real 60's cars quarter mile times (GTR, best, race car, buying)
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I think there is a little misconception over the "spin" we are talking about. Obvisouly if you are spinning throughout the run or all over the track, then it will negatively impact everything. What we are really talking about is spin out of the hole versus getting a solid jump out of the hole.
To put it simply, your 60' with something like a 1.5 allows you to get a "jump" and cover that first 60' faster (time wise).
Whereas, with some wheelspin, you might not "jump" as far that first 60' allowing you more time to accelerate.
In practical terms we are talking only minor differences of maybe 1-2 mph when you look at a perfect launch versus one where there was some wheel spin.
Additionally spinning can act as a momentum storing action. When you are spinning and then hook, the car generally "snaps" forward. So, a car that gets perfect traction is accelerating in a linear fashion across a given distance. A car that spins is generally moving forward slowly and then "snaps" and gains traction. So, the spinning car may move 1' and be going 10 mph, where as it took the linear car with good traction 5' to reach 10 mph. The car with linear acceletation will cross the finish line first time wise, but the spinning car will cross it going faster (assuming everything about the cars is equal).
The two together is what gives you the higher trap in a spinning car. Basically a spinning car has more time to accelerate (even if just a little) than a car that dead hooks. I'm no physics major to explain WHY this is the case, but it is.
Excellent discussion. Let me ask you this....on a vehicle that trap speeds at 109 mph yet only gained a 12.61 1/4 mile time due to a 2.00 60 ft, what would you say could run in the 1/4 if the 60 ft. was reduced to 1.50 and everything else was the same?
Also the 12.61 was the best time; before it ran a 12.96 and a few lousy 13 second passes, the trap speed varied from 107-109 mph.
I'm thinking 12.2 but hoping an 11.8-11.9 could be doable.
Another way to look at why terminal speed is mostly independent of the first 60 feet - consider the same car, same driver making a full 1/4 mile run and then starting from the 60 foot line, ignoring the fact that the track is cleaner at the 60' mark - how much difference in terminal speed do you think that would create?
Terminal speed is essentially the kinetic energy built up by the car, based on the application of a certain level of horsepower (time rate of doing work) for a specific length of time (and the time is roughly 11 to 13 seconds for these street cars, it does not vary all that much)
DN, it's late in the day and while I did major in physics I am not a drag racing specialst - anyway I am thinking if you cut a half-second off your 60' time that would be a half second off the total ET, since the rest of the run would be essentially unchanged. Not at all certain this is correct - but look at it this way - 2 identical cars and one gets to 60' in 2, the other in 1.5 seconds - assuming past 60' neither car spins the tires, both weigh the same, same HP, same gearing - seems to me the runs would be identical and the quicker car would stay right at 0.5 second ahead of the other car.
Excellent discussion. Let me ask you this....on a vehicle that trap speeds at 109 mph yet only gained a 12.61 1/4 mile time due to a 2.00 60 ft, what would you say could run in the 1/4 if the 60 ft. was reduced to 1.50 and everything else was the same?
Also the 12.61 was the best time; before it ran a 12.96 and a few lousy 13 second passes, the trap speed varied from 107-109 mph.
I'm thinking 12.2 but hoping an 11.8-11.9 could be doable.
Generally every tenth of a second shaved off the 60' equals one and a half to two tenths off the ET. So if you got the magic 1.5 60' the car could theoretically run about an 11.6 - 12.0.
However there is a formula used that shows that there is a constant variable of between 1,300 and 1,400 where the max trap multiplied by best ET will equal 1,300 - 1,400. If we take the midline of 1,350 and divide by your 109 you get 12.38, which seems to be very reasonable to me, since you will most likely never get a 1.5 60'. As it is 12.38 represents about a 1.7 60', which is damn good.
Here is an old article that has floated around drag sites. It probably has more than you ever wanted to know:
Quote:
1) Trap Speed will tell you about your HP to weight.
2) ET will tell you more about traction and your launch.
Of course ET is important to true drag racers, because the winner is the one that gets there first. However, we're not necessarily true drag racers in our attempt to get a power estimate. Honestly, ask 10 guys at the track "What kind of trap speed are you running?" and 8 out of 10 will answer with their ET - to one or two decimal places even. When you say, "No, no, I meant trap speed", they will fumble with a broad estimate with NO decimal places and might even have to pull a time slip out of their pocket to check. Try this question when you're at the track; it's almost funny.
THE DYNAMICS OF TRAP SPEED VS. ET
After running lots of quarter miles, it becomes clear that how well you do in the first 100 feet of the track is KEY to a good time. The last half of the track is KEY to a good speed.
Imagine that the light turns green, the truck moves two feet and the [COLOR=blue !important][COLOR=blue !important]engine[/color][/color] dies for three seconds. After restarting the engine, the driver proceeds to then complete a perfect pass. His time slip would show 22.50 seconds at 69.97 mph. The ET was 3.00 seconds high but the speed was almost unaffected.. why?? It's because his racetrack was 1318 feet long instead of 1320, and in those last two feet this truck usually gains an additional 0.03 mph. However, the clocks recorded the long time. My point? Much of a great ET is made by a great launch.
Now take this [COLOR=blue !important][COLOR=blue !important]truck[/color][/color] again, and the driver leaves right on the green light. However, he misses the 3-4 shift when he's at 1250 feet. He coasts for the last 70 feet while trying to find fourth gear. Now instead of accelerating another few mph in this final 70 feet of the track, he decelerates over this distance. His timeslip; 19.51 at 67.83 mph. Note how the et is almost perfect (only off by 0.01 second) but the trap speed is way off (over 2 mph slow)! On a good run, traveling that last 70 feet at an average of 69 mph, would have taken .692 seconds. At a 68 mph avg., that 70 feet takes .682 seconds. That's why his ET only varied by .01 seconds, yet the trap speed was 'way off'. My point here: the end of the track is critical to trap speed; shift rpm, missing a gear... these are the big players.
Hopefully these examples are clear. Neither of these runs are 'perfect' runs, it's just that one has an error at the start, one at the finish and the results are obvious. The start of the track is a big player in the ET, but a small player in the mph. The end of the track is a big player in the mph, but a small player the ET.
So for the casual T-Bricks member who wants to get a HP value, you don't have to buy slicks, or wish you had a limited slip differential. You don't really need to heat the tires in the waterbox, or launch with huge power braking. As long as people get their shift rpm right and don't miss a gear, even a rookie will get the appropriate trap speed for their vehicle.. but honing the perfect ET. requires being rude to a clutch, buying steeper gears or slicks.... hey, we're trying to make this recreational.
OPTIMIZING SPEED
If your goal is to get a good trap speed, what are your options? More power, of course - and less weight is obvious (but it will come out in the power calculations as no increase in power). Shift rpm chosen (auto or manual) and the time it takes you to shift (with a manual) are probably the most important tools you've got. Try different shift points to maximize your trap speed. Reduce rolling resistance by pumping up all tires to their rated pressure. Some people think that running lower pressure might help the traction in the rear, though. Of course more traction will help et, but with most street tires, running street tires within 5 psi of rated pressure will provide you with maximum traction in the first place.
REACTION TIME
The ET clocks don't start until you've actually moved around 8 inches (this is called the rollout)... so don't worry about trying to leave right on the green light. You could wait 5 seconds after the light turned green, and still get a 19.50 timeslip in our truck example above. Your timeslip does show a separate calculated time, the "Reaction Time", which in this case would be 5 seconds. That is the time from the light turning green until you rolled out of the starting zone. It's not a big thing for our discussion here.
THE LAUNCH
For the most part, a decrease in ET is accompanied by an increase in trap speed, but don't go overboard on the launch in your zest to rule the world. Just try to get smartly underway without spinning the tires much at all. Traction levels usually drop a solid 0.10 g when the tires start spinning.
THE HP FORMULA
Here's the formula to use to calculate HP:
Net HP = Weight in pounds* (Speed in MPH/228.4)^3
As an example, [COLOR=blue !important][COLOR=blue !important]Car[/color][/color] & Driver tested the 744 Turbo in their June 1990 issue. The car weighed 3,081 lb. without the driver.. the 'race weight' was 3,231 lb. The car ran a 15.7 second quarter at 86 mph. Let's plug it in to the formula:
HP = 3231 * (86/228.4)^3
HP = 172 Net
Volvo rated this at 162 Net. We come out a little high. Or does Volvo underrate a little? I'll say this - I've used this formula for years and that's how the 228.4 was honed - actual experience from cars that had actual power curves - and when I use it on Volvos it tends to always come out a few percent higher than the factory rating. This could simply be that Volvo underrates just a little.
Still, for such a simple formula and such a simple test, it's surprising how accurate this can be. And the best thing is - there's no arguing the numbers on a timeslip. There are always differences between a DynoJet and an Eddy Current Dyno, or G-Tech numbers, but every setup is done by someone different and subject to error. The quarter mile is arguably the best comparison a diversely located group like Turbobricks will ever have. The only real difference to argue about is the altitude of the track! You can compare ET and mph all day and have a good discussion.
HANDY RULE OF THUMB
Once you have a baseline, you should probably use a rule of thumb that each additional 6 HP will give you another mph. That's for a 3200 lb car that runs 88 mph. If you want the real formula for different weights or speeds, here it is:
HP for another mph above "X" speed: = Wt * (((X+1)^3-X^3) / (228.4^3))
For instance a 89 mph quarter vs. an 88 mph quarter for a 3200 lb car:
HP delta = 3200 * ((89^3-88^3) / 228.4^3))
HP delta = 6.3 HP
Once you're going 110 in the quarter, it would take an additional 10 HP to go 111 mph in the 3200 lb car.
60 FOOT TIME
This is the standard measurement tool to evaluate your launch. It's the time that it took you to travel the first 60 feet of the track. Naturally, patterns emerge again after looking at lots of runs and of course these correlate best to time, not mph. Typically, most everyone's 60' time will be between 14% and 16% of their quarter mile time. If it's under 13% or over 17%, this was not your best pass.
1/8 MILE VS. 1/4 MILE
After monitoring tons of good passes, patterns emerge. Typically, the mph at the quarter is around 1.26 times of the mph at the eighth, and the time at the quarter is around 1.55 times the time at the eighth. You can use these values if you only have a 1/8 mile track and get a real good idea of the theoretical 1/4 mile.
IS MY ET TO SPEED RATIO REASONABLE?
One fact of the quarter mile is; no matter how slow or fast your car is, the mph multiplied by the ET will pretty much be the same number every time. Before the NHRA changed the way that speed is measured in 1989, the product of speed and time was around 1400. Let's calculate some easy examples of this. A 14.00 et usually resulted in a trap speed very near 100 mph. A 10.00 et meant around 140 mph. A 200 mph pass usually takes around 7.00 seconds. These are still good rules of thumb to remember, but now the product is more like 1380 for us - The example from [COLOR=blue !important][COLOR=blue !important]Car [COLOR=blue !important]and [/color][COLOR=blue !important]Driver[/color][/color][/color] above comes out at 1350. (The reason for this shift is explained below). Remember, most everyone focuses on ET so much that they'll even optimize a car for slower mph if it gets them a better ET. (Rear end gearing is one way to do this). Those guys tend to have a product closer to 1300.
RESPECT MORE SPEED - A LOT. EVEN 3 MPH.
If you look at the formula again, you'll note how trap speed shows up as the cube root of power to weight. That's critical to understanding how fast one car is over another. Let's say your car does a 90 mph quarter and the guy who raced you in the other lane ran 71 mph. After the race, he wanders over to you to say the 'race was close'. Your reply: "I could have towed you and still smote you". (This might not be the best way to make friends, but yes, it is TRUE if the cars weigh the same.)
Do the math. (90/71) cubed is 2.04. Yes, the 90 mph car has 2.04 times the power to weight of the slower car. It has 2.04 times the acceleration of the slower car. It's just that the track is a fixed length, and in accelerating to higher speeds, you use up the track quicker. You accelerated to 90 in about 20% less time than he had to accelerate to 71, right?
Bottom line; Down where most of us run, a 3 mph difference between two cars is NOT a race. It was a clear win. There's a full 10% difference between these cars.
SOME MAGAZINES SHOW THE CONSTANT AS 230.5 OR 234.0. WHERE DID YOU GET 228.4?
Some people try to correct to different things. Like Gross HP instead of Net. But most commonly, these other constants that you'll see in magazines were originally published before 1989 when the NHRA changed their lights, and the 'new' journalist doesn't realize the formula should change accordingly. Here's what I mean; previous to 1989, there were three timing lights at the end of the track; one AT the end of the quarter mile, and one 66 feet before, and one 66 feet after. The middle light was used to calculate the et of the run, and the time to travel the 132 feet at the end of the track was used to calculate the trap speed. This gave the average speed at the end of the track, but you can see what this lead to. Most of the racers stayed on the gas for an additional 66 feet past the quarter to get a consistent speed to evaluate their setup. The track's 'shut down area' of course is a fixed length, but the pro racers were starting to hit 300 mph plus by the end. In an attempt to get these guys off the gas 66 feet earlier and 'make' the cars appear slower, the NHRA stopped using the last light around August of 1989. Today, the trap speed is calculated between the light at the quarter mile and the one 66 feet before. So any timeslip after 1989 is really giving the average speed 33 feet from the finish, which is pretty close to one percent slower than before. The old constant of 230.5 became 228.4 to compensate.
CORRECTING FOR ALTITUDE
If we were dealing with non-turbo cars, this would be easy and we'd publish a formula. But with pressurized cars, the correction factor for altitude depends on the boost you run.
For instance, Sea Level air pressure is 14.7 psi. If you go to a track in Boise, Idaho (2850 feet above sea level) the air pressure is now around 13.25 psi. That's 90.1% of sea level pressure. If the temperature doesn't change and you have an normally aspirated car, your power output will now be 90.1% of what it used to be, so I'd tell you to correct by multiplying your calculated HP by an extra 10.9% (1/.901, or 1.109).
However, (and this is the beauty of turbo cars!!) Let's say you were running 10 psi of boost in the first place. So at sea level, your car was really getting 24.7 psi (14.7 + 10). Now you leave the wastegate at 10 psi and race at Boise. Your manifold pressure is now 23.25 psi (13.25 + 10). Note that YOUR power isn't down as much.. it's down to 94.1% of what it is at sea level. So you should correct with an extra 6.2% (1/.941, or 1.062).
If you wish to calculate your own correction factor, here is a handy table of elevation (feet above sea level) vs. standard day atmospheric pressure (psi):
Yes, the detail oriented will notice that I'm ignoring lots of small effects of higher pressure ratios in the [COLOR=blue !important][COLOR=blue !important]compressor[/color][/color], lower density air across the intercooler and even the fact that there's less wind drag at higher altitudes, and they're right. However, the overall concepts above still hold true.
There's lots of discussion of 300, 400, even 450 HP on the Tubrobricks list. It would be great to see these power levels turn out to be true. Just keep in mind that an honest 300 Net HP in a 3200 lb Volvo (includes driver) will go just under 104 mph in the quarter. 400 HP would push it 114 mph, and 450 HP should propel the car to a trap speed of nearly 119 mph at Sea Level!
In terms of the ZO6, that makes for 19% less power at 5500' ASL (typical denver, there's a reason it's called the mile high city), so instead of 405 hp, they're making closer to 328 bhp.
If anyone else argues the point of how turbo cars are less affected by elevation than N/A cars without reading the exhausting long quote above, you are not only lazy... but an idiot as well.
bingo. I found the book I was looking for in the basement. Its a whole book of Car and drivers original musclecar tests from the 60's and 70's. Keep in mind that these cars were 'ringers' back in the day ad actually ran faster then what the public could buy.
so.. The fastest 'ringer' car ran 13.5 @105. About as fast as my 3800 lb convertible 281 cubic inch Mustang GT today runs..
I have most of those road tests, too... many from the original magazines. Also many from Motor Trend and Car Life.
Car and Driver did test some ringers, true, but not all of the above were ringers.
For instance, the '70 Duster 340. Car Life (which did not test ringers) also tested a '70 Duster 340 but with 3.23 gears. It ran 14.72 @ 94.24. Therefore, a Duster with 3.91 gears running 14.39 does not mean it's a "ringer." That is a very realistic time.
The Hemi Mopars were certainly capable of running mid-to-high 13s, with a good driver, the engine in tune and with decent traction. Not a "ringer," either. A Hemi, even slightly out of tune, would run a 1/2 second or more slower 1/4 mile time. But when tuned properly ran fantastic. 0-100 mph in the 12-13 second bracket (with '60s tires) was not uncommon.
As mentioned already, getting good traction was the biggest obstacle to overcome. It was not unusual for one to two seconds being wasted with wheelspin, which, of course, would really affect the 1/4 mile time.
Motor Trend (May, 1970) said this about their test '70 Hemi 'Cuda: "The Hemi had to be babied 'til it was well on its way down the strip." Doing that (also known as walking the car off the line) certainly is not the way to get the best 1/4 mile time but there was no choice. Use full throttle off the line and the e.t.s would be way off their potential.
Incidentally, did you forget to list the '66 427 Corvette (also tested by Car & Driver) which ran 12.8 @ 112 mph?
I have most of those road tests, too... many from the original magazines. Also many from Motor Trend and Car Life.
Car and Driver did test some ringers, true, but not all of the above were ringers.
For instance, the '70 Duster 340. Car Life (which did not test ringers) also tested a '70 Duster 340 but with 3.23 gears. It ran 14.72 @ 94.24. Therefore, a Duster with 3.91 gears running 14.39 does not mean it's a "ringer." That is a very realistic time.
The Hemi Mopars were certainly capable of running mid-to-high 13s, with a good driver, the engine in tune and with decent traction. Not a "ringer," either. A Hemi, even slightly out of tune, would run a 1/2 second or more slower 1/4 mile time. But when tuned properly ran fantastic. 0-100 mph in the 12-13 second bracket (with '60s tires) was not uncommon.
As mentioned already, getting good traction was the biggest obstacle to overcome. It was not unusual for one to two seconds being wasted with wheelspin, which, of course, would really affect the 1/4 mile time.
Motor Trend (May, 1970) said this about their test '70 Hemi 'Cuda: "The Hemi had to be babied 'til it was well on its way down the strip." Doing that (also known as walking the car off the line) certainly is not the way to get the best 1/4 mile time but there was no choice. Use full throttle off the line and the e.t.s would be way off their potential.
Incidentally, did you forget to list the '66 427 Corvette (also tested by Car & Driver) which ran 12.8 @ 112 mph?
very true. All these cars were not ringers. The elusive 12 second Vette was not in this book I have. Probably C&D knew the times were bogus. How can a tri power 435 hp 427 Vette run a 106 in 69 and the 66 version run 6 mph faster with thinner 7.75 tires? Impossible. C&D knew it and did not reproduce it.
M3 and goat hit the nail on the head. Great info guys!
DN- my experience tells me a 109 trapping car with perfect traction is a low 12 car. Hard to get into the 11's with only a 109 speed. Also a 1.50 short time is pretty difficult with just a tire change .. you would need other suspension and a tighter converter work too with an automatic.. unless you have a manual trans car and leave the line at 6000 rpm
I think there is a little misconception over the "spin" we are talking about. Obvisouly if you are spinning throughout the run or all over the track, then it will negatively impact everything. What we are really talking about is spin out of the hole versus getting a solid jump out of the hole.
To put it simply, your 60' with something like a 1.5 allows you to get a "jump" and cover that first 60' faster (time wise).
Whereas, with some wheelspin, you might not "jump" as far that first 60' allowing you more time to accelerate.
In practical terms we are talking only minor differences of maybe 1-2 mph when you look at a perfect launch versus one where there was some wheel spin. Additionally spinning can act as a momentum storing action. When you are spinning and then hook, the car generally "snaps" forward. So, a car that gets perfect traction is accelerating in a linear fashion across a given distance. A car that spins is generally moving forward slowly and then "snaps" and gains traction. So, the spinning car may move 1' and be going 10 mph, where as it took the linear car with good traction 5' to reach 10 mph. The car with linear acceletation will cross the finish line first time wise, but the spinning car will cross it going faster (assuming everything about the cars is equal).
No misconception here. I understand we're only talking about some momentary spin off the line.
But I'm still not buying into wheelspin directly causing both slower ETs and faster trap speeds in the same car. There's gotta be something else going on....like different driver actions....for this to be the case. Because after all, the slower time means a slower average speed and we know that it results from a lower speed in the very beginning of the run.
So for the "spinning" car to achieve a higher trap speed, it means that it must accelerate faster over a shorter portion of the 1/4 mile than that very same car accelerates without initial spin. Why would it - all things being equal? Makes no sense and, since I've read the same kind of comment on multiple other forums, I'm wondering if I've stumbled upon an Internet myth here.
Last edited by CrownVic95; 11-02-2010 at 06:47 AM..
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someones gotta teach these kids 
