I have a question, and this may belong in the engine department, but I have a 180amp alternator and a yellow top optima battery. The voltage is fine while the car is cold, but once it has warmed up and the rpm's drop to normal (700rpm's), the voltage can drop well below 12v.

I am not sure how to go about fixing this issue? I have tried adjusting the idle screw, but once the car is turned off and restarted, the computer must adjust it electronically, becasue it will return to normal.

Any ideas?

 

I would have the alternator checked out. mine stays at 13.4+ at idle.

Side note, what crossfire amp is that? My local shopsold me two Crossfires for my car and I love them. cheaper than most, but the sound I think is well above the price I payed. What do you think of your Crossfire?

 

It's a Crossfire VR404 (400w - 4 channel). It's the best mids/highs amp I have ever owned. I think it puts out more than the rated 400w.

The photo is a little bit outdated, I removed the capacitor in the center (discovered from trial and error that it really wasn't helping). I installed a clarion crossover (boosted preout voltage from 2v to 5v).

 

May just be the way things are. Some high output alts. put out less at idle.
Are you getting this below 12V on the dash gage? If so check it with a real meter, the dash ones are more often then not off.
Did you do the BIG 3, upgraded the under hood wiring?

 

I'd bet money that there's nothing wrong... most alternator manufacturers WILL NOT tell you that they put out less at idle... many only put out about 30-40 at idle, while making over 200 at full-output...

kind of a scam...

you really have to upgrade to a better case-style (CS-144) before you can have a decent alternator...

but on my stock CS-130 on my 3.1, it would easily go below 12... it would go to 11 sometimes... with my stereo completely turned off... and with my yellowtop with wiring upgrades...

turn on your headlights, foglights, A/C (max), fan on high, and using your windshield wipers, and at a stoplight, your voltage will dip below 12, guaranteed...

turn on your stereo, and who knows...

 

You mention this "Big 3". What is this exactly? What kind of work is involved in replacing this wiring?

Also, can I swap the alternator out for the CS-144, say 170-200amp?

Much appreciated.

 

throw an underdrive pulley on your alternator if you want, that'll get it spinning faster, at lower RPM.

do a search on the big 3.


a cs144 is a stock alternator, 140A. But like 100A at idle. You can also get them beefed up for like 200A, but I really think 140A is sufficient.

 

I actually looked into purchasing a smaller pulley, but it appears the alternator already sports the smallest pulley they had available. I believe it was 1 7/8" (I'd have to double check that).

 

Thanks for the wiring upgrade suggestion. I'll get this done as soon as possible. For anyone else interested: Car Audio : How to upgrade the Big Three

 

basically, the CS130/d is just too damn small to do much good without getting VERY expensive...

if you look at all the high-output options, the CS-144s are cheaper, and more powerful at full-output, as well as at idle...

in the thirdgens, you should be able to get them in there no problem, maybe a bigger serpentine belt, maybe even without...

my car requires bending my power steering cooler lines...

 

I suppose I could just throw a wheel on the alternator and use a hamster?

 

I have a 300A alternator and it didn't do what I wanted it to do until I installed an external voltage regulator. I keep it around 13.1 at idle but I dial it up to 16.3 at idle for competitions.

 

a lot of the good alternators already have adjustable voltage regulators

 

That is correct. Most Excessive Amperage, Ohio Generator, and Iraggi alts come with an external regulator.

 

I bought the 180amp version of this:

http://verizonsupersite.com/4alterst...o&catuid=10155

I am not sure about the whole external regular thing, I am doing some reading about that. Would be funny if my problem is a simple setting that I didn't know existed.

 

this is very strange. My stock alternator on my 2.8 puts out about 13.5 at idle everything in the car turned on. I have upgraded big three, that helped idle performance by almost a volt. My system isn't huge, but with a 600 w kenwood amp. i'd think it would take some power.

 

that link is for the stock alternator...

I've called alterstart and they told me that their alternators put out less than 40-50amps at idle, unless you get the larger casing...

basically, when you are building an alternator, you can go two ways... low-RPM output, which gives you less overall output, but you get over 100 at idle.... or you can go for high-RPM high-amp output.... you can't have both unless you just have more physical room to work with inside the alternator...

 

So I need to find me a new alternator then. This idle voltage really sucks. Can I put a larger casing alternator on my 3.1L? If so, do you happen to know any of the brand/model, website, etc?

Much appreciated.

 

the 3.1 alternator is right on top... so I'd be willing to be you can... Iraggi and Excessive Amperage make some CS140s and you can get the wiring harness from them...

 

you mean overdrive pully I'm assuming

under drive would spin the alt slower.

 

ya, but the alt pulleys included with an underdrive package are in face overdrive to keep the alt spinning normally