Hello everyone, i wasn't sure where to post my questions so i post it here
I'm interested in drag racing and for a long time i'm wondering how come that times in US and EU are always different. I'm talking exactly about two most popular sites and Youtube channels in terms of drag racing (i'm not sure if i can post the names ). The times on Russian events are always about 1 sec slower than it should be, for example: Audi R8 with 920hp are doing about 11.1-11.5 sec, while stock do exactly same normally... Porsche 911Turbo with PDK and 900-950 hp do 10.7-11.5 times, while it's stock 500-560 range... First i thought I saw maybe just not skilled drivers, bad start etc. but in time i see that even with good launch the times are always worse. Tell me why is it so? Question to all the drag experts On another forum someone told me that in US is something like rolling start, so ET starts to be measured while car is already moving and the time for example from 5-60 mph is much shorter than from stand to 60 mph and that's make the difference. Is that correct? Greetings and thank's in advance for reply.

 

The max acceleration for 1/4 mile race depends on some different factors such as on power and physics. The more power the greater the acceleration which ends, when engine power is higher than the frictional force between vehicle and track.
The frictional force formula based on Fr = m*g*y
m = car mass
g = 9,81 m/s/s (1g earth gravitation)
y = coefficient of friction

The same car meassured in US, EU or Russia has always the same mass and the same g. So the variable is the coefficient of friction, the number of how sticky is the contact between the vehicle and the track. The better the coefficient of friction, the more engine power can go to the track surface and the better the acceleration.

Best conditions may be using former F1 qualifying tires or better to say "Liquorice" and a drag strip with lots of rubber on it. Using road tires on a concrete or asphalt track produces other numbers, in case of wheelspin, some engine power can't be transfered to the track.

Comparing car vs car, so Porsche is great in drag races. The engine behind the rear axle brings lots of mass to the drive wheels and when accelerating, the dynamic axle load distribution is influenced by inertial forces at the vehicle’s centre of gravity. The rear axles receive more drive force. The greater vehicle’s rear wheels' load, the greater the traction it has.

 

Very interesting reply, really proffesionall The physic things is the true fact ofc, traction is most important, good touch with the track. I just ask about the weird examples like: Normally stock Turbo S is doing this time and this one has 800hp, GT-R 1200 hp which make mid 10s, while stock sometimes went below 11s... On this site we can find many cars with above 700hp which claimed to make slower times than their stock versions. I don't want to spam with too much content, just showed two of them. So my thought and info from some guy is that times in EU are measured in different way, it takes always a second or more ,,longer"

 

There are two points worth mentioning:

1. at unlim500 they are measuring the response time and the runtime; both are added together.
2. watch the track at the former military training area before the gates of Moscow; looks like concrete with lots of dust.

Compare with the track of same runtime on stock:

 

Oh yea, the surface is worse with no doubt Hmm, i think there are 2 times: ET and RT, also ET+RT (reaction time) but i was mentioning just ET so it's without response i think? Or the response is that little roll about which i spoke in the previous postS?

 

Yes, as I understand it, the time board at the end of the run (unlim500+) does not differ from the other drag strips.

Only for the selection of the unlim500+ winner both RT+ET are added together.

 

Yea, in this case you are right for sure So the differences came just from the worse surface? This super cars which they has on their event should be tested on proper track, where they can unleash their real power.

 

Yes, that's the physics. Fr means the force, which can be transmitted. so
Fr = m*g*y with m = car mass and g = 9,81 m/s/s (1g earth gravitation)
the most important in this case, comparing 2 track, is: y = coefficient of friction.

If the driver is using launch control, he will not really note any difference. The sensors at the front wheels are measuring the real wheel rotary speed and and the automatic throttle valve is controlled by the wheel slippage of the drive wheels.
In F1 8% wheel slippage is fine for best acceleration, I guess. So, the automatic driven throttle valve will give that amount of power to the wheels, to stay on e.g. 8% wheel slippage. On an dirty concrete track, the engine will give less power during the first 100-??? feet than on perfect drag strip with lots of rubber on.

The runtimes are much worse because the start is slower because of less power could be used and on this short distance, the car isn't able to make up or recover the lost time, because the slower speed at the beginning multiplies throughout the whole distance.

BTW, there is an influence to y on tires too, E.g. 991 Turbo S can go on P Zero or sticky Dunlop Maxx Race or may be slicks and increasing the engine power (high numbers) on a dirty track has not the effect as expected from the drivers.

 

Well said What you think, what is the best source to compare 1/4 mile times? For tuned cars i think dragtimes.com and for stock?

 

Drag Times is ok.
For tuned cars I guess a perfect drag strip is best, because lots of engine power can be transmitted to the ground and tuning makes sense than.
In generell, it's hard to say. You will never know, what tires, track conditions, ... Same track one day may be fine, next event full of dust.
But again, e.g. 991 Turbo S on stock you can take all season Pirelli P Zero or Dunlop Maxx Race, big difference, but why not taking manufactures claimed time - should be very close to the truth or taking all cars to the same strip on same tires.