Better 1/8 Mile Time=Better 1/4 Mile MPH??

[6SENSE]

Will achieving a faster 1/8 mile give you a higher overall mph in the 1/4?

I decided to look at tonights timeslips a little differently. I noticed that my 2nd halves of the 1/4, the car was moving pretty darn well. I would gain 20-22 mph in 4.9 seconds. I compared these averages to some other cars that ran faster than me and faired very well [in the second half]. In fact my mph gain often was better. The time I gained over 22 mph equaled a car I ran against that went 108mph.

So, looking at it this way, the first half is where I am lacking. Its not that Im moving out real slow, its that I am spinning like crazy anytime I try to hold a pound of boost at the line. I had to let off the pedal a couple times because I was spinning through the whole 60ft and bouncing (wheelhop). A couple times it got bad enough that it was setting off my audible knock sensor (false KR). I would get off the pedal just to be safe, and when I got back on, it was back to spinning.
IF I EVER GET MY TRACTION TOGETHER SHOULD I EXPECT TO SEE MORE THAN 99-1/2 MPH 1/4 MILES?? Or does that have nothing to do with the overall 1/4 mph?

Thanks.

P.S. Oh yeah, almost forgot. From Tlink data on one of the runs, I know that I could have gone WOT at least 106mph with no KR. Now if I could just get there before the 1/4 was over .

 

[UNGN]

Traction and 1/4 mile MPH are not really related (unless you spin your tires for an 1/8th mile)

If you have some wheelspin in the first 60 ft or so, your 1/4 mile mph won't really be affected. 1/4 mph mph is a function of Horsepower and not traction or 60 ft.

MPH in the 1/8th is related to mph in the 1/4. For a given car, the higher mph in the 1/8, the higher mph in the 1/4, unless something happens to reduce mph in the last 1/2 of the 1/4.

Many factors come into play with the "gain" in mph from the 1/8 to the 1/4. Tire height, converter slipage, RPM capability play a role in determining 1/4 speed. Some cars will never go faster than a given number in the 1/4 because they are out of RPM's.

My car has run 118.31 in the 1/4 with a 93.5 mph 1/8th. With 26" tall tires, it would only run 114 mph in the 1/4 with a 93 mph 1/8th.

 

[420]

If anything, wheel spin up to the 60' can artificially INFLATE the 1/4 mph. Alternately, hooking the crap out of the car might show a slightly lower mph, but a nice improvement in 1/4 time. BTW, that second half charge is the beauty of a turbo car

 

[6SENSE]

Originally posted by UNGN
Traction and 1/4 mile MPH are not really related (unless you spin your tires for an 1/8th mile)..................

MPH in the 1/8th is related to mph in the 1/4. For a given car, the higher mph in the 1/8, the higher mph in the 1/4, unless something happens to reduce mph in the last 1/2 of the 1/4.

Thanks for the reply.
Okay, traction [at the head of the track] doesnt have much to do for 1/4 mile mph [at the end], but 1/8 mile #s [half way down the track] do. Thinking along the same lines, focusing on the 1/8 mile here, wouldnt the traction problem play a role in the 1/8 mile mph? (If spinning half the run can affect the whole run then spinning a quarter of the run would affect the half, right?)

 

[Weazel]

Originally posted by TransAm WS6 420
If anything, wheel spin up to the 60' can artificially INFLATE the 1/4 mph.

I'm not sure I quite follow. If you're saying spinning off the line will make your MPH seem high compared to your ET, then I definitely agree. But it sounds like you're saying spinning will make your mph higher...which i dont follow.

60' time generally won't effect your 1/4 mile MPH...but it sounds like you're experiencing more than just a bad launch. If you're having to backpedal during the run, and aren't able to be WOT during or shortly after the 60', then you're not putting all your power to the ground. More power will both help your 1/8th time and your 1/4 MPH. I think that if you're spinning from a pretty decent roll, then you're leaving power and therefore MPH on the table. What are you running for tires? (didn't see in the sig). Stock suspension? Anyway, with the ability to go WOT without going up in smoke, you'll be triple digit MPHs in the quarter.

 

[6SENSE]

Originally posted by Weazel
What are you running for tires? (didn't see in the sig). Stock suspension?

255/50x16 BFG DR's, stock posi, aftermarket pinion snubber, passenger side airbag, and I boxed the LCA's.
I bought these tires used and have actually had worse 60fts since using them compared to my runs on regular street tires in the past (Im talking 2.3-2.6 60fts!!!). May not really relate though, because the car may have more power now as well.

Also, didnt want this to get lost and not seen since it seems a couple of us were posting at the same time. So Im going to quote myself :

Okay, traction [at the head of the track] doesnt have much to do for 1/4 mile mph [at the end], but 1/8 mile #s [half way down the track] do. Thinking along the same lines, focusing on the 1/8 mile here, wouldnt the traction problem play a role in the 1/8 mile mph? (If spinning half the run can affect the whole run then spinning a quarter of the run would affect the half, right?)

 

[UNGN]

If you are spinning halfway through second gear, yes your mph will be affected in the 1/8th but probably only a couple mph.

I ran at a crappy 1/8th mile where it didn't stop spinning until right at the traps and I still ran 91 mph (I usually would run 92-93)

My ET was off .5-.6 in the 1/8th but my mph was only down a couple, max.

Spinning can result in a higher mph if you think about it this way:

MPH is a result of the average HP your is making over a given distance.

If the cars tires are spinning, the motor is reving higher and therefore could be making more hp than it would if the car was hooked up and the motor was reving lower.

The spinning tires act like a slipping clutch, where a slipping clutch launch is usually always faster than letting it out and punching it at low RPM.

This is combined with the fact that the spinning drive train has stored inertia that helps accellerate the car when this potential energy is converted to kinetic energy (when the spinning stops)