for all your bracket racers, how much faster than the index should your car run in order to be in that class successfully? I was thinking of running the 12.50 index at a local track, but wasn't sure how much more ET I should be capable of then back off

 

It looks like you're planning to use the sandbagging approach to bracket racing. That approach has both its plusses and minuses. Cars that can run the fast side of the class index, or below the index can have an advantage at times, however, there isn't always an assured advantage. For example; if the slower car cuts the better light and runs their dial and you come by him at the stripe with a car the can run outside the index, you just "broke out" and lost!

WD

 

I would estimate that, in order to be assured of running under the specified E.T. under all conditions, throughout the season, you need to plan on a .25 range. In your part of the world the summer conditions of heat and humidity could produce at least that much of a variation between early spring/late fall conditions and the worst part of summer. Also, normal barometric pressure swings at any time of year could produce ranges of variation of a tenth from week to week. Track conditions will also play a role in answering your question. If the track is particularly well-prepped on any given weekend for a featured "booked-in" show, you may experience noticable differences when compared to an ordinary weekend bracket race. If you set the car up to run 12.50 on a good weekend in April you will probably be off the mark in July or August.

c

 

If this index class is where you always have to dial 12.50 then certainly be able to run 12.2 or 12.3 there-abouts. Lots of ways to detune the car so that you can smack that 12.50 in all conditions...(and you probably already know this).
One is to take timing out via the pcm (at launch rpm)
Another is to add weight via gasoline or approved balast box.

But if this 12.50 index is a class cut-off such as 12.50 and slower cars and 12.50 and quicker cars, then no matter. You can dial exactly what you want for each round. One hot day the car might be running 12.60 so unfortunatally you run in the 12.50 and slower class, (but now you have the faster car starting line advantage.....). You probably already know this too.

What exactly is this 12.50 index?

Karl

 

you have to run a 12.50 everytime down the 1320

 

12.0, 10.0 and 8.50 Indexes are becoming pretty popular around here.

If you run the 12.0 index, your dial-in is 12.0 every pass. If you break-out, you lose unless the other guy breaks out worse. You run on a pro-tree and you must qualify to get into the 16 car field.

I know around here, my car runs 10.0's in the cool weather and low 10.30's - high 10.20's in the heat of the summer. I would guess that you would need at least .20 to play with.

We're setting up a 12.0 car for me to run next year. It's a 4 door, 67 Malibu.

 

I can run a 12.0 index in any weather. I set the car up to make a 12.0 qualifing run then 11.98 for the elimination rounds. The car varies from 12.0x to 11.30 in good air. I use weight, exhaust restriction, and shift rpm to slow the car down. I set up the car according to the DA. On hot dog days I run as light as possible, shift high, and run my biggest diameter mufflers. Best days I run with added weight (200+lbs), short shift, and put on the small diameter mufflers. You need to keep a data log to see how to set the car. Its a lot harder to make the car run a specific number than changing the number on the window.