dgdoc

Incorrect. The timing doesn't start until you move through the roll-out (typically 12 inches at most NHRA drag strips).

So, at the end of that first 12 inches, about 0.4 of time has elapsed and the car is going about 3-4 MPH -- and that's when the clock starts running.

TXPearl

Thanks - didn't realize the clock started on stage exit. By "shallow" stage, you mean barely past the first staging beam, correct?

grogan545

You are absolutely correct on this issue.It's not how long it takes to go 1 foot at 100 mph,but how long it takes to go 1 foot from a dead stop.I have set my GT2 timer for zero rollout and it increased my 60' times by .3 to.35 sec.All other times were also increased by the same amount.

grogan545

Actually 24000 miles,but it may as well be a million miles.Although the traction sucks on the goodyear RSA's I can't believe how well they are wearing.I still have at least 1/2 tread left at 24000.It appears they will go 45 to 50 thousand miles.Unbelievable considering how much I have mistreated them(many smokey starts).

How is your ankle doing Zman?I expected to see some more acceleration tests from you now that the weather is cooler.

octee

Well I haven't run the drag strip with the 545 yet but will let everyone know how that goes... the truck is another story...

Ahh.. the truck has a lot going on, that's for sure... let's see, intake, exhaust, chip(s), upgraded turbo (twins), and a full billet transmission to put the power to the ground.. it sure is fun!

znod

Hi gman:

My ankle is healing very well. I got the cast off about 1 1/2 weeks ago. I have been in a weight-bearing mode, with a boot on and crutches, since then. I am supposed to give up all devices except the boot on Friday. But, you know me, I am always ahead of schedule so I am walking without crutches or even a cane now --slowly, yes, but walking. Starting Friday I am supposed to do what I am doing now. Then, a week later I am supposed to move into a lace up brace. The timing is good since come Saturday we will be out of town until after the new year. Carlsbad CA for Xmas with family and Paris for New Years Eve and beyond. I was planning to do a pass the night I broke my ankle. And, it has been cool enough lately, but I have been taking sleeping pills to help me sleep since the fall (don't usually use sleeping pills), and I have not been in the mood to get up in the middle of the night to go do a pass.

And, for Octee and someone else above. Octee have you every told us what the truck turns? And, for the whoever who said to cool thoroughly between passes--well, right on. When I go out, I need to make my first pass my best one even though I drive slowly for 10 or 15 minutes between passes. I don't feel like doing proper cooling when I am out and about. So, my second pass is almost always worse than my first one.

dgdoc

Yup - And its suprising how few people know about this.

Car and Driver was one of the few magazines to document that they are using a 3MPH rollout -- which is close to what you'd get in a 14 second car with a 12" rollout. I posted this information on CorvetteForum a while back and some guy from the UK went crazy and started accusing all American car magazines of cheating... not realizing that the magazines were just trying to line things up with the times you'd get at the drag strip.

znod

Hummm. Below is the info I collected earlier (you supplied the CD info). Has CD changed since I started the Straight-Line Performance Discussion. From the discussion,

"I have posted the following magazine information before, but I am doing so again to facilitate as correct as possible comparison of our results with those of the big-three US auto magazines. CD adjusts only for weather and goes from a 5 MPH roll. RT uses aggressive (probably more aggressive than one normally would use on the street), yet not abusive, test procedures, a 1' rollout, and makes no altitude/weather adjustments. MT adjusts only for weather and uses a 1' roll out."

An issue we have never really addressed before is the issue of a rolling start versus a standing start. Have you ever noticed that rolling 5 MPH to 60 MPH typically is slower that 0 MPH to 60 MPH in one of the mags. I forget which mag frequently does 5 MPH to 60 MPH, in addition to 0 MPH to 60 MPH, and the former times always are relatively slow. I have never been able to reconcile this fact with the CD rolling start results--since they are very much like the 0 MPH to 60 MPH results of the other two big-3 US mags.

dgdoc

Not sure if CD changed since you started your post. But in their review of low cost accelerometers, they discussed how they measure performance and the importance of roll-out:

http://www.caranddriver.com/features/9381/...of-rollout.html

In your information above, all the car magazines are using roll-out in their calculations - which is required if you want to align your times with those at the drag strip.

As to your question about why 5-60 times are slower than 0-60, the answer is that a 5-60 test is done with the car in gear without the benefit of a proper launch. (i.e., no high-rpm clutch drops, brake-torqueing, etc.)

Hope this helps.

znod

Thanks for the info and trying to help with my question/issue. While not perfectly clear, I was not asking for an explanation of why rolling 5 to 60 is slower than 0 to 60 (see below). And, if you go here and here, then you will see that I understand the things you are talking about. As indicated, I think that you missed my question/issue. Here it is again:

"Have you ever noticed that rolling 5 MPH to 60 MPH typically is slower that 0 MPH to 60 MPH in one of the mags. I forget which mag frequently does 5 MPH to 60 MPH, in addition to 0 MPH to 60 MPH, and the former times always are relatively slow. I have never been able to reconcile this fact with the CD rolling start results--since they are very much like the 0 MPH to 60 MPH results of the other two big-3 US mags.

Don't you also think that the inability to reconcile the things I am talking about is odd?