I was digging through some old stuff, and I found an old time slip from my 69 SS 355.

13.10 @ 110.56

This is my recollection of the car:

69 SS coupe
355
186 heads, pocket ported, 2.02/1.6
Comp VDM (solid) .480/.480 290 adv, not sure of .050
Edelbrock Vic Jr.
Holley 700 DP
M-20
4.10 posi
Street tires

Question: It seems they used to measure trap speed differently back then. Can anyone shed some light on that? How would that equate to todays measurement method?

Thanks!

http://img20.photobucket.com/albums/v61/gort69/69%20Camaro/ss2.jpg

I'm not sure about "back in the day" but I think the trap speed nowadays is an average taken at the actuall 1/4mi and a little before.

I know I read that somewhere, but I can't remember. I don't think your MPH is too far off, depending on the car's weight, and elevation. Nonetheless, 13.10 at a buck-ten on street tires with a stick is impressive! graemlins/thumbsup.gif

currently it is calculated on the amount of time it takes from the 1000' mark to the 1320'

remember that sticks will always trap higher

remember that sticks will always trap higher Why is that?

Probably b/c there's no slippage loss b/c the motor is mechanically coupled to the drivetrain..

pdq67

Originally posted by fast:
currently it is calculated on the amount of time it takes from the 1000' mark to the 1320'

remember that sticks will always trap higher I was under the impression the modern speed was measured in the last 66 feet of the quarter.

http://mywebpages.comcast.net/dragrace/cdrt-dragracing.html

An old time slip will show a higher mph because the measurement was taken from 66 feet before to 66 feet after the finish line. You get an extra 66 feet to accelerate.

If you go to the NHRA record pages you'll find that the mph records for stick and auto cars are very close. A stick car doesn't necessarily mph better.

Onovakind67 nailed it. It used to be that mph was averaged from 66 feet before the finish line to 66 feet PAST the finish line. That's where the phrase "ran it out the back door" came from. Guys would pedal past the finish line all the way to the last mph lite to get the big mph.
When cars started getting real fast, shutdown became an issue, especially for the TF and Funnys. To discourage running it out the back door, NHRA dropped the last 66 feet and now average from 66 feet before the stripe to the stripe.

Randy

I read what I posted somewhere, could be wrong though, of course 320 ft is a long distance to use to calculate speed now that I think a bit more on it


manual trans cars trap higher because of less slippage as pdq stated, but also less parasitic loss and that translates into more hp hitting the pavement

The 1/4 mile m.p.h. is the last 66 feet of the track. 1/8 mile is the 66 feet before the 660 mark. The pre-stage lite and stage lite are 7 in apart, and the guard beam is 16 in. past that.
You are correct, back in the day m.p.h. timers went past the finish line, I will pull out one the old Brock Yates' American Cavacade shows from the 80's and see just how much past. A lot of people don't realize all the timers on a 1/4 mile track. You have the 60 ft.,330, 660, 660 mph,1000 ft, 1320 mph, and the 1320...finish line.
Mark

Along this same line, I have always wondered if the timing computer compensates for the lack of a second timer and computes what your actual mph would be at the finish line ? If not, the mph given on the time slip is actually your mph at 33 ft before the finish line.

with todays faster computers and what not, why can't they set up lights at the finish line just a few inches apart like at the starting line? that would give you a more accurate "true" top speed at the end of the quarter, compared to the time it takes to cover the last 66 feet. then, all of us with G-tech's would have more "correct" trap speeds on our meters.

How does the g-tech meter measure speed?

g tech's use an accelerometer, must use some calculus to figure speed, so they must record the acceleration and time, from there they calculate speed, me thinks anyway.

[ 02-09-2004, 01:41 PM: Message edited by: 72muchfun ]

Just thought I would post an update on this ... I spoke to Bob at Compulink today and he verified that the mph is an average over the last 66 ft of the track. That means that the mph you get on your time slip is a bit slower than you are actually going right at the finish line. He told me that the variance is about 1.1 mph for every 100 mph of speed. So if you get a time slip that says 100 mph, you were probably close to 101 at the finish line.
Hope this helps,