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Front crash bar is a total of 6.61lb if you remove all the tow hook reinforcement like this:
It looks like my replacement bar will be just under 4lb if I use 1.5x.095 and 9 square inches of 12 gauge. Not a lot of weight to be saved here.
That's 2.5 lb at one of the farthest points forward on the car though. I'm doing the same thing for mine since I basically had to cut half of it for the intake anyway. I wonder if you could do thinner, I know FM just replaces it with some angle stock when they do their conversions. Thought I saw somewhere that it really didn't provide much of any reinforcement to the chassis, could be remembering things incorrectly though.
I trimmed my radiator/AC brackets and found 3/4lb between the two:
That plus the crash structure I am up to 7.88lb cut out of the front. Going with 1.5x.065 for the replacement bar. That should put me near 4.5lb improvement.
I'm about to do a bunch of bumper trimming and was looking around at the rear. The large horns that are used to attach a tow bar, how much of them have people removed? It looks like they also tie into the back wall of the trunk. They look heavy.
Talking about the rear, what you NB guys owner did with the returnless portion of the fuel system ? I just removed the line under hood and rerouted the rubber hose near the the vent.
Odd thing to remove.....but if you ever wondered the battery pocket weights it's 5.6lb's. I imagine the pocket on the other side is about the same, and the spare tire well would be a good bit more than that. Not sure I'll remove either right now as they aren't in the way of my exhaust.
Bumper beam and mounting brackets are right at 11 lbs.
Ahh very nice. I did the same thing, but didn't stop with just the battery area, I kept going... also removed the spare wheel space but kept the two rails as they are currently my wing mounts. I supposed they offer no other purpose and could probably be replaced with something lighter?
Made a little progress on the "race" battery. These are lifePo4 batteries rated at 30c continuous and 40c burst. So with two of them in parallel like I plan I"ll have 252 continuous amps and 336 cranking with a decent 8.4 AH capacity and none of the spontaneous combustion LiPo batteries are known for. I honestly think you could get by with one of these in a trailered car. I have a balance charger for the R/C cars so I'll pull these out and balance them every now and then until I trust them not to get too far out of wack.
I kinda lost track of the real reason I was doing this (weight) and added some nice terminal blocks and a disconnect which added quite a bit of weight relative to the battery.
OEM like battery
Still a significant 17lb savings overall for 100$ spent.
Not clear done with the install but enough to test it out, cranks better than it does with the full size lead acid with both batteries. It's a little sluggish with just one but plenty of grunt to start the car, so I'd do just one in a trailered race car. Very similar to the ETX-9 I ran in my old NA when compared to one of these. There's roughly another 2.5lb's to be lost if I would move the battery under the hood and strip out the power cable. Not quite worth the hassle for me at this point.
Last edited by Bronson M; Nov 26, 2017 at 06:46 PM.
Not clear done with the install but enough to test it out, cranks better than it does with the full size lead acid with both batteries. It's a little sluggish with just one but plenty of grunt to start the car, so I'd do just one in a trailered race car. Very similar to the ETX-9 I ran in my old NA when compared to one of these. There's roughly another 2.5lb's to be lost if I would move the battery under the hood and strip out the power cable. Not quite worth the hassle for me at this point.
I had never seen this before, nice wok! Are you worried about the weight distribution with the battery removal?
I'm not the first to use lifepo4 batteries, think I've seen a few folks on here using them actually. Yes this will "hurt" weight distribution since removing weight from the lightest corner but I'll take a less balanced car that is overall lighter. You'll never be faster adding in weight just to balance the car.
I did the same thing in my car.
And, as Bronson mentioned, just the one battery seems to work OK as long as you're not cranking too much for too long or it can hurt them eventually.
(Mounted under the dash above the gearbox, so weight savings are maximized with much shorted wiring)
LiFePo chemistry is much safer than LiPo pouch cells; however I would be worried charging them from the alternator without any sort of battery management system.
Lots and lots lifepo4 batteries running around being charged with alternators. Alternators actually follow the charge pattern that lithium batteries need in that they maintain a Target voltage and decrease amps as you approach that Target. Don't use a trickle charger or lead acid charger in them though as most of them charge to too high of a voltage . Most if not all of the commercially available lifepo4 and lipo car batteries being sold don't have battery management systems, there's some photos in this thread of the inside of a Braille battery. https://www.miataturbo.net/race-prep...s-83673/page3/
Where you have problems is if you get the cells unbalanced, then it's possible to overcharge or over discharge cells in the pack. We're talking about a 35$ or 70$ pack here if you run two of them...... They could last an awfully long time with no attention at all, and I'll balance mine a few times a year just because it's easy.
I did the same thing in my car.
And, as Bronson mentioned, just the one battery seems to work OK as long as you're not cranking too much for too long or it can hurt them eventually.
(Mounted under the dash above the gearbox, so weight savings are maximized with much shorted wiring)
You do need to share where you got that snazzy little battery tray.
Lots and lots lifepo4 batteries running around being charged with alternators. Alternators actually follow the charge pattern that lithium batteries need in that they maintain a Target voltage and decrease amps as you approach that Target. Don't use a trickle charger or lead acid charger in them though as most of them charge to too high of a voltage .
Yep, Battery Tender brand LiFePO4 battery in my car has been in use for 4-5years and still working great.
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