Alternator ability to affect fuel usage

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Alternator ability to affect fuel usage

November 29, 2019, 12:51:44 pm

A friend here in San Carlos who has a CCoach 45ft magna gave me this sheet to read as we where talking about charge output of alternators to batteries. Seems to really make a difference in long term fuel savings if you go to the higher output types.
JohnH

Re: Alternator ability to affect fuel usage

Reply #1 – November 29, 2019, 01:04:44 pm

That is why I always leave with my batteries fully charged. Years ago people used to argue they saved fuel by working at night, the alternate argument, did the alternator or generator in those days, take more fuel than they saved...But the truth is alternarors use quite a bit of power!
Safe Travels
Dave

Re: Alternator ability to affect fuel usage

Reply #2 – November 29, 2019, 01:17:13 pm

I changed to a Delco Remy 240 amp 40si ... no brushes to wear out, more efficient, less fuel, runs cooler and more available power. It is a direct replacement. It uses a sense wire. No excite wire needed. Digital voltage regulator. Works well for me.
Alternators by Model Family | Delco Remy

Most of the fuel savings comes from using less power from the engine to make the electrical power to meet your demands.

Comment:
Using a bit less engine power to run the alternator might save the cost of the alternator over time if you are a 200K mile per year over the road guy but in our coaches and the miles we drive you might save $20 a year. But if you need to change your alternator for what ever reason a more modern, more efficient alternator is worth a look.

Re: Alternator ability to affect fuel usage

Reply #3 – November 29, 2019, 02:23:10 pm

The fact page say they were looking to increase the efficiency 25%. A larger alternator may or may not be more efficient. Nevertheless a25% increase in efficiency would safe $301.40 in 50,000 miles. During that same 50,000 miles I'm planning on spending at 8mpg with fuel cost stated at $4 a gallon $25,000 in fuel. I would hope I would see a $301 savings but doubt it will be noticed. Double checking the belt tension to stay at 98% effective may prove to cost less and save more thou. Absolutely would recommend a high efficiency alternator, but would never see actual savings IMO.
Scott

Re: Alternator ability to affect fuel usage

Reply #4 – November 29, 2019, 02:25:28 pm

Guys? 746 watts equals 1 horsepower.

100 amperes at 14.4 volts equals 1,440 watts equals 2 horsepower.

Re: Alternator ability to affect fuel usage

Reply #5 – November 29, 2019, 05:25:00 pm

Figure in efficiencies (lack of) and a 100 amp alternator takes 4-5 HP at the pulley. Your 160 amp factory alternator takes more like 8-10. Maybe more. And that maybe 12 engine HP An ISM11 rated at 450 HP gets about 350 HP to the road if you are lucky. 100 HP just to turn the motor, fuel, system, pumps, belts, alternator, compressor, transmission, differential and drive shafts and turn the wheels.

If you need 80 amps a more efficient alternator uses less HP, less fuel, makes less heat.

Re: Alternator ability to affect fuel usage

Reply #6 – November 29, 2019, 06:51:25 pm

Rodger, My friend in the trucking industry switched everything to Brushless. He also switched his Foretravel. When the time comes I also will go brushless. Most alternator failure is brushes....
Safe Travels
Dave

Re: Alternator ability to affect fuel usage

Reply #7 – November 29, 2019, 07:34:19 pm

I went far enough in my testing to eliminate the alternators power draw. Fully charged. Solar running the coach while driving.

Among many other steps the results were worth the work in my opinion

Re: Alternator ability to affect fuel usage

Reply #8 – November 29, 2019, 07:36:51 pm

Quote from: Old Toolmaker – November 29, 2019, 02:25:28 pm

Guys? 746 watts equals 1 horsepower.

100 amperes at 14.4 volts equals 1,440 watts equals 2 horsepower.

It's also unlikely that you will be pulling even 100 amps for any extended length of time. Power to drive is going to be directly related to actual amperage delivered, not alternator maximum capacity. Yes, some small consideration for alternator efficiency, but a miniscule effect on fuel consumption.

Re: Alternator ability to affect fuel usage

Reply #9 – November 29, 2019, 09:14:42 pm

Most of you people go to FOT for service and pay for work on your coach and you discuss fuel mileage? SMH.

Re: Alternator ability to affect fuel usage

Reply #10 – November 29, 2019, 10:55:15 pm

Almost everyone wants to talk up THEIR fuel mileage. Just a way to score points.

On the other hand I made a deal with a customer on the idea that the prospective coach got 10mpg driven fairly hard.

"No way"

"If it does, will you buy it?"

Yes. We shook hands.

We filled the 300hp cat up together. Raised front off ground to fully fill the coach.

He drove. Went up cajon pass at warp speed.

Went back to the same station. Raised the coach again.

He ran the filler.

17.1 gallons over 179 miles.

Cost him $168k.

Fun days.

Re: Alternator ability to affect fuel usage

Reply #11 – November 30, 2019, 12:39:18 am

Quote from: John Haygarth – November 29, 2019, 12:51:44 pm

A friend here in San Carlos who has a CCoach 45ft magna gave me this sheet to read as we where talking about charge output of alternators to batteries. Seems to really make a difference in long term fuel savings if you go to the higher output types.
JohnH

The writer of the paper, Mike Bradfield was an Engineer at Remy, Inc. Over the course of his career he was responsible for the initial product engineering design that has led to over 3 billion dollars in sales and the receipt of 24 patents.

Just wanted to have more info out there than single page. I don't really trust studies like this. Results are usually skewed to show what writer wants shown and not ALL the test data is available. "White Paper" written in 2008, so applicability needs to taken into consideration.

Re: Alternator ability to affect fuel usage

Reply #12 – November 30, 2019, 09:54:31 am

Quote from: master2301 – November 30, 2019, 12:39:18 am

The writer of the paper, Mike Bradfield was an Engineer at Remy, Inc. Over the course of his career he was responsible for the initial product engineering design that has led to over 3 billion dollars in sales and the receipt of 24 patents.

Just wanted to have more info out there than single page. I don't really trust studies like this. Results are usually skewed to show what writer wants shown and not ALL the test data is available. "White Paper" written in 2008, so applicability needs to taken into consideration.

If you start with an overall efficiency of 21% with a 55% efficient alternator, move up the the latest and greatest alternator, gain 30% to give you an 80% efficient alternator, your overall efficiency rises to 31%.

But at what cost?

A brush-less alternator requires some pretty sophisticated electronics. How well with they hold up in an automotive application?

A new computer controlled DEF engine will give me better performance, fuel economy and drive-ability over the 4-speed Allison and 5.9L 12 valve Cummins. But how often will I be handing Cummins $2,500 for being serviced?

If this were an industrial application running 24 hours per day, I'd go with the latest and greatest. But traveling slowly around the country? That's using different return on investment parameters.

Re: Alternator ability to affect fuel usage

Reply #13 – November 30, 2019, 11:26:06 am

What are we arguing about? No one is claiming they are going to get significantly better mileage or save enough on fuel to pay for a new alternator. If you need a new alternator consider a newer technology, proven, more efficient brushless digital model. Or don't. Your choice. Just because you don't want to do it doesn't make someone else's choice wrong or your's right.

Re: Alternator ability to affect fuel usage

Reply #14 – November 30, 2019, 11:29:33 am

Spent the week at the ladies driving school a couple of years ago, don't recall one conversation about mileage in or out of classroom.

Re: Alternator ability to affect fuel usage

Reply #15 – November 30, 2019, 11:32:39 am

Find an old JC Whitney catalog and add up all the fuel saving devices by percentage, if you bought all of them and got over 100%
your tank would overflow.

Re: Alternator ability to affect fuel usage

Reply #16 – November 30, 2019, 12:02:29 pm

My chassis dyno has very good resolution and shows 2 hp changes easily. The alternator is a solid 2 plus hp draw on a car
I was pretty sure that my bus had a bad battery and the alternator tried to keep it at 14 volts with a bad cell . Changing bathe battery allows the alternator to catch up and the fuel use picked up a 1/2 mpg or a tick more over the 1000 mile check.

Re: Alternator ability to affect fuel usage

Reply #17 – November 30, 2019, 12:15:25 pm

Quote from: Roger & Susan in Home2 – November 30, 2019, 11:26:06 am

What are we arguing about?

I didn't know we were arguing Roger. Asperger's here behind the keyboard. My idea of fun is working, and I love percentage increase calculations.

My world is firmly mired in the past. My new car has a 16A generator.

Re: Alternator ability to affect fuel usage

Reply #18 – November 30, 2019, 12:31:00 pm

If you combine multiple modifications you can substantially increase your coaches power AND the mpg.

Rebuild then replace the alternator. Had a bad diode
Lowest rolling resistance tires. Correct pressure
Centrimatics
Alignment
Perfect batteries. Solar to turn down/off alternator after charging.
Resonator. Best flowing exhaust system
Blue tec air filter
Valve/injector adjust
Correct hydraulic fan motor controller
Non dragging brakes
M11 needs cam sensor and ambient altitude sensors upgraded.

I use the improved power at part throttle to torque up grades without the engine downshifting as much.

I waste the mpg improvement by just going faster.

At least 10 mph increase with same mpg

Re: Alternator ability to affect fuel usage

Reply #19 – November 30, 2019, 03:02:21 pm

Of course the alternator uses fuel. It uses more when the house batteries are badly discharged. It uses less when the batteries are fully charged. It also uses more with the headlights on.

So what? I've never seen a noticeable change in fuel usage.

Re: Alternator ability to affect fuel usage

Reply #20 – November 30, 2019, 04:14:59 pm

The only thing that I'm trying to sort out is the alternator mods / changes as I convert to my coming solar and lithium battery installation.
The more I read, the more confused I get cause almost every Foretravel seems a little bit different. I'm already regretting replacing my alternator ( 2 years ago ) verses haveing the original just rebuilt. The Foretravel techs told me that the new one is working just fine but the gage always reads 1 full amp less. As in gage at 12.1 and digital cig plug in gizmo says 13.1

Re: Alternator ability to affect fuel usage

Reply #21 – November 30, 2019, 04:20:20 pm

What gauge is reading low? And, assume it is reading one VOLT low. Please confirm.

And, if batteries are fully charged, by shore power, generator, solar, etc alternator draw is minimal. Said another way, if the batteries are fully charged when you start driving and your total consumption is 15 amps, it isn't going to take many HP to generate that.

Re: Alternator ability to affect fuel usage

Reply #22 – November 30, 2019, 04:29:47 pm

Correct.
It's the VDO dash volt meter that always reads about 1 volt less. Corrected example, dash at 12. verses digital cig at 13. Last nite with head lights and all on it ( VDO gage ) was close to the red zone but digital said 12.7 ish. So I wasn't to worried but still concerned.

Re: Alternator ability to affect fuel usage

Reply #23 – November 30, 2019, 04:41:26 pm

Does dash gauge voltage reading change when you turn on the headlights? If so, check for good ground for gauges or just add an additional ground.

Re: Alternator ability to affect fuel usage

Reply #24 – November 30, 2019, 04:47:27 pm

Yes, The voltage does change when the headlights are turned on. Lowers it. I will be adding an additional ground.
Thanks Brett.

And with as much chatter as I've heard on this forum about grounding issues,, I'll be embarrassed when that solves the issue.

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