1/4 times & trap speeds

Paradise bimmer · 08-01-2010, 03:42 PM

I've always looking at the stats/comparison in car magazines such as Road & Track. I have a question though regarding 1/4 times and trap speeds. Why do some cars have same times (within .3 sec) but have varying trap speeds (some up as much as 5-7 mph?

What's the explanation? Is one very quick on acceleration but lose steam/top end further down? I think it's more prominent when comparing cars with small engines to larger engines (4 cyl turbo to 6 cyl or 8 cyl).

Can someone explain the stats and how that translates into the performance of a vehicle on the street/track? Thanks.

davidkotok · 08-02-2010, 09:56 AM

higher trap speed=higher top end

mike-y · 08-02-2010, 01:20 PM

traction will also affect this greatly.. AWD cars with superior traction (like the EVO and STI) will have a quicker (lower) ET than many cars with more power, because they can get off the line a lot quicker. However, their lower hp rating shows at the higher speeds, and thus their trap speeds will be lower than a car with more power that doesn't get off the line as quick. Big hp cars tend to have problems with traction, but once they get going, they pull in big top end numbers at the end of the 1/4 mile. You can usually measure how much hp a car is making by it's weight and 1/4 mile trap speed (I can't remember the formula off hand though). this won't work with ET, because traction affects ET more than it affects the trap speed, which will usually be consistent.

I remember my friend's BPU'd Supra Twin Turbo wasn't the greatest car off the line. He'd regularly get taken by mustangs and camaros off the line, only to chase them down at the big end. He couldn't get better than 12.9 in the 1/4, but he'd trap at around 117mph, which was pretty huge, and showed the car was making a lot of power.

m1bjr · 08-19-2010, 06:39 PM

Factor in the shift times too.
And the gear ratios across the range.

Very easy to have a slow 1/2rd shift in a BMW 6MT that will cost you half a second at the low end too.

Yankees 2010 · 08-23-2010, 10:02 PM

hmmm interesting

Belarus · 08-24-2010, 11:24 AM

60'

bobbers114 · 08-24-2010, 11:29 AM

1/4 mile is all about traction. trap speeds tell how much power its making.. and then of course, you have to look at the weight of the vehicle for accurate comparisons

08-01-2010, 03:42 PM	#1
Paradise bimmer Enlisted Member 13 Rep 35 Posts Drives: E46 ///M3 Join Date: Jun 2010 Location: Hawaii iTrader: (0)	1/4 times & trap speeds - question I've always looking at the stats/comparison in car magazines such as Road & Track. I have a question though regarding 1/4 times and trap speeds. Why do some cars have same times (within .3 sec) but have varying trap speeds (some up as much as 5-7 mph? What's the explanation? Is one very quick on acceleration but lose steam/top end further down? I think it's more prominent when comparing cars with small engines to larger engines (4 cyl turbo to 6 cyl or 8 cyl). Can someone explain the stats and how that translates into the performance of a vehicle on the street/track? Thanks.
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08-02-2010, 09:56 AM	#2
davidkotok Lieutenant 17 Rep 408 Posts Drives: e92 335i Join Date: Jun 2010 Location: ny/dc iTrader: (3)	higher trap speed=higher top end
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08-02-2010, 01:20 PM	#3
mike-y just another bmw douche bag 195 Rep 3,640 Posts Drives: 1.9L of fury Join Date: Nov 2008 Location: Los Angeles, CA iTrader: (4)	traction will also affect this greatly.. AWD cars with superior traction (like the EVO and STI) will have a quicker (lower) ET than many cars with more power, because they can get off the line a lot quicker. However, their lower hp rating shows at the higher speeds, and thus their trap speeds will be lower than a car with more power that doesn't get off the line as quick. Big hp cars tend to have problems with traction, but once they get going, they pull in big top end numbers at the end of the 1/4 mile. You can usually measure how much hp a car is making by it's weight and 1/4 mile trap speed (I can't remember the formula off hand though). this won't work with ET, because traction affects ET more than it affects the trap speed, which will usually be consistent. I remember my friend's BPU'd Supra Twin Turbo wasn't the greatest car off the line. He'd regularly get taken by mustangs and camaros off the line, only to chase them down at the big end. He couldn't get better than 12.9 in the 1/4, but he'd trap at around 117mph, which was pretty huge, and showed the car was making a lot of power.
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08-19-2010, 06:39 PM	#4
m1bjr LSD - No, you're not seeing things 72 Rep 3,302 Posts Drives: Baby F36 Gran Coupe Join Date: Mar 2010 Location: Plymouth UK iTrader: (4)	Factor in the shift times too. And the gear ratios across the range. Very easy to have a slow 1/2rd shift in a BMW 6MT that will cost you half a second at the low end too.
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08-23-2010, 10:02 PM	#5
Yankees 2010 Private First Class 6 Rep 161 Posts Drives: BMW Join Date: Aug 2010 Location: NJ/NY iTrader: (0)	hmmm interesting
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08-24-2010, 11:24 AM	#6
Belarus Brigadier General 153 Rep 3,868 Posts Drives: E93 335i Join Date: Mar 2009 Location: GTA iTrader: (11) Garage List 2008 E93 335i (Conv ... [4.40]	60' __________________ 12.770 @ 112.81 mph\|\|slip\|\|JB4\|FMIC\|DPs\|DCI\|N54 DVs\|ER CP\|Koni FSD\|Eibach-Pro\|F Strut-bar\|R Sway-bar\|Hankooks V12\|DPE SP16\|BBK\|15%Tint\|CF Front Lip\|CF Diffuser\|M3 Spoiler\|SmartTop\|LUX AE\|Debadged
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08-24-2010, 11:29 AM	#7
bobbers114 Banned 0 Rep 51 Posts Drives: 335xi Join Date: Aug 2010 Location: fl iTrader: (0)	1/4 mile is all about traction. trap speeds tell how much power its making.. and then of course, you have to look at the weight of the vehicle for accurate comparisons
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