What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
(OP)
I have a very inexpensive 1000W 4-stroke inverter generator (Zipper ZI-STE1200IV) that's not quiet, but not noisy either. It's quieter than the normal generators that run at 3600rpm, but it standing next to it requires raising your voice a little to hold a conversation. Having gotten used to its level of noise, today I was blown away after encountering a Honda EU2000i powering a mobile fridge in a local market. First time hearing one in person. It was literally quieter than the sounds of people's voices nearby!
So, my question is, what are the factors that make the Honda so much quieter than mine?
Thus far I've concluded that it's probably not the "inverter" aspect. Mine is an inverter unit too, and it idles at 4000rpm. The Honda also idles at 4000rpm (3000rpm with eco throttle on).
The differences I've uncovered so far are:
- Mine is 54cc, the Honda is 98.5cc
- In mine the engine is only lightly covered by some plastic and an open frame, in the Honda most of the engine is covered by the dense red plastic panels
- Mine uses an overhead valve (OHV) engine, with a gear-driven camshaft near the crank, and pushrods to drive the valves. The Honda is an overhead valve engine with a camshaft in the cylinder head driven by an oil-immersed rubber timing belt.
- Different exhaust design? (perhaps someone can enlighten me here)
Anything else I'm missing?
So, my question is, what are the factors that make the Honda so much quieter than mine?
Thus far I've concluded that it's probably not the "inverter" aspect. Mine is an inverter unit too, and it idles at 4000rpm. The Honda also idles at 4000rpm (3000rpm with eco throttle on).
The differences I've uncovered so far are:
- Mine is 54cc, the Honda is 98.5cc
- In mine the engine is only lightly covered by some plastic and an open frame, in the Honda most of the engine is covered by the dense red plastic panels
- Mine uses an overhead valve (OHV) engine, with a gear-driven camshaft near the crank, and pushrods to drive the valves. The Honda is an overhead valve engine with a camshaft in the cylinder head driven by an oil-immersed rubber timing belt.
- Different exhaust design? (perhaps someone can enlighten me here)
Anything else I'm missing?





RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
You just explained all the reasons why the Honda is quieter.
In general terms with any engine noise produced above the idle level is a function of load. So you can't necessarily compare your generator to any other generator unless the loads are known to be the same.
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
189 Euros ( $205) vs 1000 US dollars. Some of that probably went legitimately towards Honda engineering's sound reducing efforts.
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
My question is more to do with the baseline noise at idle with no load. Granted the loads may have been different, but assuming the fridge the Honda was powering was maybe 200W (just an estimate based on its size) it is still much, much quieter than mine. Still not satisfied I've uncovered all the engineering secrets.
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
One obvious point is that the engine may be mounted on rubber bushes to the frame. The stiffness of those bushes can be optimised to minimise the transmissibility of vibration.
The Zipper appears to be open underneath, the Honda is fully enclosed. That's probably 5 dBA without even breaking a sweat. If you fully enclose the Zipper then it will overheat.
Cheers
Greg Locock
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RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
My first reply was a bit on the snarky side.. but still.
Your list of differences (full enclosure with robust materials, exhaust design details, differences in internal engine design) ARE the 'engineering secrets' which make one generator quieter than another.
Greg's points about isolation of the power unit and sound reflection off of the ground are valid as well.
In short, little generators are not terribly complicated machines. Honda certainly has a lot of experience designing good ones, but their nice little gensets aren't jam packed full of secretive skunkworks technology.
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
"With the reduction of exhaust noise over the past few years, noise radiated through the intake system is nearly equal to the noise radiated through
the exhaust system for all motorcycle sizes. They both correspond to throttle opening, engine speed, number of cylinders, engine displacement and engine
load, and are the two predominant noise sources for most modes of operation."
https://www.gpo.gov/fdsys/pkg/GOVPUB-C13-6027aa0c3...
Anyone who in their mis-spent youth had a car with a V8 and a 4 bbl carb likely ran with an unsilenced air cleaner at some time, and remembers the intake moan fondly.
https://www.youtube.com/watch?v=21NRsuVPrqQ
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
Greg - well-spotted! Makes sense too. Do you really think it will overheat? The cooling air intake is the grille around the recoil starter and the outlet of said air is around the muffler through the grille on the exhaust side (opposite side to recoil starter). Flow is left-to-right if you're looking at the side with the electrical outlet. Plastic channels direct air around the cylinder head - there doesn't seem to be significant flow around the crankcase, in fact the ground clearance is only around 5mm. I'm actually tempted to cut a piece of sound-absorbing mat so size and press it into the space underneath the engine as an experiment!
Tmoose - I love induction roar. For many months, I put up with the increased fuel consumption and poor low-speed torque (mushy throttle response) of a K&N cone filter just so my car would make that roar and I could hear the "psssht" of the stock recirculating blow-off valve. Eventually went back to the stock panel filter to get back the crisp throttle response, but here's what my car sounded like when I still had the K&N: https://youtu.be/XoZFnDGy4pk?t=29s
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
That's a question I can't answer from personal experience, but I would be that A) a lot of their solutions are covered by patents, and Honda is a company that can afford to defend its IP with veracity; B) Honda's solutions are all cost adders. Manufacturers of cheap generators almost certainly want their products to be as cheap as possible.
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
Ted
RE: What is it that makes Honda (and similar) "suitcase" portable generators so quiet?
The reverse is also true.