Battery relocation to frunk

[328FTW]

The point of the car is near perfect weight distribution. It is slightly skewed towards the back so getting weight lower and further forward is better. The other reason is it cleans up the engine bay. If you cut out the old battery tray you have so much more room that was once taken up.

But unless your a handling junkie there is no real need it is just for those of us that like to hammer the corners it is part of the unofficial mr2 weight loss diet.

[328FTW]

fail post

[Maticuno]

You're talking to a guy with an 87 that has 215k miles and still running the factory shocks and springs...

[328FTW]

So your saying there is plenty of room for improvement then?

[Jackstand Queen]

50/50 weight distribution is the ideal. A Mk I Mr2, and Mk II's for that matter, will handle better, drive better, and MORE SAFELY with less weight in the rear!

Mk I's are so light in the OEM form, that they front wheels hydroplane rather easily. I've had mine hydroplane at speeds below 60 MPH in heavy rain. Adding weight to the front reduces hydroplaning tendencies.

[AustinTxMR2]

I moved my battery to the front shortly after I spun the car. Not a sure fire way to prevent it but it couldn't hurt. I was also tired of locking the front brakes up. The added weight of the battery up front helped out with that.

Also, the battery in it's stock position is rather high. Mounted on the floor of the frunk gives a lower center of gravity.

My car is a daily driver and I do not ever plan to race it in any form or fashion. My car also has 213,000 miles on it. Last year I put 16,462.7 miles on it with an average miles per gallon of gasoline for the year of 38.2 Non of that was just highway usage, most of my driving is in the city.

John

[Timon]

^ Great MPG.

How did you spin out in city driving is my biggest question? I've only managed to spin out once, and that was obviously my own fault by tearing through a canyon at 70 mph - the back tires lost all grip (felt like I was hydroplaning on dry pavement).

So does everyone pretty much remove the terminal from the stock "+" cable and just soldered the new one on, and would it be a good idea to do that with the stock "-" cable too (I would of course still ground it off in the frunk too)?

[tjmr2]

When I moved my battery to the frunk earlier this year I used brass battery terminals (Wal Mart) with clamps to attach a bare wire to and used an 80 amp maxi fuse right off the terminal on the positive side.

I used underground 4 conductor #8 AWG - 3 stranded 1 solid flat ribbon wire (it's what I had on hand that would handle the current while providing a neat package) One extra negative wire went to a ground on the front of the frunk. I ran two negatives with the two positives = (1 ea. 4 wire ribbon cable) back to the engine bay. Wormed the wires up past the steering rack and into the frunk where the brake lines come in. Had to cut a slot for the ribbon to pass thru, then wound it around the passenger side neatly to the center of the front of the frunk to attach to the battery.

Word of caution, I wouldn't use the bottom frunk plug as a place to bring in your battery wires. Just think of the damage a rock could cause, stripping off insulation and grounding your battery to the frame....bad ju ju.......neighbor kids bring marshmallows to the weinie roast.

I think Steven King wrote a book about that very thing....

Done right it's a safe project, moves the battery from your left shoulder to forward of your feet. Shifts consistent weight foreward and down to the center.



I didn't solder anything but used bolt on clamps (got them in the home electrical section at ACE) and star washers when I connected the long leads in the engine bay. I also used an electrical anti corrosion - anti sieze on all my connections.

I think I removed the original battery leads back to their first connection and that's where I connected the leads from the frunk.

Think of it as running an extension cord from your engine bay to the frunk when it comes to the connections. A fuse is really important at the battery positive as it protects the wiring that you just ran right by your gas tank that sits under your right elbow. No good can come of hot wires and sparks!

Good luck, I chewed on that project for several years before committing, not sorry I did it but glad it's done.

After 12k + miles on the BT I haven't had any problems with the battery or it's wiring. It worked out well with my BT as the air inlet and stock air filter I received from JHOT naturally terminate where the battery was and the air filter housing rests on the battery tray pulling cool air from the bottom.

[Timon]

Originally Posted by tjmr2

I didn't solder anything but used bolt on clamps (got them in the home electrical section at ACE) and star washers when I connected the long leads in the engine bay. I also used an electrical anti corrosion - anti sieze on all my connections.

This is the part I don't understand. I'm assuming you basically laid the wires so they overlapped and then used the bolt clamp to hold them together, but what are the star washers for? Any pictures of this particular set up? It'd be nice if they had something like a distribution box, only for connecting the same gauge wiring to itself (ex. 4 gauge - 4 gauge) as an extension. I like how dist. boxes are set up with the allen bolts to just tighten the cables into.

I'm debating with the wiring. Some people have used 2 gauge, and others have used 8 gauge.
I'm debating between these for the positive:
One 2 gauge wire (expensive), One 4 gauge wire, or Two 8 gauge wires run together. Which would be the best option?

[mach5mr2]

I would use a 2g or 2 4g for the positive. I am in the process of doing it, and have a short 2g from battery positive (less than a foot), that splits into 2 4g wires. I split them because I could not find an inline fuse that is big enough, so I have a 60 amp fuse on each of the 4g wires.

John

[tjmr2]

Real need, Hmmmm, Real need, no....... no more so than needing to drive an MR2 over a 20 year old Chrysler Minivan with 250K miles on the 4 cylinder and headliner that hangs down with rust holes through the floorboards, I mean all you really need is something to get you from here to there.

Right?

[Timon]

^^ mach5, Does the 2x 4g wires seem to be able to power it without any problems? I'll probably go that route since it seems straight forward. What did you use to connect the 2g wire to the original positive cable?

I'll probably get started on this tomorrow since I really need new terminals to remedy my starting problem. While I'm at that I might as well move the battery lol.

^tjmr2, I don't know what you're talking about, wrong thread maybe?

[mach5mr2]

I have the cables ready to go, but haven't done it yet. I am just going to solder the positive cable to the cables that are currently connected to the battery positive. I will solder everything together - no connectors.

The 4g wires look like they are half the size of the 2g, so it looks like 2 4g wires should be about the same as a 2g wire. I think they will be fine. It sounds like some people have run only 1 4g wire for the positive, so I would have to believe I will be OK.

John

[tjmr2]

I was responding to Maticuno's post on 12/10.

According to the Ugly's Electrical Reverences - 1996, multi-stranded copper,
1 ea. #2 will carry from 95 to 191 Amps depending on the insulation
1 ea. #4 will carry from 70 to 148 Amps depending on the insulation

2 ea #4's are capable of double what a single will carry. I'm running 4 ea. #8, in a UW underground 4 wire ribbon cable. 2 positive, 2 negative.

Your biggest current load is at engine start, and then recharge of the battery, but this major current should never last more than a few seconds for starting and the recharge to the battery should never be extremely high or for a long duration.

The key safety factor to the whole thing is to install a fuse right at the positive connector of the battery that is rated lower than the amperage capacity of your wire.

The fuses job is to protect the wire.! NOTHING ELSE!

They taught us way back when I was an apprentice that soldering stranded wire in high current situations can be bad if the wire heats up, the solder will melt away from your connection, causing more resistance, thus getting it hotter, and leading to FIRE.

I used screw type crimp on clamps from Ace Hardware used for multistranded wire and serrated washers. Also used a conductive anti corrosion neversieze compound at the joints where the wire was clamped. I ran 15k miles this summer without any failures.

Just double check the ampacity of your wires, connections and fuses as a failure of the battery lead right by the gasoline tank which lives under your right elbow could be fatal to a happy life in the future.

'While the pieces I used worked for me, and I feel safe with them you may not feel safe with my setup. Use what is right for you, but ask those in the electrical field about your choices before you put your life on the line.

A wise friend once said, "The electrical code books were written with the blood of men who thought they were doing it right".

My aim isn't to discourage you, but to make sure your instillation always works right.

Good luck, it's a fun mod to do.

[div0]

I'm resurrecting an old thread here, but I thought this would be the right place to ask.

Objectively measuring handling data is rather difficult, and I'm wondering if anyone has measured data showing improvement to relocating the battery. I'm not sure that skidpad data can capture the dynamics of really moving through the twisties. I'm also worried about bias in the sample set, as it is hard for someone to be objective after they have spent a lot of money and effort of actually relocating the battery to the frunk. (How often have you heard people say the spent this many hours and this much money doing something, and it didn't do jack?)

I fully agree that moving the battery to the frunk will help get the car closer to a 50/50 weight distribution. Secondly, I also agree that moving the battery to the frunk will position the battery to a lower center of gravity. Both of these things are good.

However, here is my concern. One of the primary reasons for creating a mid-engined car is to minimize the moment of inertia of the vehicle. Having as much of the mass of the vehicle as close to the center of gravity as possible will minimize the moment of inertia, which allows the vehicle to rotate more easily. Moving the heavy battery to the frunk will hurt the moment of inertia of the vehicle, since it is moving the battery from a point close to the center of gravity near the middle of the car, out towards the front end of the vehicle.

So the question becomes, does the improvement in weight distribution and lower center of gravity more than make up for the hit taken by the increase in the moment of inertia?

If anyone has objective before relocation / after relocation data, that would be excellent. Maybe before / after improvements in average lap times would work well. Barring any real objective data, can I get opinions from people that have performed the battery relocation? I just ask that you do your best to be obective about the before and after performance.


Thanks!


-div0

[Kerry Phillips]

Okay, as an amateur Electronic Technician, splitting the wires and running dual fuses is not good. Not good as in dangerous or worse then nothing, but not good as in poor engineering that can leave U stranded. Ideally, if one fuse were to blow, the second fuse will quickly blow because of the additional load.
Also fuses DO NOT, I repeat DO NOT respond instantaneoulsy. Especially larger amperage fuses. For example, pulling 100 amps thru a 50 amp fuse, might take a full minute! How long does it take to start your car?

Wire size and length affect current carrying capacity, how long is the run on a MR2?

Ideally, one should run a smaller wire & fuse for the car's electrical system and a much larger set up for the starter circuitry. That way when your main fuse blows, your security system (entertainment?) systems will still function.

[Timon]

Bring back an old thread instead of creating a new one.

I managed to finally attempt this, and failed. Everything inside the car worked, but the car wouldn't turn over.

Also, I was unable to find a direct route through the front firewall. There are no slots big enough to shove a 4 gauge wire through, let alone if I had used a 2 gauge wire.

Where does everyone run it through the front end of the car?

Here's how I did it:

I put the battery in front, mounted it using a universal tray with a bracket attaching it to the spare tire mount. The battery was stable as could be.

I used a 4 gauge wire. Inside the engine bay, the cable going to the alternator, and starter already had eyelets, so did the new 4 gauge wire I ran. I used a bolt & nut to connect all the eyelets together (this is where I think my problem is).

Inside the frunk I have a 100 amp fuse within 3 inches of the positive terminal. I used a 2 gauge ground. I unbolted the black metal brace that goes around the frunk (not the strut bar), and bolted an eyelet under that for the ground cable. This isn't ultimately where the ground would stay, but for testing purposes it should work.

I had a helper looking in the engine bay at the bolt & nut scenario I had with the 3 eyelets (alternator, positive cable from the frunk mounted battery, and the starter). I attempted to start the car, and my helper said that the cables shot off bright blue electricity, and the car wouldn't start. Also, the headlights would not turn on.

I moved the battery back to the engine bay, connected it all normally, and it works fine again. I'm wonder what I did wrong. I'm by no means an electrician, so I'm admitting I have no idea. My best guess is that I need to remove the eyelets, solder the 3 wires together, but I'd prefer not to in case I have to put the battery back in the engine bay.

Any ideas?

[Jackstand Queen]

On my first battery relocation, I had the same problem.

I ended up grounding the battery inside the Frunk.

And then it went away. On my second, I did the same grounding, and never had the problem. Must be some version of a "short circuit".

[mr2tim]

I am late getting in on this thread, my apologies.

I've run my battery in the front for about 10 years in Autocross, Solo 1 and Speed/Time Trials thru-out the SouthEast Divisional area.
(Mon thru Fri it goes back to it's original location going to work)

I've done what Jackstand has, but I use a full-sized spare that matches the rear wheels.
I also use the biggest battery that will fit, my mini-floor jack and about 20lbs of tools when the Tech Inspector isn't looking.

When racing on street tires or my 10 wide Goodyear Sportsman 14" slicks I find the advantage of getting additional braking friction and less understeer far outweighs any rotating inertia losses. In fact, with extra grip in the front I find my S/C rotates in the corners even better than it it in OEM trim form.

In addition, several years back I discovered a Mark 1 S/C engined C-52 transmission performance secret hardly no one is aware of (or I have missed yet another thread?). Even though my racecar is lowered 3 inches when I take very hard corners the outside rear suspension geometry somehow induces momentary camber and eye popping toe-in, which leads to even further cornering enhancements and higher cornering speeds.
I just wanted to mention this as the thread seems to address handling too.

BTW here's a picture of the TRD Professional Ground System for you owners that were making fun of extra ground wires. We all live and learn.

mr2tim
Supercharzed Toyz Raczing

[Timon]

Originally Posted by Jackstand Queen

On my first battery relocation, I had the same problem.

I ended up grounding the battery inside the Frunk.

And then it went away. On my second, I did the same grounding, and never had the problem. Must be some version of a "short circuit".

I have it grounded in the frunk, as mentioned by the brace bar, and I'm still experiencing this problem. Can anyone post pictures of exactly where they grounded it to in the frunk?