60', ET and Trap Relationship...?
09-06-2008, 12:48 PM
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60', ET and Trap Relationship...?
Can some one explain the relationship between ET and Trap? I have 2 conflicting answer about ET and Trap. I read somewhere that as you go faster (Lower ET) your trap will be lower, but some say as you lower your ET the trap gets higher. Also they say don't lower the tires pressure more than 5-10psi (Street Tires) of the recommended tire pressure else trap may suffer. My experience is that the more I cut my 60' and ET my Trap improved, maybe it was my improved shifting that raise my Trap
09-06-2008, 06:59 PM
#2
Too many variables for a definitive answer:
a. Gearing
b. Tire size
c. Shift points
d. Traction
e. Weather
f. Rolling resistance
On the left I (#141) am running 13.8 seconds at 104.1 MPH. On the right 13.6 seconds at 103.4 MPH. Better ET - worse trap speed.
Remember that the objective of drag racing is to cross the finish line first. Here is an example above. Had this been a competition race #369 wins. #151 has the better trap speed.
Here is another example above. The difference in ET is considerable. The difference in trap speed is only 4/100 MPH. Shouldn't the 11.93 second vehicle in the left lane trap considerably higher than the 12.80 second vehicle in the right? No not necessarily.
a. Gearing
b. Tire size
c. Shift points
d. Traction
e. Weather
f. Rolling resistance
On the left I (#141) am running 13.8 seconds at 104.1 MPH. On the right 13.6 seconds at 103.4 MPH. Better ET - worse trap speed.
Remember that the objective of drag racing is to cross the finish line first. Here is an example above. Had this been a competition race #369 wins. #151 has the better trap speed.
Here is another example above. The difference in ET is considerable. The difference in trap speed is only 4/100 MPH. Shouldn't the 11.93 second vehicle in the left lane trap considerably higher than the 12.80 second vehicle in the right? No not necessarily.
Last edited by davidv; 09-06-2008 at 07:15 PM.
09-06-2008, 08:29 PM
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I think rather then comparing so many different cars for this question though, you should just compare one. Your own. David, can you look through one day that you got a lot of passes in, (this way conditions dont change that much, so trap speed shouldnt change that much.) Compare those slips and see what you get for a conclusion.
09-06-2008, 08:35 PM
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yeah to many variable but assuming every other variable remain constant (ie gearing, DA, Shift Point..etc). Let say I have an Auto to eliminate the shifting error, and every other variable remain the same, all that changed is the 60' and ET. If I launch real hard and got a good traction wont that give me a good momentum? Wont that give me a good 1/8mph ET and Trap? So I have a huge momentum on the first half, wont that help me on my last half? I'm pretty new to drag racing.... lol
09-07-2008, 09:03 PM
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Refer to my post at you know where.
There are alot of variables involved. But I generalized it with the assumption that some of those variables are constant except for a few differences to make a point.
.
There are alot of variables involved. But I generalized it with the assumption that some of those variables are constant except for a few differences to make a point.
.
Last edited by skaterbasist; 09-07-2008 at 09:40 PM.
09-08-2008, 05:52 AM
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I found this.. I broke many of the rules like lowering my Street Tires to 20psi hence gearing changed, not shifting fast enough and lastly shifting around 6000rpm on 4th gear (My dyno start to drop power at 6100rpm but I could've just stayed there a little bit longer...)
So having a great momentum from the first half because of a great launch will not help? Isn't that Trap is a combination of your HP and weight? So in a short distance race then will that make a difference?
http://forums.stangnet.com/567417-tr...ined-here.html
So having a great momentum from the first half because of a great launch will not help? Isn't that Trap is a combination of your HP and weight? So in a short distance race then will that make a difference?
http://forums.stangnet.com/567417-tr...ined-here.html
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.
Let's use an example of a stick-shift mini-pickup that on a perfect run, gets a timeslip of 19.50 seconds at 70.00 mph in the quarter.
Imagine that the light turns green, the truck moves two feet and the engine 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 truck 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, Car & 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 Car and Driver 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.)
.
.
.
.
.
.
.
..
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.
Let's use an example of a stick-shift mini-pickup that on a perfect run, gets a timeslip of 19.50 seconds at 70.00 mph in the quarter.
Imagine that the light turns green, the truck moves two feet and the engine 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 truck 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, Car & 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 Car and Driver 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.)
.
.
.
.
.
.
.
..
Last edited by athenG; 09-08-2008 at 05:59 AM.
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09-08-2008, 07:54 AM
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I'm not sure where the old wives tale that your trap speed goes up when you spin your tires more care from, but it's total bunk in my experience and in that of all of my track buddies. The only thing I can think of is that you might get a better trap speed if you go spinning off the line than bogging off the line. But when it comes to getting off the line just right vs spinning a ton off the line, getting off the line just right is going to result in a higher trap speed. It will have to accelerating at a higher rate over a larger distance. That's simple physics, something that escapes a lot of drag racers who buy into and perpetuate these myths, it seems.
I was just discussing this with some local dude on a local board. He was saying how some other member had an artificially inflated trap speed because of his 2.58 60' time, and that the dude would have trapped lower if he'd gotten a decent launch like a 2.1 60' time (fwd car here). Completely ridiculous.
I was just discussing this with some local dude on a local board. He was saying how some other member had an artificially inflated trap speed because of his 2.58 60' time, and that the dude would have trapped lower if he'd gotten a decent launch like a 2.1 60' time (fwd car here). Completely ridiculous.
Last edited by Nealoc187; 09-08-2008 at 07:56 AM.
09-08-2008, 08:00 AM
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Originally Posted by Nealoc187
I'm not sure where the old wives tale that your trap speed goes up when you spin your tires more care from, but it's total bunk in my experience and in that of all of my track buddies. The only thing I can think of is that you might get a better trap speed if you go spinning off the line than bogging off the line. But when it comes to getting off the line just right vs spinning a ton off the line, getting off the line just right is going to result in a higher trap speed. It will have to accelerating at a higher rate over a larger distance. That's simple physics, something that escapes a lot of drag racers who buy into and perpetuate these myths, it seems.
That was my main question... does getting a great launch in this case better 60' will yield better trap assuming DA, shifting and gearing stay the same. Also the article didn't say that your trap goes up when you spin your tires.. as a matter of fact the article said you lose .10g whe you spin the tires.
09-08-2008, 10:03 AM
#10
Originally Posted by athenG
That was my main question... does getting a great launch in this case better 60' will yield better trap assuming DA, shifting and gearing stay the same. Also the article didn't say that your trap goes up when you spin your tires.. as a matter of fact the article said you lose .10g whe you spin the tires.
09-08-2008, 10:42 AM
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But we are talking about a limited distance and not just the time. Yes, if you give me 11sec to accelerate vs 10sec then 11 sec will give me more time to speed up hence higher MPH. But in a limited distance, if I have that great launch then I have a better momentum and velocity, so when I get to the end the point, in this case 1/4 mile distance, I'll be traveling much higher speed hence I got a lower ET. Also if you have a huge momentum in the first half because of that great launch (60') then wouldnt that help you on the last half too? I'm a noob in Drag so I'm just trying to understand the logic...lol
I know shifting and gearing play a more important role since if you are a slow shifter then you are pretty much loosing momentum or just cruising which will hurt you coz you only have a small distance left to recover that lost of momentum.
Edit..
Isn't that the formula for speed is S = d / t, so if you decrease the time and the distance remain constant then the speed goes up.
let
D = 1320Feet (1/4 mile)
T = 13 Sec.
1320/13 = 101.53
Now Let
D = 1320Feet
T = 12 Sec
1320/12 = 110
I know 1/4 mile Trap Speed don't measure the entire distance of the race so this doesn't apply really apply to 1/4 milet trap speed.... I just don't get it why the trap will decrease as you decrease your ET. I can see it increasing or staying the same ...
I know shifting and gearing play a more important role since if you are a slow shifter then you are pretty much loosing momentum or just cruising which will hurt you coz you only have a small distance left to recover that lost of momentum.
Edit..
Isn't that the formula for speed is S = d / t, so if you decrease the time and the distance remain constant then the speed goes up.
let
D = 1320Feet (1/4 mile)
T = 13 Sec.
1320/13 = 101.53
Now Let
D = 1320Feet
T = 12 Sec
1320/12 = 110
I know 1/4 mile Trap Speed don't measure the entire distance of the race so this doesn't apply really apply to 1/4 milet trap speed.... I just don't get it why the trap will decrease as you decrease your ET. I can see it increasing or staying the same ...
Last edited by athenG; 09-08-2008 at 01:06 PM.
09-08-2008, 07:08 PM
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Originally Posted by scotts300
A better 60' will result in a better ET with all else held constant, and a lower trap. Some say each 1/10s in 60' = 2/10s of ET, which is a decent rule-of-thumb that certainly is car-type dependent. Leaving physics and all the technical aspect out of it, if I give you 11s to accelerate vs 10s to accelerate, which amount of time do you think you can go faster in (i.e. you'll have 1s extra to keep WOT)? Lower ET equals lower trap with all else held constant.
double post
Last edited by Nealoc187; 09-08-2008 at 07:10 PM.
09-08-2008, 07:10 PM
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Originally Posted by scotts300
A better 60' will result in a better ET with all else held constant, and a lower trap. Some say each 1/10s in 60' = 2/10s of ET, which is a decent rule-of-thumb that certainly is car-type dependent. Leaving physics and all the technical aspect out of it, if I give you 11s to accelerate vs 10s to accelerate, which amount of time do you think you can go faster in (i.e. you'll have 1s extra to keep WOT)? Lower ET equals lower trap with all else held constant.
By your example we could put tiny tires on our car, spin for the entire 1/4 mile and take 18 seconds to complete the 1/4 mile, and be going faster through the traps than if we had the traction to run 10s. That is NOT how acceleration over a fixed distance works.
Accelerating at the greatest average rate over a fixed distance is what gives the highest speed at the end, not accelerating at a less than optimal average rate over a fixed distance but for a longer period of time.
This is exactly the type of perpetuation of this old wives tale that I'm talking about and it's absolutely, completely, and patently false.
Last edited by Nealoc187; 09-08-2008 at 07:15 PM.
09-08-2008, 07:16 PM
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Originally Posted by athenG
That was my main question... does getting a great launch in this case better 60' will yield better trap assuming DA, shifting and gearing stay the same. Also the article didn't say that your trap goes up when you spin your tires.. as a matter of fact the article said you lose .10g whe you spin the tires.
I know that this article was correct - and I'm agreeing with you and this article. I'm just talking about all the guys that say "oh you trapped so high because you spun your tires." Those guys are completely incorrect.
09-10-2008, 10:02 AM
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Originally Posted by Nealoc187
I was just discussing this with some local dude on a local board. He was saying how some other member had an artificially inflated trap speed because of his 2.58 60' time, and that the dude would have trapped lower if he'd gotten a decent launch like a 2.1 60' time (fwd car here). Completely ridiculous.
10-31-2008, 05:53 PM
#16
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Bump... Any more?
I still see a lot of people post here and even other forum that cutting 60' will reduce trap.. Like what have been discussed here I still dont see any evidence why cutting 60' will reduce trap assuming gearing/shifting/DA remain constant..
I went to the track a couple of weeks ago and got this result with my heavy Work VSXX 19's and 285 KDW... Couldnt get any traction..
60 - 2.421 <--- horrible 60' (PowerShifted from 2nd-3rd)
330 - 6.078
1/8 - 8.960
1/8 trap - 87.15mph
1000 - 11.40
1/4 - 13.43
1/4 trap- 111.69mph
60 - 2.336 <---- Straight speedshift
330 - 6.029
1/8 - 8.913
1/8 trap - 86.16mph
1000 - 11.38
1/4 - 13.430
1/4 trap- 111.01mph
Now before people start jumping on lower 60' worst trap.. I trapped higher on my first run with higher 60' but that is because I PowerShifted from 2nd-3rd (I have logs for both run to prove it..). If I powershifted on my second run then I'm pretty sure the trap would've been higher too. I might also go back again next week and this time I'll use a much lighter wheels... My 19's + tires weight close to 60lbs each..
I still see a lot of people post here and even other forum that cutting 60' will reduce trap.. Like what have been discussed here I still dont see any evidence why cutting 60' will reduce trap assuming gearing/shifting/DA remain constant..
I went to the track a couple of weeks ago and got this result with my heavy Work VSXX 19's and 285 KDW... Couldnt get any traction..
60 - 2.421 <--- horrible 60' (PowerShifted from 2nd-3rd)
330 - 6.078
1/8 - 8.960
1/8 trap - 87.15mph
1000 - 11.40
1/4 - 13.43
1/4 trap- 111.69mph
60 - 2.336 <---- Straight speedshift
330 - 6.029
1/8 - 8.913
1/8 trap - 86.16mph
1000 - 11.38
1/4 - 13.430
1/4 trap- 111.01mph
Now before people start jumping on lower 60' worst trap.. I trapped higher on my first run with higher 60' but that is because I PowerShifted from 2nd-3rd (I have logs for both run to prove it..). If I powershifted on my second run then I'm pretty sure the trap would've been higher too. I might also go back again next week and this time I'll use a much lighter wheels... My 19's + tires weight close to 60lbs each..
Last edited by athenG; 10-31-2008 at 06:01 PM.
10-31-2008, 06:04 PM
#17
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60' means everything everthing everthing.
My car with low mid 500rwhp on a 2.5 60' goes 13.1-13.5@117 (sitting on the rev limiter in 4th before finish)
117mph is good for low 12's or hi 11's (high 11's on a slick with great 60')
hopefully I'll see tomorrow exactly what a 2.0 or less 60 will yield but assuming every 0.1@ the 60' equates to 0.2 at the big end (and in my case it will be even more time due to bogging in 1st and 3rd) I am looking at big gains dropping from 2.5 to 2.0 60'
Its hard though. I have no problem saying I can't launch this car lol.....mainly a fear of breaking something lol..tomorrow I'll man-up though and get it done
Tom
My car with low mid 500rwhp on a 2.5 60' goes 13.1-13.5@117 (sitting on the rev limiter in 4th before finish)
117mph is good for low 12's or hi 11's (high 11's on a slick with great 60')
hopefully I'll see tomorrow exactly what a 2.0 or less 60 will yield but assuming every 0.1@ the 60' equates to 0.2 at the big end (and in my case it will be even more time due to bogging in 1st and 3rd) I am looking at big gains dropping from 2.5 to 2.0 60'
Its hard though. I have no problem saying I can't launch this car lol.....mainly a fear of breaking something lol..tomorrow I'll man-up though and get it done
Tom
10-31-2008, 06:09 PM
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Yes 60' is everything on ET but I'm trying to find out how 60' affect Trap Speed. In your case it is foolish to run street tires with that power, I have much much much less power and traction is a problem already on street tires but only on 1st gear.
Please give me an update on your run.. I know DA is different from your last run but if these people are correct then your Trap should be much lower than 117 if you improve your 60' to 2.0 or lower....
Please give me an update on your run.. I know DA is different from your last run but if these people are correct then your Trap should be much lower than 117 if you improve your 60' to 2.0 or lower....
Last edited by athenG; 10-31-2008 at 06:13 PM.
10-31-2008, 06:16 PM
#19
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thats where 60' and trap are a catch-22
I'll be improving so much accellerating early from not bogging in 1st and 3rd, that I'll be going much faster much sooner...its also inherit in stick shift turbo cars.
But I'll let ya know
Tom
I'll be improving so much accellerating early from not bogging in 1st and 3rd, that I'll be going much faster much sooner...its also inherit in stick shift turbo cars.
But I'll let ya know
Tom
Yes 60' is everything on ET but I'm trying to find out how 60' affect Trap Speed. In your case it is foolish to run street tires with that power, I have much much much less power and traction is a problem already on street tires but only on 1st gear.
Please give me an update on your run.. I know DA is different from your last run but if these people are correct then your Trap should be much lower than 117 if you improve your 60' to 2.0 or lower....
Please give me an update on your run.. I know DA is different from your last run but if these people are correct then your Trap should be much lower than 117 if you improve your 60' to 2.0 or lower....