Googled emulsion tubes for images. These were on some dudes ebay store that was into alfa romeos!

I know you began to touch on the locations of holes and diameters of them and such but do you know where to find info explaining in more detail or do you know?

 

The higher the holes the leaner the bottom end. the lower the holes the leaner the topend.

the same rule applies to the amount, and size of the holes. the more holes the and the bigger they get the leaner it gets.

lol i gave up searching to early i found them on page 10

 

Those diagrams look to be straight out of the Weber Tuning guide.

Probably the best and most informative book on them carbs - and directly from the source.

I have done my share of tuning webers (not on rotarys though) and the one tool that helped the most is a wide band O2 gauge.

It shows you exactly where your lean and rich spots are, before they you can really feel them.

I have an Innovate LC-1 with the analog gauge - works great.

Questions for the Rotary experts on Webers:
- do they also need the 3rd transition hole ?
- is the 37 mm Ventury large enough for a healthy rotary?

 

I haven't gotten a wideband yet but it is on my list of to doos. I will be getting one that data logs so that I can print out my runs and adjust accordingly. I agree that a wideband is pretty much the only way to truely tune a carb

 

The LC-1 can be hooked up directly to your laptop, and with the included Datalogging software you can save and analyse whatever run you chose to.

You will probably want to also buy the RPM converter, this will allow you to log in addition to AFR, RPM and five more inputs.

 

Related newbish question: Is there any way to use a wideband without having to bung the exhaust? Tailpipe probe, perhaps?

I'm looking for a way to do better carb tuning on a stock build; the dual-layer heat-exchanger nature of the SA exhaust plumbing means it's not practical to bung the pipe for a sensor until you're aft of the heat exchanger.

 

Sure most manufacturers offer a tailpipe clamp - but I don´t really know if it is still as accurate.

You do have a point with the hotter rotary exhaust - I would check with the manufacturer - I know Innovate sells a "heat insulator"..

 

Thanks!

 

On an Ida I added the third hole and it runied the transition circut I will never do it again. All new DCO's and DCOE's have the 3rd hole from the factory.
37mm chokes are good for a stock 12a. A 13b needs 40mm chokes with a stockport, but bigger if you decide to port it. I run 43mm chokes in my 48IDA with a small street ported 13B

 

innovative sells a tailpipe clamp, its not expensive (i need one too)

 

I guess the other parts make up for that, huh?

Thanks for the advice; sorry about the derail. Carry on!

 

Thanks for the info.

On large V8s with 40mm Venturis the 3rd transition hole is the very best mod you can do. (1mm drill)

The holes can be JB Welded if it does not work as expected.
Hmmm 43 mm Venturis ! The largest I have experinced is 42mm on a stroked 427 (to 482).

Ok, Webers & Rotarys - another thing to learn.

 

yes and rember the flow requirements of a rotary are much greater than a pissed-on. per revolution each barrel of the carb has to supply enough air flow for all 650 cc's that rotor is displacing. on a pissed-on its doing half the work as each cylinder only intakes every other revolution of the engine.

 

K. So I didn't get a digital camera for Xmas, so no pix of my new tubes. The good news is that they are exactly as shown above in the charts from Weber. I put the F-7's in and it's been an instant improvement. No more stumble at all. I can still hear the smallest of stumble, but it can't be felt while driving. The F-7 is a thinner tube than the f-11 so it allows more fuel to pass by therefore allowing the main circut to start earlier. However the holes in the bottom of the tube are the same configureation as the 11, but they are lower in the tube giving it a leaner and much friendlier midrange around 14:1 as opposed to the 12:1 i had with the f-11. With less holes up top it is slightly richer giving me a happy 12.8 at WOT. All these changes were without changing one other thing in the carb. As of right now I don't think I can be any happier than I am with the f-7's but once the 16" of snow melt off I'll be able to give you more driving impressions of the other tubes.

 

Cool. Good to see some progress being made on Weber tuning, since I may end up getting my old setup back at some point.

 

UPDATE:
So I took the f-7's out after driving with them to try out the f-16's. As Brad said they are a much leaner tube. they acomplish this by placing the 8 horizontal holes above the fuel line allowing air to pass through the main circut much easier than fuel. This is a great tube if gas mileagle and midrange is your concern. However, it does spit and spitter and pop a lot of lean flames on deceleration. Plus with the bigger chokes it kills throttle response. The carb cruises along at about 15:1 afr's at 50 mph at 3k rpm. With the f-16's and any quick throttle imputs take it clear off the map for literally one or more seconds until the circut catches back up and adds the required fuel. If you're going to run a street car with stock ports and 38mm or smaller chokes the F-16 would be a great fit. On my street ported 13b with big 43mm chokes the hot lean burn givess a nice strong mid range at the expense of worse throttle response and way too lean above 6k to even consider using it. Again the e-tube was only changed running 220 main with 120 air corrector.

F-8 is up next

Side bar:
Before I took out the origional f-11's I rebuilt the carb and sealed up the 3rd progression holes. After letting them cure I added them again but this time with a 1mm drill bit instead of the 1.58 I used before. Good results the car drives better than before. I recomend it to and IDA user but I suggest you use a 0.8mm drill bit aka 0.031496 inchs.

 

I hope your tunning your carb after each emulsion tube. You can't just change the tubes and keep the same jetting to compare each tube. Once you change the tube you need to rejet the carb for that tube. Each one will be different.

 

I know, but they best way to get a direct compairison of each tube is to keep everything else the same. Then tune with the desired tube... Just changing the tubes allows you to feel the difference that only the tube will make.

 

Okay I thought I'd update this with my finds. F-8 in the car now and they make great power and drive ability is near perfect, but they're just a little too rich on cruise so I'm going to try out f-2's and f-3's to see if those help. I'm making 189whp and getting 15mpg. I'm hoping to get 18-20pmg and not lost any power.
Here is what I consider a list of the only acceptable weber emulsions tubes that should ever go in a rotary. List is fron rich to lean.
F7 ->F8 ->F2 ->F3 ->F11 ->F16
I havent got my f-2's or f-3's yet the design is as though they should place right where I listed them. I will post results as I get them.

 

have you considered the f5, my list of acceptable tubes is very similar to what your working on, but I have the f5 placed between the f8 and f2. I am awaiting spring to try out the f5, and get back to work so i can get a few more sets. it should tip the main in very early, helping with transition/throttle opening stumble(large venturies), I am expecting it to let me run a smaller idle jet as well due to it tipping the main in early and rich, this should help out low rpm cruise, wich i find to always go way rich when better acceleration has been the tunning goal.
I was expecting the f8 to remain a very rich cruise due to the low ring of 8 holes, and I am going to start this spring off with an f5, as it seems to favor starting the curcuit rich and quick, but then still mixing plently of air at low signal.

the f8 is one of the tubes I was quite intrested in, as it should have similar tip in characteristics, the f5 should mix more air earlier, but mix about the same in the end, maybe.

 

Try a smaller idle fuel jet and/or smaller main fuel jet.

 

idle jet has no effect after 3K RPM.

 

Idle fuel jet doesn't bleed off as quick as people think. It seems to go up into the upper rpm range, strange but what I've seen with the wideband. I've put in a leaner idle fuel jet and it leaned out in the main circuit range too. It doesn't have as radical an effect during main circuit operation, since it's such a small jet to begin with.

But there still is a vacuum on the progression holes and idle mixture screw during main circuit operation. Which draws fuel.

 

I'm running a 70 idle right now. It won't even drive with a 60, wiating for some 65's to come in the mail.

 

With 38 or 40mm chokes I've gotten it to run with 65's.