That's good to know. I'm pretty lucky in the climate department so I don't really see that kind of stuff.

 

Same. Back when my car wasn't a jackstand queen I did 5+ years of daily driving summer/winter + track with a small subwoofer. Even fired up well in in -40*C. I'm not saying grounding through the chassis couldn't be a source of electrical issues but I'm not keen to change my setup if it's still working.

 

I just watched that video. 3 tons of downforce!

 

Definitely a neat vid. HPA does a pretty thorough job covering technical details with their vids which is nice. I can't wait to see the V2 run at WTAC and Tsukuba.

Also, I found this video pretty interesting too:

 

Moving the engine back alters the front/rear weight balance, obviously, but they're also adjusting the vehicle's polar moment of inertia. Rally cars are sideways a lot, so they do a lot more rotating than we do on a road course, making this an even more important factor in vehicle handling. Two cars can have the same front/rear weight balance but have very different moments of inertia depending on where that weight is distributed.

Regarding the importance of front/rear weight balance: I think people are debating different things above. Lighter is always better, but for a given weight I'd rather have a 50/50 split than a 60/40 split.

If you have a 3000lb car, it's better to have 1500lb on the front axle and 1500lb on the rear axle than to have 2000lb up front and 1000lb out back. Tire lateral grip doesn't increase linearly with vertical force, so making one outside tire work harder than another is sub-optimal. We can play games with suspension to shift the vertical loads around and try to make the front inside tire do more work (this is why our rear inside tire can leave the ground during cornering) but it's not without tradeoffs.

The reality is that 90% of the time we're not actually choosing between a lighter car or a better weight distribution. In the rare case that we can shift some weight backward at the small cost of increased overall weight (battery relocation, ACD pump relocation) I still think it's a net handling win to shift the weight backward. Putting a 15+lb battery in the trunk with 4lb of 1/0 wire is still a win, however small, for handling. The only exception would be if you have a super lightweight Lithium battery, in which case the weight of the wire starts approaching the weight of the battery. Just keep it in the engine compartment, perhaps with some attention to heat shielding and airflow to keep it cool.

 

If it ain't broke don't fix it. Coming from an automotive electrical background I am of the belief there is no such thing as too much grounding. Ground loops are a super PITA and when you are dealing with sensitive electronics with faster and faster sampling rates electrical noise can wreak havoc. So many electrical issues come down to bad grounding that at this point I'm not even interested in rolling the dice. When you are engineering a solution you want to know it's going to work and what its parameters/specifications will be.

Everything might work great until you take that vacation to the mountains. You get up early its like 0F outside and snowing. You're running literally every electrical system in the car: windshield wipers, headlights, defroster, heater and A/C, stereo (gotta have tunes), plus all the stuff you may have upgraded (Ignition, fuel pump w/e) and then you find out your car wont start again after you get done boarding or W/E because your battery has gone flat. When you are planning a modification you have to also plan for edge cases. Now if this is a garage queen that only sees the light of day for the occasional cars and coffee then you might not ever experience the above scenario and think "Hey it works fine for me so it should be good for everyone in any possible scenario". I'm not saying this is you guys, just trying to illustrate a point.

 

I would take 45/55 over 50/50 if I could :P. But I think best I can get is 55/45 with my most extreme list of changes with still being limited to 2900lbs.

Batt relocation also has the benefit of a big *** power source to worry less about. And some things (like aftermarket ECUs or injector timing) are sensitive to voltage. Tiny lithium battery works great, but they can also be heat sensitive if say road racing for example. So the relocation is more than just a weight distribution effect.

 

So....just got the call from the shop. 0 compression in Cyl 3 where that melted spark plug was. Won't even move the needle. Oil is sparkly. Big sigh. Pulling the head to see what else may be broken. So the MAP block didn't last what....1 dyno session and about 10 laps...total. Could still be the 1 injector cascading effect though.

 

yikes.. sorry to hear. still working on cause? or it was the block itself?

 

Yes.

 

For sure. There's no debate that an even weight dist would be worse than an uneven one. I'm just of the opinion it's not worth sacrificing weight to improve balance.

Dallas' point about voltage sensitivity is pretty true too. In my case, the only wiring that goes back past my A pillar is for my tail lights and fuel pump and outside of my headlights and what's needed to run the engine, there's no excess electrical loads on the battery so it's pretty easy to get away with a small battery that doesn't suffer voltage drop issues and the same is probably pretty true for anybody building a purpose built racecar. That may not be the case with a street car that has HVAC and a sound system and interior lights etc. so having a larger battery that can buffer against voltage losses would be smart.

 

I've been running a small battery for a few years now. A/C, stereo, power everything, the works.
No problems, that I know of.

 

OEM batteries are far bigger than necessary to just run the car. Lead-acid batteries last longer if they're not discharged much in between charges. The bigger the battery, the less it gets discharged between drives. We don't actually need huge currents to turn over our low-compression 4 cylinder engines and the alternator puts out plenty of power to run all of the accessories while we're driving around.

If my car is sitting for a while, I'll pull the yellow fuse block up in the engine bay. It disconnects the radio and accessory circuits, which is where I have my gauges wired. I lose my radio presets, but the parasitic battery drain drops to less than 1mA, IIRC.

 

antigravity released a set of car-spec batteries earlier this year, i picked up their D51. Pretty amazing for the weight, and the restart feature is killer. i always leave mine on a trickle anyway because i dont drive very much, but it's hard to complain about a 5lb battery that's got 900+ cca (not the one i picked, i got a heavier one with more reserve and cca) for me, anyway

 

Actually, my car spent years as a winter fun car... snow, salt, ice, low temps, fast night drives with uprated headlamps.... never missed a beat with a monster optima battery in the trunk. In my experience, grounding problems are usually related to the grounding point where you attach that cable, not the couple hundred pounds of chassis steel in between..