How we used data acquisition to find lost speed

J.G.
By J.G. Pasterjak
Mar 1, 2024 | VBOX, VBox Motorsport | Posted in Data & Communication | Never miss an article

Photography by J.G. Pasterjak

The data said it all: I was too slow down the straights.

The likely culprit? I was also too slow through the turns.

This was the quick interpretation from the VBox Motorsport data-acquisition crew when comparing my laps to one of my competitor’s.

VBox Motorsport had invited us, along with several other journalists and influencers from the motorsports world, to an intensive training …

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Comments
codrus (Forum Supporter)
codrus (Forum Supporter) GRM+ Memberand PowerDork
10/6/23 11:25 a.m.

BTW, I spotted a couple of minor typos in the article -- the OEM rear end ratio for the NB 5-speed is a 4.3, not a 4.4.  Also, at one point the article says that the other car was finishing the straight in 5th, which doesn't seem to be reflected in the data (starting in 2nd, 2 shifts puts it in 4th).

As for the conclusion:

Also note that we didn’t use any esoteric functions of our data equipment. A simple speed trace was the most valuable tool in our arsenal when it came to solving this mystery.

I would argue that an RPM trace wold have solved the mystery sooner, because the gearing ratio discrepancy would have been immediately apparent in the data instead of something you had to infer from shift points. :)

 

Tom1200
Tom1200 PowerDork
10/6/23 12:00 p.m.

Mmmm what happens when you don't have access to the other car's data???

JG Pasterjak
JG Pasterjak Production/Art Director
10/6/23 1:25 p.m.
codrus (Forum Supporter) said:

BTW, I spotted a couple of minor typos in the article -- the OEM rear end ratio for the NB 5-speed is a 4.3, not a 4.4.  Also, at one point the article says that the other car was finishing the straight in 5th, which doesn't seem to be reflected in the data (starting in 2nd, 2 shifts puts it in 4th).

As for the conclusion:

Also note that we didn’t use any esoteric functions of our data equipment. A simple speed trace was the most valuable tool in our arsenal when it came to solving this mystery.

I would argue that an RPM trace wold have solved the mystery sooner, because the gearing ratio discrepancy would have been immediately apparent in the data instead of something you had to infer from shift points. :)

 

Thanks for spotting the typos. I'm a zillion miles away but I'm sure the CFla-based web crew will get th ecorrections made.

As for an RPM trace, I don't completely disagree, but an rpm trace wouldn't necessarily instantly reveal a higher mid corner speed the way a speed trace would. If you just looked at an rpm trace, you'd also see lower rpm on corner exit, and it could be just as easy to work under the assumption that that also meant lower cornering speed, hence less exit speed, hence less straightaway speed. 

Ultimately I think the real takeaway message is that people tend to get really intimidated by data, and they can get overwhelmed by the sheer amount of information they car produce. It's a fair and reasonable fear. But the reality is you really don't need many channels to produce a TON of usable info.

codrus (Forum Supporter)
codrus (Forum Supporter) GRM+ Memberand PowerDork
10/6/23 1:43 p.m.
JG Pasterjak said:

As for an RPM trace, I don't completely disagree, but an rpm trace wouldn't necessarily instantly reveal a higher mid corner speed the way a speed trace would. If you just looked at an rpm trace, you'd also see lower rpm on corner exit, and it could be just as easy to work under the assumption that that also meant lower cornering speed, hence less exit speed, hence less straightaway speed. 

Ultimately I think the real takeaway message is that people tend to get really intimidated by data, and they can get overwhelmed by the sheer amount of information they car produce. It's a fair and reasonable fear. But the reality is you really don't need many channels to produce a TON of usable info.

Yeah, an RPM trace by itself is not useful.  RPM + speed trace viewed together would make it very apparent, though.

A speed trace by itself will identify problem areas and will let you infer reasons as to why the area might be a problem.  IME, though, to really solve those problems you want the driver input traces.  Throttle position and brake pressure will confirm (or reject!) your inferences (in the case presented above, a throttle trace could have definitively ruled the "late to throttle" argument).  TPS and brake pressure traces will also give much better feedback when you go back out to try to fix your pedal work.  You can make a similar argument for steering angle, but I don't find that I actually use it all that often -- I guess steering is just easier to get right than brakes or throttle! :)

I would say that 95% of the time I'm looking at data I'm using the three primary traces of speed, TPS, and brake pressure, plus the derived trace of delta-time when comparing two different runs.

 

PT_SHO
PT_SHO New Reader
10/6/23 2:06 p.m.

My '06 car apparently does not have brake pressure or steering angle available in the OBD-2 stream.  All I have seen that is useful (using Solostorm) is throttle position and RPM. 

I will look into whether I can graph out the speed trace.  Right now I just use the course segmenting feature to look into where I was quicker, aka shorter segment times, to pick out which section to focus on.  So I don't see an advantage of the VBOX for my situation, though I welcome comments.

A truism generality from drag racing is that cars with similar horsepower will have similar trap speeds, but that other aspects of setup will drop elapsed times.  Clearly if JG was only in third and competition was in fifth, there was some massive difference in gear ratios.  But if a specific corner was in his /optimum/ powerband for his transmission, his rear end would give him an advantage AT THAT POINT over the other car that was not, and if the transmissions were identical other than rear end ratio then the drop ratio between each gear would be the same.  If the drops between gears are too large to stay in the optimum torque range (hard to believe with a 6 speed) then the higher numeric transmission would have slighly tighter drops and that too could end up as an advantage.

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