Weber DCOE tuning swap shop - sticky?

[Lazeum]

That's why they look beautiful, it is because they are powerful!

The reward is the power & the sound out of them. When you tune them right, their sound becomes better also. You can use O2 sensor, butt dyno but ear is also a good tool to know if they are healthy.

[Lazeum]

Does anyone have a table of absolute hole sizes and number of holes for the air inlets for the above parts? I think it is time to raise the bar from symbols to real numbers. Assigning a cross sectional effective hole size to each symbol would be a first step.

go look at the chart in the link below

Then we need to do some maths to find out what is which.

Lat's take an example to compare __f11 & __f9 with same inlet orifice (the 55 in front of 55f9). they have only one hole each so it is easy to compare.

F9 is having air hole at Ø1.00mm & outlet at Ø2.00mm.

whereas

F11 is having air hole at Ø1.20mm & outlet at Ø1.50mm

So for the facts: f11 is having more air going inside it ==> leaner than f9

On the other side: Outlet orifice is smaller on f11, it means suction is higher with f11 than f9 at same intake pressure. It means to me gas & air would be sucked harder. Gas being more dense than air (and inlet orifice being a restrictor for gas), more air versus gas will be added to the flow compare to f9.

So to me, f11 are definitely leaner than f9.

Maybe I'm wrong with my theory but this is how I analyze idle jets. I'll be pleased to hear what everybody's thinking.

To try something new on my car, I wanted to try richer jet than f9. So I went with f6 since outlet orifice are the same size, only air orifice is changing so it is easy to find out.

Same goes for f8 jets, they are leaner than f9, only air orifice is changing so analysis is straightforward.

Edited August 23, 2012 by Lazeum

[Zedyone_kenobi]

Blue, could you drive in 4th gear up to 3000 rpm with the main Etubes removed? That is fascinating.

[240260280z]

Yeah it was strange. It is a 4 speed, I cant recall if I was in 4th or still in 3rd but I was surprised to see the high rpms.

I'll do some empirical runs with lots of data hopefully on Saturday.

[240260280z]

Edited August 23, 2012 by Blue

[Lazeum]

to make sure we're on the same page.

the air inlet is the side hole, the gas inlet is the bottom hole and the outlet is the top hole.

see diagram below:

[240260280z]

First 200mi ~ 13mpg, next 160mi ~26mpg.. same jets...idle enrichment, throttle plate position progression holes have very interesting interplay I hope to start investigating soon.

btw the 3000rpm with mains removed was when pig-rich 13mpg setting.

Edited August 26, 2012 by Blue

[pjoe]

I have set(6) of 65f9 idle jets, 165, 170 air correctors if anyone needs them. Im running 45's(152) on a stock L24 with 2.5" 3-2-1 headers. Chokes 36, 60f9 idle, 145 main, 195 air, f16 e tube. I dont have a o2 sensor but it runs very good right now. Definately rich at idle but transition is pretty smooth. All of my jetting decisions have been made based off of spark plug color. I thought about trying a 60F8 to see if idle will lean out some without affecting transition to mains but my guess is that it will. Glad to see people willing to contribute...jets get expensive. Oh yeah...last time I checked, probably with little different jetting, my milage was about 20 mpg.

Brian

Edited August 26, 2012 by pjoe

[Zedyone_kenobi]

wow you are running 45's with 36mm chokes on a stockL24! Great googley Moogley!

[pjoe]

Yeah thats about what everyone says. I also live in the city and most of my driving is short trips around neighborhood. My biggest challenge was getting the throttles to open at EXACTLY the same time. That made all the difference in the world when it came to just off idle driving. I also have the air bleed screws turned out 1 or 2 turns past what was needed to ballance air flow between barrels of carb. Its fun around town but really fun out of town.

[Lazeum]

that was my first thought: you're having big chokes. your next move could be to source smaller units but you would have to tune everything again...

[pjoe]

If anything I'll bolt on SU's and save webers for later use but Im not even close to given up on them yet. They run pretty good for how I drive. I assume everyone agrees 60f8's will not help. Your 151's have 3 progression holes too, right?