I should have mentioned, the PVC sewer pipe is much lighter than the Sched 40 (which I tried), and lighter than the HW heater vent pipe. The three piece sewer tube is 4.5 lbs. total, vs 9 lbs. for the heater vent.

I just wanted to say thanks to Bill G and the others for posting the information on the homemade gen-turi exhaust.

I have a 91 Country Coach and was just doing a search trying to find the best price for one and stumbled on this forum and read about making your own.

Following Bill G's info, I did just that and probably spent about $40 all told. Great forum, and thanks

Welcome to the Forums! There will be 12-15 Barth motorhomes in Seffner for a get-together 2/28-3/4 at the Lazy Days park just north of I-4 on SR 579; link here.

Thanks, I may be by.

Bill: I'm getting ready to make one of these. What did you use the steel bar stock for?

Thanks

Robert,

I had some stainless steel bar stock (1/16" X 1/2") so I used that for the connection and support pieces. I used aluminum pop rivets for most of the connections, but 1/8" X 3/4" aluminum would also work. That stuff is available at the hardware store.

Bill G

quote:

Originally posted by Bill G:


My genny is powered by a four cylinder Kubota diesel and I would really like to quiet it down. I have wondered if a different muffler would make a difference.

I have measured several Kubota gensets, in both Barths and Country Coaches. The same genset in a Barth was 2 to 3 db quieter than in the CC. The Barth had a slightly smaller grille, and a less direct path for the sound to exit, so we can believe that a lot of the noise is from the mechanical clatter rather than the exhaust.

This is typical.

If you really want to hear how much of the genset noise is mechanical and how much is exhaust, just hold a ball of rags over the exhaust for a few seconds. That will almost silence the exhaust, allowing you to hear the rest better.

To illustrate, I reduced our genset noise by 7 dbA at 20 ft by blocking the hatch grille with a lead loaded foam panel. I can reduce my noise at 20 ft a further 3-4 dbA by hanging a 3' X 5' rubber-backed rug over the genset compartment area, reaching down to the ground.

These quick and dirty experiments have dropped my Kohler 7K down to a measured 58/59 dbA at 20 ft.

I am sure that some decent material designed for the purpose (and more intelligently installed) would yield a much better result, but my Kohler will be history as soon as we get back home.

Are we talking flaming venturi????

quote:

Originally posted by davebowers:
My goodness Bill, I wonder how delightful you are to live with. Oh, you are the high school principal aren't you. Well that answers some of those questions.

By the way is a Genturi anything like being metro-sexual?

Can one be a Genturi and like football too?

------------------

I made a DIY genturi, mainly from scrap out of my shed, using a galvanized electrical conduit elbow with matching connector, a leftover, 3' section of 4" galvanized double-wall stovepipe for an expansion chamber, 1/8" by 3/4"hardware store aluminum bar stock for bracing, & a rubber reducer to connect the galvanized stovepipe to the PVC electrical conduit chimney. The only thing I bought was the galvanized elbow & connector.

It never got hot enough to do more than warm the rubber connector to the touch. It would have been lighter if I had bought some thin-wall PVC for the vertical components, but I used materials that I had.

quote:

Originally posted by olroy:
I made a DIY genturi, mainly from scrap out of my shed, using a galvanized electrical conduit elbow with matching connector,

Yeah, that's what I use, too. since my gen exhaust is now pointing abaft, it is a simple matter to use a little stainless flex to run it up the ladder (recently relocated to the left side). It only goes a few feet up, but it seems to do the job, as the velocity carries the fumes up the rest of the way so as to be undetectable by my CO meter.

A permanent up pipe is envisioned, but we use the gen so seldom, and camp near others so seldom, that it is not high on the list.

A number of the events we attend have generator-free areas.

And some of the areas we visit ban generators.

Bill: When you made your Genturi I think I understood that there is a lower section and an upper section (to be able to store it). I have made the lower section with the elbow and the piece of pipe that reaches to where the suction cup support is mounted. My question is what did you use to connect the top section to the lower section. I am leaning towards marine quick release pins through the joint but I wonder if it will hold the pipes together if a wind comes up.

quote:

Originally posted by Tom K:
Bill: When you made your Genturi I think I understood that there is a lower section and an upper section (to be able to store it). I have made the lower section with the elbow and the piece of pipe that reaches to where the suction cup support is mounted. My question is what did you use to connect the top section to the lower section. I am leaning towards marine quick release pins through the joint but I wonder if it will hold the pipes together if a wind comes up.

Not sure which Bill you mean, but, I would agree with you on the lack of security of the ball lock pins. They are only good when the load is exclusively shear, and the engagement surface is fairly long.

When I had my rigid homebrew genturi, I had three bent bars connecting the large tube to the small tube. The bars were welded to the large upper tube. (I bolted it up first to get it right) The lower end of the bars were welded to a smaller tube, which, in turn slid over the ell tube from the exhaust. The lower end of the slipover tube was slotted and a T-bolt clamp held it tight, although it wasn't really needed, owing to the good fit and decent overlap. The clamp was mainly to keep it from slipping farther down and becoming difficult to remove.

My first version used pop rivets, but they didn't stay tight. My Kohler is not a smooth runner.

I used a PVC union, with a slip/friction fit for the pipes. The aluminum straps and poprivets have held up well with the Honda genset

I completed mine yesterday using foam core PVC sewer/drain pipe. It has a max temp rating of 140 degrees, the same as solid wall but weighs 30% less (about 1 lb per foot using 3" pipe). I used a hand held pyrometer and measured the temp at the outlet of the metal ell at 200 degrees and at the inlet to the PVC union 2.3" above it was 126 degrees and did not rise after 40 minutes of running. I have the Kohler Klanker 10 KW diesel generator and a custom critical grade silencer muffler. I could set grass on fire and melt asphalt with the original down-turned exhaust tip but now the genturi was only warm and I found no damage upon removal for storage. At a few bucks even if it does fail somehow I can always try to order CPVC in the future as many have stated - the big box stores don't carry 3" stuff and I was unable to find it even at the plumbing supply distributor in Houston. As a last observation there are lots of hits from SOB owners trying to research this contraption. How about we make up a Bill of Materials and Instructions and offer it online for either a donation or small price to support the site.

I had done a similar thing for automobile exhaust way back in the late sixties when CA started roadblocks for exhaust sniffing. The idea was to get a little clean air into an automobile exhaust.

That idea was not my original, either. It was lifted from the P&W/Convair system on the 240/340 exhaust augmenters. P&W/Convair, of course, were after better air flow through the cowling, but the idea of exhaust flow sucking in outside air is the same. http://photos1.blogger.com/blo...67/1600/DSCN0388.jpg Later versions had a single rectangular outlet, which, I believe, was retrofitted to older aircraft by some users.

The RV application came way later, with no input from me. Unless they ended up with one of my cheater systems.

The funny thing about that whole roadside test thing is..................I had a motorcycle carrier that slipped in and out of tubing on the back of a station wagon. True to form, I used what I had on hand, and one of the tubes into which the rack slipped was round instead of square. It, of course, was welded to the frame and stuck out underneath the bumper.

Well, since the station wagon had an electric roll down tailgate window, I converted the exhaust to a pair of side dumps, each just ahead of the rear axle. (like my Barth now)

You guessed it............the smog checker stuck his probe in the MC rack tube. He complimented me on how clean my exhaust was. I said, "yeah, I keep it tuned up pretty well". I took a look at his (analog) instruments, and they were expanded scale, reading only in the range where they expected exhaust readings to be. My MC rack mount emissions were below that threshold.

Funny thing was, the engine was cammed, carbed, CAI, headers, etc, etc. Even the state-mandated NOX kit was modified to work only when I wanted it to.

Nowadays, they have exhaust sniffers on selected uphill freeway on ramps where they sniff you as you go by, and mail you your ticket. Next thing will be an automatic Paypal or credit card payment of your sniff test fine. That's how they charge for toll roads.