Negative battery cable size?

[JeffKeryk]

After @The Critic thread on the 51R to 35 group size upgrade, I did a similar upgrade to out 2006 TSX (212K) as the 51R toy battery was on its last legs after 5 years. I live in Silicon Valley; it's pretty warm and the car is garaged.
I bought a Costco Interstate 35, which was a super tight fit in the TSX chassis. I also picked up a Standard 2 AWG negative cable from NAPA, about $18 including the governor's tax. I always keep my car batteries clean and service the terminals about once a year. I lightly wire brused the frame where the short cable grounded. The factory negative cable is a pretty small gauge. Maybe it was worn? Is that possible?

All I can say is, that fat cable woke up that K24 engine. I was thinking placebo so I sent a text off to The Critic and he replied that improving a ground can help.
I know the V6 Honda Accords use a heavier gauge cable than the 4 bangers, not sure if they are 2 AWG.

I asked wifey to let me know what she thought going to work today as she loves her TSX. She said wow, it's really different and I am getting 32 miles per gallon. The K24 and automatic usually deliver 26 mpg, or thereabouts.

Your thoughts? And a big thanks to @The Critic for his guidance.

 

[CharBaby]

See how the MPG settles out.
When I disconnect the battery of my Altima, the MPG usually jumps some(summer time) after the 3rd tankful.

 

[javacontour]

Any fuel economy boosts are likely from the ECM being reset when the battery was swapped. Mileage will return to previous values once the ECM learns it's adaptive values.

 

[kschachn]

Wow if disconnecting the cable gave me a 19% fuel economy increase I think I’d drive around with it disconnected all the time.

 

[carviewsonic]

I upgraded the battery and ground cable at the same time, so I couldn't say if the new cable alone made a difference. The new V6 cable was inexpensive, and it sure looks better than the small k24 cable.

 

[JeffKeryk]

Wow if disconnecting the cable gave me a 19% fuel economy increase I think I’d drive around with it disconnected all the time.

If you think that's good, try a Tesla!
I'm sure she was just watching the mpg gauge on her usual 15 mile commute.

 

[Trav]

I do a big 3 or 4 upgrade and add additional flat braid cables on almost every car I own, it makes a huge difference on some of them other not so much.
I get cable and lugs from this company, I use the marine tinned fine stand cable and tinned lugs, never have corrosion issues.

AC/DC WIRE AND SUPPLY

AC/DC WIRE AND SUPPLY

www.acdcwireandsupply.com

 

[eljefino]

Ground to the frame? That's just for accessories and whatnot. You should have a thick ground to the engine block as the starter motor will be using that. There should be a few other redundant grounds between engine and chassis, mostly so sensor signal voltages don't stray from calibration.

 

[Trav]

Some grounds from engine to frame are also to prevent aluminum erosion caused by galvanic reaction. Wide tinned braided straps work best. Ground straps from firewall to engine and hood are also best with tinned braided and can help with AM radio interference noise.

 

[ripcord]

Your fuel mileage increase may have been partially due to a weak battery with high resistance pulling more amps from the alternator. That energy has to come from somewhere.

 

[SC Maintenance]

Perhaps your forced MPG improvement is from a forced ECU reset, and it will continue at least somewhat. One can hope.

OEM's cheap out on the ground cable because its usually very short - from the negative cable to the frame and body nearby for example - and the entire car is part of the return loop to that point so a short, thin gauge cable can carry a lot of current a short distance - not very far for resistance to come in play. However upgrading is usually a worthwhile investment - IMHO.

 

[Jetronic]

Your fuel mileage increase may have been partially due to a weak battery with high resistance pulling more amps from the alternator. That energy has to come from somewhere.

If you pull from the battery or the alternator, eventually the alternator has to put it back in the battery anyway.

 

[brianl703]

Your fuel mileage increase may have been partially due to a weak battery with high resistance pulling more amps from the alternator. That energy has to come from somewhere.

A weak battery with high resistance will not pull more amps from the alternator. (Ohm's law says that a high resistance load will pull less current than a low resistance load).

A battery with a shorted cell will, but it's unlikely you'd notice the gas mileage loss.

Probably, if a battery somehow failed that it'd pull enough current that it would effect gas mileage, you'd notice a strong smell of rotten eggs as the electrolyte inside is boiling away due to the heat. The energy has to go somewhere, and it will heat the battery up.

 

[ka9mnx]

I looked at the posted pictures of the installation and the negative cable was so short I felt the upgrade was a mute point. I've found best results when locating negative cables from a schematic and going around and cleaning the connections from the cable to the body most useful.

 

[JeffKeryk]

I appreciate all the comments. Electricity is pretty foreign to me. I just might learn something!

 

[ripcord]

I appreciate all the comments. Electricity is pretty foreign to me. I just might learn something!

Says the engineer with sarcasm in his veins

 

[f355spider]

15 or 16+ years ago, I was bored at some car shop and was reading the "car porn" they had in the waiting room. One of the magazines was some Japanese import modification magazine and they were doing testing on "grounding kits" commonly sold online. These are the kits that come with four to six sets of ground cables of various lengths. They may or may not come with a new battery ground cable, but do have three or four cables to "improve" grounding to the cylinder head, transmission and alternator. I forget the car they tested (less than a year old) but did multiple dyno runs before, after adding the cables, then final runs after removing the cables. The car was only rated for around 250hp stock...but showed consistently a 5 or 6hp improvement. Just from a $25 set of cables.

I can see on a older car, that all the grounds can get dirty, broken or missing. This would be an area for repair or replacement.

 

[ka9mnx]

I forget the car they tested (less than a year old) but did multiple dyno runs before, after adding the cables, then final runs after removing the cables. The car was only rated for around 250hp stock...but showed consistently a 5 or 6hp improvement. Just from a $25 set of cables.

I find that hard to swallow.

 

[eljefino]

I find that hard to swallow.

Agreed, the ignition module will be grounded to the engine block which is also the alternator's ground. That's as good a zero reference as you can get. (Yes I know there are some ECMs that control alternators that are grounded to firewalls.)

 

[Jetronic]

grounds are easily checked with a volt meter though. Remember that if there's a voltage drop there's an equal amp drop aswell. so losing 10% voltage during cranking, results in 10% less amperage and 21% less cranking power.