F1 engine RPM

[strad]

I must rephrase. Why would it slow down that quick? I'd imagine an F1 engine would have more inertia. After all, you don't see the cars massively slowing down as they lift through corners such as Pouhon.

I think the difference is the wheels turning with the car in gear...That and the spark and fuel not being cut.
Try this,,,I have others but this was first.
http://www.stradsplace.com/VIDEOS/F1-fire-up.mpeg
A good tight engine should always stop rotating quickly

[aussiegman]

I know Strad has answered, but...

When compared to a standard road engine, an F1 engine has substantially less inertia due to the much lower rotating mass of the engine components and the virtual zero weight of the clutch & flywheel assembly. Add to that the substantially lower overall weight of the F1 car vs. a road car and you see the much lower inertia of the package as a whole as well as the lower engine inertia.

The inertia is so low that lifting off the throttle in an F1 car and not braking generates as much deceleration as standing on the brakes of most modern road cars and some GT category race car due to the force required to keep the engine moving coupled with the low overall package weight of the F1 vehicle. This manifests due to the lower rotating inertia of the engine being unable to maintain the speed of the car for any discernible time frame and then the drag of the engine as well as the drag of the aero slowing the light weight package so dramatically. But it is the engine that provides the most deceleration force outside of braking at all but the very highest speeds.

So the reason the engine keeps rotating through the corners such as Pouhon is that the clutch is still engaged. This is where the inertia of the chassis (however small) and the off throttle mapping of the engine itself keeping the package moving.

Think of it this way, an F1 car traveling at 200kph has substantially less inertia than a McLaren/Ferrari/Lamborghini GT race car traveling at 200kph. Jump off the throttle in both and what happens?? The GT car decelerate at a much slower rate than the F1 car which will very quickly come to a stop.

[bhall]

I've always seen that quality of an F1 car attributed to drag, though.

Notwithstanding compression ratio, wouldn't the lower mass of F1 engine components also mean that it takes less outside force to move them in such a scenario?

I must rephrase. Why would it slow down that quick? I'd imagine an F1 engine would have more inertia. After all, you don't see the cars massively slowing down as they lift through corners such as Pouhon.

I don't think drivers completely lift off the throttle in those types of corners.

[aussiegman]

I've always seen that quality of an F1 car attributed to drag, though.

Attributed to what type of drag?? Engine/driveline drag? Aero drag? Rolling resistance? There are various drag elements that work to decelerate the car. The two primary drag factors are aero drag and driveline drag from the engine. Why this drag has such a big effect is the lack of inertia that usually comes from a rotating high mass, high moment flywheel and clutch assembly that releases energy during deceleration and extends the time over which a deceleration event takes place.

Notwithstanding compression ratio, wouldn't the lower mass of F1 engine components also mean that it takes less outside force to move them in such a scenario?

Hang on, isn't compression ratio vitally important in the equation regardless of if the engine is running or not?? So what would make you disregard it??

As said previously:

"There is virtually no flywheel and clutch inertia to keep it spinning and with such tight tolerances/high compression ratios there is a sizable amount of internal resistance to over come.

The low mass of components reduces the inertia of the engine similar to reducing the weigh of an attached flywheel. The compression ratio and tight tolerances work to increase the resistance to rotation when not in operation.

I must rephrase. Why would it slow down that quick? I'd imagine an F1 engine would have more inertia. After all, you don't see the cars massively slowing down as they lift through corners such as Pouhon.

Let me try again, drivers do not lift off through a corner like other categories or fast road cars. In an F1 car you lift during braking and downshifts, the throttle mapping during this time (milliseconds) gives the engine a % of throttle over idle openings (and also varies ignition retard etc) and then drivers are back on the throttle and actually drive (not coast) through the corner on the throttle.

This is why throttle travel distance is variable and some drivers (like Schumacher particularly) like greater amounts of throttle pedal travel to provide more throttle "resolution" to the driver. This in turn allows more throttle control mid corner to balance the car for an individual drivers preferences and driving style. More aggressive drivers are more digital on the throttle, its on or off and they simple more between small variations of this very frequently. Others are more analog and smoother by having more control over the throttle %.

I don't think drivers completely lift off the throttle in those types of corners.

Totally agree, a driver should never be completely off the throttle excepting during downshifting. As a general rule, when downshifting an F1 car is the only time you are off the throttle. If your not then your not leaving your braking late enough, or so I am told!!

Remember the various electronic systems decide things like the exact timing of the selector drum and clutch actuation events, ignition cut or throttle % for downshifts or upshifts respectively. Also the engine mapping also only drops throttle to a preset % that is determined as optimal for maintaining required engine RPM's (and hot blowing diffusers etc) during low throttle openings. Only when the manual clutch is engaged by the driver in the pits or during an off track excursion or when the anti-stall kicks in does the engine actually go to the idle throttle opening and sit around 6,000rpm.

[bhall]

Yes, I should have stated that more clearly. I was referring to aerodynamic drag.

And, indeed, compression ratio is an important factor here. In fact, I'd say it's paramount, because I think it has a greater effect on the coasting characteristics of a car than does the mass of engine components. Removed from the equation, I think coasting is more a measure of vehicle mass rather than a measure of engine component mass.

[Greg Locock]

and you believed him?

Umm, yeah why wouldn't I?? Regardless it sounded like it was in the right general vicinity. Have you tried timing or ever timed an F1 engine switch off event??

I've seen some logging and I wouldn't be surprised if it was sub 0.5s for a full RPM to zero no load switch of. There is virtually no flywheel and clutch inertia to keep it spinning and with such tight tolerances/high compression ratios a sizable amount of internal resistance to over come.

People are very bad at estimating short time events. Racing crews make things up if they don't know the answer or don't want to tell.

No I have never timed switching off an f1 engine from 19000 rpm. But it would be easy to do from an audio signal. Does anybody have a wav (preferably) file of such an event?

Quick estimate is that to slow the engine from 19000 rpm to a dead halt in 0.2 seconds would take more than 150 Nm, continuous. That seems rather a lot to me in context. 0.5 seconds seems more likely.

[aussiegman]

Yes, I should have stated that more clearly. I was referring to aerodynamic drag.

And, indeed, compression ratio is an important factor here. In fact, I'd say it's paramount, because I think it has a greater effect on the coasting characteristics of a car than does the mass of engine components. Removed from the equation, I think coasting is more a measure of vehicle mass rather than a measure of engine component mass.

Definitely critical. As for coasting, I think you should not underestimate the effect of rotating mass and the high moments of inertia that come with large mass item such as a flywheel spinning at various RPM's.

A flywheel is just an energy storage device that is used to smooth an engines power delivery by resisting changes in engine speed. This helps keep RPM's more consistent and prevent the car "jerking" under acceleration or quickly decelerating, to release it stored energy for part throttle cruise and when moving up inclines. All of which typically give better better fuel economy. Not the priority for F1, torque and response is more vital.

Another important factor is all the stored energy that is in the flywheel is released through the drivetrain and their effect is relative to the gearing of the drivetrain they are running through. The lower the gear generally the greater the effect.

People are very bad at estimating short time events. Racing crews make things up if they don't know the answer or don't want to tell.

No I have never timed switching off an f1 engine from 19000 rpm. But it would be easy to do from an audio signal. Does anybody have a wav (preferably) file of such an event?

Quick estimate is that to slow the engine from 19000 rpm to a dead halt in 0.2 seconds would take more than 150 Nm, continuous. That seems rather a lot to me in context. 0.5 seconds seems more likely.

Absolutely agree people are very bad at estimating most things, like time distance or size.

From the way the discussion went the inference was that the time wasn't so much an estimate be an actual figure from telemetry, but as said it was an inference and wasn't specifically said. For me by ear, there is no way I could tell if it was 0.2 or 0.5 seconds, but it was certainly seemed less than 0.5s.

Very interested in how you got an estimate of 150Nm? Did you/do you know the weight of the rotating assembly and the exact compression of the engine? It certainly sounds within the bounds of possibility. As the pneumatic valve system shuts off as well and all valves subsequently close, then the combined compression effect of the engine could approach close to this number, especially considering the light weight and extremely low moment of inertia of the rotating assembly.

A good example of how quickly the engine can change speed and stop is the party trick Renault and Toyota used to perform with one of their engines, getting it to "sing" various tunes such as "We are the Champions" or "God Save the Queen" by altering RPM's. The speed with which the engine changed and held various static RPM levels was very impressive.

Renault
http://youtu.be/8aArSn4IhHI
http://youtu.be/HSNAtKhzBKQ

Toyota at their factory farewell for F1
http://www.youtube.com/watch?v=2GYqHbiFa5M&NR=1 (go to 1:15 to see the engine)

[hardingfv32]

As the pneumatic valve system shuts off as well and all valves subsequently close As the pneumatic valve system shuts off as well and all valves subsequently close....

Expand on this, are you claiming that the pressure is dropped ?

Brian

[hardingfv32]

Totally agree, a driver should never be completely off the throttle excepting during downshifting. As a general rule, when downshifting an F1 car is the only time you are off the throttle.

That is ridiculous... If your are braking your should be off the throttle. Why tax the brakes and waste fuel?

Brian

[aussiegman]

Totally agree, a driver should never be completely off the throttle excepting during downshifting. As a general rule, when downshifting an F1 car is the only time you are off the throttle.

That is ridiculous... If your are braking your should be off the throttle. Why tax the brakes and waste fuel?

Brian

Ridiculous hmm...OK lets give this some more colour and context.

Firstly, how often and where do you think the brakes would be most often applied??

They are predominately applied during downshifts prior to corner entry. Very little "braking" is done otherwise excepting extraordinary emergency situations such as avoidance, recovery or off track excursions as there are other methods to slow the car during normal racing which help save the brakes and not overheat various associated components. Couple this with the engines narrow torque range and downshifts and gear changes become more common when the car is slowed to keep the engine in the optimum RPM range.

So perhaps I should have been clearer and not assumed my personal interpretations of "downshifting" and "off the throttle" would be understood as well as context. Sorry about that my honest mistake.

From my racing experience, a "downshift" includes the braking application and the gear change events which invariably tend to happen roughly at the same time or in very close proximity to each other. As soon as you are off the throttle you should be as soon as possible on the brakes and moving down through the gears. Timed right there should be as close to zero time differential between throttle off and brake application followed by a lower gear selection to maximise speed prior to slowing for downshift and corner entry. I have personally heard drivers being criticised for "coasting" which is being too slow on the brakes when the telemetry showed much less than 0.4s - 0.5s between throttle off and brake application prior to corner entry.

I have always been taught that brakes are mainly for use in slowing into and/or through a corner or an emergency stop. In a formula car this translates to braking being part of downshifting due to the nature of the engines torque delivery.

As such you are off the throttle, on the brakes and changing gears at very nearly the same time which means that you are off the throttle when doing both braking and changing down gears. This to me is downshift.

It should also be noted that formula cars can decelerate very quickly without brakes (I have driven a few formula cars, but not an F1 car unfortunately) and it is not unusual to be able to slow the car enough without brakes by simply a partial lifting of the throttle (not getting off the throttle, see below for the difference) and not using the brakes at all. The brakes are mainly for decelerating prior to corner entry and when normal throttle lift will not sufficiently slow the car such as to avoid hitting something and in both these instances you would be off the throttle anyway to help slow the car as quickly as possible.

Also to me, the term "off the throttle" is very different to a partial "lift of the throttle".

A lift of the throttle may be used to settle a car or adjust speed typically prior to or through faster corners that do not require a downshift to a lower gear to keep the engine in its optimum operating RPM range. This is a momentary and partial lift of the throttle and not getting off the throttle 100%.

The reason these are separated as terms as they are two concepts that are very different things for a driver and crew to communicate to each other. A downshift is different to braking, which is different to a move down the gearbox to a lower gear which is a gear shift which happens without braking.

Similarly you can lift the throttle and still have throttle opening, but off the throttle is zero throttle input from the driver.

So a clearer way to put it may have been:

"During normal racing conditions, a driver should always try to never be completely off the throttle except during downshifting which usually includes associated brake application required to decelerate the car.."

Ridiculous or not, that is what I know and was taught. It has also served me well enough during my half arsed attempts at punting various cars quickly around in circles...

[aussiegman]

As the pneumatic valve system shuts off as well and all valves subsequently close....

Expand on this, are you claiming that the pressure is dropped ?

Brian

ABSOLUTELY NOT!!! A serious WTF moment has just been had!!

I needed to read your post twice to make sure I read it right the first time as it seemed more like you're trolling than asking a serious question, as exactly where did I say, infer or even give the slightest hint that the pneumatic valve pressures were dropped?? No where as far as I can tell.

The system should never drop the pressures as if they do drop below a predetermined point it would have the exact opposite effect of opening all the valves and then seeing the pistons crowns smash them in to tiny little pieces. This is apparently what happened to the Renault in Malaysia when the pneumatic system failed, the pressure dropped and a valve or valves impacted the piston crowns. I have been present for an engine being removed from a car and a remote gas cylinder was connected for exactly this reason, to stop the valves dropping and touching the piston crowns.

I know this because I asked "What is that gas cylinder used for??" when I saw it. Their reply is above..

Regardless, why would they drop the pneumatic chamber pressures anyway????? What would it possibly achieve?? If anything they could possibly increase the pressures as the nitrogen reservoir is usually at approximately 2500+psi at race start which would increase the pressures on the cam and so on...

As per my previous post, the system simply shuts off (not looses pressures) and the valves close. As they are following the cam lobes some cylinders will be undergoing their compression stroke and this will create resistance to the engines rotation.

As there is 100+psi in the pneumatic valve chambers, this in turn presses the followers against the cam lobes with some degree of force that causes resistance to the engine rotation however small. The magnitude was not the point.

So to complete the expansion you trolled for, sorry requested:

A pneumatic valve system does not use a standard coil spring, it uses compressed gas held in a chamber in its place. The cam follower on the valve tip is effectively a piston that moves against this pressurised chamber of gas to compress it resulting in what is effectively a "pneumatic spring".

The gas held in the chamber is compressed by the cam follower/valve tip piston as the cam lobe pushes the valve open. As the cam lobe moves past peak lift and along the downward ramp slope, the gas in the chamber acts as a spring by expanding to refill the chamber and close the valve.

The chambers are pressurised to approximately 100+psi as far as I know. The pneumatic systems suffer some pressure leakage during use that necessitates cars carry nitrogen reservoir at around 2500psi to top off the system as pressures drop through operation cycle. As with tyre inflation, nitrogen is used because of its stability under differing temperatures which help maintain cam lobe to follower clearances within tolerances. Regardless the high operating temp can see over pressurisation and chambers use a bleed valve to expel excess gas pressure. If ti drops to low it is replenished by the nitrogen reservoir.

The main benefits are light weigh, no springs to bind under compression and less impact from harmonic and resonance interferences. The seals are the worse aspect of the system and it biggest weakness as they preform two functions. As a seal and a type of "movement damper" for the valve. The seals press mainly against the chamber walls, though there is also some resistance from the valve stems seals, to create an amount of friction that is used to slow the valve at is peak travel so it does not jump off the cam lobe at peak lift or bounce off the valve seat when it returns. These seals have failed in the past dropping valves into the engine where they impact with the piston crowns up to 19,000 time a second.

Hows that????? Do I pass with a gold star???

[strad]

One foot or the other should be on the floor in theory also you sometimes are on throttle and brakes together to get the car to take a set.

[hardingfv32]

As per my previous post, the system simply shuts off (not looses pressures) and the valves close. As they are following the cam lobes some cylinders will be undergoing their compression stroke and this will create resistance to the engines rotation.

How do you shut off a pneumatic valve system?

Brian

[aussiegman]

As per my previous post, the system simply shuts off (not looses pressures) and the valves close. As they are following the cam lobes some cylinders will be undergoing their compression stroke and this will create resistance to the engines rotation.

How do you shut off a pneumatic valve system?

Brian

Brian, why is it that most of your posts provide nothing more than word play in semantics and in so doing provide little if any intelligent discourse and as such appear to be nothing more than trolling for adverse reaction for your personal enjoyment???

Never the less, I will feed the troll called Brian as to what determines something as "shut off" such as a pneumatic valve system.

Firstly, I specifically and purposely described the "pneumatic valve system" and not a singular component or ancillary thereof. If the inference of your question is that you are trying to imply that I said or inferred to shutting off the pneumatic valve systems pressure then you are
a: wrong, and
b: delusional.

To define shut off:

Shut off: To cut off, isolate or to stop operation of a system or systems so that it or they can no longer perform its primary function or functions.


So the pneumatic valve "system" in its entirety is governed and/or controlled by elements external to the individual components, only one of which is the nitrogen pressure feed. This includes things such as solinoids, monitoring systems and ECU's that require electrical input to function as well as gas chambers that require kinetic energy input to actuate them.

So to "shut it off" you provide zero energy input to provide for continued operation and as such it is no longer performing its intended function. This reduction to zero of the systems movement, input and actuation, be it lateral, rotational or otherwise whereby the mechanism itself or its components no longer are able to do work means it is shut off.

So how do you shut off a pneumatic valve system?? Remove either the electrical input that forms part of its operation and/or remove the kinetic energy input that actuates the system.

Or more simply, turn the engine off...Easy once you know how eh...

[Greg Locock]

"Very interested in how you got an estimate of 150Nm? Did you/do you know the weight of the rotating assembly and the exact compression of the engine?"


0.016 kg m^2 just a WAG

Compression is an interesting one. Does an engine with the ignition off slow down more quickly with an open throttle or a closed throttle? If you /know/ stay schtum for the time being, if you don't, explain the reasoning for your answer and give a rough guess as to the size of the effect. How much does CR affect it?

On a directly related note, if the engine is running at 19000 rpm in the garage roughly what MAP is it running?