Qualifying Conditions Thoughts

[Hoop-98]

There was a fair amount of discussion about qualifying conditions. Disclaimer; My expertise is in vehicle diagnostics and telematics, I am only an amateur race engineer ;)

Weather:

http://i43.tinypic.com/fm6ucx.jpg

The HP difference (Based on 650 @ STP plus 20 with ram effect corrected SAE J1349) is at most 10 BHP which is roughly .6 MPH.

The primary components are Baro (more is better and humidity, less is better). You have to subtract the vapor pressure from the total pressure to get the dry air pressure, to know the combustible air per volume.

The air density range is 95.9% to 97.1% which gives a drag variance of about 8 HP, but when you add more wing to make up for the lost downforce it is about a zero sum gain.

Note: Humidity decreases drag and downforce and decreases HP.

Track Temperature is unknown, ideal Track Temps are about 60 - 90 degrees, after that the track loses grip. This varies based on asphalt and tire compound.

Wind Gusts were likely the biggest factor:

Gust
19.0mph
17.0mph
5.0mph
8.0mph

You end up adding downforce and therefore drag to deal with the worst case scenario.

So .6 MPH for HP, net for air density as far as drag and downforce, similar for track temp and then a wild guess of .7 for Wind Gust loss and I am calculating that the best run condition on Sunday was about 1.3 better than the worst time on Saturday.

Gotta do something when the track is closed.


Thoughts

rh

[garyshell]

Disclaimer; My expertise is in vehicle diagnostics and telematics, I am only an amateur race engineer ;)

...snip...

Note: Humidity decreases drag and downforce and decreases HP.



Maybe an amateur, but one hell of an amateur!

I always thought that humidity INCREASED drag and downforce, because the air was thicker and heavier, just as cooler air is thicker and heavier? No?

Gary

[dataman1]

I believe you are both saying the same thing. Hoop was referring to barometric pressure then humidity.

[Hoop-98]

Water vapor is less dense than nitrogen or oxygen (look uo at the clouds)!

Rh from crackberry

[garyshell]

Water vapor is less dense than nitrogen or oxygen (look uo at the clouds)!

Rh from crackberry


Doh! Back to Science 101 for this guy.

Gary

[Hoop-98]

So what were the conditions in 08? :)

[SportscarBruce]

One lingering question I've had centers on the tendency of fast laps occurring early then falling off during cool conditions, whereas the booth was surprised with late qualifiers adding speed once the track was warmed by sunlight. Yon's theory of increased humidity and ambient air temps affecting drag and downforce didn't wash. Also, the need for taking it easy during the warmups doesn't jive with what I've seen in sports cars, i.e. tire temps and pressures only come up after race pace levels of cornering friction.

Does anyone know if the spec Firestones have a dual compound rubber construction, i.e. a soft layer laid atop a long-duration harder compound? The rationale I can see for doing this is to assist the driver during out-laps. As the temps come up the ultra-soft top layer would be wearing away, providing a even transition. But if the track is too cool those coiled up molecules that make up the harder compound would simply slide...

Just musing.

[Hoop-98]

In Decreasing order of magnitude:

Wind Gusts: Teams must make the worst corner
{Baron= HP, Humidity=HP, Track Temp, hotter the more DF needed the more Drag}

Based on empirical data and opinion;

2008 was ~.5-.9 better than 2009 pole day

The mufflers and tires are about 1 MPH slower than 2008 offset by development.


rh

[SportscarBruce]

Wind gust were absent during lap 1, and only for lap 1, for each and every competitor during the first 3 hours?

[Hoop-98]

Wind gust were absent during lap 1, and only for lap 1, for each and every competitor during the first 3 hours?

Not sure I understand the question? Obviously not except for a few hours in 08.


rh

[SportscarBruce]

At this moment RHR is putting down incrementally faster laps, as opposed to qualifiers running early on pole day (fast lap 1, the rest incrementally slower).

If this was Bonneville the temp & humidity charts would represent the most impact on car performance by matter of drag and downforce, but at Indy you have to take 9 degrees of gentle banking at very high speeds. Track temps matter most IMO. It all comes down to the contact patch.

Earlier today Dan Wheldon made mention of new tires from Firestone making it difficult to nail down the car balance. I firmly believe out of a desire to add safety Firestone/Bridgestone fielded a dual-compound tire similar in concept to the Uni-T, only reversed - a thin soft layer over a harder compound designed to hold up over, and even many laps past a single fuel stint. Recall how the Alex Zanardi incident unfolded. Think of late race splash and goes. That new tire is why the grip went from high to low on a cold track.

[SportscarBruce]

OMG Jack Arute and the Firestone rep is exactly hitting on these points!!!

[SportscarBruce]

And, as is almost always the case when league and vendor suits attempt to engineer racing through memos and conference calls, the result of good intentions are actually counterproductive. These tires are actually making it tougher on the lower-tier teams who don't have an armies of CFD aero geeks, carbon fabrication people, windtunnel on-call, and infinite budgets. There isn't enough mechanical grip. I don't buy the engineer's explanation that these difficulties will go away under race conditions. A low on mechanical grip tire that never goes away removes options for the smarter, wiser driver. If my speculation on this new tire construction is correct put this idea in the common template/restrictor plate/F1 redesign category. Spec sucks. Draw up a basic set of parameters and leave the racing equipment selection process to the racers....

[EagleEye]

There was a fair amount of discussion about qualifying conditions. Disclaimer; My expertise is in vehicle diagnostics and telematics, I am only an amateur race engineer ;)

Weather:

http://i43.tinypic.com/fm6ucx.jpg

The HP difference (Based on 650 @ STP plus 20 with ram effect corrected SAE J1349) is at most 10 BHP which is roughly .6 MPH.

The primary components are Baro (more is better and humidity, less is better). You have to subtract the vapor pressure from the total pressure to get the dry air pressure, to know the combustible air per volume.

The air density range is 95.9% to 97.1% which gives a drag variance of about 8 HP, but when you add more wing to make up for the lost downforce it is about a zero sum gain.

Note: Humidity decreases drag and downforce and decreases HP.

Track Temperature is unknown, ideal Track Temps are about 60 - 90 degrees, after that the track loses grip. This varies based on asphalt and tire compound.

Wind Gusts were likely the biggest factor:

Gust
19.0mph
17.0mph
5.0mph
8.0mph

You end up adding downforce and therefore drag to deal with the worst case scenario.

So .6 MPH for HP, net for air density as far as drag and downforce, similar for track temp and then a wild guess of .7 for Wind Gust loss and I am calculating that the best run condition on Sunday was about 1.3 better than the worst time on Saturday.

Gotta do something when the track is closed.


Thoughts

rh

You nailed it with wind being one of the biggest factors. There are multiple factors involved, however. The engines like cooler conditions (more HP) but the aerodynamics like hotter conditions (less drag) and this is one of the biggest factors.

The cars run unusual setups...nose high, rear end down. The do this to get the front and rear wings as level as possible...some teams are actually producing a bit of lift with the rear wing in qualifying trim. The wings are just tuning devices, while the majority of downforce is generated by the under tray.

That gets us back to the wind. When the cars are trimmed out and the wings are producing little or no down force, the cars are extremely aero sensitive. A head wind can pin the nose, and the car will push. A tail wind can give you a good push down the straight, but make the car feel loose. A good cross wind could move the rear of the car around.

The engineers do calculations for each of the conditions (cool track, more mechanical grip, faster corner speeds possible, more drag, slower speeds, etc., etc.) It goes on and on.

Usually, the race engineer will have his support engineer or DAG do some software simulations based on the conditions and different setups on the car. Based on your thread, I think you might have a future here.

Next time you are at the track, look at all the little aero devices. Upper undertray wickers, wing support struts, etc. all tuned to help aero.

All this math gives me a headache, but let me know if you will be at the track Friday/Saturday/Sunday and I could give you a good look see.

[Hoop-98]

EE, I'll take you up on that at Texas on Saturday if possible...

When it's all said and done, 50 degrees air temp, 80 degree track temp and no wind is about as good as it gets ;n)

rh