Stabilizing system voltage at idle

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Stabilizing system voltage at idle

Post by cgrey8 » Mon May 08, 2017 1:50 pm

I have a rather unique issue that most people easily solve in other ways. I've been able to tweak the tune on my truck to get it to idle right about 550-600 and thanks to a relatively mild cam, it does so quite well. However one of the problems I get is that the voltage dips and spikes. Apparently when Ford alternators go below a certain RPM, they completely cut out. What I witness is that at idle, I can watch my voltage fluctuate between say 13v and 12v and it isn't an organic floating. It is a very sharp transition that bounces between very specific voltages. When the voltage dips, I can just touch the throttle to bump the RPMS up to say 650 and the voltage jumps up. And as the RPMs drop back down, I get the fluctuation again. It's also related to load. It'll drop to 12 more quickly if I increase electrical load such as turning on headlights or turning the blower motor on high. But as soon as I touch the throttle and get it above about 650, voltage is restored and is solid again despite the higher load.

Now the problem is this sharp change in voltage also causes a sharp change in the Injector Offset and thus causes fueling to bounce rich or lean as the voltage drops from 13-to-12-to-13. I've adjusted the Injector Offset curve to correct for this and the AFR fluctuation isn't as bad as it was, but it is still present.

As I said, the average person would just bump idle RPM up a tad and avoid the issue. But not wanting to do this, I'm considering how effective putting super capacitors in the system would be to help blunt the sharp transition in voltage and make the transition more gradual. The battery doesn't "want to be above 12v. But supercaps have no problem sustaining the voltage they were charged to be at. So I'm wondering if when the voltage drops if the supercaps would gradually discharge down to 12v and as the alternator wants to spike, the supercaps could absorb the spike and again make the increase more gradual. I've never worked with supercaps to know if this would work or if they have a different behavior. But others here might have worked with high-end car audio to have a feel for whether this would work or if they would introduce some other characteristic into the mix that I'm not considering.

One thing I do know is capacitor technology has come A LONG way since the original car audio 1-2 farad "Coke-can" caps came out years ago. They have 350 farad super cap arrays that are only a tad bigger than laptop power supply boxes and can easily crank a 4 cylinder engine. I was just curious if anybody here had any experience with these and what the likeliness is a supercap array capable of ~15-16v would have any affect on this issue.
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Tue May 09, 2017 8:05 am

I would install a smaller alternator pulley to spin it faster and should be problem solved.
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Wed May 10, 2017 8:53 am

Most of the aftermarket is interested in slowing accessories to increase performance. Where would I find an alt pulley to do just the opposite?
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Wed May 10, 2017 9:03 am

First would be to measure your current pulley with a dial caliper. I am pretty sure you are using a Ford 3g Alt with the stock pulley. An overdrive pulley is probably what you need along with the next size smaller belt:

http://www.ebay.com/itm/Ford-3G-Alterna ... 2548.l4275
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Wed May 10, 2017 5:35 pm

Nice. I like that solution.
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Wed May 10, 2017 5:46 pm

Its definitely worth a try for $15 bucks. If it gives you an extra 20 amps at idle; it may be just what you need. I wish I could idle my car as low as yours.
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Re: Stabilizing system voltage with super caps

Post by 85GT » Thu May 11, 2017 8:14 pm

That's the size I put on a few years back for same reason. Works great. Idling at 600 with a cam a step higher then yours.
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Sat May 13, 2017 5:49 pm

Doing some research, Explorer 5.0l alts are 4g. The auction doesn't indicate the pulley works on 4g, however all my reading seems to indicate 3g and 4g are very similar. Is there a reason it wouldn't work being a 4g?
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Sat May 13, 2017 6:07 pm

The difference is the case and mounting locations. Shaft size is the same.
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Sat May 13, 2017 7:18 pm

I guess I can get the pulley and if it doesn't work, I'm only out $15.
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Sat May 13, 2017 7:25 pm

cgrey8 wrote:
Sat May 13, 2017 7:18 pm
I guess I can get the pulley and if it doesn't work, I'm only out $15.
If it doesn't work, Ill buy it off you. 8)
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Sat May 13, 2017 8:51 pm

I found this while googling around:
Image
Notice the spacer thickness difference. I could be wrong, but I believe the 4g is the one with a shorter spacer. Thus what isn't compatible is belt alignment.

But I wonder if an 8 groove might work?
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Sat May 13, 2017 9:21 pm

An 8 rib would work but I wouldn't go that route. I think you are correct between the two pulley differences. Let me see what else I can find. You definitely have a 4g?
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Sat May 13, 2017 9:35 pm

I am not finding anything 4g specific but I don't see why the spacer couldn't be machined down. Looking at the specs on ASP's site, I would machine the spacer down close to .10" out off the face.
24-2272_CTWY.jpg
24-2272_CTWY.jpg (8.88 KiB) Viewed 1098 times
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Sat May 13, 2017 9:45 pm

Yeah, it's a 4g. Multiple places have confirmed that the Explorers (both V6 and 5.0L V8s use the same 4g).

Although from what I can tell, the 4g is the thicker backspace, not the thinner one. So you wouldn't want to machine anything off a 3g/6g pulley. You'd need to shim it out.

I messaged the ebay seller asking him his thoughts on all this. He answered back confirming the backspace issue. However he hinted that there would be other issues trying to use a 3g/6g pulley on a 4g. He did warn that trying to use shims to make it work was a bad idea. I didn't disagree with that, but he didn't really answer back with options...just "no." He was a little condescending basically asking what I didn't get about this being a 6g pulley and to not use it on a 4g alt. I guess he didn't get that I was more interested in knowing what something "can" do not what it was designed to do.

Anyway I too came to the 8-groove 3g/6g pulley idea. And from what I can tell, that would work since it would put some additional grooves out further from the alternator where my setup would expect them to be. My guess is my 6 groove would use the center 6 grooves leaving a groove on the inside and outside of the 8 groove pulley. The only issues that I could imagine there'd be would be some clearance issue with the pulley and the alternator housing or maybe shaft length issues. Based on drawings of the 8 groove pulley (like the one you have above for the 6 groove), they don't require a longer shaft. They just locate the mounting bolt deeper inside the sheave.

Note all this is making the assumption that the thicker backspace pulley is a 4g AND the same 4g that's on my Explorer alternator. In the pic, I believe he said that pulley came off a van. I got it off a CrownVic forum.
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Sat May 13, 2017 10:04 pm

From the pic you posted the thicker spacer is the 3g and the thinner is the 4g. If you machined down the thicker spacer of the 3g it should in theory fit eliminating the need to worry about the shaft length. The shaft thickness should be identical. That's too bad the ebay seller was condescending towards you. This is how people are these days. The problem with using any other pulley than the 3g overdrive is that its not going to give you the desired overdrive percentage you need since all the other pulleys are 50+mm and the 3g od is 47mm. Just food for thought. What would your thought be to try a smaller crank pulley that would spin everything a little faster with no adverse effects instead of the alt pulley?
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Sat May 13, 2017 10:17 pm

Smaller crank pulley would be an underdrive...slowing down all accessories. That's what most people want for better performance.

To overdrive accessories via the crank pulley, the crank pulley would need to be bigger.


But its not an option for 2 reasons.

First off, my balancer is an explorer balancer with intigrated pulley. That pulley balancer was never used on anything else...at least not that I'm aware of.

Second, the machine shop had to machine out a lot of the counterbalance to work with my 331 crank. So if my balancer goes bad, an oem replacement will have to be modified to work.
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Sat May 13, 2017 11:46 pm

You're right on the crank pulley sizing. Brain fart on my part. I still think you can buy that 3g od pulley and have the spacer machined off to mach the measurment of your current pulley and be good to go. All you have to do is put a micrometer on your current pulley and give the measurement to your machinist or just give him both so he can match it...machine it...install it...done. Now do you think all that is worth 20 amps and will it help you as much as we anticipate?
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Re: Stabilizing system voltage with super caps

Post by cgrey8 » Sun May 14, 2017 8:07 am

That I don't know. But it might be something I do just to do it. Or I might play with the injector offset curve a tad more.

What I'm dumbfounded on is why there aren't more articles or forum posts discussing the differences in 4g pulleys and the rest. It seems 4g is something of an oddball meant only for very specific tight-fit applications.
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Re: Stabilizing system voltage with super caps

Post by EDS50 » Sun May 14, 2017 8:52 am

I think its the least popular alternator due to it being a pancake style case and is the oddball out of the family case wise. You probably dont see anything out there other than 1g, 2g and 3g since they are the most popular and the 3g is the most versitile spanning a wide range of aftermarket installs. The 4g and 6g are very specific alternators due tontheir mounting styles. The 3g is the easiest to adapt tonjust about anything out there. I dont think messing with the offset will net you any favorable results and you would be better off raising the idle to boost the amp output. Me personally, I would try the 3g pulley route and have it machined properly since thats the easiest and most cost effective option in my opinion.
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Re: Stabilizing system voltage at idle

Post by cgrey8 » Sun May 14, 2017 9:57 am

If I did do this, I'd probably see if I could get a used 4g alt so I would have a stock pulley and a housing I could confirm fitment with. And I'd have a spare in hand if I ever needed it.

In all this looking at alts I've done, I'm noticing eBay listings where what they are describing is not what's pictured. I found a $20 inc s/h listing for a 4g off an application that did use a 4g, but the picture of the alt in the listing is clearly a 3g. Prior to me looking into this, I'd have never known the difference.

Even if I do nothing, just the discussion and research has been useful.
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Re: Stabilizing system voltage at idle

Post by cgrey8 » Sun May 14, 2017 5:48 pm

I went down and looked over my truck's alt and compared it to the alt on my stock 97 Ranger 4.0L. The 89 Ranger with the 97 Explorer setup is definitely a 4g. Interestingly the 97 Ranger has a 3g. I would've thought the 97 Explorer and 97 Ranger would be very similar...but no. After looking at it closer, I can see why the 97 Explorer uses the 4g. It is a TIGHT fit even with the 4g. So it's no surprise that the pulley with the shorter sleeve is the 4g. That was just part of making a much more compact alternator.
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