Here is a thought.... what would be the amount of car lengths away be if you were racing a car that ran a 14.2 and a 13.9? and while i know that the amount of MPH in the trap counts on that as well.... obviously a car traveling at 145 MPH would need a lot more space between his rear end and his opponents front bumper, than a car only going the average 100MPH at 13.9 but is there any way to estimate that? so at least if you are on the street and you run a few car lengths behind/ahead you can estimate to some degree the ET of your opponent. anyone?

 

You have to know the mph for each car, otherwise, there is no way to obtain a reasonable estimate of E.T.

You also need to know the estimated distance between the 2 cars.

Without both, you simply cannot get any kind of reasonable E.T. for both cars.

100 mph = 146.6667 feet per second
105 mph = 154 feet per second
110 mph = 161.333 feet per second

 

Very good question!. . . .I've always wondered about that myself.

 

yeah but if the car doing 13.9@100mph... and the other car doing 14.2, that could only determine one possible amount of space between the other driver, and the one doing 100MPH... obviously if his opponent was doing any more or less than whatever his MPH is... he would be either farther behind, or more ahead... maybe thats not good logic for this estimate? i dont know... what about if they both were @ 100 mph?

 

I'll give you one example:

Two cars run the quarter mile. Both run 105 mph, but car 1 finishes in 13.2 seconds, and car 2 finishes in 13.5 seconds. Since 105 mph = 154 ft/sec., and since car 1 finished 0.2 seconds quicker than car 2, it was roughly
--- 0.2 sec x 154 ft/sec = ~31 feet ahead of car 2. This all assumes that both cars had roughly equal 60' times and reaction times. If those are not close, you simply close, the calculation simply becomes too complicated for any type of "rule of thumb" type of distances.

If the cars in question are running in the 100 mph to 110 mph range, you can use the rule of thumb of about 1 car length for every 1/10th, or said another way, if both cars are doing about 105 mph through the quarter, each car length is roughly 1/10th of a second. Again, ASSUMING that both had roughly equal 60' times and reaction times.

Since it seems you want to know what's happening on the street, since this would be a silly question to ask about dragstrip races, just spend the $100 and buy a G-Tech or equivalent.

 

1 car length per 10th? damn! sounds a bit steep dont u think? i know my friend is a few car lengths ahead of me... and hes only about .2 seconds ahead of me....

 

That's why it's only a thumb rule. Look at this another way...

You have 2 cars that are as identical as any 2 cars can be. Both LS1 FBodies, both A4, same mods, same weight, same horsepower. Same A4 shift points and firmness, same gear ratios, same tires.

Now get two drivers and line them up. Which car wins in a head-up race? Depends on the 60' and RT, right?

You aren't going to get an answer any closer than what I've alread told you, because there are just too many variables.

Your car, I'm guessing, runs high 90s to very low 100s in the quarter, given that my old 95 Z28 with cold air and full exhaust (shorties) ran low 100s, and it was an M6 (generally better mph than A4).

100 mph = 146.667 feet/second, or 14.667 feet in every 1/10th of a second.

With your example, you were behind by 2/10ths and about 3 cars. My example says it should have been 3/10ths if it was 3 cars. Oh well, that's about as close as you're going to get with a rough thumb rule.

 

Yes for 100-110 mph cars 1 carlength is about 1 tenth at the end of the 1/4 mile.

 

damn.... i must be in the high 13s then... cuz i hit 100MPH like nothin.... ill stomp on it...and 2nd gear will take me to about 70 - 80... and the gears run their course very quickly as well.... so i must be in the upper 13 range... i think my car was a factory freak... its faster than any other Z around here with the same little mods i have... freeway is another story though another Z might play with me on the freeway... just cuz i have those gears... but if i got him from the starting line? psh...... its over...

 

you could go to the track and FIND OUT... it's a whole different ballgame there.

 

yeah but i still have a lot of things i want to do with my car before i take it to the track... the suspension isnt exactly fully functional right now, im thinking new shocks all the way around and i know i need new bushings and a new rack and pinion... so i have my work cut out for me before i take it to the track, i want everything fully functional before i run it... i want my brakes redone, all that... so it will be a while before you guys get any ET info about my camaro...

 

You won't take your car to the track and run it under safe, controlled conditions because it "needs repairs"...but you'll run it on the street where those controls and safety measures aren't in place.

 

yeah but on the street i dont go ***** out either... i usually just kinda slam on the gas for a few moments and see how the acceleration is between us... i never reach even 100 mph, and i rarely even reach 80 mph if i start from a dead stop... i dont street race in the sense that i am a little fast and the furious nut... and my biggest priority is NOT safety..... its ET times... i want everything working and functional 100% so that i can get the best ET without having to talk about "oh my front end is a bit sloppy, making it harder to control at high speeds" or some other BS excuse.... the safety part would be in my brakes, i need brakes, not dire, but i will need them if im doing 120 and need to come down to 0 in a flash.... the only thing i worry about, is getting to the track, racing, and having to be towed home....... i cant afford that.... so im going to make sure i can race it, win, and drive home before i take it there...

 

and

 

LOL funny.... but you should also consider i was talking about 2 totally different things... i CAN reach 100 mph... but sorry to tell you i dont usually get that high on a drive to the liquor store you know...... what i meant by that is that when street racing i dont get that high.... but when i take it on the freeway..... god i love the onramp... i usually bust 110 before i merge on it.