Running a Generator at high Altitude

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Running a Generator at high Altitude

Postby Elderberry » Tue Jul 20, 2010 7:58 am

Here's some important information to know if you are planning on buying a generator for use on the playa.

Power decreases 3.5% for each 1,000 feet above an altitude of 500 feet. For
example, to operate at 4,500 feet (4,000 feet above rated generator altitude)
multiply 3.5% x 4 (4,000 ft) = 14% power loss. Then multiply .14 x your
generator’s power rating: 4,000 watts x .14 = a loss of 560 watts at that altitude.

Power decreases in extreme temperatures by 1% for each 10° F (5.5° C)
above 85° F (29.4°C).

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Re: Running a Generator at high Altitude

Postby 1durphul » Thu May 05, 2011 4:26 pm

jkisha wrote:Here's some important information to know if you are planning on buying a generator for use on the playa.

Power decreases 3.5% for each 1,000 feet above an altitude of 500 feet. For
example, to operate at 4,500 feet (4,000 feet above rated generator altitude)
multiply 3.5% x 4 (4,000 ft) = 14% power loss. Then multiply .14 x your
generator’s power rating: 4,000 watts x .14 = a loss of 560 watts at that altitude.

Power decreases in extreme temperatures by 1% for each 10° F (5.5° C)
above 85° F (29.4°C).

JK


Wow, this is great info JK. Somebody else should have told you. I would have had I read it before you posted the "nobody responded" thread.
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Postby CapSmashy » Thu May 05, 2011 4:27 pm

unless of course your generator adjusts for altitude conditions.
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Postby Trishntek » Thu May 05, 2011 5:41 pm

Generally speaking, any internal combustion engine loses efficiency with altitude. Nothing demonstrates this more vividly than motorboats. Water applies such tremendous resistance that a 100MPH boat at sea level will only achieve 85MPH at a mile high. So a 15% decrease in performance is pretty accurate for that which JK puts forth.

Modern engines with electronic fuel injection and ignition mitigate this to a point. But most generators do not have the bells and whistles of an automobile engine. Oxygen sensors, altitude sensors, air temperature sensors, humidity sensors and so much more goes into electronic engine controls.

The typical one-lung genset engine is nothing more than one found on a typical lawn mower.

edit to add: About the only way you could overcome the altitude issue would be with a turbocharger. The cost of that would buy a bigger genset.
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Postby EspressoDude » Thu May 05, 2011 8:35 pm

same general loss of efficiencies occur on the cooling towers of the Cherynobl design nuclear power plants. please consult operations manager at Apokiliptika Labs
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Postby CapSmashy » Fri May 06, 2011 9:30 am

Trishntek wrote:Generally speaking, any internal combustion engine loses efficiency with altitude. Nothing demonstrates this more vividly than motorboats. Water applies such tremendous resistance that a 100MPH boat at sea level will only achieve 85MPH at a mile high. So a 15% decrease in performance is pretty accurate for that which JK puts forth.


With a carbed engine, all you need to do is rejet the carb and you are good to go, no loss of power.

Modern engines with electronic fuel injection and ignition mitigate this to a point. But most generators do not have the bells and whistles of an automobile engine. Oxygen sensors, altitude sensors, air temperature sensors, humidity sensors and so much more goes into electronic engine controls.


I was referring to the genset on my bus in terms of adjusting for altitude automatically. Altitude is not an issue on the modern rv style gensets until you start going over 12k feet.

For portables, based on discussions on the various rv discussion sites, modern units like the EU series from Honda, do not start suffering any appreciable loss of power until the 5k foot range. A quick rejet, keeps you humming right along at full power.

The typical one-lung genset engine is nothing more than one found on a typical lawn mower.

edit to add: About the only way you could overcome the altitude issue would be with a turbocharger. The cost of that would buy a bigger genset.


Yeah, put put style generators are little more than a lawn mower engine for their power plant, but, rejetting the carb for the altitude solves the problem.

Edit: Takes about 10 minutes on a regular carburetor, lawn mower size or car size.
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Postby Elderberry » Fri May 06, 2011 11:45 am

CapSmashy wrote:
With a carbed engine, all you need to do is rejet the carb and you are good to go, no loss of power.

Edit: Takes about 10 minutes on a regular carburetor, lawn mower size or car size.


For those of us (me) that are not mechanically inclined, can you explain this in greater detail please?
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Postby Trishntek » Fri May 06, 2011 12:08 pm

IIRC, when I rejetted my carborators in Wyoming i lived over 7k feet elevation. It required a small adjustment of the spark plug gap and timing adjustment.

It ran like crap when I would drop into the river valleys and I would have to stop and adjust not only mixture but also timing.

That was,,,,, oh fuck! 30 years ago,,,, my memory may be fading a bit so YMMV.
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Postby gyre » Fri May 06, 2011 5:47 pm

Without adjusting compression you can only mitigate the problem and make the engine run as well as possible.
There will still be a power loss.

There is software for calculating power changes with altitude, usually presuming best tune.
My big ford is estimated to lose 90 hp in Denver.
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Postby ygmir » Fri May 06, 2011 7:21 pm

gyre wrote:Without adjusting compression you can only mitigate the problem and make the engine run as well as possible.
There will still be a power loss.

There is software for calculating power changes with altitude, usually presuming best tune.
My big ford is estimated to lose 90 hp in Denver.

I agree with Gyre:
I would submit, no matter what, short of turbo charging (or super), you will still experience power loss. Even with an intake compressor, at a point, you still lose. They just extend that elevation.
Lower O2 concentration, will effect the amount of fuel that can burn.
It's why you have to lean the carb as you gain elevation, so as not to run rich from unburnt fuel.
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Postby MyDearFriend » Sat May 07, 2011 5:51 am

Can I just interject here, that these kinds of practical applications of the principles drilled into my head so many years ago, make me

(((swoon)))


Y'all are blinding me with science, here & in the battery thread, and I love it.

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Postby gyre » Sat May 07, 2011 8:00 am

Nice.


I'm corresponding with someone from optima now, if anyone has any questions, esp about their stuff.
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Postby CapSmashy » Sat May 07, 2011 8:13 am

jkisha wrote:For those of us (me) that are not mechanically inclined, can you explain this in greater detail please?


Copied from another forum:

"Replacing Carburetor Jet for High Altitude Operation
Honda EU2000I

Tools Needed: Flat blade screwdriver, 8mm socket, and 10mm socket.

1. Turn ENGINE SWITCH to OFF.
2. Turn FUEL TANK CAP VENT LEVER to OFF.
3. Remove the MAINTENANCE COVER.
4. Remove the AIR CLEANER COVER and MAIN and OUTER FILTERS.
5. Drain GAS from the carburetor by loosening the SCREW on bottom of carburetor bowl. Close DRAIN SCREW when finished.
6. Remove HEX BOLT holding the black air box on. (8mm)
7. Remove TWO NUTS holding the air box and carburetor. (8mm)
8. Slide AIR BOX off carburetor studs and fold down out of the way.
9. Slide CARBURETOR out being careful with GASKETS (two, front and back).
You may have to remove one or two hoses from their brackets in order to slide off of studs.
10. Remove HEX BOLT holding carburetor bowl. (10mm)
11. Remove CARBURETOR JET by unscrewing with flat blade screwdriver and replace with NEW JET. Do not overtighten.
12. Reverse procedure for reassembly.

Elevation Honda Part No.
0 – 4000 ft, 62
4000 – 7000 ft. 60
6000 – 10000 ft. 58
Carburetor: KEI HIN
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Postby CapSmashy » Sat May 07, 2011 8:32 am

ygmir wrote:I agree with Gyre:
I would submit, no matter what, short of turbo charging (or super), you will still experience power loss. Even with an intake compressor, at a point, you still lose. They just extend that elevation.
Lower O2 concentration, will effect the amount of fuel that can burn.
It's why you have to lean the carb as you gain elevation, so as not to run rich from unburnt fuel.


Right, you have to lean them out, but you still get consistent power output. Its why NHRA bracket racers can still hit their bracket marks whether they are running at sea level in Houston or at 5800 feet at Bandimere in Denver.
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Postby ygmir » Sat May 07, 2011 11:25 am

CapSmashy wrote:
ygmir wrote:I agree with Gyre:
I would submit, no matter what, short of turbo charging (or super), you will still experience power loss. Even with an intake compressor, at a point, you still lose. They just extend that elevation.
Lower O2 concentration, will effect the amount of fuel that can burn.
It's why you have to lean the carb as you gain elevation, so as not to run rich from unburnt fuel.


Right, you have to lean them out, but you still get consistent power output. Its why NHRA bracket racers can still hit their bracket marks whether they are running at sea level in Houston or at 5800 feet at Bandimere in Denver.


at elevation:
how, would you get the same h.p. of you are running less fuel, and, less O2, per explosion?
sans an extra oxidation additive in said fuel or compressed intake air?.
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Postby CapSmashy » Sat May 07, 2011 12:18 pm

ygmir wrote:at elevation:
how, would you get the same h.p. of you are running less fuel, and, less O2, per explosion?
sans an extra oxidation additive in said fuel or compressed intake air?.


A pro bracket car may not have been the best example in retrospect due to the nature of the engine, but they do put down the same amount of power for their runs.

In terms of generators, specifically RV gensets, they have to perform equally at any "normal" elevation you would taking a coach. I have room to play with on the bus set up, but prefab coaches typically do not. They'll use damn near every last available watt to power the roof top air conditioners and other electrical items in the coach.

They compensate with fuel injected engines with computer control to keep the mix optimal for altitude, etc. and have to perform equally at sea level as they do at 10k feet to avoid destroying compressors on the ac units due to not enough power getting to them.

As mentioned earlier, the reports on the Honda EU's and Yamaha units from the camper forums are not showing any appreciable loss of power at elevation if they are rejetted for the altitude range as needed. The Hondas are good to 5k feet before you need to consider rejetting and my Hondas will power everything here at 800 feet as well as they power everything on the playa at 4k feet.

But, that is also why you pay a premium for RV specific gensets and for portables like the EU series from Honda due to the consistency of output power.
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Postby gyre » Sat May 07, 2011 12:51 pm

Bracket cars are only shooting for time, not power.
Their charts include altering shift points to compensate for other variables.
The ones I've driven had direct control af advance timing from the cockpit too.

Most engines don't compensate for altitude, except indirectly.
The superior form of injection deals better with it, but it isn't common.

The strategy with my colorado built engine was to build for altitude, leaving excess power at low ground.

If most engines work as well at altitude, they are losing power with settings most of the time, or have excess to start with, which I would think most common.
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Postby ygmir » Sat May 07, 2011 1:23 pm

I can see a few ways, to design around power loss at altitude.
such as putting a 5KW genset in, when a 3800 would do......so, even with diminished output, it'll still handle the load.
Or, if it need 16 h.p. to run a 4KW, put in an 18 h.p. engine, again, so it still has enough at altitude.

But, I'm unconvinced, that an engine that produces 10 h.p. at seal level, can produce 10 h.p. at 6K ft. compressed air intake notwithstanding.

There is a set amount of available energy in a given measure of fuel.
and, it takes a set amount of O2 to burn said fuel.

if, you lower both, for elevation (smaller jetting and lower O2 content),
I can't see any way, the engine will still make 10 h.p.

'course, I'm no engineer, or chemist, but how does less fuel and less oxygen, equal the same output?

Maybe, someone can 'splain that for me.
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Postby Trishntek » Sat May 07, 2011 4:15 pm

Nodding head in agreement.
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Postby gyre » Sat May 07, 2011 4:46 pm

All engines have more potential power when run leaner, but the price is obvious.
This is one way to get seemingly unreasonable power from a car.
You still have to flow adequate oxygen, of course.

The use of specialized cooling often allows more exploitation of this, like evans fluid, high pressure cooling, etc.
But doing it at altitude is not equivalent tuning.
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Postby oneeyeddick » Sat May 07, 2011 11:56 pm

Just for the record my poofers didn't seem any bigger at sea level than they did at BRC or anywhere else for that matter.
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