Time vs MPH
Thread Starter
Le Mans Master
Joined: Mar 2004
Posts: 5,107
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From: Dublin CA
Time vs MPH
Okay, looking at some of the other posts concerning time slips and track performance can you explain this to me. I ran a 14.4 for my first time at the track last year with a 97.5 MPH. Some of the posts I have seen show times of 13.9's with 97 - 98 MPH. I would have thought that the quicker the time the higher the MPH would be. This does not seem to be the case all the time. I would have thought that 13's would have been 99-100+ MPH. Time and MPH don't seem to tie together.
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Guys running drag radials are going to pull 4 tenths off their ETs without much effect at all on MPH.
I'd probably trap a 13.5 in the 1/4, but only at 96mph or so.
I'd probably trap a 13.5 in the 1/4, but only at 96mph or so.
Elite Torch Red Member
Joined: Sep 1999
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From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
Cental/South NJ Events Coordinator
CI 1-2-3-4-5-6-7-8-9-10-11-12 Vet
CI-II Burnout & Drag Champ
St. Jude Donor '03-'04-'05-'06-'07
The MPH is an indicator of the power you have, the ET is more like how you use that power.
We at our track notice that a bad launch which will result in a poor time always nets us a better MPH.
Also, the quicker we get off the line, the farther forward we advance therefore not giving us enough time to actually achieve the maximum MPH.
It may not make sense, but these are thing's we've noted.
If you look at my sig, the times got quicker as the MPH went down.
I lost a little power when I removed my mufflers, but as I got better with the car the ET's improved.
There's more to it and I'm sure someone will chime in with a more scientific approach.
We at our track notice that a bad launch which will result in a poor time always nets us a better MPH.
Also, the quicker we get off the line, the farther forward we advance therefore not giving us enough time to actually achieve the maximum MPH.
It may not make sense, but these are thing's we've noted.
If you look at my sig, the times got quicker as the MPH went down.
I lost a little power when I removed my mufflers, but as I got better with the car the ET's improved.
There's more to it and I'm sure someone will chime in with a more scientific approach.
Drifting
Joined: Feb 2004
Posts: 1,277
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From: Santa Maria CA
depends on if its a well set-up car for launching. If you get a GREAT or perfect launch in an auto car then a 13.9@97 is just right. Theres nothing wrong with a 14.0@101 or 13.5@96mph. just depends on the cars set-up. They are all different.
Generally a manually equipped car will turn a slightly better MPH than an auto do to a lighter trans to get power through it to the tires better or also better gear ratios in the trans itself. Also a manual car is more difficult to launch than an auto so ET is hurt in the first 60ft but if shifting is good,the MPH will be higher.
Generally a manually equipped car will turn a slightly better MPH than an auto do to a lighter trans to get power through it to the tires better or also better gear ratios in the trans itself. Also a manual car is more difficult to launch than an auto so ET is hurt in the first 60ft but if shifting is good,the MPH will be higher.
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Gear ratio affects it also.
I changed gear ratios, improved my ET, but trapped less MPH.
Basically, if your gear ratio puts you at the peak of your powerband near the end of the track, you'll be accellerating hard at that point, and get a good MPH, but your ET may suffer because you didn't get to use up the whole powerband in that gear.
I'm in the top of 3rd gear at the end of the 1/8th, the car is ready to shift, so I'm not making peak hp or pulling very hard, and it shows in the trap speed.
I changed gear ratios, improved my ET, but trapped less MPH.
Basically, if your gear ratio puts you at the peak of your powerband near the end of the track, you'll be accellerating hard at that point, and get a good MPH, but your ET may suffer because you didn't get to use up the whole powerband in that gear.
I'm in the top of 3rd gear at the end of the 1/8th, the car is ready to shift, so I'm not making peak hp or pulling very hard, and it shows in the trap speed.
Melting Slicks
Joined: Mar 2003
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From: Toronto ONTARIO
There are too many variables to mention.
one thing that is interesting to note is a 600 cc supersport bike would generally run high 10s to low 11s @ 124-128 mph. My corvette was running 13.0's @ 111.
But as stated above, generally et can be gained in so many ways when comparing the same car. picture 2 identical 1993 LT1s stone stock. One removes the front sway bar, installs drag shocks or the like, drm bars in the back, drag radials and numerous other mods that give ZERO hp gains. the same car would run the 1/4 guestimating .5 quicker.. but the mph would be the exact same.
Personally i could care less for et. I like to watch everyone run quicker than me and leave them scratching their heads
one thing that is interesting to note is a 600 cc supersport bike would generally run high 10s to low 11s @ 124-128 mph. My corvette was running 13.0's @ 111.
But as stated above, generally et can be gained in so many ways when comparing the same car. picture 2 identical 1993 LT1s stone stock. One removes the front sway bar, installs drag shocks or the like, drm bars in the back, drag radials and numerous other mods that give ZERO hp gains. the same car would run the 1/4 guestimating .5 quicker.. but the mph would be the exact same.
Personally i could care less for et. I like to watch everyone run quicker than me and leave them scratching their heads
Last edited by Mr Mojo; May 1, 2006 at 10:56 PM.
Thread Starter
Le Mans Master
Joined: Mar 2004
Posts: 5,107
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From: Dublin CA
My 85 has since gone through several upgrades, so I expect to do better this year. This will be my 4-5-6 + runs at the track. So you can see NO EXPERIENCE. This is a auto trans with what I believe is 3.07 gears. I just wasn't not pulling at the end of the track...I had reached the wall of the L98. If the cat was semi plugged that may have been part of the hold up. It will be interesting to see that happens this year.
It just seems confusing to have a lower time without the increase in MPH.
It just seems confusing to have a lower time without the increase in MPH.
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Elite Torch Red Member
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From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
Cental/South NJ Events Coordinator
CI 1-2-3-4-5-6-7-8-9-10-11-12 Vet
CI-II Burnout & Drag Champ
St. Jude Donor '03-'04-'05-'06-'07
Well, let me take this a little further based on the other replies.
My '93 completely factory stock ran a best of 13.37@102.
With 15 x 3.5 Weld wheels up front and 15 x 10 Weld wheels out back with drag radials, Corsa exhaust,2800 stall torque converter,3.45 gears(stock is 2.59), no front swaybar, no spare or carrier, the car went 12.50@108. A gain of 6 mph and a reduction of almost 9 tenths.
The only power gain may have come from having teh Corsa, though that didn't make a difference on my '95 and I doubt it made a difference here, the biggest gain came from the torque converter and gear swap.
They don't increase power, but they definitely put it to better use.
The engine is still completely 100% stock.
My '93 completely factory stock ran a best of 13.37@102.
With 15 x 3.5 Weld wheels up front and 15 x 10 Weld wheels out back with drag radials, Corsa exhaust,2800 stall torque converter,3.45 gears(stock is 2.59), no front swaybar, no spare or carrier, the car went 12.50@108. A gain of 6 mph and a reduction of almost 9 tenths.
The only power gain may have come from having teh Corsa, though that didn't make a difference on my '95 and I doubt it made a difference here, the biggest gain came from the torque converter and gear swap.
They don't increase power, but they definitely put it to better use.
The engine is still completely 100% stock.
Race Director
Joined: Oct 2001
Posts: 19,653
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From: Melbourne Florida
Cruise-In IV Veteran
As said above, MPH is an indication of the HP you are making while E.T. is an indication of how well you put that HP to the track...
My car ran a 13.41@104.98 with a stock motor, street tires and a few bolt on's...I put in a Dana 44 with 3:73's, 3200 stall converter, full race shift kit and drag radials...I went 13.18@102.94 three months ago...
None of the mods added any HP but they did lower my 60' time to 1.79 resulting in the lower E.T.....my MPH would have been about the same as before but I had a hiccup at about the 1000' mark due to the computer locking up the converter (since reprogrammed)...
My car ran a 13.41@104.98 with a stock motor, street tires and a few bolt on's...I put in a Dana 44 with 3:73's, 3200 stall converter, full race shift kit and drag radials...I went 13.18@102.94 three months ago...
None of the mods added any HP but they did lower my 60' time to 1.79 resulting in the lower E.T.....my MPH would have been about the same as before but I had a hiccup at about the 1000' mark due to the computer locking up the converter (since reprogrammed)...
Team Owner
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From: altered state
St. Jude Donor '05
I dont understand how people can say "my car ran XX in the 1/8", so it should run XX in the 1/4"...Some make no power in the last 1/8, some run like raped apes. Impossible to tell unless you run down the track unles theres some magical formula to fiure it out according to torque curves.
Melting Slicks
Joined: May 2001
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From: Raleigh, NC
Imagine a car spinning the tires for the first 100 feet of the track. All that imaginary driver has done is shorten the track by 100 feet. He has 100 less feet to accelerate now. How much MPH do you think the imaginary car would gain in the last 100 feet of the track? Not much, especially considering that the MPH displayed at the track is the average speed you were travelling the last 66 feet of track.
Picture the same car dead hooking at the line. Instead of spinning that first 100 feet, he is accelerating. He will gain that 100 feet of track to accelerate, but again, how much MPH is there to gain in the last 100 feet of track? Not much.
That is why people say that MPH is a good indicator of power, while ET is indicative of traction.
Another way to look at it is like this: If you run a 15.00 second ET and trap 100 MPH, you have had 15 seconds to acellerate to your trap speed of 100. If you run a 14 second ET, your car is accelerating for less time, and has less time to build MPH.
A higher MPH when spinning is due to the slingshot effect the tires have when they slow to match vehicle speed.
Picture the same car dead hooking at the line. Instead of spinning that first 100 feet, he is accelerating. He will gain that 100 feet of track to accelerate, but again, how much MPH is there to gain in the last 100 feet of track? Not much.
That is why people say that MPH is a good indicator of power, while ET is indicative of traction.
Another way to look at it is like this: If you run a 15.00 second ET and trap 100 MPH, you have had 15 seconds to acellerate to your trap speed of 100. If you run a 14 second ET, your car is accelerating for less time, and has less time to build MPH.
A higher MPH when spinning is due to the slingshot effect the tires have when they slow to match vehicle speed.
Race Director
Joined: Oct 2001
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From: Melbourne Florida
Cruise-In IV Veteran
Originally Posted by cuisinartvette
I dont understand how people can say "my car ran XX in the 1/8", so it should run XX in the 1/4"...Some make no power in the last 1/8, some run like raped apes. Impossible to tell unless you run down the track unles theres some magical formula to fiure it out according to torque curves.
Le Mans Master
Joined: Aug 2004
Posts: 5,141
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From: Metairie Louisiana
Originally Posted by neat
Imagine a car spinning the tires for the first 100 feet of the track. All that imaginary driver has done is shorten the track by 100 feet. He has 100 less feet to accelerate now. How much MPH do you think the imaginary car would gain in the last 100 feet of the track? Not much, especially considering that the MPH displayed at the track is the average speed you were travelling the last 66 feet of track.
Picture the same car dead hooking at the line. Instead of spinning that first 100 feet, he is accelerating. He will gain that 100 feet of track to accelerate, but again, how much MPH is there to gain in the last 100 feet of track? Not much.
That is why people say that MPH is a good indicator of power, while ET is indicative of traction.
Another way to look at it is like this: If you run a 15.00 second ET and trap 100 MPH, you have had 15 seconds to acellerate to your trap speed of 100. If you run a 14 second ET, your car is accelerating for less time, and has less time to build MPH.
A higher MPH when spinning is due to the slingshot effect the tires have when they slow to match vehicle speed.
Picture the same car dead hooking at the line. Instead of spinning that first 100 feet, he is accelerating. He will gain that 100 feet of track to accelerate, but again, how much MPH is there to gain in the last 100 feet of track? Not much.
That is why people say that MPH is a good indicator of power, while ET is indicative of traction.
Another way to look at it is like this: If you run a 15.00 second ET and trap 100 MPH, you have had 15 seconds to acellerate to your trap speed of 100. If you run a 14 second ET, your car is accelerating for less time, and has less time to build MPH.
A higher MPH when spinning is due to the slingshot effect the tires have when they slow to match vehicle speed.
Good explaination. Thats how I try to explain it in my own head too but you made it sound much better in writting. Now if I could only get that dead hook.
Safety Car
Joined: Dec 2004
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From: Poop land
Originally Posted by Fuzzy Dice
You are correct, they are just guessing in reality...there are formula's you can use to convert 1/8 to 1/4 but it's only a rough "idea"...my stock motor LT-1 can hang with or beat just about any stock vette for an 1/8 mile due to my set up...past that the C5 and 6's eat me up with their cheatin', from the factory, power...
Race Director
Joined: Dec 2002
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Originally Posted by Mr Mojo
The MPH is an indicator of the power you have, the ET is more like how you use that power.
I had it explained to me long ago that mph was most dependant upon power, and ET was most dependant on gearing. While I'm not sure I agree 100%, I do know that ET and MPH are rarely tied together inextricably.
Larry
code5coupe
Safety Car
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From: Poop land
You can see it when big 7000 lb turbo diesel trucks run 11.50s @ only 105 mph. The torque curve is pretty broad down low, e.g. 1400 ft-lbs @ 1400 rpms and only 350 hp @ 2200 rpms.
Now you can look at a 2300 lb 92-95 Honda Civic hatchback with a B18C5 swap and see them run 13.5 @ 105 mph. Their top end power is at the 8000 rpm range and torque curve is pretty peaky!
ET, mph, gearing, weight, traction... it gets only more complex from there. But in general, cars with a bunch of low end power will usually run good ETs and trap lower mphs. Its the exact opposite with a high revving engine making power up top. But its usually who finishes first.
Now you can look at a 2300 lb 92-95 Honda Civic hatchback with a B18C5 swap and see them run 13.5 @ 105 mph. Their top end power is at the 8000 rpm range and torque curve is pretty peaky!
ET, mph, gearing, weight, traction... it gets only more complex from there. But in general, cars with a bunch of low end power will usually run good ETs and trap lower mphs. Its the exact opposite with a high revving engine making power up top. But its usually who finishes first.
6th Gear
Joined: Apr 2006
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From: Old Orchard Beach Maine
"neat" has a good explanation. At the track, when you recieve your time slip, you read your times in feet. These are 60, 330, 660,1000, and 1320. you can also use your "split times" 60 to 330, 330 to 660, 660 to 1000 and 1000 to 1320. All the times indicate how you are ACCELERATING. If you are not accelerating you are coasting! Depending on your gears, this is how quickly you accelerate. We have been doing this a wile and I believe that an automatic trans will far out perform better and be more consistent than a standard. How you "stage" also playes a big part.
Team Owner
Joined: Jun 2001
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From: Orlando FL
St. Jude Donor '08-'09
Originally Posted by Fuzzy Dice
As said above, MPH is an indication of the HP you are making while E.T. is an indication of how well you put that HP to the track...