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

Mine didn't change at all. But perhaps it has to do with it being a newer car. Maybe the alt rewire helps aging systems. After having my stage 1 volt booster it and out serveral times, I finally took it out for the last time and noticed no changes either.

Originally Posted by 02BlueGT

^^Just use a 100amp in-line stereo fuse ?? they are pretty cheap

You want more than 100A, as the alternator is rated for 110A. 150A is a good choice, and Mega-Fuses are readily available in that size. I actually went with a 150A circuit breaker, as it was available in AutoZone for about the same price as a fuse and the holder for it. Here is the thread I had going on the matter:

http://www.grandprixforums.net/f81/a...nk-s-3304.html

So this is a good idea but get a 150 amp fuse or circuit breaker in case the alternator fails?

Ok, but i am going to measure voltage drop first.

When I pulled my alternator wire completely out of the harness, I measured it and then took some resistance measurements and then plugged those into the formula to calculate voltage drop. My overall resistance was between 0.4 - 0.5 ohms, so on the lower end you are loosing about 0.9v and on the upper end you are loosing as much as 1.1v. Which may not seem like a lot but its roughly 7 - 8% of your voltage and that's just for the alternator wire alone.

Alright - I just bought a 30" 4ga battery cable and went for it. I'll attach some pictures. (note that the original cable is still connected).

First, can someone confirm that my install is proper and safe (specifically noting the route of the cable)?









I don't think there's enough slack to get anywhere near the belt.

My second question is this:
I had the neg of the battery disconnected when I did the install - after I had it put back together, and started the rig up, I heard a couple of unusual clicks from under the hood before the engine got rolling... I turned the car off, and then back on to have it happen again. I figured I goofed something up, and was going to remove the re-wire, but I let the car sit for a few and then turned it back on and it started up normally.
I've only had the car since June so I figured it may have had something to do with my disconnecting the battery (it's the first time I've done such). I was also parked a hill, maybe fuel wasn't being delivered initially - I'm just throwing some ideas out there. I cant imagine it being the rewire that was cause... but it seems to have gone away. Any ideas about the mystery clicks?

Thanks guys.

The routing looks good. As for the unusual clicks, I dont think that is unusual. I know mine goes through and resets the locks and what have ya, though Ive never noticed anything under the hood.

im doin this later on today muuuuuhahaha

Originally Posted by sassygtchick

"I fill my tank up until it will take no more. As a result I have very accurate fuel mileage history"........ I've always been told this a bad thing to do. I used to do it all the time and a friend of mine's husband said I shouldn't do it cuz it will cause problems.

Going off-topic a bit, but I have a question..... I've noticed when my gas hand get to the 1/4 mark it will start "floating" so to speak when accelerating. Is this normal? Should I have it looked at? I might have a quarter tank, but the gas hand will move up to almost 3/4's.

My old GT did that,the sending unit was bad.

Originally Posted by SyntheticShield

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.

The first time ive done this was in my wifes 00 montana. I was only getting 13gallons out of a 18gallon tank. topped it off and got 16 gallons in it. yeye. Wrong, started up and engine light was on and it was the evap code. I did this a week ago and still tying to figure it out. i went from 27mpg to 15mpg. Im not sure if its the canister or what?????? any idea on that

And question 2. the same van i have noticed at night the headlights dash dim a bit..its like its surging for power. Even the motor sounds like it drops up and down a 100 or 200 rpms. my dad has a Olds sillouette that does the same thing, do you think this wire from alt to fuse may help? And is there a voltage booster for it to.. I know this isnt GP related but im doing it to my GP later on today so maybe it is related??lol

hmmm this happend the other week with my gp too, when it went down to almost empty where the low fuel light comes on i filled it up and all i got was like 11 or 13 gallons i dont remember but all i know is that i have a much bigger gas tank than that.

I use alldata too it's verry handy. But yeah i wonder whats up with that?

that always works, just make sure you got another ride to the gas station.

Originally Posted by 98GT3800

when doing the Alt rewire. DO you have to take the old wire from the fuse-block that wraps around engine and back to alt off. or do you just add the one from fuse-block to alternater

Leave it on. Electricity takes the shortest/easiest path, so it will use the re-wire. Yes, there were be a few electrons that will want to take the long way, but the work involved in taking it out isn't worth the trouble. I left mine in place on both cars.

Originally Posted by Deezul_AwT

Leave it on. Electricity takes the shortest/easiest path, so it will use the re-wire. Yes, there were be a few electrons that will want to take the long way, but the work involved in taking it out isn't worth the trouble. I left mine in place on both cars.

It is a lot more then "a few electrons" in this issue...by running the two lines in parallel like that, you are greatly increasing current flow. There is a decent discussion I had on it, here:
http://www.grandprixforums.net/f81/a...nk-s-3304.html