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Discussion Starter #1 (Edited)
Yesterday’s planned gathering of C5ers and Z06ers at Cecil County Dragway was rained out. But my racing buddy, Steve Row, called mid-morning today and we quickly decided to head out to Capitol Raceway in Crofton, Maryland. Not a very good track; gotta drive through, not around, the water; but heck I have a new set of BFG 315s on CCW 12"x17" wheels that I thought might bite even at Capitol. I was right.

Here are the best two runs:

60’ 1.8220
330’ 5.0751
660’ 7.7572
1000’ 10.0549
1320’ 12.0116
Trap: 116.0305

60’ 1.8234
330’ 5.0069
660’ 7.7017
1000’ 9.9955
1320’ 11.9476
Trap: not recorded, but I suspect it was around 116

Weather was 53 degrees; humidity 47% barometer 30.24 for a DA of –151 feet
Only engine mod is a Halltech Tric with CF Cobra
Tires were BFG drag radials @ 18 psi

This was my last day of the season. Great way to finish.

I'll produce a jpeg of the time slips tomorrow. Can someone help me post it in the PDC?

Ranger

Late edit: finally figured out how to post a pic.

Here's the timeslip:
 

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Great times!

Given your hook factor of 1394, I would expect the mph to be 116.65. The Standard Day performance would be 12.065 sec @ 115.68 mph.

The DAs that you posted before and now don't compute for me. The conditions you quote produce a DA of -614 feet and an AD% of 101.8. I don't know what system you are using but that number is not density altitude. I have seen some weather station systems that use another number given in feet. I suspect that is what you have but I don't understand what it means.
 

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Congrats Ranger!!


Sorry I missed your last run. I knew you would bust into the 11 sec zone after seeing the 12.01 run.

Great Job!! Hopefully I'll be right behind you next year after mastering my launch technique, a good Cool Air Induction System and some Drag Radials.
 

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Nice times.

When do those strips close down? If I would have know about the planned event I would have tried to make it. MD isnt that far for the NVA crew. Would be great to meet up.


:cheers:
 

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Discussion Starter #7
Thanks Guys

Roger Ramjet said:
Great times!

The DAs that you posted before and now don't compute for me. The conditions you quote produce a DA of -614 feet and an AD% of 101.8. I don't know what system you are using but that number is not density altitude. I have seen some weather station systems that use another number given in feet. I suspect that is what you have but I don't understand what it means.
Thanks, Guys. And I'll appreciate the assist with posting the slip tomorrow, JC.

Roger Ramjet, Thanks for the help in calculating the notional trap speed.

The DA that I cited for my 12.145 run in Sept came from a TAG Wx station belonging to a fellow racer and the reading was at the time of my run.

The -151 DA that I cited for today's 11.95 was computed by the DA calculator at the GA F-body site using the actual wx conditions listed in my post:
http://rshelq.home.sprynet.com/calc_da.htm

Guess it's time to buy a TAG.
 

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Discussion Starter #8
Normjack, Sorry you missed it two. Was good to meet you. That was some good air. We'll meet up in the Spring and see your times continue to drop.


You and BADASSZ06 might want to consider Cecil County next Saturday. Test and tune on a well-prepped track. Mid 1.8s on stock tires. Gates open at 0800; racing starts at 0900. I'd be there but I'll be skiing.

Both you guys drop me an email and we'll put you on Steve Row's list for email notification of drag racing events in our area.

Ranger
 

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Discussion Starter #10
Burn-out of Drag-radials without a line-lock

I was asked via email to post some details on burn-out and launch. Here goes:

No claim that what I'm doing is the best. But it seems to be working for me.

Burn-out of drag radials without a linelock Back into the waterbox if possible and immediately spin the tires just enough to get a full rotation of them, but NOT enough to thrown much water up into the wheel wells. Roll forward out of the water. Make sure you're in COMPETITION DRIVING mode. Put the 6-speed in 2d gear. Drop the clutch and feed the throttle and quickly lightly apply the brakes with your left foot. Bring the revs to about 5000 until the tires smoke and start to grab. Release the brake and you'll roar forward. The tires are heated. I don't count seconds but just spin them until they grab hard.

The launch I am holding the launch rpm (last Saturday it was 3700-3900 on a poorly prepped track) and then quickly but smoothly releasing the clutch with a full engage occurring over the first 4-10' of movement. I try not to feed it more throttle until I think the tires are hooked; this is the hardest part for me. There is a delicate balance to find. But as PowerShifter has written, it entails trying to squeeze the throttle progressively to the floor between 10-25 foot off the lights. The drag radials will take throttle a little quicker than the stock tires but it's still a "squeezing" action rather that just "stomping it." I should also say that I frequently practice launching on the road in front of my office. Keeps the guards amused, I'm sure, as they are car nuts.

Ranger
 

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Density Altitude

Ranger said:

Roger Ramjet, Thanks for the help in calculating the notional trap speed.

The DA that I cited for my 12.145 run in Sept came from a TAG Wx station belonging to a fellow racer and the reading was at the time of my run.

The -151 DA that I cited for today's 11.95 was computed by the DA calculator at the GA F-body site using the actual wx conditions listed in my post:

http://rshelq.home.sprynet.com/calc_da.htm

Guess it's time to buy a TAG.
I went to the site you listed. I think I see the problem. To use that calculator, you must first have pressure altitude (PA). PA is what an altimeter shows when the reference pressure window is set to 29.92 in hg - Standard Day Conditions. You can estimate PA by using the local measured barometric pressure (not corrected to sea level). Subtract the local baro pressure from 29.92 and multiply x1000. Enter this number into the ref calc. Use 29.92 as the alt setting.

Notice I said 'estimate'. This method is not exact. Plus, that calculator doesn't compensate for humidiy (RH). The water vapor from the measured RH must be subtracted from the local observed baro pressure before you use their calc.

Sounds complicated! My suggestion for anyone who is serious about drag racing and/or dyno performance, get a weather station that provides HP correction factor, air density %, that will predict ET/MPH off of short times, correct times/speeds to Standard Day Conditions. Use only your instruments - readings varry between units. My choice is the Computech.
www.computechsys.com

OBTW - I don't think DA is of much value. It's a non linear representation of pressure expressed in feet. ????
I think HP correction factor and, therefore, AD% are much more useful and easier to understand.
 

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Re: Density Altitude

Roger Ramjet said:


I went to the site you listed. I think I see the problem. To use that calculator, you must first have pressure altitude (PA). PA is what an altimeter shows when the reference pressure window is set to 29.92 in hg - Standard Day Conditions. You can estimate PA by using the local measured barometric pressure (not corrected to sea level). Subtract the local baro pressure from 29.92 and multiply x1000. Enter this number into the ref calc. Use 29.92 as the alt setting.

Notice I said 'estimate'. This method is not exact. Plus, that calculator doesn't compensate for humidiy (RH). The water vapor from the measured RH must be subtracted from the local observed baro pressure before you use their calc.

Sounds complicated! My suggestion for anyone who is serious about drag racing and/or dyno performance, get a weather station that provides HP correction factor, air density %, that will predict ET/MPH off of short times, correct times/speeds to Standard Day Conditions. Use only your instruments - readings varry between units. My choice is the Computech.
www.computechsys.com

OBTW - I don't think DA is of much value. It's a non linear representation of pressure expressed in feet. ????
I think HP correction factor and, therefore, AD% are much more useful and easier to understand.
Roger some of "us"(me) have trouble just figuering out what runs to put in the station to get automatic predictions for et's that are beter than my own guess. Thanks for your post, I think I understand more clearly than I did. Ric
 

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Re: Density Altitude

PowerShifter said:
Roger some of "us"(me) have trouble just figuering out what runs to put in the station to get automatic predictions for et's that are beter than my own guess. Thanks for your post, I think I understand more clearly than I did. Ric
This is another point about the Computech setup. You can use the data base (slope, intercept) method of prediction or you can use the single run method. The single run method uses 1 good run, it can be a time trial or any run on a similar track surface, to predict an ET and MPH. A lot simpler!
 
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