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Author Topic:   60' vs. ET vs. MPH
Ryan Wilke
Gearhead

Posts: 2494
From: Stanton, Michigan 49707
Registered: Oct 2000

posted 01-14-2002 12:54 PM     Click Here to See the Profile for Ryan Wilke   Click Here to Email Ryan Wilke     Edit/Delete Message   Reply w/Quote
OK, guys - I've got another question on my learning curve:

I've 'heard' some of you comment that a person is having traction problems based on their 60 ft. times, 1/4 ET and MPH....

What would you say about these season AVERAGES:
60' time: 1.83
1/4 ET: 13.26
MPH: 103.1

The BEST PASS put down was:
60' time: 1.75
1/4 ET: 12.99
MPH: 104.7

There were a number of known tire-spinning passes and bad weather days figured into the AVERAGE numbers. However, I don't suspect traction or conditions were much of a problem on the BEST PASS..........

Does anyone have any guesses as to where I can find any more ETs in the 12's based on the above numbers?

Thanks, Ryan

P.S.
3280# car & driver, 306", 4spd, 4.56 gears to 9" ET streets.

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steve'66
Gearhead

Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000

posted 01-14-2002 01:49 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
I borrowed this from CDRA's site,


Analyzing your time slip

Are you getting the most benefit out of the drag strip time cards? If your track uses state of the art timing equipment like the "Compulink System", you are provided plenty of data. But how can you use this data? Most race tracks provide you with an elapsed time, trap speed and reaction time. But in 1988, most tracks started using multiple timers that provide 60 foot, 1/16 mile (330 ft.), 1/8 mile (660 ft.) and 1000-foot times also. The newer systems measure the trap speed differently from the old (pre-1988) systems. In the old (NHRA) system, a light beam was placed 60 feet in front of the finish line and 60 feet after the finish line. The computer would calculate your average speed through this 120 foot region. To get a true trap speed, you had to stay on the throttle until you cleared the last light.

Today, the trap speed is measured with two light beams only 60 feet apart. A light beam is placed 60 feet in front of the finish line and the finish line is the last beam.

Use the 60 foot, 660 foot and 1/4 mile elapsed times for evaluating each run. The 60-foot time is dependent upon traction, gearing, launch rpm and staging depth. It varies little with day-to-day horsepower changes. The 60-foot times can vary by .02 sec. during the evening and up to .15 sec. between a hot track and a cool track (with a leaf spring suspension and 10" tire) or as little as .03 all day on a car with 4-link and 14" tires).

The 1-2 shift occurs beyond the 60-foot mark and 2-3 shift occurs before the 660 foot (1/8 mile) point. If you subtract the 60-foot time from the 660-foot time, you will see how well your car is pulling through the gears. I call this the "1st-2nd" figure. The difference between 60-foot & 1/8 mile will be good indication of the proper shift points and whether you are operating in the proper torque range. This value with vary with amount of horsepower production, shifts or weather (headwind, barometer).

The 3rd gear pulls through the remaining 1/8 mile. Take the 1/4 mile elapsed time and subtract the 660 foot time. I call this calculation the "3rd" figure. This is a long pull showing brute horsepower which encounters variables like wind, density altitude (temperature, humidity and barometer) and aerodynamic drag. Changes in jetting, valve lash, ignition timing, etc. show up on this calculation.

The difference between the 1/4 mile ET and the 1/8 mile (660-foot) ET will vary greatly with a head or tailwind. Take calculations of this figure during time trials and compare to past races where there was no wind to figure out how much effect (in ET) the wind has on your car. Then if the wind dies down for first run, you'll know how much to lower your dialin, while everyone else breaks out.

Breaking these figures down into 60-foot, 1st-2nd, & 3rd encourages more research and development. Let's suppose you've increased the shift points by 200 rpm and you notice the ET dropped .05 sec. You think you're on the right track until you notice the 60-foot time went from 1.69 to 1.64 sec. Unfortunately, the .05 sec. was not the result of a changed shift point. It was due to a sudden "gain" in traction! The shift point had no effect! The 60-foot time is related to the tire's temperature and pressure. Cold tires which have not been run in a while need a lower pressure because the relative increase in pressure during burnout is greater with cold tires.

After enough smoke is off rear tires in water box and line lock is released, you have two choices for proceeding: (1) spin out of the water and continue up to the line or (2) Stop the car, roll forward and due two extra burnouts as approaching the line. Tire manufacturers frown on the extra burnouts. They say that the first launch will be the best after the waterbox.

The remaining part of the run after 60-foot time will closely follow the Density Altitude (D/A). The D/A makes only a fraction of a difference in the first 60-feet. Keep track of D/A for each run. With a common 60-foot time calculated for each, you should be able to predict your next run.

The most difficult time to pick a dial-in is during sundown because everything is changing. Keeping records from week to week will help iron this out. Here are some of the variables.

When the sun is going down, traction increases, due to the lack of direct sun rays, which reduces the 60-foot time.
Watch for the winds dying down at sundown. Lack of a strong headwind can make a doorslammer go .10 sec. faster!
Your reaction to the Christmas tree is different when in bright sun compared to a black background at night
The temperatures may fall 10 degrees F creating a lower density altitude and more horsepower
The cooler temperatures cause slicks to deflate by up to 1.5 psi.
A long delay before first round may allow the carburetor to cool which can change the response time of full throttle.
There are many variables involved in racing a car. When you are testing at the dragstrip, be on the lookout for anything causing a reduction of horsepower. You may need to optimize something else first. This is in response to changes made with jetting, timing, valve lash, staging depth, tire pressure, ladder bar adjustments, etc. If you experience several weeks of losing first round, you must review what you have been doing wrong.

Not enough concentration on third yellow bulb.
Need more attention to opponent's dialin and his expected speed capability. This is so you can figure out what to do, in case you are not in the lead at the end of the track.
Concentrate on expected 60-foot time. Compare with traction in similar round last week
Look at direct sunshine. A track which does not have direct sunshine will be stickier than one with sunny weather.
Concentrate on the density altitude and what times are expected in similar weather for proper dialin.


SteveW

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steve'66
Gearhead

Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000

posted 01-14-2002 03:24 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Ryan,

Getting consistant 60'ers with the et streets and a 4 speed is a challenge. We couldn't guarantee 12's every time out with Melissa's car w/ the 4 speed and it had a few more mph than you. The best 60'er for us was a 1.68, but somedays 1.8-1.95 were about it. A few more mph/h.p. would help you run it the 12's consistantly, and more traction would help too. Good luck!

SteveW

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badazzcougar
Gearhead

Posts: 132
From: Seattle
Registered: Oct 2001

posted 01-14-2002 07:38 PM     Click Here to See the Profile for badazzcougar   Click Here to Email badazzcougar     Edit/Delete Message   Reply w/Quote
OK heres a question Ive had for a while. Am I better off launching strictly off the throttle or power braking it a bit. I can only bring it up to 2200 rpm and expect the brakes to hold the rubber down . Am I losing more traction that way or by flashing the converter ? And when is the best time to launch? As soon as I perceive the third yellow is lit or what? I havent raced a whole lot on the drag strip but I think I'll be doing a bit more this year. but unfortunately our racing season is rather short due to ever present spring and winter rains

[This message has been edited by badazzcougar (edited 01-14-2002).]

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kid vishus
Gearhead

Posts: 6590
From: middle of NC
Registered: Oct 2000

posted 01-14-2002 08:05 PM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by badazzcougar:
And when is the best time to launch? As soon as I perceive the third yellow is lit or what?


I havent footbrake raced for yrs so I'll leave that for some one else better informed. But, you will have to experimnet as for the proper time to leave in your car. Depending on how quikly the car reacts, how fast it is, and a couple of other factors can really change the point from where you leave. An example, in my car, I have to wait till the last yellow is solid before I go, or else it goes red. When I raced the granada, and it was substantially slower, as soon as I saw color, I could go, (during the day, at night,, I had to wait a little).

Most good bracket races will tell you there are three stages (that they can see) to the yellow lighting up; coming on, on solid, going out. And depending on how their car reacts, they pick a spot in there to leave from.

Personally, I would leave in your car as soon as I saw any color in the last yellow. (and I would probably power brake it some too, that will help it react a little quicker)

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Just Strokin
Gearhead

Posts: 754
From: Tuscaloosa, Alabama
Registered: Dec 2001

posted 01-14-2002 08:06 PM     Click Here to See the Profile for Just Strokin   Click Here to Email Just Strokin     Edit/Delete Message   Reply w/Quote
Badazzcougar....the answer to your question has to do with the roll-out of your front tires (height, air pressure, etc) and how quickly your car reacts to nailing the gas peddle. Some cars are so slow on reaction, they can start to leave as soon as the 2nd light comes on or goes off.

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steve'66
Gearhead

Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000

posted 01-14-2002 08:22 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
It would have to be a real dog to leave on the 2nd yellow. Usually deep staging will allow even a tow vehicle to leave on the 3rd yellow.

SteveW

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I65Stang
Gearhead

Posts: 6575
From: Folsom, CA
Registered: Jun 99

posted 01-14-2002 08:23 PM     Click Here to See the Profile for I65Stang   Click Here to Email I65Stang     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by steve'66:
It would have to be a real dog to leave on the 2nd yellow. Usually deep staging will allow even a tow vehicle to leave on the 3rd yellow.

SteveW


Maybe I should try the 2nd yellow with the '88 .

------------------
Tim

M&M Member #35
1965 Mustang coupe, 200 I6, Holley 2300, Clifford header, true duals w/ 26" Smithys
1988 Mustang GT AOD vert, 15.810 @ 88.871 mph 100% stock w/ no traction
1976 Silverline Comoro 18' trihull ski boat, 188 hp 302 I/O, another toy
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https://mustangsandmore.com/ubb/I65Stang.html

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TomP
Gearhead

Posts: 6120
From: Delta BC Canada
Registered: Dec 99

posted 01-15-2002 01:32 AM     Click Here to See the Profile for TomP   Click Here to Email TomP     Edit/Delete Message   Reply w/Quote
depends on how hard you are hitting the tires too. Launching at a lower RPM doesn't always mean better traction. At a lower RPM you may be closer to the torque peak and make it spin worse. Further from the torque peak the power doesn't hit the chassis as hard and make it work.
On a stick car the clutch engagement is everything... too much clutch (spring pressure) will spin the tires no matter what size and compound. You can make it hook on small ET streets (or snow tires for that matter) by reducing the clutch grab. A couple ways to do this... one is to not release the pedal as fast, the other way is a metallic disc and weaker springs in the pressure plate.

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Moneymaker
Administrator

Posts: 27499
From: Lyons, IL, USA
Registered: May 99

posted 01-15-2002 01:28 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Test, test, test! Trial and error is your best teacher. Most stock cars respond to some amount of power braking.

------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
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