small engine CC's

So most of you probably noticed by now that virtually all small engine driven items are now sold with engine size listed in CC.

Doing some shopping for a few new small engine items and it occurs to me. Do i trust the new CC numbers anymore than i trusted the old HP numbers from before?

i submit
Amazon.com: Portable - 7000 Watt / Generators / Generators & Portable Power: Patio, Lawn & Garden

all 7K generators.

I see 389CC, 410CC, 420CC... and some generic "13hp"

i also compiled a list of conversions from various internet postings.... I post all of them as the conversion is not an exact science

205 cc = 8 to 9 Gross Torque = 5.5 to 6 hp
250 cc = 11 to 11.5 Gross Torque = 7 to 8 hp
305 cc = 13.5 to 14.5 Gross Torque = 9 to 10 hp
342 cc = 15.5 to 16.5 Gross Torque = 11 to 12 hp

123 cc = 4 hp
179 cc = 5 hp
208 cc = 5.5 to 6 hp
277 cc = 7 to 8 hp
291cc = 9hp
305 cc = 9 to 10 hp
342 cc = 11 to 12 hp
357 cc = 13 hp
420 cc = 13-15 hp

123 cc = 4 hp
179 cc = 5 hp
208 cc = 8 to 9 Gross Torque = 5.5 to 6 hp
277 cc = 11 to 11.5 Gross Torque = 7 to 8 hp
305 cc = 13.5 to 14.5 Gross Torque = 9 to 10 hp
342 cc = 15.5 to 16.5 Gross Torque = 11 to 12 hp
357 cc = 14 hp
420 cc = 15 hp

so are the 410CC just 389/390 overstated? Is it possible in todays world to take the same 420CC engine and really have that 13-15hp range depending on???? (tune?)

can you trust a harborfreight 420cc engine to put out the same power as a honda 420CC (notice i talk about power output and not longevity) Why/why not?

What say TBN?

Thanks for posting

These new rating drive me batty, just tell me rated hp.

Well in an automotive application for example look at the size of the engine from manufacturer to manufacturer and the different power outputs. I think the horsepower could vary on a small engines that are comparable in CC's but who know by how much unless you would dyno them. I would not expect a harbor freight engine to put out the same power as a Honda or last as long. I have seen some Chinese engine parts and the casting is very poor.I would trust the harbor freight engine as much or maybe even more than a Briggs.

Quote:

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Originally Posted by 94BULLITT

Well in an automotive application for example look at the size of the engine from manufacturer to manufacturer and the different power outputs. I think the horsepower could vary on a small engines that are comparable in CC's but who know by how much unless you would dyno them.

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I like the generator comparison because i KNOW they all run at the same rpm. Most automotive differences can be linked to various RPM measurements (not everyone measures at the same point) and i think most differences can be linked to head/intake designs.

but that isnt the case with small engines. They basically all use the same cross flow head designs. OHV are OHV engines.... perhaps you have some differences with the exhaust side of things, cheep engines with small noisy mufflers vs expensive ones with tuned quiet mufflers. (again a good generator comparison)


Is there a consumer report type that take OEM small engines and dyno them? I just dont trust marketing from anyone these days.

Quote:

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Originally Posted by schmism

I like the generator comparison because i KNOW they all run at the same rpm. Most automotive differences can be linked to various RPM measurements (not everyone measures at the same point) and i think most differences can be linked to head/intake designs.

but that isnt the case with small engines. They basically all use the same cross flow head designs. OHV are OHV engines.... perhaps you have some differences with the exhaust side of things, cheep engines with small noisy mufflers vs expensive ones with tuned quiet mufflers. (again a good generator comparison)


Is there a consumer report type that take OEM small engines and dyno them? I just dont trust marketing from anyone these days.

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Automotive horsepower rating are peak. Most small engines are rated at 36000 RPM. Alot of these small engines now are OHC like Honda and Subaru. One a enige there is not much power to be made from the short block. There still could be variations in the head, intake, carb, and cam to make different amounts of power for certain CC.

One thing I never understood about small engines is you take a 5HP engine they increase the CC a little and change the carb and cam and now it is 6HP. I would like to see you get gains percentage wise like that on a larger engine with similar upgrades.

If I were going to buy a generator I would prefer a propane or a diesel.

While we all know it takes true 2 HP engine to produce 1K so a true 7K generator would have to be powered by a true 14 HP engine.

All that is unknowable anymore.

What I have learned to trust is actually the rating like 6K full time load/8K surge rating which is often counted in seconds.

Never the less by dividing 8000/2 I can bank on acting/loading the generator as if it is a true 4K generator.

We live in a world of generator JUNK today.

Some are numbering the 6000/8000 generators today only as 8000 watts on the generator in big letters and covering the 6000/8000 in small print in the manual.

Has anyone seen the largest number/2 greatly over/understand a realistic 24/7 output capacity?

Quote:

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Originally Posted by schmism

So most of you probably noticed by now that virtually all small engine driven items are now sold with engine size listed in CC.

Doing some shopping for a few new small engine items and it occurs to me. Do i trust the new CC numbers anymore than i trusted the old HP numbers from before?

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There's no direct conversion, but you may be able to get in the ballpark. CC is a physical measurement of the engine, sort of like what size shoe you wear. There's not going to be much variance in this once the engine is built. HP depends on how well the engine is running, what the weather is like, what the fuel is like, how the seals are holding up, etc.

You can't take someone's shoe size and figure out how fast they can run 50 yard dash. You can sort of guess that size 12 means a certain length stride, and look at how many strides it would take to cover 50 yards, blah blah blah and maybe get in the right ballpark. But its just a guess. The CC measurement of the engine is going to remain constant if the carb gets gummed up, if the valve gets toasted, if the head gasket leaks, etc. The HP rating will not. The low output and small range on the small engines makes it a bit easier to guess as you're just guessing from a smaller pool of numbers. Most will fall in-between 5 and 15 hp so you basically have a 10% chance of guessing it right by throwing a dart at a dartboard.

Just pick a car engine and look at how many times the HP rating of that engine changes over time. Look at the Chevy 350, which is 5,700cc. Since it came out, the factory horsepower has changed from 145hp to 370hp.

Keith

Quote:

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Originally Posted by Gale Hawkins

While we all know it takes true 2 HP engine to produce 1K so a true 7K generator would have to be powered by a true 14 HP engine.

All that is unknowable anymore.

What I have learned to trust is actually the rating like 6K full time load/8K surge rating which is often counted in seconds.

Never the less by dividing 8000/2 I can bank on acting/loading the generator as if it is a true 4K generator.

We live in a world of generator JUNK today.

Some are numbering the 6000/8000 generators today only as 8000 watts on the generator in big letters and covering the 6000/8000 in small print in the manual.

Has anyone seen the largest number/2 greatly over/understand a realistic 24/7 output capacity?

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I think you're onto something there.
The electrical output is UL rated, right?
If so, you have a measure that can't be tweaked (much), and from which you can back into a reasonable estimate of HP.

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Small engines run approx 30-35cc per HP. Like some one else said, it depends on cam, carb, muffler, etc.



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