First time at track 1/8 mile
05-11-2009, 08:12 AM
#1
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First time at track 1/8 mile
I have a 95 T/A M6 that I got a couple months back. The only mods are a CAI, no cat, flowmaster exhaust, B&M short throw, and Nitto 555R drag radials. The races were just "heads up" and there wasn't a timer, however I was running a consistant speed of about 75 each time. Is there a converter to see about what I would be running in the 1/4? My first race was against a 2009 G8 GT that was brand new. (The dealer brought the car to drive) It still have the window sticker in it and the little foam things on the doors. I lost but it was actually a very close race. I am guessing that he didn't get a very good launch because he should have killed me. All in all it was a great time...except for the sunburn...
05-13-2009, 12:22 AM
#4
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Location: 51°N 114°W, 3500' elevation
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If geared properly so that if you do run a 1/4 mile, it will top out at or just before the 1/4 mile, I've always used 1.56 as the conversion number but again, it will only give you a rough estimate of the 1/4 mile ET. Too many variables affect the top end to give an exact number.
One of my timeslips near the end of last year has a 5.923 1/8 mile. 5.923 x 1.56 = 9.239 and I slowed down to a 9.433 probably to keep from breaking out.
In a flat out time trial run a month before, I did 5.994. 5.994 x 1.56 = 9.350 and I ran 9.393 for a much closer conversion.
Using 1.53 for a conversion is a much too generous number. Chances are, a street car will falter on the top end and a 1.57 or 1.58 conversion number may give a better conversion factor. It's unlikely that you will improve on the top end to get a number that the 1.53 conversion will give.
One of my timeslips near the end of last year has a 5.923 1/8 mile. 5.923 x 1.56 = 9.239 and I slowed down to a 9.433 probably to keep from breaking out.
In a flat out time trial run a month before, I did 5.994. 5.994 x 1.56 = 9.350 and I ran 9.393 for a much closer conversion.
Using 1.53 for a conversion is a much too generous number. Chances are, a street car will falter on the top end and a 1.57 or 1.58 conversion number may give a better conversion factor. It's unlikely that you will improve on the top end to get a number that the 1.53 conversion will give.
05-13-2009, 07:52 AM
#5
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since these races were not timed, and I am just going off of the MPH, is there any way to calculate that into a quarter mile time? I am just kind of curious as to about what it would run. Nearest 1/4 track is 3 hours from here one way.
05-13-2009, 02:23 PM
#8
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Using MPH, you can't get an accurate conversion for 1/4 mile from 1/8 mile. Many years ago when I was running a 383 SBC, I had 26" tall tires and 3.27 gears.
The gearing was all wrong since I was shifting into high gear somewhere between the 1/8 mile and 1000' mark. I don't have any timeslips that old but do know I was running 12.0 at 117 mph. That mph says I should have been running deep into the 11's and a 12.0 car should be somewhere in the 108-110 mph range. I don't think my 1/8 mile MPH was excessively high for my times but that car pulled hard on the top end as it was just getting into it's power curve by the 1000' mark.
If I was paired up against another 12.0 car in a heads up race, I'd be slow off the line and have to play catch up all the way down the track then blow past the opponent right at the finish. We could both run similar ET but MPH was greatly different. It was deceiving to race against me. At the 1000' mark I was still behind enough that it didn't look like I could catch the car except I was still accelerating faster than the other car and could catch up or pass the other car at the finish with big MPH.
Other cars can do very well in the first 1/8 mile building a high mph but don't accelerate as quickly at the top end and have a lower mph. ET is more consistent for a conversion than MPH is.
Dragstrip MPH is a calculated number. ET is the time it takes to break the beams as you go down the track. MPH uses 2 beams 60' apart. The time it takes to break the 2 beams is calculated by the distance and a MPH is calculated. Because of this, dragstrip MPH is not a true MPH since you're going faster exiting the beam 60' past the first beam where you're going slightly slower.
Think of it more in feet per second. If you're doing 100 mph, you're traveling 146.66 feet per second but on a dragstrip, you're not traveling at a constant speed. You're always accelerating. Depending how fast you're accelerating, your feet per second time will change. Over a distance of 60', that change may not be very much but it's still a change. During the first half of the track, you're going through gearing so you're getting torque multiplication and acceleration is quick. At the top end of the track, you're relying on HP since the torque curve has decreased and you don't accelerate as quickly.
Looking at one of my timeslips, I got up to 115 mph in the first 1/8 mile but the 1/4 mile speed is only 143. In the first 1/8 mile, I accelerated from a dead stop to 115 mph. In the last 1/8 mile I only increased my speed by an additional 28 mph. I was still going fast but the rate of increase has decreased drastically. That's why some people enjoy 1/8 mile racing. Everything happens in the first 1/8 mile. The last 1/8 mile is just a high gear, brute HP pull to the finish.
Even top fuel cars, when they still ran the full 1/4 mile, didn't accelerate as quickly at the top end. They would reach 280 mph in the first 1/8 but cross the 1/4 at 330. That's only an increase of an extra 50 mph.
Because the engine's powerband and diff gearing play so much in what the MPH will be, it's hard to do an 1/8 to 1/4 conversion. An all out drag car tops out at the 1/4 mile. Acceleration is slowing down as it crosses the finish line. A street car with highway gears would be very slow off the line and hopefully could get up to a decent speed by the 1/8 mile. As the engine builds up into it's power curve, the car can cross the finish line and still be accelerating faster since the engine hasn't topped out yet. The 1/4 mile mph would be faster for this car than a drag car that would run the same ET and be at the top end of it's power.
The only true way to know what your car will do in the 1/4 mile is to take it to a 1/4 mile track. Any conversion number you use to try and calculate a time or MPH will only get you a ballpark number. So many people think they have a 12 second car, or quicker, until they take it to the track to find out it really only runs 14's. Track elevation and weather conditions will also make an impact on the times. A 12 second car in Denver is a lot faster than a 12 second car in Florida.
The gearing was all wrong since I was shifting into high gear somewhere between the 1/8 mile and 1000' mark. I don't have any timeslips that old but do know I was running 12.0 at 117 mph. That mph says I should have been running deep into the 11's and a 12.0 car should be somewhere in the 108-110 mph range. I don't think my 1/8 mile MPH was excessively high for my times but that car pulled hard on the top end as it was just getting into it's power curve by the 1000' mark.
If I was paired up against another 12.0 car in a heads up race, I'd be slow off the line and have to play catch up all the way down the track then blow past the opponent right at the finish. We could both run similar ET but MPH was greatly different. It was deceiving to race against me. At the 1000' mark I was still behind enough that it didn't look like I could catch the car except I was still accelerating faster than the other car and could catch up or pass the other car at the finish with big MPH.
Other cars can do very well in the first 1/8 mile building a high mph but don't accelerate as quickly at the top end and have a lower mph. ET is more consistent for a conversion than MPH is.
Dragstrip MPH is a calculated number. ET is the time it takes to break the beams as you go down the track. MPH uses 2 beams 60' apart. The time it takes to break the 2 beams is calculated by the distance and a MPH is calculated. Because of this, dragstrip MPH is not a true MPH since you're going faster exiting the beam 60' past the first beam where you're going slightly slower.
Think of it more in feet per second. If you're doing 100 mph, you're traveling 146.66 feet per second but on a dragstrip, you're not traveling at a constant speed. You're always accelerating. Depending how fast you're accelerating, your feet per second time will change. Over a distance of 60', that change may not be very much but it's still a change. During the first half of the track, you're going through gearing so you're getting torque multiplication and acceleration is quick. At the top end of the track, you're relying on HP since the torque curve has decreased and you don't accelerate as quickly.
Looking at one of my timeslips, I got up to 115 mph in the first 1/8 mile but the 1/4 mile speed is only 143. In the first 1/8 mile, I accelerated from a dead stop to 115 mph. In the last 1/8 mile I only increased my speed by an additional 28 mph. I was still going fast but the rate of increase has decreased drastically. That's why some people enjoy 1/8 mile racing. Everything happens in the first 1/8 mile. The last 1/8 mile is just a high gear, brute HP pull to the finish.
Even top fuel cars, when they still ran the full 1/4 mile, didn't accelerate as quickly at the top end. They would reach 280 mph in the first 1/8 but cross the 1/4 at 330. That's only an increase of an extra 50 mph.
Because the engine's powerband and diff gearing play so much in what the MPH will be, it's hard to do an 1/8 to 1/4 conversion. An all out drag car tops out at the 1/4 mile. Acceleration is slowing down as it crosses the finish line. A street car with highway gears would be very slow off the line and hopefully could get up to a decent speed by the 1/8 mile. As the engine builds up into it's power curve, the car can cross the finish line and still be accelerating faster since the engine hasn't topped out yet. The 1/4 mile mph would be faster for this car than a drag car that would run the same ET and be at the top end of it's power.
The only true way to know what your car will do in the 1/4 mile is to take it to a 1/4 mile track. Any conversion number you use to try and calculate a time or MPH will only get you a ballpark number. So many people think they have a 12 second car, or quicker, until they take it to the track to find out it really only runs 14's. Track elevation and weather conditions will also make an impact on the times. A 12 second car in Denver is a lot faster than a 12 second car in Florida.
05-13-2009, 04:03 PM
#9
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Location: Fort Myers Florida
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.... I was running 12.0 at 117 mph. That mph says I should have been running deep into the 11's and a 12.0 car should be somewhere in the 108-110 mph range. I don't think my 1/8 mile MPH was excessively high for my times but that car pulled hard on the top end as it was just getting into it's power curve by the 1000' mark.
If I was paired up against another 12.0 car in a heads up race, I'd be slow off the line and have to play catch up all the way down the track then blow past the opponent right at the finish. We could both run similar ET but MPH was greatly different. It was deceiving to race against me. At the 1000' mark I was still behind enough that it didn't look like I could catch the car except I was still accelerating faster than the other car and could catch up or pass the other car at the finish with big MPH.
If I was paired up against another 12.0 car in a heads up race, I'd be slow off the line and have to play catch up all the way down the track then blow past the opponent right at the finish. We could both run similar ET but MPH was greatly different. It was deceiving to race against me. At the 1000' mark I was still behind enough that it didn't look like I could catch the car except I was still accelerating faster than the other car and could catch up or pass the other car at the finish with big MPH.
The mustang is simular but not so extreme 14.10's @101mph.
Bottom line for the thread is that it's almost impossible to predict times from just MPH. I think its time for you to make a day trip to the track.
Last edited by kazman; 05-13-2009 at 04:06 PM.
05-14-2009, 07:45 AM
#10
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it kind of seems that way. Maybe I will just make it a 2 day trip to the track. Driving 3 hours one way, then being in the car all day at the strip, then 3 hours back home in one day, would be a long time...haha
05-15-2009, 10:53 PM
#11
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Oops. I made a mistake and nobody noticed or mentioned it. The MPH lights are 66 feet in front of the 1/8 and 1/4 mile lights, not 60, but you still get the idea.
Kazman: You need more gear.
You'll also notice turbo cars have a different ET/MPH than a naturally aspirated car. They're typically slow off the line resulting in a slower ET but as the boost comes in, they make a huge top end charge and have big MPH.
If I wanted to throttle stop my car to slow it down, I could have the stop come on for a couple of seconds right after I launch. My ET would be back into the 10's but my MPH would stay roughly the same.
Travis: Next year that's what I have to do to race. Local track is being forced to shut down. Closest tracks are 2-1/2 and 3 hours away. Makes for a very long day.
Kazman: You need more gear.
You'll also notice turbo cars have a different ET/MPH than a naturally aspirated car. They're typically slow off the line resulting in a slower ET but as the boost comes in, they make a huge top end charge and have big MPH.
If I wanted to throttle stop my car to slow it down, I could have the stop come on for a couple of seconds right after I launch. My ET would be back into the 10's but my MPH would stay roughly the same.
Travis: Next year that's what I have to do to race. Local track is being forced to shut down. Closest tracks are 2-1/2 and 3 hours away. Makes for a very long day.
Last edited by Stephen 87 IROC; 05-15-2009 at 10:57 PM.
05-16-2009, 09:30 PM
#12
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Location: Fort Myers Florida
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Not really. 4.11's on a 27" rear tire. I run 12.0 @118 because I have an advantage bracket racing. I love racing a quicker ET'ing car that can't match my mph on the top end. Shifting at 7k instead of 5k gives me low 11 second ET's. It's all part of the bracket racing game.
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