Less torque to reduce tyre wear?

[bryanbrink]

The Helmholtz provides a smooth transition between "on" and "off" throttle, in terms of exhaust gases. It's a partial "off throttle blowing" - in effect. The effect of adding the Helmholtz is in the same direction as the mapping - to keep stuff flowing out of the exhaust.

They debuted the Helmholtz in Silverstone IIRC - before said mapping.

Has anyone been able to show that the Helmholtz does provide a smooth transition between "on" and "off" throttle or is it anecdotal? I've seen this fact quoted in many articles and posts but without any more proof than stating it is so. It just seems counter-intuitive to me that with the chamber size and volume of gasses involved you could achieve much of a positive effect (but fluid dynamics can often be counter-intuitive). Just by eye-balling; the Helmholtz seems to add at maximum 15% to the total exhaust volume. Even considering full exhaust flow pressure, is that going to result in a significant "smoothing" effect? I know F1 is all about the incremental benfit each small change brings, but to me the exhaust flow smoothing effect seems too small even for F1.

Is it not possible the the Helmholz is actually related to the engine map and exhaust blowing? In that, it is being used for tuning at a certain RPM range and this is needed due to compromises made in the exhaust geometry to improve exhaust blowing overall? The Helmholtz tuning in this case would be for RPM values where exhaust blowing is less critical, i.e. high rev range.

Or another, maybe not so serious suggestion. Helmholtz resonators are often used to reduce unpleasant exhaust noise in road-going vehicles. In F1 unpleasant exhaust noise would be when your competitors and the FIA can clearly hear you're using excessive exhaust blowing - reduce the noise with a Helmholtz chamber!

Bryan

[smellybeard]

Has anyone been able to show that the Helmholtz does provide a smooth transition between "on" and "off" throttle or is it anecdotal?

Is it not possible the the Helmholz is actually related to the engine map and exhaust blowing? In that, it is being used for tuning at a certain RPM range and this is needed due to compromises made in the exhaust geometry to improve exhaust blowing overall? The Helmholtz tuning in this case would be for RPM values where exhaust blowing is less critical, i.e. high rev range.
Bryan

I would tend to agree with you. This is to achieve some resonant effect (like the expansion cambers in a two-stroke exhaust do) to fit or fight some characteristic quality of the exhaust timing at a specific rev range. It's like a capacitor (aka condenser) in an electrical circuit.

[Cam]

Does anyone know if the new map 'clarification' relates to dry running and/or can the wet setup still be tweaked?

[jz11]

when I think about Helmholtz resonance effect, I think of the following things:
1) it is an expansion chamber, it has a resonant frequency,
2) exhaust gasses flow not as a uniform fluid, but in pulses, different frequencies and intervals depending,
3) exhaust by itself is an expansion chamber, it also has its own resonance, the idea is that when a pulse reaches end of the exhaust, it hits a "brick wall" (atmosphere), some of the energy is dissipated as the gas mixes with atmosphere, but some of the energy is reflected back towards the engine,
4) when that reflected pulse reaches closed valve, it bounces back again, and the inertia of that mass creates a weak vacuum, that effect help to extract more gasses out of the cylinder and also helps to draw more air/fuel into the cylinder,
5) similar effect is also on the intake side of the engine and is quite well know, understood and used throughout the whole automotive industry

this resonance "works" in pretty narrow rpm range and significantly increases volumetric efficiency of the engine

I'm not totally aware of the F1 specifics related to intake/exhaust resonance, but my thoughts about Helmholtz benefits are following:
since the chamber itself has its own resonant frequency, it maybe could be tailored to resonate outside the normal exhaust resonance range, thus, when the "weak" pulses are boosted by the chambers resonance, they may make the exhaust resonance range wider, thus affecting the engine VE and widening the torque curve

edit: the second effect or use, might actually be the other way around, it can absorb some of the individual pulse energy and release it in between the pulses, to smooth out the overall flow from the exhaust to atmo

those are my thoughts anyway, but maybe there is more voodoo behind it

[thearmofbarlow]

you CAN NOT do that, it makes no sense, the car isn't static during the race, so is not the track itself, they both are changing, so it makes very little to no sense to tailor the torque to one specific window when the variables are just right

Do you honestly think that ACTIVE traction control systems are 100% right all the time every time in every circumstance?

Yes, you CAN do that because RED BULL WAS DOING JUST THAT. Your refusal to accept reality is staggering.

[jz11]

I see no real evidence here of the usefulness of that technique, there is just talk of it being legal, or if it is traction control or not, here are my thoughts about it:

first off - the accelerator pedal has no control over the fuel mixture or throttle body opening, it doesn't, it is an input for the ECU, and ECU decides how and what to do to get that performance out of it, and FIA didn't find anything bizarre about that map, so I concluded that they cut the torque by delaying the spark

so next we have 2 examples:

1) downtuned version, engine produces lets say 20% less torque at X rpm (will add explanation to X later), driver floors the pedal, ECU does the calculation, opens throttles at a%, fuel mix this, ignition that - result A Nm of torque @ X rpm,
2) normal version, engine produced 100% at the same X rpm, driver holds the pedal at 80%, resulting in the same A Nm of torque @ X rpm.

it is very important to understand or make a good guess where that X range was, because that is essential to understand what was the benefit or the aim of RB to go and map the engine that way, so:
my idea behind the X range, I would not under any circumstances sacrifice the power output in the normal acceleration rpm range, simply because there are plenty of corners where you accelerate in low gears (5-7, just to clarify) where you might want to use all the power you can have, and cutting torque here to gain aero (on of the accusations) would increase traction where you would want even more power, simply because you got more grip, contradiction right there
so in my opinion, the affected rpm range was below the effective acceleration rpm, for the sake of argument, lets say it was 12-15k, now where that would be useful - extremely slow corners, so from 1) and 2) I conclude that the amount of traction is the same, no aero gain*, all the driver has to do to not risk any rule breach is to hold torque demand at 70-90%, now call me stupid, but I would say that any of the drivers can do that much in 1 or 2 corners

* I suggested in one of the earlier posts, that delaying the spark in that range will increase exhaust gas temperature, thus volume, in turn there might be some sort of aero effect, too bad there was 0 response from other contributors, not knowing the specifics, it's hard to make an educated estimate about how much would that volume increase

[gato azul]

maybe this helps to illustrate your point - for the ones with a modesty of technical understanding and interest in the matter.



think about reduced torque in the 15k-16.7k rpm band as an example.
don't get hang up on the 19k rpm max. does not matter in the context of what is discussed here.

[xpensive]

What I don't get, is how to determine the engine's torque at a certain rpm, isn't that dependent on how much throttle you give?

[jz11]

in current F1 context you don't "give throttle", you, by pressing the accelerator, demand certain amount of power from the engine control unit, and then the ECU gathers the rest of the data, picks up variables from different tables, does the calculation, and produces output to drive throttle valves, open fuel injectors, ignite the mixture resulting in the amount of torque you asked for, this is even the case with a few late model road vehicle engines

older style engine management systems incorporated mechanical linkage from accelerator to throttle valve, then the ECU reacted to the amount of throttle opening, gathered rest of data again, peeked into the mapping tables, did the math, and produced the control variables

the benefit from using fly-by-wire throttle is the extra control you have over the engine, because there are certain rpm ranges, where you can get more air flow by actually limiting the throttle to NOT wide open position, but as Brian suggested here earlier, there are ways of designing that mechanical linkage to incorporate some of these extra features, the non-linear response to the amount of accelerator pedal actuation (that would actually become a traction control system according to some people) and even modulation

[rjsa]

The rules expect that any given time, let's say 50% throttle position will deliver close to 50% of the maximum torque possible at that given RPM.

What I understand RBR is doing is that let's say between 50% and 70% of the pedal position the engine will always deliver 50% torque. And in the process, delay spark timing and thus having a much more energized exhaust flow.

The rule mending came something like this:

The clarification says: "Above 6,000rpm, the maximum engine torque may vary by no more than +/- 2% (from the reference map).

"And the ignition angle may vary by no more than 2.5%."

We have to keep in mind this should be done on a track by track basis. Get a rough set of turns and RPM/Gear combinations and optimize the engine to behave best around these points.

FIA by adopting a base map makes this much less effective.

[hardingfv32]

[Do you honestly think that ACTIVE traction control systems are 100% right all the time every time in every circumstance?

Please provide an example active TC is wrong.

Brian

[thearmofbarlow]

What I don't get, is how to determine the engine's torque at a certain rpm, isn't that dependent on how much throttle you give?

No. Not at all. The amount of throttle only changes how quickly you pass through the RPM range (a simplification, but good enough for this purpose).

It's better if you think of this three dimensionally. There's a graph that gato azul posted a while back that will help. On one line you have the torque curve (A). On another line you have the RPM range (B). The third line is composed of the physical throttle position (C).

A and B are connected to each other. At any given RPM there will be X torque coming out of the engine under steady load. Where the clarification comes in is the way the throttle was being mapped in relation to A and B. Red Bull were (from what I can surmise) altering their engine mapping in such a way that changes in throttle input could control the amount of torque produced in a non-monotonic fashion. Roll into the throttle slowly, like out of a low-speed corner, and you get a mapping that produces less torque in certain places which is very useful if your engine produces torque spikes at known corner exit speeds/RPM. Stab the throttle (like you lifted for a high speed corner but are now back on the gas) and you get the full amount of torque since it's less likely you'll go shooting off into a tree.

Basically it's a passive traction control system controlled by the driver's right foot.

[bhall]

What I don't get, is how to determine the engine's torque at a certain rpm, isn't that dependent on how much throttle you give?

Yes. That's why the regulations refer to torque demand rather than torque itself.

[Raptor22]

What I don't get, is how to determine the engine's torque at a certain rpm, isn't that dependent on how much throttle you give?

Torque is a function of cyclinder pressure, and ignition timing. There are fixed elements like the bore, stroke and conrod length that cannot be altered of course.\
Altering the torque is fairly simple with a pneumatic valve train. simply drop the exhaust valve for a microsecond and bleed off cyclinder pressure.

[bhall]

And that's where the real rub starts here. Despite everything else in the regulations, they explicitly allow a reduction of cylinder pressure, for "reliability," when the engine is between 15,000 - 18,000 RPM and accelerator travel is between 80 - 100%.