1 tenth in 60 foot = 2 tenths in 1/4 mile ET - myth?

Audi 1/4 mile, List & discussion forum
#1

We always hear how 1 tenth of improved 60 foot usually translates to 2 tenths of improved Elapsed Time (ET) at the 1/4 mile. Very popular thing people reference when talking about what coulda/woulda/shoulda been.

"I went 11.7 with a 1.9 60’, so if I just had a 1.7 60’ I woulda gone 11.3!’

This dragracing maxim was coined in the days of RWD domestic muscle cars however, for whom launching is a completely different exercise to launching our AWD equipped Audis.

Reality? 1 tenth in 60 foot on an AWD quattro Audi equates to 1 tenth of 1/4 mile Elapsed Time.

Unless your 60 foot time is like 2.5…at that point the run is a complete mess so who knows what will happen. However 95% of quarter mile passes we see from quattro Audi S/RS cars are in the 1.7-2.0 range. We’ve seen time and time again that when people shave a tenth off 60’ time, they also tend to shave a tenth off their 1/4 mile ET. There are certainly exceptions…example shaving a tenth on 60’ does nothing to ET. And vice versa…adding a tenth to 60’ might result in no change in ET. Lots of variables in shifting and the car itself etc. But in general, the 1:1 rule is a good one to keep in mind.

We also see that better ET = worse MPH. I don’t get this one…however it works. For example someone might cut a 1.89 60’ time and run 12.4 @ 113.8, then they cut a 1.75 60’ time and run 12.25 @ 112.5. Or they cut a 1.96 60’ time and run 12.5 @ 114.0.

Anyway, I have compiled the list here so I see TONS of timeslips for these Audis and have noticed this over time. I have also noticed that lots of people erroneously quote this 2 for 1 thing on the 60’ time to extrapolate what they could have run. Certainly not accurate and shouldn’t be relied upon so I thought I would clarify what I see in the data, rather than what people hear through the grapevine.

Here’s a good example of this working from last night. Manual transmission B8 S4 with a good driver. The 60 foot time is going to be the only big variable on the slips as he can shift consistently well and the car is running well. The best time had the best 60 foot. The best ET was about 9 hundredths better than the second best. And the 60 improved by 6 hundredths. Interesting to note that if you look at the farthest to the left timeslip, the 60’ was the same as the second best one…1.93. However the 1/4 mile ET was off abit. If you look at his 330 time you can see he lost some time from 60-330 on the run. At 330 feet the car is going around 70-75 MPH. That means he likely lost some time on the shift from 1-2 or from 2-3. All fo this info jumps off the timeslip.

http://i1219.photobucket.com/albums/dd440/Auditude20T/null_zps9b389052.jpg

#2

Good info albeit dissapointing. Wish it were true and there was hope in shaving off even more time with better launches gained by experience, repetition and practice.

#3

And it should be noted…the biggest thing to take away from this discussion is that extrapolating what you ‘could have’ run is fine if you do it in your head and work towards that goal.

However talking about it publicly saying ‘could have run XX.XX if only I had cut an X.XX 60 therefore my car can go XX.XX’ is pretty lame.

If you’re a shop saying ‘here’s our timeslip, but you can see the car is obviously an XX.XX car’, you really need to rethink your place in this business lol.

That’s like saying ‘I could have fucked Kate Upton if only I was at the party at fashion week where she was drunk and I had my chloroform rag with me’.

YOU RAN WHAT YOU RAN!

#4

Too true! 13 sec car ftw :D>:(

#5

I was looking for this post the past few days.

Let me help on the better et=lower mph. Generally you can say better 60’= a lower mph. When spesking about most cars. Here is why… most time in big hp cars they will spin off the line. This effects the mph by increasing the mph…once the car catches up with the spinning tires the result is a better mph… spinnig off the line will help get the speed up faster…The spinning effects the 60’ because your spinning early on…when the tires bite hard there is no wheel spin and no time loss every inch of 1/4 mile is acceleration down the 1/4 mile.

#6

If you’re getting full grip down every inch of the 1/4 mile, wouldn’t you expect the resulting mph to be faster since you’ve been applying full force for a longer distance?

Or are you saying that slipping the tires produces better acceleration than having full grip (not to the point of bogging of course)?

I still can’t wrap my head around this lol

#7

me either!

I think the thought is that when you’re spinning and the car grabs, you have a bigger longitudinal acceleration hit and then are just moving faster at point x on the track than when you accelerate smoothely without wheelspin.

I don’t know how true it is, or if I have it right.

#8

I’ll take a nerdy approach at it…

Sounds like a marginal amount of tire slip at launch creates potential energy. When the tires finally grab hard they convert all the car’s stored potential energy into kinetic energy and the car shoots ahead and posts a higher MPH. The cost of the higher MPH is the millisecond or so during the first 60’ it takes to develop all that potential energy. Sort of like a slingshot - if you put it back just a little more it takes you an extra second to do so but the rock flies further and faster.

Conversely, if the tires grab before the cars generates enough potential energy it gets out of the blocks sooner (lower 60’ split) but peaks sooner down the track and doesn’t reach the max MPH at 1/4 mile.

#9

I like the nerdly explanation

#10

I think it would be interesting to plot out velocity and acceleration with a very sensitive/high polling gps. Overlay a quick 60 and slow 60 and see how they compare.

Does a pbox give you individual points when you pull the data? Phones and navi gps’s don’t have that high of a polling rate.

#11

Yes it gives you a crazy amount of data

#12

a 3 axis accelerometer logger could work well to get that data. I use an Onset UA-004-64 G HOBO Pendant Data Logger at work and you can get some very precise measurement. The full kit is $145. You can log at a maximum rate of 100 Hz.

#13

This is almost word for word what I said…its just more coherent. Also a lot is dependent on if your spinning or the car just making no power in that part of the power band…something like a turbo car with too big of a turbo for that range

#14

When I was at the track last week my fastest times were in the left lane that for some reason I got wheel spin on. I was looking at my slips scratching my head wondering Wtf. Your explanation seems to be a good one.

#15

What rpm did you launch at? Or did you use launch adjust the whole time?

#16

check these 2 passes out , same mph same 60 ft and 3 tenths difference.

http://i1270.photobucket.com/albums/jj615/Garrett_Hargreaves/Mobile%20Uploads/IMG_20140807_001140_zps730e1ff0.jpg

#17

Weird. Did you botch the 3-4?

The pass on the right, based on the 1/8 time /mph was on pace for 12.6@110

If you botch your third - fourth shift it will cost you mph but won’t cost you much et

Also note that the pass on the left is pretty much bang on what the car should have done the whole way down the track so I imagine this was I’ve of the hot passes

#18

When I was at the track last week my fastest times were in the left lane that for some reason I got wheel spin on. I was looking at my slips scratching my head wondering Wtf. Your explanation seems to be a good one.

#19

What rpm did you launch at? Or did you use launch adjust the whole time?

#20

check these 2 passes out , same mph same 60 ft and 3 tenths difference.

http://i1270.photobucket.com/albums/jj615/Garrett_Hargreaves/Mobile%20Uploads/IMG_20140807_001140_zps730e1ff0.jpg