Rebel73

Hey guys,

I plan on going to the nearest track soon, which is a 1/8 mile track. Is there a formula for calculating approximate 1/4 based on 1/8?

My Blue Heaven

Yes, do a search on Google for quarter mile calculators and you'll find all that and more. Wallerracing.com is one I use often.

Rebel73

thanks!

korinwoodo

Wouldn't you have to do the true 1/4 to get your time. (due to shifting or forward acceleration or whatever)?

GregS2005GT

Based on some of my 1/4 mile time slips, this one is about .23 slow when I enter my 1/8 mile time.

I have a 5 sp manual and I entered times where I knew I had good smooth runs. Also my car is stock except for Flowmasters and I've only made about 10 runs = novice.

Actual Example:
1/8 mile at 9.324
1/4 mile at 14.33
99.13 MPH

Calculated:
1/4 = 14.57

Wallace Racing

Maybe some others can validate this for our cars.

Scott

The calculators are a "Good guess" only. Anything can happen in the 2nd 1/8th mile, but, using the calculator will give you a rough guess.

MSP

Thats just great.. Check out this 05V6.. LOL!! Don't ever give me an opportunity, cause "I'll stick it in!"... LOL!!

http://www.tammyandjohn.com/Mustang/Video/ublydrag2.wmv

Those 05 V6's are pretty good huh!

MSP

Stock GT 5 Spd's should be around 13.4 ET.. So you have alittle work to do yet... 14.57 is no where close.. Its possible your shifting too soon or to late.. Might want to ask the other GT guys what a good shift point, to allow the 3.55 gearing to work its magic.. but definatley your about 1 whole sec off of the pace of all stock GT's..


Also, I just need to add that based on the GT's stock gearing which is 3.55, the 1/8th mile calculation is not being fair, when trying to figure out the 1/4 mile, because the GT's 3.55 gearing does not kick in until the 2nd 1/8th... So when looking at the 1/8th mile run, you have not allowed the gearing and the HP of the motor to link up and make magic.. So the 1/8th mile test to determine a good 1/4 mile run is really not fair to a GT, so forget about it..

Now if you had on 4.10's, or 3.73's, then you would be able to match up the engine HP and gearing in the first 1/8th of a quarter mile, and that would be a more fair calculation for an 1/8th to 1/4 conversion..

So based on your calculation, and what we all know to be fact, the GT makes its name sake in the 2nd 1/8th and with the 3.55 gearing and HP and TQ available to a stock GT, is actually able to make up the 1.17 sec with HP and gearing only in the 2nd 1/8th.. The problem with the calculator is its not giving credit for HP and TQ combined with 3.55's in the 2nd 1/8th.. So I wouldnt use that calculator as a good measure, unless your running 1/4 mile gears such as 3.90's, 4.10's, or 3.73's... Any lower gearing than that, and credit for Turbo Lagg, and HP, and TQ must be calculated into the program..

MSP

Here is another video of a 10 sec GT running the 1/4 mile.. Notice how he does not make up anything on the car he is racing until the last 1/8th mile..

http://169stang.2005stang.com/powerhouse0510.67.mpg

The point is, if this is a 1/8th mile run, he loses.. So 1/8th mile racing is really circumspect as far as I am concerned.. Its like a Porsche 993 Turbo, is designed and built for 1/4 mile racing, and not 1/8th mile runs.. So to me, to claim a victory in an 1/8th mile race, does not mean the car is faster in the 1/4, and is why the 1/8th mile races should not be really considered..

max2000jp

MSP your 13.4 time you stated above is really hard to achieve. That's going to be only done in perfect weather and a great driver/launch. A decent time for an stock 05 manual seems to be around 13.6ish.

MSP

You are correct, about optimal conditions.. My point mainly, even keeping the ET to 13.6, is the GT's unless Blown or running Nitrous, must first climb to the top of the 3.55 gearing which doesnt happen until the 2nd section of the run..

The calculation based on the tool used to acquire the 14.57 does not give the GT enough credit to finish the run based on gearing combined with HP..

Like I said, a blower or nitrous will be able to get a GT into a situation where its a good 1/8th racer. However, the gearing never intended the car to try and be impressive in the 1st 1/8, only the 2nd..

Fazm

Trying to hook up at the track is a lot harder than trying to hook up on the street. Doin a 13.6 run in a manual gt would be a pretty decent run in my opinion. Most of the people on here have a tune, intake/exhaust and are only running 13.2-13.5.
Took my gtech to the track with me the last time to test its accuracy. The largest amount it was off was .11 (and 2 runs within .02). With the gtech i was running 14.86 bone stock on the street. And at the track i still cant get under 15.2 even with an sct tune.

Rebel73

Yeah,

I realize that the calculator is only a rough guess. I guess my real question is, what would be a "respectable" time for the 1/8 ? Especially for a newbie racer like myself.

My Blue Heaven

With the set up you see in my sig I've run a best of 8.89 two weeks ago at the local 1/8th mile track. That was with a 2.18 60' time. That night I didn't go slower than a 9.05 and I did around 10 runs.

Bone stock I was running a best of 9.03 and averaged 9.1's with the same crappy 60' times.

Hope this helps.
Chris

don_w

Over the past few months, I have been collecting data from the many 05 GT 1/4-mi runs I see posted on several different forums. I have them all in a spreadsheet and have looked at the comparisons of the 1/8 ETs to the 1/4 ETs. And in well over 95% of the cases, the 1/4 ET is about 1.55x the 1/8 ET. Unless someone shuts off early or there is some other anomaly, it rarely varies outside the 1.53 - 1.57x range. The average is actually 1.548x.

The attached table is a good reference chart for comparing the two. Take a look at your own timeslips... you might be surprised at how close it comes. And no, it's not perfect, but it is pretty sound and is based on a bunch of empirical data.

MSP

In my 05V6 I have also used the GTech, and I have a manual.. I have matched your time with my Gtech, without a tune, gears.. I only have a Magnaflow XPIPE dual exhaust..


Would you mind explaining for us how it is, your only chipping off a 14.86 run?

Here is my Gtech, which you have already verfied its accuracy..



You also have a V6.. Thats great.. Now we know the Gtech is really accurate..

don_w

Note that these numbers fit very close to my data as well:

14.33 / 9.324 = 1.537 (within the 1.53 - 1.57 range I see over and over again)

MSP

Very nice work on the chart Don_W!! Somebody has got to do it..

I have a question for you however.. Do you agree, that a Mustang GT is not geared to impress in the 1/8th mile race stock? Based on your really nice observations and data logging?

What is your conclusion based on this info? Of course when comparing the times to other stock GT's you will be jaded by the same numbers.. But analyzing these numbers against other cars, do you get a picture of the GT needing more RWTQ from a logistical stance? What I mean is, wouldnt you like to see the GT with a different stock cam from the factory, which could place the stock TQ number closer to about 350RWTQ? I truley believe Ford short changed the stock GT, based on whats really out there on the market.. I am a V6 owner, however I do have the same passion for the GT's that I carry for the V6's.. In my mind, I want the GT's to carry 350RWTQ from the factory.. Does this sound realistic?

Basically, I feel the GT's should have been released with 300RWHP, and 350RWTQ.. They atleast deserved this, IMHO!

don_w

MSP... of course more power (i.e. torque) from the factory would obviously be good... who wouldn't want more!! But it is what it is, and we work with what we have.

By the way, the data I have been collecting involves a wide range of 05 Mustang GTs... all the way from bone stock automatics (w/3.31 gears) up though cars with power adders running in the high 11's, with gear ratios as high as 4.56. And it is uncanny how often they fall into that 1.53 - 1.57 range. It doesn't really seem to matter what rear ratio they are running. Obviously, there will always be a small number of data points that fall outside the range, but like I said before, it is much less than 5%.

So... I guess my conclusion would be that it works as well in the 1/8 as it does in the 1/4.

In fact, I only have 1/8-mi tracks near me... so I get a lot of track time on the 1/8. I have made only eight 1/4-mi passes (back in June at a track 100 miles from my house), and since then I have made about 200 1/8-mi passes.

Rebel73

Don,

thanks a lot! Now this is a simple formula that can give me a real good idea of how well I do. Good job on compiling the data.