High Idle / How much fuel per hour

I will be installing an inverter in the truck to run various items around the property, saws, drills, etc. I figure while I am at it I might as well install one big enough to run the freezer and fridge if / when the power goes out.

So, using the truck as a mobile generator 10k watts I am sure the truck will need to run @ high idle.

How much fuel does a 7.3 utilize per hour say at 1300 rpms with just the load of the accessories?

14 volts times 150amps only = 2100 watts FYI.

PsRumors said:

How much fuel does a 7.3 utilize per hour say at 1300 rpms with just the load of the accessories?

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Stock idle burns about 1/2 gal/hr. I figure I'm a little over 1 gal/hr at 1200rpm's with A/C cranking. High-idle is recommended for ANY extended idling on these engines - regular idle runs too cool and coking in combustion chamber and downstream of exhaust valves is common (due to LOW combustion chamber temps).

10k inverter is HUGE. Not sure stock alternator and batteries will be able to keep up with that for extended periods of time... :shrug:

I would say the watts tells the story.

Tom S said:

14 volts times 150amps only = 2100 watts FYI.

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Yep, watts are watts. A battery bank would alleviate some of that as it would store any unused wattage as long as there were periods where the full capacity of the charge source wasn't being maxed by the load. If you were running at max load then you would still eventually run into diminishing returns. I did something similar as I live off the grid and used to build homes off the grid and I got sick and tired of the constant drone from the generator. I bought the ambulance package single alternator which is 220amps I believe. There may be other alternator options out there. As I understand it, trying to put the dual alt package on a single alt truck is quite involved due to the massive wiring harness differences.


As to how much fuel per hour at a certain rpm, that's a somewhat complex calculation, as it would vary based on load from the alternator. We can easily figure theoretical fuel flow at a certain rpm based on cc's of fuel flowed at WOT, but beyond that at reduced throttle as far as I can tell you would simply be guessing at how many cc's the injectors are flowing. HRT or Gearhead may have some math for that based on percent throttle input.

Big Bore said:

We can easily figure theoretical fuel flow at a certain rpm based on cc's of fuel flowed at WOT, but beyond that at reduced throttle as far as I can tell you would simply be guessing at how many cc's the injectors are flowing. HRT or Gearhead may have some math for that based on percent throttle input.

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Actually after typing that I think percent throttle might be the key to the equation. If a scan could tell you what throttle percent is required under full load from whatever load you are putting on it, then possibly that percentage could be crossed over to percent of injector flow. I'm not sure how accurate that might be, but it could give you a rough idea, maybe.

Tom S said:

I would say the watts tells the story.

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Not really.

My plan is to run a bigger alternator, deep cycle batteries and there is no plan to run 10,000 watts 100% of the time.

PsRumors said:

Not really.

My plan is to run a bigger alternator, deep cycle batteries and there is no plan to run 10,000 watts 100% of the time.

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Yep, your available wattage would be based on amp hours translated to Kwh when using batteries. Tom is addressing the idea some people have that they can put a 5000w inverter in their vehicle and expect it to work properly and the fact that voltage is irrelevant, watts are in fact watts. It will work, right up until you drain the batteries down and you are relying on available watts from the alternator. And since most people aren't running deep cycle batteries in their trucks, that wont be long on a full load. And if the alternator is charging the batteries and powering other systems in the car, you wont have anywhere near the max output of that alternator, which BTW is usually rated in cold amps, not hot amps, so you will never be making anywhere near the cold rated amps output.

In any event bigger alternator and a battery bank should take care of it

How pricey is an invertor of the size you are looking at? I might have taken the wrong read on your post in regard to what you were wanting to do.

Tom S said:

How pricey is an invertor of the size you are looking at? I might have taken the wrong read on your post in regard to what you were wanting to do.

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His original post said he wanted to turn his truck into a mobile 10K generator so I think you were on track. He later said he was going to have a battery bank and larger alternator, so he's headed the right direction now.

Tom S said:

How pricey is an invertor of the size you are looking at? I might have taken the wrong read on your post in regard to what you were wanting to do.

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$900 is the best price I have found so far.

Big Bore said:

His original post said he wanted to turn his truck into a mobile 10K generator so I think you were on track. He later said he was going to have a battery bank and larger alternator, so he's headed the right direction now.

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I was headed in the right direction then just didn't go into all of the detail.

My main question / concern is fuel consumption.

I would be tempted to experiment. Fill one tank all the way to the neck and let it fast idle for two hours and refill it to the same point. There might be some marine data on this on the internet somewhere.

jphelzer said:

Found this while checking out Vegistroke's site:

How Thirsty do you think your PSD is at
an idle ?

Maybe a gallon an hour?
How about a gallon in 2 hours? Close, but not quite.

In my testing(+ - 10%) our 7.3's consume 1oz every
1min 12sec, So round that down to an 1oz/min. And of
course we all remember our basic measurements and
that there are 128oz/gallon. So with that in mind it will
take 2hrs and 8min to use one gallon of fuel.


PSD_idle

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Something I stumbled across

With that info above taken into account im pretty sure, at High idle, 1gal/hr would be safe to assume.

My truck in stock from (01 7.3) burns just under 1 gallon an hour on high idle..filled it up to the brim at my shop pump, let it idle 1 hour filled it up again and it took just about 0.89 gallons to fill it back up...

To get the best mileage per hour running, Watch the mass fuel being used under load then play with timing and ICP pressure till you reach a point of diminishing returns.

A cool idea of you had to do a lot of high idle for some reason.

Powerstroke Racer said:

To get the best mileage per hour running, Watch the mass fuel being used under load then play with timing and ICP pressure till you reach a point of diminishing returns.

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the same concept can be used for better fuel millage on the road to...


But you already now that LOL Well a hope you do.!!!!!!

Take a peek at this....http://cgi.ebay.com/10000w-Power-In...20660752015?pt=BI_Welders&hash=item4aa8dec68f

Tom S said:

A cool idea of you had to do a lot of high idle for some reason.

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I built an engine for a Not to be named company for a project armoured personnel carrier that ran strictly off hydraulics, engine had to make 600fwhp at 4200 RPM and had to be run at constant RPM with no throttle input just Idle RPM. When all was said and done the Army was quite happy with the results.

Powerstroke Cowboy said:

the same concept can be used for better fuel millage on the road to...


But you already now that LOL Well a hope you do.!!!!!!

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That is correct, you could have a 600+rwhp truck and get 26+mpg on the highway(that is where I stopped anyway)I think more is possible if you put enough time into it.