Starting Line Ratio

[TheSilverBuick]

My Camaro has 5.57 rear gears and a 2.88 first gear. I launch from 6500 to 7500 rpms depending on the hook. And it is really fn cool!

[CDMBill]

It took me awhile to find this SLR stuff. These are two pages from Dick Miller's How to Hook and Launch. Starting Line Ratio based on stroke and weight and yields the recommended SLR.

The second shows ideal 60 ft. times vs. ET. This is a measure of efficiency.

[BBR]

Well, by that chart, I am right in the ballpark. Thanks for posting!

[BlueCuda340]

Great chart thanks Bill, that chart confirms what I need...more converter! I tried the numerically lower SLR and saw no change. I really need to throw this 4" crank I have in something so it can have the sack to get this heavy pig off the line.

[stormts71]

so the first cart says im close 4"x3500lbs = 9.75 . 3.89gear x 2.47 low gear = 9.61 in the ball park . and the next cart is telling me the same as Jeff and the rest said i went to low on the converter . 123-125mph 11.0-10.88 et 7.0-6.94 60ft 1.54 all last # are bests .

[quick 52]

hope I didn't screw up I drop the stall from 4500 to 3500 well will find out in a couple weeks...

[JeffMcKC]

And to throw more numbers out Take your ET X MPH and have a number between 1290-1300

[stormts71]

10.883 x 125.24 =1363 so what do we do with this ?

[quick 52]

And to throw more numbers out Take your ET X MPH and have a number between 1290-1300

Check my best of 11.33 x 115 = 1302.99 average is 11.55 x 115 = 1328.25 Are these number for converter or gearing

[JeffMcKC]

Gearing and Converter, there is a relationship between what you run on the ET and MPH look at it as a balance.

Take Docs Camaro 8.92 @ 154 MPH

Jakes Car 9.94 @ 134 MPH

Mine 9.67 @139 MPH

Your car can be light on MPH or ET but the right balance with come very close to the 1290-1300 number

I wish I could explain it better but you see the mph the same, but your number went high on the second it tells you there was inefficacy in the combo. for the MPH ran.

[JeffMcKC]

OK I butchered trying to put it in words so here is someone else on another site explaining it better.......

You are referring to another form of a term called Hook Factor which is just ET x MPH. The lower the number the harder the hook. It is different for all kinds of cars for a number of reasons that include HP, gearing, weight etc. Normally the number is between 1300 to 1360 for most cars in the 1/4 mile.

If you look at a fast door car vs a fast dragster with the same ET's, the door car usually has more MPH for the same ET so the HF will be higher. Weight and aerodynamics cause this.

Take a low powered Stock car, they are geared to ET and not MPH so they are hanging on up top so their MPH is low for the ET so their HF's are real low.

You will find that as HP gets up there, so will HF because you get to a point that you just can't apply all the HP without killing the tires on the starting line.

So you can use this to compare how well your combo is vs others as long as you compare apples to apples.

[CDMBill]

Gearing and Converter, there is a relationship between what you run on the ET and MPH look at it as a balance.

Take Docs Camaro 8.92 @ 154 MPH = 1374

Jakes Car 9.94 @ 134 MPH = 1332

Mine 9.67 @139 MPH = 1344

My best at DW '11 w/ a bit more stall than peak tor and 28" tires 9.70 @ 141 = 1367, at DW '12 with 30" tire and slightly less stall than peak torque 9.82 @ 141 = 1384

I've also looked at this as starting line efficiency and therefore of the cars and ET's posted here Jake is getting the best ET out of his combination given the weight and power and I'm getting the least. However, see what happened with a better combination of converter spec and tire size despite slighly worse D/A. Obviously gear ratios play a role too, I just didn't happen to change mine over the two years.

[jaybnve]

This is an interesting thread. Here's a few more:

DW05, 69 Mach 1, 10.60 @ 127 MPH, 4.11 rear and 2.46 first, 3650 pounds, SLR=10.11, Hook Factor = 1346
DW07, 69 Mach 1 with supercharger, 9.40 @ 145 MPH, 3.50 rear and 1.78 first, 3750 pounds, SLR=6.23, Hook Factor = 1363
DW09, 64 Galaxie, 9.50 @ 143, 4.11 rear end and 2.46 first, 3935 pounds, SLR=10.11, Hook Factor = 1358

[BBR]

My hook factor is not nearly as efficient as some. 10.46 @ 130 = 1360

[TheSilverBuick]

I will make all feel better.
SLR= 11.16
HF = 1399