same regulated as the exhaust. Before that, you can do whatever you wish with bodywork and positioning of the wastegates.

I also believe that with the previous set up with having wastegate and normal exhaust being in the same pipe, you had too many variations on exhaust flow to create a controlled environment to reliably activate/deactivate the fluid switch.

Ok Ringo and I solved the F-duct for you guys back in 2010. Demonstrated the Renault blown floor operation modes.I disproved that there was ever any Octopus exhaust..and that is was really a "Fan." Showed that the RB6 EBD is more similar to the strakes on a fighter jet than to the old time EBDs.. solved the Coanda exhaust using CFD.. haha... so much little investigations. I like the challenge of this one. I said it can work but you have to create a low enough pressure at the wastegate tips... then shark fins are banned now so you don't have a straight shot at the rear wing.. and rear wing slits are banned too. That leaves the Renault "slitted pylon." I tried this in CFD and I posted it here on F1-tech. It was a bitch and I never got it to stall the wing. That is why I was thinking of stalling the monkey seat alone... but hey.. might as well try the main wing again...

[bhall II]

Well Bhall.. Those EDB had a different function than the modern day ones. Those were directed at increasing diffuser throat speed by directly routing the exhaust after the throat. That can be disruspted under many circumstances. The Newey EDB of the 2010's were very different. The aim then was to seal the sides of the diffuser using a strong vortex. The downforce was more consistent because the vortex was not in the path of the air stream nor disrupting it.

I know that's the most prevalent take on the functionality of the 2010-13 EBDs, but it's not a view I share.

With or without the assistance of exhaust gasses, vortices form just inside the outside edges of a diffuser as a result of the pressure differential. The effect of those vortices is one of force enhancement: the stronger the vortices, the greater the force enhancement. In fact, if you were to literally seal off the diffuser, downforce would be reduced as a result of the greatly weakened vortices.



All else being equal, the strength of the vortices is ride-height dependent: the lower, the better (to a point).

The most recent EBDs were a way to mitigate rear downforce losses that resulted from increased rear ride-height concomitant with added rake. In other words, it was ultimately all about getting the front wing as close to the track as possible to enhance ground effect. Without the reinforcement of energized exhaust gasses, adding rake is much more difficult, because increased rear ride-height not only reduces downforce, it also makes the diffuser more susceptible to stall, and a stalled diffuser kills aerodynamic efficiency all over the car (unless it's controlled, but that's a different conversation).

In any event, the solution was wholly enabled by off-throttle blowing. Without it, for example, the drivers below would have needed to awkwardly stand on both the throttle and the brakes to get the desired effect, which, in this case, was added stability on corner-entry...



But, that's why I can't see the benefit of any aerodynamic system that operates as intermittently as a wastegate. Without sufficient control, its likely just going to destabilize the car.

To be fair, though, I'm not necessarily saying anything is definitely impossible, just that I can't see a viable strategy. The most I can come up with is a system that somehow sends pulsed flow tangential to the underside of the wing, because it's been experimentally shown that pulsed flow is great for delaying separation, and that would allow higher AoA.

[rich1701]

hi, Layman here.

From what i understand this regulation change does not necessarily increase to total area of the exhaust/wastegate output. only the possibility (if the teams consider it advantageous) to use multiple number of exits that equates to the same area that already exists?

So is this regulation guaranteed to produce a louder exhaust note or not?

[turbof1]

hi, Layman here.

From what i understand this regulation change does not necessarily increase to total area of the exhaust/wastegate output. only the possibility (if the teams consider it advantageous) to use multiple number of exits that equates to the same area that already exists?

So is this regulation guaranteed to produce a louder exhaust note or not?

Honestly it'll be a lot already if we will notice anything.

[scarbs]

To entrain air you need a lower pressure fluid stream. Not a lot you say, not a lot is subjective I know. Well the F-duct worked by creating a near vacuum. In the Mclaren car, the driver blocks off a hole cutting off all entrained air flow that was coming from the cabin. This dropped the pressure even more in the "X" shaped junction in the system ducts: The main stream duct, the switching duct, the wing blowing duct and the "vent" duct, thus creating an momentum change diverting the main stream of air away from the duct leading to the Rear wing, stalling it.

With that said, you can see the challenge you will face using the waste gate exhaust to do this without creating a low enough pressure. I am at work but maybe I can do a quick sketch.. or maybe I can do it tomorrow.

I think you need to redo your Homework on the operation of McLaren F Duct. The wastegate switched F Duct is still a realistic concept.

[Nickel]

To entrain air you need a lower pressure fluid stream. Not a lot you say, not a lot is subjective I know. Well the F-duct worked by creating a near vacuum. In the Mclaren car, the driver blocks off a hole cutting off all entrained air flow that was coming from the cabin. This dropped the pressure even more in the "X" shaped junction in the system ducts: The main stream duct, the switching duct, the wing blowing duct and the "vent" duct, thus creating an momentum change diverting the main stream of air away from the duct leading to the Rear wing, stalling it.

With that said, you can see the challenge you will face using the waste gate exhaust to do this without creating a low enough pressure. I am at work but maybe I can do a quick sketch.. or maybe I can do it tomorrow.

I think you need to redo your Homework on the operation of McLaren F Duct. The wastegate switched F Duct is still a realistic concept.

I know you envision some ecu controlled differentiation between the two wastegate pipes, one for situations where drag reduction is undesirable, the other when it is. I assume this means only one pipe is used in quali and that no drag reduction effect will be achieved in that situation or do you see a way this won't be a race effect only?

Say hypothetically you did wish to produce downforce with these pipes, during quali when all gases flow through the wastegate you could better drive the monkey seat downforce because all gases now bypass the turbo. This would present no disadvantage during the race, as you'd be going between main exhaust and wastegate exhaust on (probably) the same device.

What happens to the gases right now during quali when they bypass the turbine? Back into the existing exhaust or directly vented to atmosphere?

[hollus]

I think Scarbs' idea is brilliant. While the whole F1 world was looking at blowing, and clearly the rulebook is looking directly at that possibility; this, well, sucks!

So a wastegate, or possible only the second wastegate, could trigger flow in a tube connecting to another tube blowing through the central rear wing pillar, and this could stall a significant portion of the rear wing. We know that it is possible, we've seen it before:


Now, how to reliably activate this wastegate only when we want it to be active?
The obvious passive trigger is speed. It was suggested to do this via the ECU. Is it legal to have the ECU change the behavior of anything in the car relating to road speed? I am not quite knowledgeable in ECU regulations, but I am guessing that it can't use speed directly as this would be too close to applications in launch control, traction control, etc. Correct me if this is wrong. Alternatively, a physical behavior linked to speed could be used, for example inlet pressure, but this looks more difficult. In any case, using speed limits the function to speeds well above those in the fastest corner of any track, and since mechanical parts of the PU cannot be changed race by race, possibly to speeds above 300km/h.

Can this signal be put directly under driver control instead? How about using certain gears that are reserved specifically for this function?

The rules do not specify that gear ratios have to be in any order, just 8 ratios fixed for the season. One could chose to run the whole season using only gears 1 through 7, which essentially is what was used to win the 2014 championships, and reserve 8th gear for this f-duct operation.

Possibilities:

a) ECU rules allow to link wastegate behaviour directly to a gear (does anyone know if this is possible?). Then one can set it up so that 8th gear is approximately as long as 7th, but f-ducted, and thus effective, say, between 270 and 340km/h, but only when the driver wants it to, allowing for normal downforce in very fast corners. This also allows the driver to disengage the f-duct, by shifting to 7th, before the braking area, while still at 3xx km/h. This is the ideal scenario.

b) If ECU rules do not allow that but they allow to link behavior to certain RPMs, either directly or indirectly via pressure effects, one could chose to activate this f-duct whenever RPMs hit 13000. I'll now introduce a second condition for this to be effective: the fluidic switch should be bi-stable, that is, once it changes its mode of operation it tends to stay in it until a deactivation trigger happens, not just when the activation trigger disappears. This is more difficult to build, but I believe it has been done before. In this case, one could use gears 1 through 7 to run the season as explained above, but then make 8th gear shorter than 7th, say as short as 6th. The driver is in 6th at 12500rpms and changes normally to 7th with 10300rpms. Then he shifts immediately to 8th, which being shorter than 6th puts him at 13000rpm, and hence triggers the fluidic switch into f-duct mode. He stays there for a tenth of a second, still accelerating, for the flow to stabilize, then shifts back to 7th, now at 10500rpm as he has been accelerating the whole time. And now the fluidic switch stays in f-duct mode all through 7th gear.

This is a bit farfetched and requires a bi-stable switch (maybe the wastegate can be built to be reluctant to close again, requiring full off-throttle to do that?) and an engine happy to be above 13000rpms (but only for minimal amounts of time).
This is all hypothetical, but let's assume that either (a) or (b) above can be engineered. Shall we stretch the scenario a bit more? One builds the engine so that the useable rpm band is even a bit wider than now, so that one can effectively race with 6 gears, physically 1st through 6th. This is not that far a stretch as some cars barely use 1st gear for lunch, and even make their pit stop entries, and Loews, in second gear. If might cost a bit of peak power, but this is what one could gain: two gears dedicated to the f-duct modes of operation. One could be a 7th gear equivalent as above, dedicated to work from approx 270km/h, or maybe 250km/h. Then the second f-duct gear, the physical 8th, could be dedicated to work from 200km/k or say, 170km/h. It would be weird to be in 4th gear at 170km/h and then very quickly go 5th-6th-7th-8th(f-duct activates)-7th-6th-5th to accelerate, and it would see the revs dropping low for a moment, but then you effectively have an f-duct as effective as those of 2010, that can be used in a lot of straights in any given circuit, and we all know that this allows the teams to run a lot more downforce, in exchange for a few tenths of reduced acceleration.

[ME4ME]

So a drag reducing system like this is supposed to reduce drag at straight without DRS, where DRS isn't activated (not following a car) or when DRS is disabled for the entire field (first few laps). But how would this F-duct style system behave in combination with DRS, are there any gains at all in that situation? Also surely there would be some drawbacks from such as system including drag from tubing/inlets.

iirc Red Bull used the DDRS to stall the diffuser, wouldn't it make sense to go that route and use this fluid-switch system for that purpose rather than stalling the rear wing?

[Matt Somers]

The RBR DDRS stalled the beam wing to then stall the diffuser, I've been preparing a post on the use of the wastegate(s) to stall the rear wing in pretty much the same way as Craig has already mentioned. I'm going to be a few days though as doing some illustrations and covering historic applications such as RW80 and DRD whilst I'm at it.

[bhall II]

iirc Red Bull used the DDRS to stall the diffuser, wouldn't it make sense to go that route and use this fluid-switch system for that purpose rather than stalling the rear wing?

Even though the aerodynamic interaction between the rear wing and diffuser isn't as potent as previous interactions between a rear wing, diffuser, and beam wing, a "connection" still exists, and getting the most out of either component inherently requires getting the most out of both. In the end, that means it's probable the diffuser would stall concurrently with the rear wing in the proposed scenario. It's a near certainty for any design that consists of a highly cambered main plane allied with a relatively small flap set at a high AoA, like the current Ferrari design...



Aerodynamic strategies of this variety favor peak downforce over consistency, and their efficiency tends to rest on a knife edge even in the best of conditions. Post-stall, how can flow be reattached fast enough to remain competitive?

If both the rear wing and diffuser are stalled, they can't help each other. A monkey seat can't help, either, because it won't be possible to run them, as a solution that trips boundary layer flow on the low-pressure side of a wing is diametrically opposed to a device that's specifically designed, in part, to guard against such eventualities.

That then begs the question, is modest relief from induced drag worth the loss of stability and consistency afforded by a monkey seat? Infrared imagery during race broadcasts illustrate how rear wing flow is fortified with energy from the exhaust plume in addition to the redirected air flow. Again, that's incompatible with the proposed system.

Combined with the difficulty of controlling everything with a device that's deliberately sporadic in nature, this seems like an awful lot of trouble to go though in order to realize an environment for potential gains that haven't been proven effective. (Lotus' DDRS was never raced.)

I dunno. Just some food for thought, 'cause lord knows I'm no expert.