What are the options for alternators that fit on a 6.2 (alternator is mounted on the passenger side, truck has A/C and V-belts).

Is there an alternator that puts out about 65 amps at idle at about 230F underhood temperature?

Is it possible to run two alternators despite the A/C? Do they do that on the military ambulances, or do those have 24V alternators?

If I'd go to a junkyard to find something like a ~100 amp alternator, at which vehicles would I look for one (they have only gassers on the junkyards here)?

This is something I have been wondering about fer a while. I am planning to convert my truck to run on Waste Vegetable Oil and I was wondering how much spare amperage I have for any electrical goodies such as injector line heaters I would have. But, anyway, that is another subject altogether.

I was actually looking for something about alternator charges because of a recent example of God's perfect timing. I was changing my erl and I just happened to look down and said, 'hey, how come I ain't gots no alternator belt?, oh there it is, wrapped around the fan pulley.' The truck started fine a couple times and the voltage was just getting low, so I'm assuming it happened right before I pulled into the driveway and shut er down, which I am very thankful for because I was pulling a horse trailer.

So, after I put a new belt on there, I observed the charge on the factory gauge. It showed, what it did before, just shy of 13 volts. I was wondering. Is this a good reading? I thought it was supposed to charge a bit higher, but I isn't at all familiar with this diesel concept and the fact that this big beast has two honkin batteries.

So, as Mr. Lee was wondering, I think I need to go look at mine and see if it's a big 100 amp. I hope so. I was also noticing you put yer operating temp, Mr. Lee, at 230. Mine hangs around 200. Why is that, do ya think? I am planning to use the heat for my vegetable oil fuel. If there is something helping to cool it, I'm thinking I would like to remove it.

John

my 6.2 i had only had the standard gm 55amp alt. worked fine for the 4 years i had it. and it was cheap....less than $50

So, after I put a new belt on there, I observed the charge on the factory gauge. It showed, what it did before, just shy of 13 volts. I was wondering. Is this a good reading? I thought it was supposed to charge a bit higher, but I isn't at all familiar with this diesel concept and the fact that this big beast has two honkin batteries.


If your gauge has always been showing that voltage and you didn't have problems with empty or low batteries, then it's ok. These gauges are not very precise, and they are very likely supplied with cabin voltage which is very likely lower than battery voltage because the manufacturers try saving money on the wiring. You could grab your voltmeter and check battery voltage at idle. You should see about 13.8V, but it can be anything between 13.2 and almost 15V.

There's no difference to the alternator/battery in a gasser. They work the same, charging and discharging are the same. That you have the second battery with the Diesel only means that you have an increased capacity because the batteries are wired in parallel.


I was also noticing you put yer operating temp, Mr. Lee, at 230. Mine hangs around 200. Why is that, do ya think?


Not operating temps, but underhood temps :) Coolant temperature with the A/C on is a bit above 200F. The electrical fans blow through the A/C onto the radiator, and the clutch fan sucks all the air they blow through the radiator and blows it onto the engine. So I have a steady stream of lots of 200F air going under that hood, heating everything up. Add to that radiated heat from the engine (and think of the exhaust manifolds), and underhood temps will probably be somewhere between 200 and 250. The alternator also generates heat by itself and heats itself up, and the coldest air it can get to cool itself is already between 200 and 250F.


I am planning to use the heat for my vegetable oil fuel. If there is something helping to cool it, I'm thinking I would like to remove it.


Nah, your coolant temperature should be 195 and can go to maybe 220. At 220, I'd pull over and open the hood and turn on the heater to let it cool down. If it was going to 230, I'd have a problem that I would need to fix ...

There seemed to be some agreement that 170F is a good temperature for VO, but maybe that has changed over time. So if you get it to 170 or 180 when it enters the IP, that should be ok. The more you heat the fuel, the more power you loose, and I'd think that the IP can use some cooling and won't like it when the fuel is too hot.

my 6.2 i had only had the standard gm 55amp alt. worked fine for the 4 years i had it. and it was cheap....less than $50

Yeah, at the time I got the one I have, I was thinking that 78amps should be plenty for anything I'd might want to do, and the lifetime warranty on it was more important to me than getting a more powerful one. It was cheap and it works just fine, but I need more power.


As far as I could find out, the casing is a 10-SI, and the 12-SI is an improved version that has the same casing. They should also be pretty common.

Can anyone confirm the casing?

I think I'll go to a junkyard and see what they have. If they have something we can't tell the amperage of, I could buy it and take it to a parts store to have it tested; that should reveal how much it puts out. If it's lower than 100 amps, I could return it --- I'd tell them what I'm planning in advance to be fair, and if I get a test slip printed, I'd give it to them. If I can get a 100 amp alternator for cheap, I'll try that before spending $160 or so on a 140 amp version.


PS: Summitracing lists the CS130 as an alternator that would fit a 6.2. Can anyone confirm that a CS130 would fit in place of the SI-10/SI-12?

If your gauge has always been showing that voltage and you didn't have problems with empty or low batteries, then it's ok. These gauges are not very precise, and they are very likely supplied with cabin voltage which is very likely lower than battery voltage because the manufacturers try saving money on the wiring. You could grab your voltmeter and check battery voltage at idle. You should see about 13.8V, but it can be anything between 13.2 and almost 15V.

There's no difference to the alternator/battery in a gasser. They work the same, charging and discharging are the same. That you have the second battery with the Diesel only means that you have an increased capacity because the batteries are wired in parallel.



Not operating temps, but underhood temps :) Coolant temperature with the A/C on is a bit above 200F. The electrical fans blow through the A/C onto the radiator, and the clutch fan sucks all the air they blow through the radiator and blows it onto the engine. So I have a steady stream of lots of 200F air going under that hood, heating everything up. Add to that radiated heat from the engine (and think of the exhaust manifolds), and underhood temps will probably be somewhere between 200 and 250. The alternator also generates heat by itself and heats itself up, and the coldest air it can get to cool itself is already between 200 and 250F.



Nah, your coolant temperature should be 195 and can go to maybe 220. At 220, I'd pull over and open the hood and turn on the heater to let it cool down. If it was going to 230, I'd have a problem that I would need to fix ...

There seemed to be some agreement that 170F is a good temperature for VO, but maybe that has changed over time. So if you get it to 170 or 180 when it enters the IP, that should be ok. The more you heat the fuel, the more power you loose, and I'd think that the IP can use some cooling and won't like it when the fuel is too hot.


Yeah, I have spent considerable brain power to diagram what exactly I plan to do. There was concern that heating the IP more than 140 or so would cause it to die. On the other hand, speculation, that I agree with, is that it's thermal shock from going from cold diesel to hot VO, or vice versa. So, I was thinking of maybe heating the diesel and VO just before the IP. The catch is, I have read that it's not good to heat diesel above 140, I think it was, because air bubbles will form. So, it is convenient that the new debit card the bank sent me got lost and they had to send a new one. It means I can't rush to spend the money I had set aside for this. Being an old, disable veteran-type I don't have an abundance of dollars, therefore I need to have a clue before I spend the ones I gots.

Thanks for the response. Checking the voltage at the battery is a good idear. I would have done that before posting this question, but, unfortunately, my multimeter just died so I need to either make it worky or get a new one.

John

Ok, I found some things to read:

http://oljeep.com/gw/alt/edge_Alternator_Theory.html#Section_2
http://www.bzerob1.com/tech2/csupgrade.html


Even AcDelco says that an 78amp 12SI alternator makes only 23amps at 1600 RPM[1, 2]. That would be totally insufficient. However, if you look at [2], it appears that they have confused RPM and alternator shaft RPM[3].

What's the rate between alternator pulley and crankshaft pulley?

It's interesting to note that an "Optional R-terminal is available for use on models with electric tachometers, tach hourmeters and other devices."[1]


A CS144 alternator seems the be the best choice. I'm still trying to verify if there is a chance to fit it in place of the SI12. A CS130 might fit right in, but they are said not be good alternators --- but if I can pick one up on a junkyard for cheap and it makes an improvement and fits right in, that would be an option. I know that their successor, the CS130D, has serious problems with the bearings which can be worn out after only 50k miles.


[1]: http://www.acdelcotechconnect.com/html/tas_alt_12si.jsp
[2]: http://www.acdelcotechconnect.com/html/tas_alt_12si_output.jsp
[3]: http://www.acdelcotechconnect.com/html/tas_alt_12si_curve.jsp

Nice find lee!

Ok, I found some things to read:


What's the rate between alternator pulley and crankshaft pulley?




Lee, here's a good article on pulley ratio and alternators.
http://www.svapowerproducts.com/html/pulley_ratio.html

Lee, here's a good article on pulley ratio and alternators.
http://www.svapowerproducts.com/html/pulley_ratio.html

Thanks!

But they can't be right saying that "an alternator requires approximately 1hp for every 22.5amps of output". At 14V, that would be only 315W, and the alternator efficiency would be about only 23%. A 100amp alternator would eat 5HP, that's ridiculous. That same 100amp alternator would have to get rid of about 6000W in heat. I don't believe this.

They also say: "So the lower the pulley ratio, the less the hp the alternator needs to take from your engine." They would have to explain how the alternator could generate power out of nothing. No matter what the pulley size, it takes so much power to generate so much power.

Hm, read on, they have no clue of what they are talking about.

this is not bs...

had my caddie alt tested and it went over the rated 150 amps pulling MORE than 7hp.

tested at a alt shop, not the parts store. i dont know the equipment but he said its very expensive and had about 10 types of meters on it

Hm, 7HP would really be a lot. I tried to find out what efficiency alternators usually have, and they seem to be around 50%, with some "high efficiency" models that get 70%.

That's really poor, even at 70% --- I'd have expected them to get at least 80%, more like 90%.

Still what does the size of the pulley matter? The pulley doesn't change the efficiency of the alternator.

And I talked to the guy at OReilleys where I got my current alternator: I can trade it in and get the 108amp for about $20 more. That's really great service! I'll go for it since the CSx alterators are larger and won't (be easy to) fit. That should make a bit more power at idle and be able to charge the batteries while driving, and it won't have to run at or close to full output all the time.


Voltage on the batteries at idle with the A/C, the lights and transmission cooler fan turned on was 11.68V --- that clearly indicates that the 78amp alternator is insufficient. The batteries are probably like half discharged now. I'll see what voltage I get with the stronger alternator ...

from what i have seen in the past....thought this was awhile ago ....the higher output alts only put out higher amps at cruising speed.

The one i saw put out lower amps at idle than the factory 55 amp and twice as much down the road.....

Might want to look into that......

Hm, 7HP would really be a lot. ...

Ya its got a 3/4 wrap of a serpentine belt and still manages to slip at times.

the higher output alts only put out higher amps at cruising speed.


Yeah, it seems so. But since it would be very difficult to fit an alternator that has higher output at idle --- like a CS130D or CS144 --- there's not much I could do. The alternator will just have to recharge the batteries at highway speeds, but apparently the output of the 78amp version is too low to sufficiently do that. The voltmeter gauge hasn't been up to where it used to be since I'm running the three fans. It's like I'm draining the batteries very slowly, and turning off the A/C or the lights to recharge isn't really an option. Actually I tried that today, but suddenly it started to rain so that I had to exit the highway to stop and close the windows, and I turned the A/C and the lights back on. The wipers were going slower or faster, depending on RPMs, and too slow to keep up with the rain. That's the next thing I need to do something about, make a better power supply for the wipers.

And as you say, a stronger alternator can make the belt squeak. If you look at the CSx, they either have serpentine pulleys or dual V-belt pulleys. It's probably troublesome to run a CS144 on a single V-belt.

Bah, the new alternator doesn't fit. It's a bit larger.

Following with interest your alternator / charging system thread...

1) Have you done a load calculation, that is, your low beam headlights, running lights, a/c fan blower, and your (3) :eek: cooling fans? I know that just the headlights alone on low beam can pull 10~11 amps depending on type. The fan blower can pull another 15 or so. Then add the running lights for, say, 5 amps. Now not one, not two, but three cooling fans each pulling what, 10 amps? I come out with a possible 61 amps with all that stuff running... I would definitely recommend a bigger alternator even if it meant fabricating a new bracket, etc to make it fit... or, I'd find a way to cut your lighting loads (maybe make your own DRL resistor / relay circuit and cut your headlight power consumption?)

2) The other thought involves the batteries: In Texas (and where I live too) cold cranking amps are not what you need in abundance. You need the highest reserve capacity rating you can find. That way, when the accessories are all operating at idle and the alternator can't keep up, the batteries drop less voltage. Then when you're rolling again, the alternator has a fighting chance to get the charge back into the batteries.

Hm, 7HP would really be a lot. I tried to find out what efficiency alternators usually have, and they seem to be around 50%, with some "high efficiency" models that get 70%.

That's really poor, even at 70% --- I'd have expected them to get at least 80%, more like 90%.

Still what does the size of the pulley matter? The pulley doesn't change the efficiency of the alternator.

The horsepower draw isn't as noticeable on our high-torque engines... I recall noticeable RPM drops at idle with carbureted gasoline engines just by turning on the headlights. And when the a/c clutch kicked on there was usually a 'throttle kicker' solenoid to bump up the idle to handle the load... BTW, when I first got the beast that's what I thought the fast idle solenoid was for and I was beginning to troubleshoot why it didn't kick in when the a/c clutch engaged... my brother-in-law, the PO, quickly corrected me...

And of course, the pulley size will not only determine how fast the alternator spins relative to the engine, but also how much drag for a given load. You're right, the pulley doesn't determine efficiency... the alternator rectifiers, windings, etc. all have losses, mostly proportional to output.

1) Have you done a load calculation, that is, your low beam headlights, running lights, a/c fan blower, and your (3) :eek: cooling fans?


Yes --- I measured the fans and the blower. Each fan draws about 5.5amps, blower draws about 9 (and more than 15 to start running). Lights are 2*55W headlights plus (afaik) 2*10W taillights plus 2*5W markers/parking plus 5W license plate light. The A/C compressor clutch may be 10amps (i. e. close to that, I didn't measure). That adds up to roughly 50amps. The lift pump needs about another 5, the fuel shutoff solenoid needs like 2--4 I guess. Turn on the wipers, and about 70amps are used already. If I turn on the brights, it's about 10amps more. I don't have fog lights yet ... and I might put the radio back in ... So what I should have is at least a 140amp alternator, but they just don't fit. It also should put out 100amps at idle, but I don't think you can get one that does.


However, I've got a 94amp SI12 now, and it helps. The gauge is up to a good 13V now at highway speeds, and I'm hoping it'll get back to where it was once the batteries are fully recharged.

The 94amp made the belt squeak after I had been driving 1/2 mile, so I put on the new belt I kept as a spare, and it doesn't squeak anymore. If I had a more powerful alternator, I'd probably have a problem with the belt squeaking.



Now not one, not two, but three cooling fans each pulling what, 10 amps?
About 5.5 --- but the A/C definitely needs the two fans, it doesn't work with only one because it can't get rid of the heat, I tried that first. The third fan is on the transmission cooler --- I can turn it off depending on transmission temperature, but once the transmission fluid is warmed up, it needs the fan when the TCC is unlocked. Once it's warmed up and I turned on the fan, I don't like turning it off because I might forget to turn it back on ... I should have another transmission cooler with another fan on it (the front of the truck is full with coolers, I'd have to put it somewhere else) because on a hot day, I'm seeing up to 212F on the trans gauge as outlet temperature of the cooler. But there's not enough electric power now to run another fan. And if the voltage goes down, fuel pressure goes down and I loose power ...


I would definitely recommend a bigger alternator even if it meant fabricating a new bracket, etc to make it fit...
Yeah, but I don't have the means to make a new bracket. And it's far from easy to make one ...


or, I'd find a way to cut your lighting loads (maybe make your own DRL resistor / relay circuit and cut your headlight power consumption?)
A resistor would only turn some of the electricity into heat. What I could do is put in a switch so that I could turn on the headlights only --- that would be easy because I already rewired them --- but it would save only 2--3amps. What I would need is special DRLs, but I haven't seen any here yet. I don't like them very much anyway, I prefer the normal headlights.


2) The other thought involves the batteries: In Texas (and where I live too) cold cranking amps are not what you need in abundance. You need the highest reserve capacity rating you can find. That way, when the accessories are all operating at idle and the alternator can't keep up, the batteries drop less voltage.
Well, I need both :) That means, the batteries have to be able to provide enough current to get the engine started. But I also want to be able to run a compressor fridge box and eventually a parking heater. If I ever get a parking heater, I'll probably put another two batteries in to supply that --- weight doesn't matter much with this truck, and there is plenty of room.

The batteries are 800cca and 110 reserve capacity each. Larger ones don't fit on the battery trays ...


Then when you're rolling again, the alternator has a fighting chance to get the charge back into the batteries.

Yeah --- when I'm stuck in traffic, I can still turn off the lights. The fan on the transmission cooler doesn't need to run all the time, it settles in at 160--180F at highway speeds with the fan turned off, depending on ambient temperature. It has to run in traffic, but can be turned off on the highway. I think the 94amp alternator will have some power left to recharge the batteries; the 78amp one didn't.

The horsepower draw isn't as noticeable on our high-torque engines...


Well, I do notice when I turn on the A/C, that's a lot of drag. I also notice the 7 blade fan instead of the 5 blade, that's a lot of drag, too. Between the 78 and the 94amp alternator, I didn't notice a difference --- if anything, it seems to drag less, but that's probably because I had more power because the fuel pressure went up with higher voltage. But then, the belt was squeaking on the new alternator which would indicate that it drags more ...


I recall noticeable RPM drops at idle with carbureted gasoline engines just by turning on the headlights. And when the a/c clutch kicked on there was usually a 'throttle kicker' solenoid to bump up the idle to handle the load...


They have that on the electronically controlled 6.5s. When the load goes up, the PCM adjusts idle back to 650 RPM --- you can hear/feel RPMs go down for a second or two before the adjustment kicks in. I had a '96 Cadillac Eldorado with a Northstar, and it had an electric windshield defroster. When you turned on the windshield defroster, RPMs would go down some despite the PCM compensating, and the engine had to struggle to turn the alternator at idle.


BTW, when I first got the beast that's what I thought the fast idle solenoid was for and I was beginning to troubleshoot why it didn't kick in when the a/c clutch engaged... my brother-in-law, the PO, quickly corrected me...


Hehe :) I've started thinking about turning up the idle speed a bit to compensate for the drag of the A/C compressor, but I'm unsure if I should. I guess I'll wait how it turns out now with the new alternator. If the voltage is ok, I shouldn't have to turn up the idle speed, and when the fuel pressure is too low, it won't work anyway.


And of course, the pulley size will not only determine how fast the alternator spins relative to the engine, but also how much drag for a given load.

How would it be possible that a different pulley size makes for more or less drag at the same alternator output?

If you have an alternator putting out 100amps at 14V with 50% efficiency, it takes 2800W to turn that alternator. You can use whatever pulley you want (within reasonable limits, i. e. you can't make it so small that the belt can't turn it or so large that the alternator doesn't fit on the engine), but you will have to put in those 2800W to get that output.

Ok, it seems that alternator efficiency depends on shaft RPMs, so you might get less drag with a smaller pulley due to increased efficiency. But alternators already have small pulleys, just large enough to transfer the power. So the only way you could get less drag by changing pulleys would be to run the alternator at shafts speeds where it's more efficient --- but since alternator pulleys are already small, there's not much you can do.

The better way would be to build more efficient alternators ... That can't be too difficult.

Now the alternator belt keeps squeaking :( I retightned it two times today, and it's as tight as it gets.

Are the alternator pulleys really all the same? The belt sits a bit deep in the pulley maybe. Otherwise, it might just not be possible to drive a 94amp alternator with a single V-belt?

What can I do?

What belts are you using?

I cut/paste this from a forum post quite a while back.

DAYCO and Delco Part # 15480, HC41, or #88934343 { Effective Length 48" / Outside Circ 48.57" / Top Width .44" / Angle 36 degrees. for Fan & Alt. This one is the proper width.

GATES Part # 7480 {High Capacity V-Belt (Standard) HC41 3/8" x 48 5/8"}
Fan & Alt., Optional Belt This one is too thin and will slip.

GATES Part # 5725 {Special Belt HC47 7/16" x 48 7/8"}
Fan & Alt., Preferred Belt. Proper width.

ACDELCO Part # 5725 {HC47 7/16" x 48 7/8" #88933926}
BELT,V FAN & ALT.; PREFERRED BELT; SPECIAL BELT This one is the correct width.

It's a Delco 15480. That should be ok, they have never been squeaking with the 78amp alternator.

It says "13/32" x 48-5/8" OC".

Hmmm ... What do all these numbers mean? I guess 48-7/8 or 48-5/8 is the length, 7/16 the width? But 7/16 would be 0.4375, so are the 7/16 ones not as wide?

And 13/32 is 0.40625. Do I need a wider belt?

When the belt was first squeaking with the new alternator, I compared the pulleys. The pulley on the old one somehow looked less wide, but actually comparing them, I couldn't see a difference.

when i had my 6.2 they gave me a belt for a diesel....it physically had more belts or cords or whatever they had in them. It never slipped on me after using that one. But then again i also had the 55 amp alt.....i think those are under rated though.....

I had a squeaky alternator belt, but replaced that with a thicker belt and problem went away. Take the belt to parts store and ask for a thicker belt. Guess there is better grip with the wider belt.

My AutoZone 94 amp alternator went out last week, It squeaked all the time, I never could get it to stop, Now I have a 78 amp installed and it squeaks a bit but I think I can tighten the belt a bit more and get it to stop since I made a point not to get it too tight. I would like to go back to the 94 amp, let me know if you get the squeak to stop and what belt you use.
Rusty

BTW, take the old alternator back to autozone, they'll give you your money back.


I'll go back and see if I can get a wider belt. Maybe he can find out what vehicles the alternator he took the pulley from is for and what the width of the belt is that is used on those.

If you look at 13/32 vs. 7/16, the difference is only 0.79375mm. That's not so much that I would think it can make a difference --- I'll need something else. I think part of the problem is that the belt is drawn tight on the drivers side which makes it a bit sloppy on the passenger side so that it doesn't run as tight on the pulley as it sits when the engine is not running ...

Gates 9485: 1/2" x 48-7/8 --- 12.5/13mm x 1240mm --- that's wider and longer than the other ones, seems to work well so far. It had to be a bit longer because it's wider/thicker and won't be long enough to get it over the pulley. If you can't get that one, you can go even somewhat longer.


PS: Follow the instructions: Install, run 5 minutes, retighten. I didn't do that before with the others, but it seems to be a good idea --- in particular with this belt because it's pretty stiff.