Making an Onan Quiet Generator Quieter!

[IdleUp]

Making an Onan Quiet Generator Quieter - Mike Mas



Hello - I thought I would share one of my recent projects - For the most part the “Q” Onan generators which stands for “Quiet” have very respectable noise levels today, since unlike earlier generators which had thin steel cases with no insulation, modern generators use composite cases and some insulation.

Onan generator noise levels can be easily reduced further if Onan would add a throttle/ load speed control, so instead of running near wide open all the time, they could just idle when not under heavy loads somewhat like a Honda generator. Instead Onan runs their engine almost at full rpm even with no loads at all, which wastes fuel and adds extra noise.

For the most part - I find both my Onan 3600 LP generator on my Leisure and my Onan 2500 LP on my Sprinter very quiet. Even though the noise levels are respectable, I figured if I can spend a few hours and make it quieter, it would be an improvement.

Fortunately, I ended up with half a box of Road Kill from my last project, so I decided to use it on my genny to reduce its noise level further. If you’re not up to speed on Road Kill;

https://stingerelectronics.com/catal...ping-roadkill/

It's an amazing product which I use on aircraft, cars, trucks motorcycles, etc. which consists of a layer of thick composite type rubber which is foil backed on one side and sticky on the other, so you can apply it to almost anything and its heat resistant as well. For vans with generators side mounted or under belly, you can add this to the generator box or even the undersides of the floor to help deaden noise, let me tell you, this stuff works!



On my Leisure Wonder the generator is very quiet already thanks to the fact its mounted behind a thick fiberglass door and the exhaust exits on rear drivers side, but since the generator is on the "Patio" side, I wanted it as quiet as possible.

Before I began the project, I first wanted to record the sound level on my iPhone DB meter. As I opened the app, I registered 56 DB in general noise with everything shut down. Next, I started the generator and stood back 6 feet and registered around 79-80 DB, which is very quiet for a generator when considering a vans diesel engine registers about the same noise level.





To begin the project on my coach - I decided to first cover my Leisure’s generator door with Road kill since some noise was passing through the door itself. On this coach the door is fiberglass which deadens the noise somewhat, however many coaches use a thin aluminum door which will actually amplify noise from the generator, this is where you'll see an amazing difference.







Next, I removed the generators inspections panel and and added some Roadkill to the areas the that were not covered from the factory to kill so noise.



To keep the noise from spreading to the right and left of the generator, I added a few pieces to the right and left side panels of the generator housing box to deaden some of the noise.



After I completed all my stick-on RoadKill applications, I noticed there was a void on top of the generator between the coaches floor, so I cut some non-sticky double sided foil backed insulation material we had in the shop from a roll, then slide it on top of the generator and held it in place with some foil tape. This will help deaden noise from reaching the floor of the coach.







After I wrapped the job up, I moved the coach back outside and started the generator again. With a full load, I noted a major difference of 5 DB less noise for a reading of only 75 db, which is now no louder than a Powerstroke or Sprinter diesel engine running at 1500 rpm, therefore making the project well worth the time that it required.

Regards - Mike

[booster]

Onan's can't use a throttle for speed control as they are fixed rpm AC generators and would lose 60 hz power. They would have to totally redesign to be an inverter generator to be able to run rpm control instead of governor/load control at fixed speed.

[IdleUp]

Thanks for the reply Booster - Onan needs to advance their systems, piratically every generator available today had a throttle / load feature, it would reduce both the units noise level and fuel usage.

Thanks!

[Bud]

Originally Posted by IdleUp

Thanks for the reply Booster - Onan needs to advance their systems, piratically every generator available today had a throttle / load feature, it would reduce both the units noise level and fuel usage.

Why should they? "I thought I would share one of my recent projects - For the most part the “Q” Onan generators which stands for “Quiet” have very respectable noise levels today"

Bud

[booster]

Originally Posted by IdleUp

Thanks for the reply Booster - Onan needs to advance their systems, piratically every generator available today had a throttle / load feature, it would reduce both the units noise level and fuel usage.

Thanks!

I think you will find that statement only to be true for smaller portable units where the inverters are more practical. The last time I looked the bigger units are still fixed speed design, just like the Onans are. I don't ever recall seeing an mounted RV generator that was inverter style. If you know of some let us know.

[IdleUp]

Thanks for the replys - More than likely some of you guys would not remember just how noisy generators actually were back in the late 70's when I started RV'ing in my 1978 26' Winnebago Brave. When you started the generator, everyone knew it was up and running. All the noise from the rattle of the engine and exhaust was amplified by the thin sheet metal shrouding.

Onan Q generators are fairly quiet, especially when you get in the 6-8-10Kw diesel range which were really loud. Most new QD generators are mounted in the nose between the frame rails and you can barely hear then in the coach or even on the patio side.

I spoke to one of the top guys at Cummins years ago, asking why they didn't lower the speed according to load like other generators and was told they wanted the engine to stay "Ahead" of the load for the heavy amperage to start a AC compressor. Even if they reduced the RPM 50% during compressor cycles it would be a major improvement. My Kawasaki generator drops down to idle when needed and it's now well over a decade old. I used it for pull behind AC units and it never choked when starting the AC unit.

As I mentioned, my Newmar New Aire was equipped with the Xantrex 3000 inverter and during compressor starts the inverter drops in the line with up to 5000+ watts to help the grid power start the compressors. In fact, in my garage the amperage is so low it never would start a AC unit on my older coaches, but the Newmar 15Kbtu AC started fine.

If you're going to run an AC unit the best choice is the EU3000 (20 amps) which is quiet @ 55 DB. It has its own electric start system, which can run overnight on its 3.5 gal tank. The only problem its heavy if you're not going to hitch mount it, its 130 lbs requires a few guys to get in the back of a truck or in an RV.

Regards - Mike

[booster]

Originally Posted by IdleUp

Thanks for the replys - More than likely some of you guys would not remember just how noisy generators actually were back in the late 70's when I started RV'ing in my 1978 26' Winnebago Brave. When you started the generator, everyone knew it was up and running. All the noise from the rattle of the engine and exhaust was amplified by the thin sheet metal shrouding.

Onan Q generators are fairly quiet, especially when you get in the 6-8-10Kw diesel range which were really loud. Most new QD generators are mounted in the nose between the frame rails and you can barely hear then in the coach or even on the patio side.

I spoke to one of the top guys at Cummins years ago, asking why they didn't lower the speed according to load like other generators and was told they wanted the engine to stay "Ahead" of the load for the heavy amperage to start a AC compressor. Even if they reduced the RPM 50% during compressor cycles it would be a major improvement. My Kawasaki generator drops down to idle when needed and it's now well over a decade old. I used it for pull behind AC units and it never choked when starting the AC unit.

As I mentioned, my Newmar New Aire was equipped with the Xantrex 3000 inverter and during compressor starts the inverter drops in the line with up to 5000+ watts to help the grid power start the compressors. In fact, in my garage the amperage is so low it never would start a AC unit on my older coaches, but the Newmar 15Kbtu AC started fine.

If you're going to run an AC unit the best choice is the EU3000 (20 amps) which is quiet @ 55 DB. It has its own electric start system, which can run overnight on its 3.5 gal tank. The only problem its heavy if you're not going to hitch mount it, its 130 lbs requires a few guys to get in the back of a truck or in an RV.

Regards - Mike

How do you lower the speed on an AC generator that requires 3600 or 1800 rpm (depending on winding style) to generate 60 hz power? It just plain can't be done that I know of. You can't run a 60 cycle AC air conditioner on 30 cycles as even if it would start it would quickly fail. If they switch to a DC generator and you had to add your own inverter it would work, by why would they do that when everyone wants AC power anyway?



I have heard that same statement from Cummins, but what they told me they were talking about when I asked a development engineer about it (he showed up to buy a saw I was selling on Craigslist) he said they are talking about he questions they get about why the units are running at slightly above 60hz, like 62hz or so. This is to allow for the rpm sag in the engine when a big load is added to keep the frequency from dropping to low and causing a death spiral of power.


We need to see how this could be done without a full redesign to inverter technology, so please fill us in on how they would do that.

[IdleUp]

Originally Posted by booster

How do you lower the speed on an AC generator that requires 3600 or 1800 rpm (depending on winding style) to generate 60 hz power? It just plain can't be done that I know of. You can't run a 60 cycle AC air conditioner on 30 cycles as even if it would start it would quickly fail. If they switch to a DC generator and you had to add your own inverter it would work, by why would they do that when everyone wants AC power anyway?

.

It's simple you just run the output of the generator into an inverter!

In most cases the generator puts out multiphase AC current from an alternator which is converted to DC. This DC current is feed to the generators inverter which converts it back to 120 volts AC @ 60 cycles regardless of generators speed. The inverters microprocessor maintains a solid set voltage at 60 cycles and controls the generators throttle to maintain the constant amperage needed for the load.

Regards- Mike

[SteveJ]

Originally Posted by IdleUp

It's simple you just run the output of the generator into an inverter!

In most cases the generator puts out multiphase AC current from an alternator which is converted to DC. This DC current is feed to the generators inverter which converts it back to 120 volts AC @ 60 cycles regardless of generators speed. The inverters microprocessor maintains a solid set voltage at 60 cycles and controls the generators throttle to maintain the constant amperage needed for the load.

Regards- Mike

I'm running a 2800 watt(3100 surge) Champion inverter genny. It has a switch for eco or full speed, eco being the setting for variable speed. My 10k BTU room type A/C on the R/T starts just fine on the eco setting, though I can hear the genny doing all it can to bump up the speed. It comes up fairly quickly. If nothing else major is drawing current the bump up in speed is minor. Kick in the toaster oven and that genny is singing like an Onan, though still quite a bit quieter.

[IdleUp]

Originally Posted by SteveJ

I'm running a 2800 watt(3100 surge) Champion inverter genny. It has a switch for eco or full speed, eco being the setting for variable speed. My 10k BTU room type A/C on the R/T starts just fine on the eco setting, though I can hear the genny doing all it can to bump up the speed. It comes up fairly quickly. If nothing else major is drawing current the bump up in speed is minor. Kick in the toaster oven and that genny is singing like an Onan, though still quite a bit quieter.

Steve thanks for the reply - hey what would be nice is if the gen companies would give us a "variable" user throttle setting, so if we're using high load devices, we could turn up the high-idle a bit so the engine can stay on top of the loads.

Mike

[booster]

Originally Posted by IdleUp

It's simple you just run the output of the generator into an inverter!

In most cases the generator puts out multiphase AC current from an alternator which is converted to DC. This DC current is feed to the generators inverter which converts it back to 120 volts AC @ 60 cycles regardless of generators speed. The inverters microprocessor maintains a solid set voltage at 60 cycles and controls the generators throttle to maintain the constant amperage needed for the load.

Regards- Mike

Yep, but the generator unit is not a standard AC generator as it is generating many (300?) ovelapped sine waves so you can't just slap a rectifier and an inverter on an Onan style generator and have an inverter one. Apparently they need that many phases to smooth out the AC at lower rpms. You need a completely different AC generator section.



Back to what I said originally, the only way Onan can have throttle control is build the generator as an inverter generator. Your statement that all you need to do is add a rectifier and inverter won't do it, I think, or someone would have kit for it. To me if you have to change the generator design, add a rectifier, and add an inverter, and likely have to have a computer controlled throttle to vary the speed, you have just redesigned the generator from a conventional to an inverter style as all you have left is the engine. I know you will disagree with that, but that is certainly the way it appears to be from what I have seen.

[booster]

Originally Posted by IdleUp

It's simple you just run the output of the generator into an inverter!

In most cases the generator puts out multiphase AC current from an alternator which is converted to DC. This DC current is feed to the generators inverter which converts it back to 120 volts AC @ 60 cycles regardless of generators speed. The inverters microprocessor maintains a solid set voltage at 60 cycles and controls the generators throttle to maintain the constant amperage needed for the load.

Regards- Mike

Yep, but the generator unit is not a standard AC generator as it is generating many (300?) ovelapped sine waves so you can't just slap a rectifier and an inverter on an Onan style generator and have an inverter one. Apparently they need that many phases to smooth out the AC at lower rpms. You need a completely different AC generator section.



Back to what I said originally, the only way Onan can have throttle control is build the generator as an inverter generator. Your statement that all you need to do is add a rectifier and inverter won't do it, I think, or someone would have kit for it. To me, if you have to change the generator design, add a rectifier, and add an inverter, and likely have to have a computer controlled throttle to vary the speed, you have just redesigned the generator from a conventional to an inverter style as all you have left is the engine. I know you will disagree with that, but that is certainly the way it appears to be from what I have seen.

[IdleUp]

Originally Posted by booster

Yep, but the generator unit is not a standard AC generator as it is generating many (300?) ovelapped sine waves so you can't just slap a rectifier and an inverter on an Onan style generator and have an inverter one. Apparently they need that many phases to smooth out the AC at lower rpms. You need a completely different AC generator section.



Back to what I said originally, the only way Onan can have throttle control is build the generator as an inverter generator. Your statement that all you need to do is add a rectifier and inverter won't do it, I think, or someone would have kit for it. To me, if you have to change the generator design, add a rectifier, and add an inverter, and likely have to have a computer controlled throttle to vary the speed, you have just redesigned the generator from a conventional to an inverter style as all you have left is the engine. I know you will disagree with that, but that is certainly the way it appears to be from what I have seen.

Thanks Booster however I think you misunderstood me, I didn't mention adding a rectifier and and inverter to an Onan. You asked how a generator could run at slower speeds and still retain 60 cycles and I mentioned its accomplished by having a AC generator which convert to DC and runs it though an inverter.

You're right Onan needs to advance their generator technology, it would be a no brainier for them to offer a more advanced generator for RV's. As I mentioned, I have a 6500 watt Kawasaki generator that is over 10 years old and it has that technology. Onan has the business and they just keep putting out the same old technology generators. Maybe this lithium thing will get them improving their gen sets.

Mike

[avanti]

Sadly, given the limited size of the market and the fact that interest in having a genset seems to be rapidly waining, RV genset technology is unlikely to attract the engineering investment dollars that developing a state-of-the-art unit would require. ICE is dead, and the R&D money goes elsewhere.

There is a vicious cycle: Onan gensets are ridiculously noisy, therefore almost everybody hates them, therefore they seek alternatives, therefore the momentum is with second-engine alternators and large batteries. That, combined with the hope that a practical propane fuel cell is on the horizon makes me extremely dubious of the chances that we will ever see a small RV genset that is quiet enough to be practical.

[booster]

Originally Posted by avanti

Sadly, given the limited size of the market and the fact that interest in having a genset seems to be rapidly waining, RV genset technology is unlikely to attract the engineering investment dollars that developing a state-of-the-art unit would require. ICE is dead, and the R&D money goes elsewhere.

There is a vicious cycle: Onan gensets are ridiculously noisy, therefore almost everybody hates them, therefore they seek alternatives, therefore the momentum is with second-engine alternators and large batteries. That, combined with the hope that a practical propane fuel cell is on the horizon makes me extremely dubious of the chances that we will ever see a small RV genset that is quiet enough to be practical.

I would certainly agree, and the fuel cells are the prime hope at this point. Of course, we also need one that will run on gasoline and another for diesel

[IdleUp]

I'm not sure which generator you're referring to, but 60 db is just about the level of conversation, so we're talking Honda type quiet operation on diesel generators. On my New Aire 8KW, once you walked around the either side of the coach, the gen was for the most part inaudible. Keep in mind, Onan is not going to put a lot of money in making gas generator quiet as the diesel, simply for the fact of the price point. They have to keep them affordable.

Both my cheapie propane generators 2500 and 3700 are around 74 DB, which is more than acceptable and no louder than the vans engine running, so neither is "Noisey" by any means. Regardless, if you need to run a microwave to make dinner or turn on the AC for a snooze, a generator will always put a smile on your face! I've been using generators in RV's for 40 years and I never had one complaint or even a one breakdown. I also never had one neighbor tell me my genny was too loud.

I guess the old saying "It Is What It Is" applies to generators.

Mike

[avanti]

Originally Posted by IdleUp

Both my cheapie propane generators 2500 and 3700 are around 74 DB, which is more than acceptable and no louder than the vans engine running, so neither is "Noisey" by any means.

You keep saying this, but anyone who has lived with an Onan knows that the claim is beyond ridiculous.

Regardless, if you need to run a microwave to make dinner or turn on the AC for a snooze, a generator will always put a smile on your face! I've been using generators in RV's for 40 years and I never had one complaint or even a one breakdown. I also never had one neighbor tell me my genny was too loud.

What a joke. NP campgrounds (and many, many others) won't even ALLOW running genesets at night.

I guess the old saying "It Is What It Is" applies to generators.

Well, we can agree on that, at least.

[booster]

The diesels in class A RVs that are Onans are orders of magnitude quieter than the air cooled ones and especially the 2800/2500 ones that are in almost all class b's. Water cooling is inherently quieter because of the water jackets, and it also requires less cooling air to the block so the case can be more enclosed and insulated.



We had first hand experience with the difference at Teddy Roosevelt Nat Park, North the last time we were there. We were on a big circle of pull off campsites so they all faced a wide open field in the middle. The sites, because they are nose to tail pull offs are further apart than back in sites by a quite a bit.


The site next to use had a huge old super C with an Onan diesel maybe 100' from us. A couple of sites further down the same side was a Roadtrek Sprinter with a 2500 Onan and probably 300'. Almost directly across the open area from the Sprinter was fiver with a 3K Champion inverter generator and was a bit further so about 350' away.


The diesel Onan, that was lots closer to us was the quietest by far and we could barely hear it when out of the van and not at all when inside with the windows shut. The Champion was much further away but louder than the diesel by a noticeable amount. It was irritating when outside and still very hearable when in the van. The Onan that was nearly as far away as the Champion was louder than the other two generators combined and extremely irritating as they ran it a lot, either charging batteries or watching movies in the evening. There was truly no comparison of the three and the diesel Onan was far and away the worst, and the gas air cooled Onan was far and away the worst. Our solar kept us full all the time we were there, which was about 5 days IIRC, running the microwave and watching movies, etc, and with the vent fan and circulating fans running all day, and we didn't irritate anyone with the noise.



We had a 2800 Onan and it was horribly loud, shaking, and smelly.


So, in the short term picture, with big battery banks getting more common and air conditioning desires also wanted, along with the big inverters now used, would it be more desirable to just have a 2500 watt DC generator, which would just be a motor and alternator with regulator. That would get rid of the issue of slow battery charging off the generator that is currently limited by the shore charger size but still allow AC use continuously. The overload shutdowns at compressor restarts would just be absorbed by the batteries similar to the hybrids now but with nothing special needed like a hybrid. This would also allow it to be set at whatever speed, output you wanted/needed either manually or automatically like Idleup would like it to. If only AC running, it could be at 1000 watt output probably. Basically replace the engine generator with the same thing, different power source so no autostart conflicts, possible idling rules, running vehicle engine all the time, etc. Certainly not the long term solution to it all, but might be a decent compromise in between.

[IdleUp]

You guys are great - Your reply's are interesting and for the most part, I think we're all saying the same exact thing!

Forget generators, whoever invests in piston generators is going lose money - It's all going to end up with lithium gentleman - Tesla's (Elon's) cells from his mega plant are setting all new standards in lowing the price to where lithium will be commonplace in most every vehicle and RV.

All we have to do is wait a few more years so they are affordable!

Regards - Mike

[booster]

Originally Posted by IdleUp

You guys are great - Your reply's are interesting and for the most part, I think we're all saying the same exact thing!

Forget generators, whoever invests in piston generators is going lose money - It's all going to end up with lithium gentleman - Tesla's (Elon's) cells from his mega plant are setting all new standards in lowing the price to where lithium will be commonplace in most every vehicle and RV.

All we have to do is wait a few more years so they are affordable!

Regards - Mike

Yeah, but you still need a method to replace all the power to the batteries, hopefully without having to drive or idle the van all day. Some here drive plenty to not have an issue, but others like to stay put in one place for longer periods so that can get complicated if you are using big power for air conditioning. Ideally, the fuel cells will get big enough, cheap enough, and small enough to be able to keep up with all that energy replacement when necessary, but until they, or something else, is ready we are realistically looking at either engine generators or standalone generators, as there really is no other non grid option available.