will having a sucky 60ft afect your trap speed any? b/c it seems to me that everytime i lower my 60ft. my trap speed goes up. Oh yeah one more question. The best ive been able to run is this:

9.788@72.5 mph
2.35 60ft.
1/8 mile times

about 85 degrees

now, i made these runs with sucky goodyear h rated tires. I'm planning on getting some z rated tires, and installing my posi. Now my qusetion is this. if i can manage a 2.10 60 ft. would this be enough to put me at a 9.35-9.4 @ 74-75 mph on a cool 60 degree evening?

Also im planning on porting my heads, getting some 1.6 ratio rockers, getting my chip reprogrammed, installing the slp runners i have in the garage, shift kit i have in my gargage, and installing a afpr (it is running real lean) is it too much to hope for a 9 flat with some tration. I would like this 305 to go 13's then pull it for a 400

 

Lowering your 60' time will have more effect on your ET than MPH. I don't know how much the 60' time affects 1/8-mile times, but it's usually .2-.3 for every tenth you gain at the 60' mark.

I've had runs where I've totally f'ed up the launch (2.5+ 60') and had around the same MPH as when I got a good launch (2.1-2.2).

 

i guess the better traction you have the better you can launch and that puts more power to the ground affecting the time you get to the end and thus a better mph..

but when your talking from going like from 2.5+ to a 2.1 you will see more a change in et than mph..

 

Yes the mph is affected by the 60'. Basically the faster you get to any distance, the faster you have to be going!

 

I have noticed no real trend in my 60' times related to MPH

my best 60' (a 1.98) netted a 14.46 ET. I've also ran some real crappy 2.4 60's, with a 14.9x ET. MPH was the same within 1mph (92-93mph).

 

With 60' times in the range of 2.1 to 2.2, I was getting ets in the range of 9.1 to 9.3 at the 1/8 mile track near my house. The best I got was 2.09 with 9.0something, so I think you should be able to get lowere thant the 9.35 to 9.4 you were mentioning. My MPH went up a tad with the lower 60' times but miniscule amounts, like 75.5 to 76 mph.

 

With wheel spin,you are putting less usuable HP to the ground,so less trap speed.

 

I beg to differ.

As said above, it will affect your ET, but not speed. Sounds counter-intuitive, but it's true.

To expound, with my 3.08 gears and TA Radials earlier this year, I'd have 2.40 60', 15.2 ETs, 96 mph (1/4 mile). Now with 3.73 gears and Drag ETs, 2.26 60', 14.6 ETs, 96 mph.

Looking at my time slips from yesterday, I had an early run with 2.29 60', 14.8 ET, 95.9 mph; late run with 2.26 60', 14.7 ET, 95.9 mph.

60' times and ETs are made with torque to the ground (engine torque times gearing) plus traction. MPH is made with HP.

 

True.MPH =HP, but if for first 40 or so feet car is getting 1/2 or so power to the ground do to wheel spin,you have less distance to run under full throttle.Like starting 40 ft out from line,you will MPH less.

Maybe , sorta ,kinda ??? , This has always been rather confusing

 

Watch a throttle stop car make a full pass vs. delay pass. You'll be amazed at how close the MPH's are between the two.

 

delay? as in delay box...............? reaction time?????????

My boss has a 8.10 car thats throttles stopped to 8.90 class ,hasnt hit a real run using T stop ,just crap like 11.10@133 kinda stuff.All out runs best of 8.10@170.Ive been trying to get a "real on paper math"kinda answer to this discussion for a while.I can see where you are coming from on your view,but I still have trouble with the lack of full HP put to ground issue.


damn.now my head hurts!

 

another thing to consider...

if HP = MPH (roughly)

and HP = Horsepower is defined as the amount of energy or work required to raise a weight of 33,000 pounds a height of one foot in one minute of time [...] Therefore in simplified terms, a horsepower is 33,000 foot pounds of work done in one minute (sited from http://www.ytmag.com/articles/artint142.htm)

HP is affected by time. The same amount of ft-lbs applied to the rear axle over half the amount of time is HALF the horsepower.

Thus.....(using my car as an example)

my 14.9x run with a poor 60ft, compared to my 14.46 run with a decent 60ft, my car has half a second LESS to apply ft-lbs to the rear axle. This affects the "apparent" HP because the engine is applying torque to the rear axle for a lesser period of time.

So, you get going off the line faster, but you have less time overall to accelerate, which maybe is why MPH gains are kind of a washout when compared to 60ft times. You gain on the launch and you give it up due to less time spent in the 1/4.

:lala:

 

My belief is that in the full quarter your 60 doesn't effect the MPH as much, but in a short distance like 1/8th it has a more profound effect because you have less time to make up the speed. Just been my experience running both.

 

What 91L98Z28 said. I agree.

 

i agree with most of the people saying that mph really isnt affected by 60' too much. for example, i just recently got a 91 formula 5.7, one of my runs i ran a 9.9 w/ a 2.7 60' (i know, i really need new tires bad plus it was the very first day i drove it), and i trapped at 76, the times i managed to pull a 2.5 60', i still trapped 75-76. i am wondering however, if i manage to get a good 60' (maybe a 2.1-2.2), what do you think i'll run? my best time of the night was 9.7 w/ a 2.5 60'

 

I didn't bother reading many of the posts here, but yes...if you spin off the line you'll tend to have a slightly higher mph.

Why?

Think about it like this...either way, you're covering 1320 feet, but one way you may get there in 14.0 seconds while the other you may get there in 14.4 seconds. In other words, on the latter of the two runs, you've got an extra 4/10ths of a second to be accelerating at the top end of the track. Thus, you trap a little higher. The inverse is true as well. Most of the time, when you lower your 60' your mph will come down slightly. This is because you're getting to the other end of the track quicker and have less time to accelerate.

 

Assuming you have no wheel spin, the lower the 60' time, the quicker and faster the car will be.

If however a 12.0 second car running 108 mph and has good 60' times gets lots of wheel spin for whatever reason, the ET may drop to 12.5 or slower but the mph will still be close to 108.

 

My own personal experience has been like this.

With a stock torque converter car, spinning off the line will give a small increase in mph.
With the vigilante, the better i hook an launch, the more mph it makes.

I think the reason you might see the increase in mph in a stock TC car is not due to the longer ET of the run as someone earlier suggested, it's because by spinning you let the engine get into it's powerband earlier, and even though you're not accelerating forward, the engine is also not 'bogging' either. This is kind of an abstract idea, but i have a menetal picture that makes it work, and i could be crazy.
With a nice torque converter though, the harder it launches, the more acceleration i get and the more mph i have at the end of the run. And like someone else said in here, the change in mph is usually more dramatic at the 1/8 mark than at the big end.