1986redbird

I'v read that you can convert your 1/8th mile time into 1/4 mile time (roughly) by multiplying it by 1.55. now, the question is----is this conversion based on the assumption that the car is set up properly for the 1/8th and then re-setup for the 1/4 ???

or to make it clearer: if my I was running a car set up to make the most of it's available power band in the 1/4--- and then ran it on the 1/8th with the same setup---would the conversion still be fairly close???

kind of like comparing a long distance runner to a sprinter--- the sprinter would be faster on the short track but slower on the long track because he would run out of air before the end. and the long distance runner would be slower on the short track but be faster on the long track because he is conditioned (setup) to be optimal on the long track.

does this make any since or am I just REALY TIRED ????

smithtc

iTrader: (5)

It's based on the assumption the car is set up for the 1/4...which is all in the gearing.

1986redbird

OK, so what your saying is-----if my car is setup (geared) for the 1/4 mile and all I have is 1/8th mile times, the conversion would be off due to me not using all of the cars potential on the 1/8th.

would that mean I would actually be faster in the 1/4 than the conversion says I should be ????

I know the best thing is to actually run the 1/4 but that track is about 30 min. further away from me than the 1/8th, I am going the first weekend in oct to super chevy so I'll know for sure then. I'm just trying to get a feel for the whole conversion thing.

smithtc

iTrader: (5)

ok, I'll try again.

My car is a 3.27 rear geared, 700r4 tranny. I shift ito 3rd usually about 50-100' before I get to the 1/8th mile line. This means I will be in 3rd gear last half of track. Car is really setup more for the 1/4.

1.56 (a normal conversion factor) * 8.72 = 13.6
1.56 *8.76 = 13.67

That's about what my car would run in the qtr, give or take a little depending on variables. Other cars on this board that run similar times to me in the 8th run simlar times inthe qtr as the number above.

Now, I think:
If my car was set up for the 1/8th a little more (4.10s or something like that) then my car should do much better in the 1/8th but the miles per hour would not improve much..., and I would have less to use over the last half of a qtr track. Thus, the conversion would not work for this situation.

AlkyIROC

Since everything happens in the first 1/8 mile, a car should always be set up for 1/4 mile racing. The last 1/8 mile should be a high gear full hp pull to the finish line. Since the variables are very limited in that last 1/8 mile, it's easier to calculate the 1/4 mile time from an 1/8 mile pass.

In the first 1/8 mile traction plays a big part as does all the shifting. If properly set up, a car should be in high gear at or just before the 1/8 mile.

If gearing is too high to max out in the 1/8 mile, it too easy to lose traction because of the increased torque multiplication of the gearing. If my car goes well on the 1/4 mile with 4.56 gears I would need something like 6.xx or higher to max out in the 1/8. I'd produce so much torque with those gears that I would probably spin the tires during the entire 1/8 mile. That and the shift points would be so close together that I would propably overrev before I got a shift in.

1badTTA

The conversions from 1/8th to 1/4 are taken from thousands of 1/4 mile timeslips that also show 1/8th mile times and MPH. That being said, your car should be setup for the 1/4 and not the 1/8th since the only difference is the gearing as stated already, and would make the 1/8th mile setup totally unstreetable.