Latest project done, home built "Genturi"

[ernieh]

Scott, I don't spend much time on this forum since I traded my Winnebago for a Tiffin, but I have followed the work that you have done on your coach since you were looking for access to the BR slideout cylinder.

Just about everything that you have done displays a degree of care and craftsmanship that is far above average, but in my opinion you took several steps backward on the downspout. You have a beautiful coach that you have spent hundreds of hours restoring/improving.

You and your coach deserve something better than a homemade downspout hanging off the side.

[DonDee]

Have a permanent genturi on our old SW. 1-1/2in exh. flex into 2in emt. Works just fine.

[Libero]

Originally Posted by DonDee

Have a permanent genturi on our old SW. 1-1/2in exh. flex into 2in emt. Works just fine.

Cool, how much ground level noise reduction was realized by this?

With no apparent cap or deflector on the top and no opening below, does rain and snow get into the pipe?

[Dunner]

I would say 1-2 db noise reduction. The main purpose it to get noxious gas away from other campers.

[dengraham]

I thought I read someplace that you had to be concerned about back pressure on the exhaust system. Too much and you cause the generator to run hot and shorten its life. I think the system you designed will not have a problem but I have seen some people place the pipe well into the larger pipe which would indeed increase the back pressure. Just say'n.

[DonDee]

Originally Posted by Libero

Cool, how much ground level noise reduction was realized by this?

With no apparent cap or deflector on the top and no opening below, does rain and snow get into the pipe?

1/4in gap all around. The flex is stainless so no rust, I start it after rain and so far no geyser! The noise seems about the same, the engine/gen makes the most racket.

[Dunner]

I've heard putting a piece of carpet below the generator helps absorb some of the mechanical noise.

[ernieh]

I think that some are missing the point on how a Genturi works. It's not simply an extension to the existing exhaust. The whole idea is to use the exhaust pulse to draw in extra air for cooling. That same idea was used for many years in the aircraft industry and was called an augmenter. The combined system is similar to a venturi in many respects, thus the name.

I'm far from an expert in fluid dynamics, but I strongly suspect that a round pipe is going to do a much better job of "controlling the pulses" than any other shape. I also have a strong feeling that the further the exhaust pipe is inserted into the Genturi, the less effective it will be at drawing in air.

[DonDee]

I know my set up draws air into the 1/4in gap. I tested with some paper towel pieces held near the gap and the draw pulls them in and they soon pop right out the top. Ran it for one hour on a 80 degree day and it never got hot even near the flex. Can touch it without fear of getting burned. The flex gets very hot.

Very pleased.

[DonDee]

Originally Posted by Dunner

I've heard putting a piece of carpet below the generator helps absorb some of the mechanical noise.

I do that when boondocking, lay a piece down before I start it and no dust either.

[Dunner]

You could also use a leaf.

[FIRE UP]

Well Gang,
Here's the latest. I finished putting my generator back together from tearing it apart to replace the stator. Now, I could do a real test of that genturi system. Well, nothing like putting a full load on that gen with the A/C unit on full blast. Then went to a high RPM and, the A/C was putting out some seriously cold air.

It took that new genturi system, "the plastic down spout gutter part" about 15 minutes to start to show signs of too much heat. It showed some warpage and tweaking. Now, by that time, I'd had the gen on for about 1/2 hour at that speed and load and while those plastic down spout parts were not looking good, there was not collapse of any particular part.

But, I think I'm going to change to an aluminum down spout. They are the same dimensions and, should fit in to the cradle at the top of the bent EMT tubing. We'll see. Oh well, another experiment with less than desirable out come. Back to the drawing board.
Scott

[Dunner]

My PVC one warped slightly when I ran both ACs for about 1/2 hour. Something I do not plan to do. I built mine to direct the noise upward and away from fellow campers. I used an anemometer to set the inlet tube for the highest air speed.

[D Lindy]

FIRE UP; like we'd talked about before if you're going to redesign the unit and go to metal spout try increasing the air gap at the bottom to at least 1 & 1/2" to promote better cool air flow from the bottom of the spout. Look on line at the genturi install on the CW site and to me it look like their air gap is closer to 3" then not.

[bghunt]

I went CW and measured 1 1/4" gap air gap.

[danleininger]

The plastic used in the Genturi is more heat stable than any plastic component you will find at Lowes, etc. I did melt a section of my Genturi because I had a metal bracket lodged inside the tube and it deflected the exhaust directly at the side. So I cut off half of the first section of the Genturi and added a 4 foot PVC extension at the top (I needed to extend anyway due to a taller MH). I was worried the PVC extension might melt, but so far so good. I'm now using this on my 12kw. It definitely gets hot but I haven't melted anything yet, but it's been pretty cool in NY mostly in the mid 80s. I'm not sure how well it would handle things if in were in the 100s.

[MRUSA14]

Guys, spend $118 at Amazon and buy the real Genturi. It is well made and it just works. Nothing melts, and it lasts forever. Mine is 12 years old and on its 2nd motorhome. It is still like new except for the carry bag that is a bit worn.

I do not mount the attachments to the side of my RV as I think they impair the looks of the RV. Instead I use large suctions cups attached to the RV side and bungees to hold the Genturi in place. Installs and removes easily and nothing shows afterward.