RPM ?????

[Reca]

I made a small routine to extract rpm from sound analysis and I’ve found that the main problem is the choice between the length of the interval and required accuracy. Without entering too much in the details when you have to analyse the engine sound you have obviously to separate the audio sequence in intervals and then find the rpm in each interval. But, the more you reduce the length of the interval (trying to follow the rpm variation), the more you are sacrificing your sensitivity on the rpm determination (meaning for example that you’re unable to distinguish 17500 from 17800 rpm). “Unfortunately” a F1 engine has a fast rate of rpm variation, so you have to choose between ability to follow the rpm variation, but with poor precision, or great accuracy but on a large time interval, meaning an average of rpm in that interval and a stepped signal. The latter is surely good for an analysis of the peak rpm (just consider a straight line near peak speed, rpm variation is relatively slow) but the tacho during the race requires to follow the rpm variation => bad accuracy. Add to this that any perturbation on the signal can generate peaks at different frequency, and that downshifts or TC can generate more confused signals. Once you have the graph of the rpm during the full lap it’s quite easy to eliminate meaningless data and also to improve precision post processing the data, but in real time it isn’t, hence the crazy figures we see sometimes.
About the indication of selected gear, I had during the race the suspect that the downshift was manually operated, it seemed to me there was an inconstant lag between the actual downshift and the change in gear indication, at least that was my impression. Upshift is quite easy to recognize, but downshift can be a nightmare.

About the marcush observation that it’s not a rpm race, I totally agree. You can just imagine the jokes here in Italy when BMW declared they broke the 19000 rpm barrier in qualifying and the day after Ralf car stopped at the 4th lap in the race...
But the point of a good analysis of engine sound isn’t only to know peak rpm, it allows lot more. For example, analysing Alonso start in Malaysia I was able to obtain, still considering the approximations, the speed vs time from about 140 km/h to about 280 km/h. That’s the polynomial fit (speed in km/h, time in seconds) :
v = -0,0137 t^4 + 0,3328 t^3 - 4,4305 t^2 + 39,32 t + 138, 0 < t < 8
A more accurate analysis (mine surely isn’t as good as it could be) and the knowledge the teams have of all the involved parameters (tyre grip and his variation with speed load, typical aero coefficients etc) would allow to know a lot about opponents cars/engines just from the engine sound.

[rodders]

thanks guys that's all over my old head . I thought the TV was using the telemetary from the race car for the RPM now I am better informed thanks . In other words I wont believe what I see

[marcush.]

think of it as watching a movie :it looks realistic but the actors do not really die...
Seeing something is no proof of reality ,especially nowadays...When Mr
Theiseen or any other big head in Formula 1 tells a bunch of crap publically it is not the truth ,or reality ,just because it was made public...
anyone who ever saw his own interview broadcasted will be shocked to see himself being interpreted and biased by ommiting and cutting of the whole thing.And you could not even say h no I didn´t say this...
So the numbers we see is actually what the broadcaster wants to be seen..

[Reca]

Then if you’re able to explain that simple concept to the tv commentators I’ll propose you for the Nobel. In Australia or Malaysia they spent minutes talking about the 18658 rpm of the Ferrari compared with the 18743 of the BMW.

[Monstrobolaxa]

Tv comentatores aren't engineers or mechanics....and don't know too much about the technical part of any kind of Motor Racing......most of them are complet morons.....here in Portugal one of our comentators spent 15 minutes talking about something from the cooling system....and he kept on saying the same thing.....and he repeated it in qualifying and in the race.....that's why most of the times I don't even pay attention to them......most of us know more about the tek side of F1 then most them.

[Guest]

I dunno about you guys but we have Steve Matchett here in the U.S. He was a Benetton mechanic from 92-98 I think. He even has a book on mechanics. I tend to believe him...

[Becker4]

yeah, steve actually said that it was an acoustic method they used to get the rpms - and, when all that discussion about renaults launch control was being batted about, he was putting out some pretty reasonable theories, that were later re-stated by some other teams mechanics in interviews. at least, i can gaurantee that he knows more than me, haha

[marcush.]

you must be lucky ...in german TV ,they spend the whole race commentating about their own life ...and have no clue what is going on in the race....Mr Danner a one time F1 driver gives proof of why he didn´t make it there every other week...the theme is who has how much Fuel in the tank and how will it affect the times and the tenor is :fast times are always due to low fuel
If it weren´t for the sound of the cars I would surely tune of the sound.
The RPM debate ..yes that´s the other topic...

[Alex M3]

I was under the impression that the FIA had access from the teams that agreed to it to display their telemetry numbers? I didnt think they were using acoustic analysis?

[Alic01]

Here in the UK Martin Brundle is constantly, going on about the "superb accuracy" fo the microphones. I am not highly educated on engine dynamics etc, but i do know about recording and as mentioned earlier in this post the level of data created is dependent upon the frequency and resolution of the recording.

As the data is displayed "real time" the amount of data generated must be small enough to be transmited from the car in the constant stream of telemetry data, this either requies Bernie E to give the teams previously unavailable technology to increase the size of the stream or the amount of data is so small it goes unnoticed.

As it is unlikely that any team would have had (or would give up) any spare telemetary room on the constant stream i would guess that the amount of data transmitted is very small and therefore very unreliable.

24 Bit PC based recording (essentially what this is) @ only 100hz would requie approximately 300kb/sec of bandwitdth and this would only be accurate to approximately 180 revs as the sampling interval is too slow.

Sorry to waffle but it does show that the silly 22,000 rpm figures are probably downshifting overrevs misrecorded by equipment which through no fault of the teams was never going to do the job!

[tipcapman]

v = -0,0137 t^4 + 0,3328 t^3 - 4,4305 t^2 + 39,32 t + 138, 0 < t < 8
.

Reca et al... funny how that thread evolved from engine thermodynamics to acoustic analysis.

I had trouble with that equation... put it into Excel and got a straight line... is it my mathematical dysfunction or is the equation wrong?

Regards..

Len

[Reca]

Hi Len.

I copied it and I get the right curve, also a step of 1 for time from 0 to 8 is enough to see the trend.
Honestly I can’t know were your problem is so I describe the procedure as I would do to someone knowing little about Excel, obviously there’s the possibility you use Excel everyday and you know it better than me (that wouldn’t be difficult), in that case I’m sorry, it’s not my intention to underrate you.

You just have to put numbers from 1 to 8 (with the step you prefers, as I said 1 is enough) in column A and to copy the following formula in the cell B1 :

= -0,0137*A1^4 + 0,3328 *A1^3 -4,4305 * A1^2 +39,32 *A1+138

Then drag it in all the remaining cells of column B and plot the two columns of data.

It’s a curve starting at 138 km/h and ending at 283 km/h and with a decreasing slope (not surprisingly). Consider that that’s an approximation of the original curve I obtained from the analysis but anyway there are so many mistakes that also the original one was a big approximation... It was just to show that from engine noise you get many info, these could be quite precise if you have some true figure for the parameters as the teams surely have.

[tipcapman]

Reca...

Thanks..... that works now. I must have made an error in copying the formula last time. I like to do things like that to keep me sharp!!!! Obviously I failed my first try!!!!

Regards...

Len