Drag Racing Discussions > Front Engine Dragsters

floor / firewall....electronics mounting

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225digger:
 looking for suggestions/ideas for floor and electronics mounting

 engine is 50" out with a short glide so i have room to play with behind the trans, i was thinking of making a 2 piece floor/firewall and mount the ignition and battery behind and to the outside of the transmission, ignition is a 7al and battery is a small go lithium, battery is 9x7x3 8 lbs so not worth it to try and put it up front. i dont think there would be any issues with doing it this way ? firewall would be there so its not in the driver area.

i would like to make the floor removable so some small bolts instead of dzus fasteners, the floor would extend beyond the firewall and this is where i would mount the battery and ignition. rules are vague but must the battery be mounted to a frame rail or would it be ok to mount to the removable floor? what material would you use? steel or aluminum ?

thoughts, ideas, suggestions ? any pics if you have your stuff mounted inside would be great.

denverflatheader:
225digger - very much agree some nhra rules are vague, probably done that way on purpose.  My guess about the “Batteries” General Rules, I think the intent is towards installing battery in a doorslammer (e.g. must be of sufficient capacity to start vehicle, relocated to trunk needs rear firewall, must be fastened to frame or frame structure with two 3/8 bolts).  For most part, dragsters have more leeway, I’ve seen batteries and ignition boxes in the front, middle and rear of chassis; have not yet seen a dragster with a trunk : )  The only rule which stands out which you mention is no battery in driver’s compartment.

For dragsters, I’ve seen batteries mounted two ways; permanent steel welded brackets or on removable aluminum plate, both ways integrated into chassis tubing.  All I would add is design your battery placement and ignition box so you have fast access, easy to service/remove, and routing of positive side shutoff so not complicated.  As you know, passing track tech, they rarely look at your battery placement or ignition, but every single one of those techs looks at your shutoff switch. 

One final thought, your idea places the battery immediately adjacent to the starter motor and decreases the cable length.  With such a small battery, voltage drop may be a consideration. The shorter cables minimize resistance (i.e. heat) to abating voltage drop.  You could use 2 feet length of 6 gauge and maintain a 300 amp circuit with a 2% or less voltage drop at 12 volts; I’d upgrade to 4 gauge.  Alan

p.s. No picture to post, my setup uses remote battery with quick disconnect.

p.p.s.  normal car starters draw 150-250 amps with peak around 300 amps.  Higher compression engines like diesel draw 500+ amps and peak around 700-1000 amps depending on size.

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