Thread: The alt rewire mod actually DOES increase fuel mileage!!

Originally Posted by SyntheticShield

Okay, if that is true then, then it would go to show that the rewire has some effect. If the system is aging and stressed or pushed to the limit and this simple mod relieves some of that and is noticeable by way of brighter lighting, better shifting (I noticed this on my last vehicle I did this to, not so much on the GP, Rodeo is manual tranny) then that would prove that it is changing for the better the electrical system.

So therefore, why would it be such a stretch to believe that this could help mileage? That said, if you want proof it helps, then go out to your car, reduce the system voltage to lets say 11.5 volts or even 11.0 volts and drive for a week or two and report back on your fuel economy.

I would have never ever believed it in a million years myself had I not done it on the number of vehicles I have and seen the results I have.

All I can say is you've got to be kidding me, run at 11.5 V. for a comparision.

It can be done and your mileage will suffer.

Originally Posted by SyntheticShield

Second, nearly everyone fills their tank up until the handle clicks off. And there is SO much variance in that it isnt even funny. I fill my tank up until it will take no more. As a result I have very accurate fuel mileage history.

Variance there may be, but "topping" your tank can be harmful. The evap system doesn't like getting liquid fuel into it very much, and replacing the canister can be a *****. There's a reason pumps cut off when they do...

And dropping your system voltage below that of the battery will only make it so your battery takes over the load until it drains below the system's voltage. And it won't recharge at such low volts (hence why the car operates at 14.4V and the battery works at 12V).

With regards to topping off, I would agree that the EVAP system probably doesnt like getting fuel in it but you'd be kinda hard pressed to do that and there is some type of overflow/fill drain hose on the tank I believe. As well Ive been doing this for years. My last Grand Prix I owned for probably 6 years, had nearly 200k on it when I sold it and it was still running strong then and I always filled the tank up on it until it could not hold another drop. And Ive done the same thing with every car since including my current GP.

With regards to the voltage, I agree its probably not the best thing you can do for your vehicle or battery for that matter and may not even be easy to do, but you can do it and it will show the effect of electrical system efficiency and power has on fuel economy.

You dont really even have to drop your voltage down to those levels, all you need is a battery that is marginal and/or an alternator that is not doing what it should and you'll get the same effect. And ultimately all the statement was meant to show is the correlation between fuel economy and electrical/ignition voltage and how small changes in those areas can have profound effects.

Exactly. Its not one large change that does it, its several smaller things that add up in the grand scheme.

ok so this is sorta on topic . i ordered the alt. volt booster and alt. re-wire is this a good combination to run along with re-doing my neg. wire to a thicker 1 ?

Yes. I'm also doing the voltage booster here soon. Make sure your ground has a good connection to the frame or wherever you attach it.

I have the alt booster and rewire. Can't comment on how it affects mileage since I made other changes at the same time. But the electrical system does seem more healthy. I also took my battery's ground and sanded/cleaned it. I plan on replacing it, as well as the engine->chassis ground cable. The Big 3 would be complete.

In regards to topping off, I had heard that it was harmful for a while. Then, while I worked for a Pontiac/GMC/Hummer dealership a couple years ago I asked the service manager about it. He was adamant about letting the cut-off do its job. He said several times weekly they replaced evap canisters or otherwise serviced the evap system from problems caused by overfilling. Plenty of GP's were in there.

I'm not saying you might have an issue, but in the grand scheme plenty of people aren't doing it right. Just a word of caution, I guess, to everyone else.

does anyone have pics of the alt. rewire installed ? i know this is probably a very stupid question but i dont want to install this wrong . from what i think i remember seeing you basically hook it up to the +alt. to the +on the fuse box but i dont remember if you are suppose to remove the other 2 wires or leave them installed ? so the question is do i remove those wires or leave them in ?

there is nothing to the alt rewire. You can go to easyperformance.com an see the install instructions. One end goes under the positive nut on the alternator along with the stock one, and the other end gets put under the not on the fues box. Piece of cake. Yes all of the stock wires stay in their stock location.

__My point about dropping the voltage that far is that it is just plain rediculous. You are then operating outside of it's designed lower limits and proves nothing as a result. Same goes for stepping up the voltage too far.

In case you haven't followed the many V boost and alt rewire threads, it is a mixed bag of reviews. Like I said it is a good thing, but your results may vary. Why some see no appreciable results others see big results, and a handful for some reason, bad results, is beyond me. Note that I have the alt rewire, fuel pump rewire, and the stage 1 Volt booster.

Originally Posted by IndeedSS

there is nothing to the alt rewire. You can go to easyperformance.com an see the install instructions. One end goes under the positive nut on the alternator along with the stock one, and the other end gets put under the not on the fues box. Piece of cake. Yes all of the stock wires stay in their stock location.

ok so on easyperformance it says to leave all stock wire connected but does that mean have them both connected or should i just have the new wire hooked up to the alt ??

It means to simply slap on the new Alt rewire ontop of your already existing wiring. You just take the new piece and connect it to the Alternator, leaving on the original wire and then lead the new Alt Rewire to the post ontop of the Fuse box and securly fasten it to the post.

And you're done

I hope that clears it up for ya?

Originally Posted by GeddyLee

It means to simply slap on the new Alt rewire ontop of your already existing wiring. You just take the new piece and connect it to the Alternator, leaving on the original wire and then lead the new Alt Rewire to the post ontop of the Fuse box and securly fasten it to the post.

And you're done

I hope that clears it up for ya?

sure does . thanks . i just didnt want to mess anything up .

No worries Bay. I went took some snapshots of my Alt Rewire Setup. I hope they help ya.

With the rubber boot over the alternator wiring.



With the rubber boot removed you can see the new wire coupled with the factory alternator wiring...(I probably need reposition the Alt Rewire to have the cable face into the engine bay and not against the alternator)



Up close picture of the fusebox post with the Alt Rewire hooked up to it. (sorry its a tad bit blurry)



A little further back shot of fuse box post with the Alt Rewire. (sorry its a tad bit blurry) ((All the other wiring you see on there is for my HID Wiring Harness and one for my Foglight Harness. The other is just some factory thing that Pontiac stuck on there. And soon I will have one or two more for my amps once I get them.))



Sorry I did not post these up sooner for ya

Oh crap James with it hooked up like that you have no fused protection.
















j/k

I dont know about you all, but I would not want two wires hooked up like that. Obviously it is not causing any issues, but it aint that hard to take it off at both ends and tape it up. Now that I got my car tore down I aim to pull that wire completely out of the harness. It might be useful for hanging up some parts for painting or something.

Originally Posted by SyntheticShield

I dont know about you all, but I would not want two wires hooked up like that. Obviously it is not causing any issues, but it aint that hard to take it off at both ends and tape it up. Now that I got my car tore down I aim to pull that wire completely out of the harness. It might be useful for hanging up some parts for painting or something.

*Deer frozen solid staring into the headlights of an oncoming car*

I am not quite sure what you meant by that Scotty? Could you better elaborate on what you are trying to say?

Well you got two paths now to the fuse block from the alternator. True, it will for the most part, take the path of least resistance, so the vast majority will be carried by the alt. re-wire run, but you still have some going across that original wire thats considerably smaller and pushing about 8' in length.

From just purely an electrical standpoint, Id want all the power going across the one wire. Unless you're keeping the stock wire in there for back up, and at that point if that is the case, why not install two alt. rewires?

James, don't worry, your install is fine. It's is just like adding more strands to an already stranded wire. Current travels on the outside of a wire. The more surface area the more current carrying capability. Why would you deleted a wire that is effectively increasing the total gauge of wire in use?