Can anyone explain....

When I stage my car there are 2 staging lights..

it seems depending on where my tires stage my MPH is way different at the end on a simular run.

For example, if I nudge up and stage the 1st light then I nudge up and get the 2nd light, it seems my MPH is high but my R/T is higher too like .800's, but if I pass the 2ng stage light then back up to light it, I am nailing .500's R/T but my MPH is like 1-2 MPH slower. I am wondering is this a flaw in the drag racing system? How can a couple of inches affect my trap speed? the R/T part I understand..

Does any of this make sense? If so, whats a good rule of thumb for staging lights?

-Bat

P.S. my best time so far is:
13.0@108 2.0' .588RT
I know my car can easily hit the 12's I just need more practice racing. Since I got my car and started modifying it I've only done 4 runs at the track so far. I'm anxious to become a better drag racer I just wish the track was closer.

 

It shouldn't. Your trap speed is measured by timing lights at the end of the track. It's the average of the last 60 ft of the track I believe. Starting forward or back a few inches should not noticably effect your trap speed.

 

BTW, the rule on sig lengths here is 5 lines. Yours is over 25! <img src="gr_eek2.gif" border="0"> Please trim it down. If you want to tell us every single option your car has and your dog's name too, please make a website with that info and put a link to it in your sig.

Welcome to the board and thanks for your understanding. <img src="gr_stretch.gif" border="0">

 

5 lines! Damn I guess I should read the rules too! <img src="graemlins/gr_devil.gif" border="0" alt="[devil]" />

 

1-2 MPH is a lot, and likely more of a coincidence than anything else. However, what you are talking about is related to something called 'roll out', and is affected by how 'deep' or 'shallow' you stage. It essentially works like this...

First, it doesn't really matter how you light the re-stage light. If you just barely turn on the staged light (2nd light) by bumping in very, very slowly and stopping as soon as it starts to flicker on, then you are shallow staged. When shallow staged, you actually get an extra few inches of rolling start (roll out) before you move far enough forward for the staged light to go out, and thus start the timers. A few inches may not sound like a lot, but it can be a few hundreths of ET at the big end, and a little bit of MPH too. Shallow staging will most certainly affect your R/T, and everything else being equal (ie, you don't change your routine), R/T's will get worse. Of course, you can change your routine somewhat to compensate.

The opposite of this is called deep staging, or just staging deeper than what I described. If you continue to pull forward slightly when the staged bulb is lit, you will reduce rollout, which will give you slightly slower ET/MPH, and possibly better R/T's.

Deep staging is actually pulling forward far enough to turn off the pre-staged bulb. This will significantly reduce R/T's, possibly enough to redlight. It's used a lot by 'heads-up' racers that run on a Pro Tree, and also by cars that react slow on a full tree. Deep staging will produce noticeably slower ET/MPH.

So for best ET, get pre-staged, and then bump it in as carefully as you can, until the staged bulb just barely comes on. Forget about R/T, just go for your best launch. You've got a 12 second car there - easily - just get some practice and you'll get it. <img src="gr_stretch.gif" border="0">

Hope this helps, and good luck to you.

 

Good information Bob thanks!
I had it backwards all this time LOL!
Cheers,
Chris

 

Excellent write-up Bob! Shallow staging vs. deep staging will definitely play a role in your RT and MPH. When you stage shallow, you have more distance between your front tire and when you clear the "stage" beams. Considering it more of a running start, so to speak. When you stage deep, you have less distance before you clear the stage beams, therefore less of a running start. Staging shallow allows you more distance to build speed before the clocks are triggered by your front tires clearing the stage beams (2nd set of bulbs). This is why your RT is quicker, your ET is lower, and your MPH is higher. I bracket raced a '67 Chevy II w/ full electronics (delay box, trans brake, etc.) from '97 through '01, and I would consistently see .07 and 1.5 MPH in the 1/4 from shallow vs. deep staging. I also raced at tracks that ran a .500 full tree and a .400 pro tree. When running the .500 full tree, I would stage shallow and adjust my delay box accordingly (depending on the track, roll out, night or day, etc.). However, when I was running a .400 pro tree, I would stage deep to still allow for a good RT and not use the delay. The .1 difference between the yellow and green light on the .400 pro tree makes a big difference.

 

Thanks Bob!

This was exactly what I was looking for.

Last night I got to the track at 7pm it took 1-1/2 hours to get through tech. It was like waiting in line at an amusement park. There was probably close to 400 cars. I got my first run of the night at 9:15pm and my 2nd run at 11:15pm, we almost didn't get a 2nd run because the track closes at 11.

I'm thinking about getting to the track on Sunday for the Outlaw drag day, its usually not that busy.I don't get a time slip and all but I can get in some more practice runs, I am definately going back for test and tune next Wednesday night.

Thanks again.

-Bat

[ February 21, 2002: Message edited by: TheBat ]</p>

 

I propose that shortening the track (which is exactly what deep staging does of course) by 6" makes very little difference in trap speed...

The track is 1320' long as we all know. Over the course of that 1320' we accelerate to a trap speed of say, 120 MPH.

How much of that MPH is picked up in the last 6" of that 15840" (1320')? How much MPH would we lose if the track were only 1319.5' long? There is obviously FAR less acceleration taking place at the end of the track than there is at the beginning so the last 6" should be some of the (if not THE) least important of all of the 15840" on the track as far as where the MPH is being made, right?

So, even if acceleration were constant throughout the run (which again, as we know it is far greater ealier in the run than later) then that last 6" would be worth only .045 MPH. 120 MPH/15840x6=.04545 That takes our trap speed down only to 119.95 MPH and that's IF acceleration were as great at any point in the 1/4 mile as at any other. Really, it would be much less than this.

Let's even go so far as to shorten the track by 5' (which is obviously far greater than what you can actually shorten the track by changing staging depth.) Again, even assuming that acceleration is constant we only drop the trap speed to 119.545 MPH. In real life where you pick up most of your MPH in the first half of the track we would have changed the trap speed by even less.

[ February 22, 2002: Message edited by: Colonel ]</p>

 

Colonel, wouldn't it make a difference given that the MPH on the time slip is the average of your MPH at 1320 ft and your MPH at 1254 ft? If it's lower at both of these increments, wouldn't the average be affected more? I mean, if we're talking about even a difference of 120.02 mph and 118.92 mph, a person can look at the big numbers and say, "Yeah, my MPH varied by 2 based on staging," when it actually only varied 1.1...
Just a thought. I'm certainly not a math whiz. FWIW, my ET tends to vary about .09 in the 1/4 mi between very shallow and very deep staging when bracket racing. I rarely look at my MPH at these times and I ALWAYS stage very shallow when I'm just T&T-ing because I want every tiny bit of ET that I can get <img src="gr_stretch.gif" border="0">

[ February 22, 2002: Message edited by: Kristi ]</p>

 

I sure would like to know once and for all how the trap speed is measured. <img src="images/icons/confused.gif" border="0">

I've always heard that's it's the average of the last 60 ft of the run. More recently I've heard that it's actually the average of the last 66 ft of the run which I believe really is the case. But, does this mean...

a. Actual speed at 1254' plus actual speed at 1320' divided by 2.

b. Average speed through that distance calculated by the time between the two points (I would think this would be the way to do it.)

or

c. Something else.

In either of those two cases I still don't see where a half foot is going to make that much impact on the trap speed of a car that is only slowly accelerating (by comparison to the beginning of the run) at the point of 1254-1320.

Maybe we could look at it like this. If your car suddenly stopped accelerating with a 1/2 FT to go to the finish line, how much would your trap speed be effected? Now keep in mind I said only that it stopped accelerating, NOT that it started decelerating. Ok, I understand what you're saying about the average of two points. In this case only the reading of the 1320 would be changed and not the 1254....

1. We're already assuming that acceleration is constant which it isn't even close to being. This point is giving the idea that 1/2 FT makes a significant difference in trap speed a REALLY big head start. This is giving it a HUGE benefit of the doubt to say the least.

2. We'll give it one more big head start. We'll assume that because of the way it is measured from two points that somehow shortening the track could make TWICE as much difference as it would if it were measured only at the 1320. That still only brings our 120 MPH down to 119.91 MPH for a 6" difference, 119.82 MPH for 12", and 119.64 for a 24" difference. Still not even a half MPH difference despite all of these concessions.

I don't know how to properly figure this problem but in my ideas above I am giving in ALOT to try to help bring the MPH down so that I can better understand how it could be so, but still, I can't.

Admittedly, I'm no math guy, physisist, nor do I even have a clear view of how trap speed is measured. So, if anyone can help me to better understand how shorteneing the track by a foot or so can make even 1 MPH difference in measured trap speed I would certainly appreciate it. <img src="gr_stretch.gif" border="0">

[ February 22, 2002: Message edited by: Colonel ]</p>

 

My eyes glazed over about halfway through your last post ( <img src="gr_images/icons/wink.gif" border="0"> ) but I can say I know for sure that MPH is the average (however its taken) of the last 66 feet of the track, not 60 ft.

 

Wish I would have read this earlier.
Staging
There is 2 sensor 12" apart that make the staging lights work. The 1st is the prestage and the 2nd is the stage light. The 12" area is called the roll out area. You can use it to get a rolling start that is why it is called a roll out box. The only thing that is not figured off of this box is the 1/4 mile speed (The ET is).

1/4 mile trap speed
The 1/4 mile trap speed is figured off of a calculation of the last 66' (1/20th) of the track. There is a beam that you will cross 66' before the finish line that works with the finish line beam to calculate trap speed. The speed is calculated off of the time it takes to cover the 66' thrown into a mathematical formula for computing.

Staging effects on 1/4 mile trap speed
The effects of staging on 1/4 mile trap speed are almost none. The only difference is you can travel up to almost 1 foot more (1255' instead of 1254') before the 66' measurements are taken. This 1 foot means very little at this part of the track as far adding mph. For instance say you run 109 MPH at the 1/8 and 136 at the 1/4. (BTW this formula just to show you what I am talking about over calculates the mph that would be gained between 1254' and 1255'.) That is 37 MPH over 660' or .056 MPH a foot. Resistance is increased the father down the track so the gains are less. I believe you can see know what I am talking about as this car would only gain as much as .056 of a MPH. The MPH differences you are experincing are based on other factors and not the 1 foot when it comes to the 1/4 mile trap speed. <img src="graemlins/burnout.gif" border="0" alt="[Burnout]" />