Weight off the nose

KStromberg

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I'm looking to get a battery relocation kit and was wondering what you drag racing guys have done there and where you purchased your kit? NHRA rules? Also I am looking at picking up some M&H front runners. They are 27" diameter. Will those work with 26.35" tall drag radials in the rear or is that too much of a height difference? I ran 26" drag radials back in 2010 with stock (26.6") tires up front without issue. Please help. It's game time.
 
But it adds more weight with the size and length of cables you have to run.

Technically speaking yes, but my bigger intention here is weight transfer. I can deal with the extra weight of the cables if it means the car is going to transfer the power better. Also the rolling weight on the end of the axles is a different concept even than that of the dead weight removal with the ac compressor. There is actually 3 different intentions that I have going on here.
 
You can download a new rule book from nhra racing. Here is the short version.
Make sure you read the master cutoff switch section as well.
"Batteries may not be relocated into the driver or passenger compartments. Rear firewall of .024-inch steel or .032-inch aluminum (including package tray) required when battery is relocated in trunk. In lieu of rear firewall, battery may be located in a sealed .024-inch steel, .032-inch aluminum, or NHRA-accepted poly box. The sealed box may not be used to secure battery and must be vented outside of body. Relocated battery must be fastened to frame or frame structure with a minimum of two 3/8-inch-diameter bolts. Mandatory when battery is relocated, an electrical power cutoff switch (one only) must be installed on the rearmost part of each vehicle and be easily accessible from outside the car body. This cutoff switch must be connected to the positive side of the electrical system and must stop all electrical functions including ignition."
 
How bout the passenger/rear seat delete mod? Dump the spare and jack too. Probly 100+ pounds there
 
pass. seat is heavy. rear is almost nothing. its mostly hi density foam.

the external cut off switch is disappointing for a daily driven car. does anyone know of a good system for a street car with a rear battery?
 
Put the cut off switch behind the licence plate. Mount it to the crash bumper and make a hole in the plastic large enough to rotate the switch. Pull the rear plate while you're at the track! You could also put remote jumper leads there if you wanted.
 
Also you will find that most kits do not give you enough cable for a long car like a Mark. When I was racing my Thunderbirds I just went to the local welding store and bought cable by the foot. I mounted my cut off switch to the bumper right below the tag so all I had to do was shim the tag out a little to cover it when I drove on the street. Remember you will also want to disconnect the alternator with the cut off to prevent run on or volatage spikes.

-Alan
 
Sounds like it would be easier to buy a lighter racing battery and keep it where it's at.

Are you on air or springs?
 
Sounds like it would be easier to buy a lighter racing battery and keep it where it's at.

Are you on air or springs?

T-bird SC springs with Tokico blues up front and fully-adjustable Koni sports out back. This year will be my first runs ever on springs.

Also there IS such thing as light racing batteries. I did not know that! Thanks Micah! :D
 
Did you remove the blower/dryer when you swapped to springs? That's about 15-20 lbs....:cool:
 
NHRA Rules

8.1 BATTERIES

All batteries must be securely mounted and may not be relocated into the driver or passenger compartments. Rear firewall of .024-inch (.6 mm) steel or .032-inch (.8 mm) aluminum (including package tray) required when battery is re-located in trunk. In lieu of rear firewall, battery may be located in a sealed .024-inch (.6 mm) or .032-inch (.8 mm) aluminum, or FIA accepted poly box. If sealed box is used in lieu of rear firewall, box may not be used to secure battery, and must be vented outside of body. Strapping tape prohibited. A maximum of two automobile batteries, or 150 pounds (68 kg) combined maximum weight (unless otherwise specified in Class Requirements) is permitted. Metal battery hold-down straps mandatory. Hold-down bolts must be minimum 3/8-inch (9.53 mm) if battery is relocated from stock and other than stock hold-downs are used ("J" hooks prohibited or must have open end welded shut.).

8.4 MASTER CUTOFF

Mandatory when battery is relocated, or as outlined in Class Requirements. An electrical power cutoff switch (one only) must be installed on the rearmost part of each vehicle and be easily accessible from outside the car body. This cutoff switch must be connected to the positive side of the electrical system and must stop all electrical functions including magneto ignition. The external control switch for this cutoff switch will be clearly indicated by a red flash inside a white-edged blue triangle with a base of at least 12 cm (see drawing 25). The positions must be clearly indicated with the word "OFF". If switch is "push/pull" type, push must be the action for shutting off the electrical system, pull to turn it on. Any rods or cables used to activate the switch must be minimum 1/8-inch (3.2 mm) diameter. Plastic or keyed switches prohibited. Switches and/or controls must be located behind rear wheels on rear engine dragsters.


Here are pics of the setup in my XR7. Hopefully they'll give you some ideas.

When running on the street (kill switch is on the right, next to the methanol tank):
P1110057.jpg


When I go to the track, I swap the passenger taillight out for one with a hole through it, and install the pusher assembly on the switch.
killswitchpusher.jpg


The car also has a NHRA-legal aluminum rear firewall and package shelf (since I'm not running a sealed battery box), and the subs are removed for runs at the track as well. I used 2/0 fine-strand welding cable for the positive lead to the starter and for the main ground.

P1090165.jpg



I'd recommend a 200 amp mega fuse on the cable from the battery to the kill switch (as close to the battery as possible) and another on the cable from the alternator to the battery or battery post of the kill switch (as close to the alternator as possible).
 
As far as weight loss just take out all interior except driver seat. And for power run the back straight to trunk and just run the one power and ground from under the hood to trunk.
 
Unless you have issues hooking the car up off the line, I don't see it worth the time in relocating the battery for weight transfer..because in the end like psyhostang mentioned, you'll be adding weight by adding 6 more feet of larger gauge cables to the trunk. Why not try and cut some weight from it instead as right on the mark did.
 
I was gonna say I think I used closer to 25 feet for each cable and you need to run 3 of them.....

-Alan
 
6 feet lol. i needed 18 feet.

I was thinking more just the distance between the firewall and the rear seat approx..but yea I guess you'd need quite a bit more to make the bends around stuff and whatnot..eitherway that makes it even worse then lol
 

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