Folks,

I've grown tired of chasing my voltage fluctuations in the vehicle. Already blew up an alternator at high RPM by having it geared too high to keep the idle volts consistent (yes, it was interesting!). So, I'm shooting for mild alternator abuse (larger pulley) and adding a step-up/step-down power supply for the ECM and wideband.

This has been discussed here and elsewhere, and I'm going to go ahead and try it out. I figure so long as the ECM and O2s are getting something solid (say 13.8 volts), the rest of the vehicle systems (fans, lights, water pump, etc) can do what they want with the variability of the alternator output.

I found several products out there, such as the following:
12 volt DC/DC converters regulator from 100 to 700 Watts.
Seems cost effective and compact, with decent packaging.

Anyone go down this path and come up with a solid recommendation?

Many thanks,
-Craig

 

What's the problem that you're trying to cure?.
Is there some performance lose due to the fluctuations?.
While the PW might hunt a little, if the battery voltage corrections are close that shouldn't be an issue.

I've did a new harness for the EFI on the GN over that, and I didn't notice any change. Next up is using switches instead of relays to see if that cures it.

 

Bruce,

Voltages fluctuate down below 12, say 11.5 or so at low idle dips. Above 1500, it's plenty good at 13+. The ECM itself seems OK, and the fuel management seems OK, but the wideband sensor keeps flaking out when it gets those low voltages. I've got it tied in with the simulated narrowband output feeding the 730 ECM for fuel trim changes, so when it takes a nap, it doesn't help.

There are no wiring or relay issues, since I've chased through all that and put all new in anyways, followed by voltage surveys to ensure no drops anywhere to speak of (all within a couple tenths).

So, I figured it couldn't hurt to give the WB enough juice to stay consistent and feed the ECM while I was at it. Maybe go ahead and feed the ignition as well. I'm thinking 10A should be enough, maybe 15A for some headroom.

Root cause is really a slightly under-driven, high-current, one-wire alternator, along with the extra draw of the A1000 fuel pump, 55 gpm electric Meziere pump, and a couple other things. But even still, I'm hunting after ever-lower stable idle setpoints, so directionally I need all the idle help I can get.

-Craig

 

I don't know what type of alternator you've been using, but maybe you want to investigate a later model, high amp version. I've never really noticed much problem with newer alternators, might be something to try. Oh yeah, also, there is an alternator website that upgrades the CS130 style alternators with dual rectifiers, and other stuff to give you a nice high current stable voltage output.....let's see....here it is:

High Output Alternators,Alternator Parts, High amp alternator, Chrome Alternators,Quick Start Rebuild Kits, alternator part

that being said, if you are experiencing alot of voltage problems, it could be the age of your harnessing and connections. might be time to check out all the interconnects and upgrade some wiring. My cluster voltages are all out of whack, I know I have a rock solid voltage at the alternator, but the voltmeter in the dash is all over the place.

 

How about a DC-DC regulator? Anyone have recommendations? The alternator / harness issue is moot. i understand what is going on, but would like to add a regulated power supply for the WB and ECM. That's all.

 

The root cause is not the underdrive. The root cause is the one wire alternator. Throw it away. They are the worst thing ever invented/sold. The voltage regulator sense line is tied directly to the output line and not to a point after wiring losses occur. Look at the older GM stuff for the correct wiring on an alternator. One wire alternators are the worst thing you can put on an EFI engine. If you do chose to go step-up then look at national semiconductor or linear technologies. National has some easy to use design software for 90%+ efficient step-ups. Keep in mind that Powerin = Powerout+Power_eff_loss.
The one wire has no chance of accounting for wiring losses. I would just fix that. Hacking it is not really the best way to go about it.
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I guess you don't care about the cool fan, lights, fuel pump, fuel injectors, etc. not working optimally. If you really only want the step-up then take a look at National Semiconductor.

 

Blah. A lot of those DC-DC modules are nice and small and pack an amazing amount of current for their size but they are an achilles heel. I've long lost count on the number that have died in the enviro lab at work ($20,000+ circuit boards).

Try the CS alternator first...

 

I agree. The DC-DC modules (bricks) are not all that reliable. I was referring to National Semi for the IC controller that would use an inductor and capacitors on a custon PCB. The controller ICs have good reliability.
I have thought about making one for the DIY-WBO2 controller to give it a steady 14.5 volts with the key on (engine running and engine not running).
It is fine without it, but it would be nice.

Yes, any 100+ Amp three wire alternator wired properly is the real way to fix the problem. Watch out on using the CS series.....some had reliability problems.

 

What are you running for a battery?. It might be time for duals.....
That water pump, might be the real cause of the problem.

Yes, as mentioned the CS alternators are a good answer. The one on my GN has the 200A kit in it. At 1,500 RPM it can put out an honest 185A.

Which WB are you running that drops out that easily?.

 

Yes, it cropped up since adding the WP. Most folks I know that run electric WP run into that challenge.

You figure, monster fuel pump, that's 12A right there. Water pump, another 12-15A. Fans? 20+A. EFI running static on the injectors, good for another 8A or so probably.

So yeah, it introduces significant load. Hard for the alternator to keep up, even with perfect wiring. I understand about the feedback voltage and what-not, particularly on the 1-wire. It's a billet piece though, so I probably won't be going down the path of alternator diddling.

The WB is an Innovate LC1, tied to the 730. The battery is an Optima Red.

I'm going ahead with one of the 20A units listed on the link I posted above to power the WB and the ECM. If it works out, that'll be cool, and I'll probably add the ignition/MSD to it as well. Those are the most voltage-sensitive components in the vehicle.

While the fans, fuel pump, and water pump are also critical, they aren't as sensitive to under-voltage. So I'll see how it plays out with those supplied directly via the alternator/battery/etc (appropriately relay switched of course).

Anyways, I'll let you folks know how it turns out.

 

oh, yeah, I just thought of something that's kind of wacky. How about adding in one of those mega-caps or whatever you get for car audio? They're designed for heavy inductive load filtering/bulk capacitance for 'peak' power or whatever. Maybe something like that will help smooth out the voltage ripple. I know the battery provide most of this, but it certainly can't hurt to try if you have one lying around.

just a thought. In any case, what you are suggesting will work, but just be careful of the operating temperature, the actual current load you expect to power (igntion, MSD, quite noisy). I've had issues with supplies crapping out due to high peak currents upsetting the control loops, on the primary side!(not really relevant, but....)

 

I have been down the underdrive 1-wire road before. If your injectors are static then the engine is sensitive to FP voltage. You must be running dual fans for 20+ Amps. A stock GM usually runs about 10 Amps. The biggest aftermarket fan I could find draws 17 Amps. Enough that it would blow a 30 Amp fuse at turn-on. The ignition runs on sort of A/C square wave power. You might want to check how well the DC-DC can handle dynamic loads. Take a hard look at the output caps. They are going to take a beating if the ignition is connected to them.
I wish you the best of luck with the step-up. Remember, chrome don't get you home. If you have the cash to experiment then by all means try it out. I am interested in the outcome.

Junk

 

Try another battery.
I had one, and it developed a memory for staying at 12.8 (or close to it). After my experience with it, I've since decided to stick with a cheaper battery and replace it more often.

How about a Fuel pump controller, for dropping it's voltage at idle, and maybe regulating the water pump speed......

 

12-11.5 isnt that much of a fluctuation. It will drain the battery over time, but all the electronics in the car should be designed to deal with having something other then the ideal 14.5V. Id also vote for a new high output stock style alternator. Maybe its not the voltage, but some sort of fluctuation or noise at low alternator speeds.

 

Try MadElectrical.com - Mad Enterprises and see what he says about a 1 wire. There are issues with using one because it needs a minimum RPM to energize. You may also want to tie into the alt at the source for the WBO2, pump, etc. The wiring section is very good and his suggestions work well even for a PhD in EE.

 

How about replacing the one wire regulator in that billet alt. with a standard reg. that is connected to the harness closer to the loads. Mike

 

Now there's an idea, anyone do this sort of thing before?

 

If you are running a serpentine belt system you can get an adapter that bolts onto the existing setup for a CS-144 alternator rated at 140amps and will put out about a 100 amps at 1k RPM. Do that in conjunction with the remote junction block and relays like madelectrical and you will be good to go. The early 90's Caprice cop cars and taxi's in the yards will have alt adapter and you want a 96 Caprice alternator that is a second design CS-144. Zero issues having enough power for anything you throw at it.

 

Pull the reg and take it to a local rebuilder.
They should recognize it on site.
Probably make some comment along the lines of what a POS.
If you can't find a rebuilder.
Send me a pic of the regulator. I have an independent rebuilder
about a mile from the house. The are a direct swap usually for a std and 1 wire reg.

PS, if they see the billet alt, you know what they'll do to the price for the reg....

 

Better yet if it is a 12SI you can get a rebuild kit for about $10 includes regulator, bearings, brushes, etc. from your local Autozone. If it is a CS130 then it is about $40 for a kit.

 

Yes