36 idf on 1600 cc idle jets fine tuning

[samotorsport]

Hey gents , i ve got a question for you .
My engine 1600cc is running on dual 36 italian idf carbs. I did the lean idle adjustment , ran not to bad . After a day i pulled the plugs and they are slightly grey white , only #4 is light brown .
So i gave the remaining 3 cylinders 1/4 turn more on the mixture screws. The car runs great ! No flat spot nothing .
AFR are all where they are supposed to be .
Idle 13,6
Cruising 13,3
Full throttle 12,5
Seems pretty good to me .
Downhill without throttle maximum of 15,2

My question is, i ve got 52 idle jets , but the mixture screws are out now 2 3/4 turns . Speed screw 1/2 turn.
As per the procedure i would need 55 idles at least to get under the 2 turns out.

But where is the difference of having 55 with 2 turns out vs 52 idle with 2 3/4 ?
Where is my advantage or disadvantage ?

Thanks in advance
Sam
_________________
1958 Dragster 1835cc Topchop
1962 Split Panelvan Camper
1967 Herbie the love Bug
1970 Karmann Ghia 14

[Danwvw]

Actually, that is not bad I got 3/4" turn with .60 Idle Jets and with 52's about what you have. I like the way it drives down low in the rpm better with the .60's than with the 55's where it would stumble on a cylinder at 2200 RPM under a load. Your idle mix screws adjust the difference anyhow as far as the crossover circuits go. But 2 3/4" is at the max you would want sounds like yours wants .55's
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[[email protected]]

the idle jet sizing will be different for 009 and SVDA. You didn't say.
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[modok]

the normal range is 2-5 turns out, because the idle mixtures screws are fine thread.

[Danwvw]

That is the first time I had heard 5 turns but if you say so. Anything Idle jetting effects other than the adjuster when jetting between the min and max turns?
My richer idle jetting with less open on the adjuster seems to stop my 36 drla's from popping after startup when cold. And it clears up a stumble I have on #4 at low rpm under load. Well, that and a tighter gap on the spark-plugs. Who knows mine is much better with .60's and 3/4's Turn on the adjusters than it was with .55's.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[[email protected]]

idle jets should be changed in increments of "2" or so. 5 is way too much, a 20% change in fuel.
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[modok]

A lot of people think that the number of turns out is important, when it isn't.

It may be caused by how we call them "idle jets", which is of course misleading, because they do not control the amount of fuel at idle. They control the amount of fuel between idle and about 1/4 throttle.

If the idle adjustment is out of range, then the first thing to look at is the throttle position. If the throttle position is ok, yet it still isn't right, there is more that can be done, but I won't go into it because 99% of the time you'll never need to know.

[samotorsport]

Oh yes i forgot , i run a german 009 from Csp shop .
In fact i am happy the way it drives , no stumble stall or what so ever .
_________________
1958 Dragster 1835cc Topchop
1962 Split Panelvan Camper
1967 Herbie the love Bug
1970 Karmann Ghia 14

[samotorsport]

So i drove it for a day, all the plugs are grey/gold light brown , so spot on .
Still found a little hassle, at the range 2000 rpm cruising AFR 13,2 13,3 , slowly accelerating with very light throttle it leans out to 15,2 (not stumbling but no real acceleration either) for half second, then falls into the 11 on the AFR gauge for a second and stabilzes at 12,7 during acceleration.
When going full throttle in one go it goes off like hell
So the problem only occurs during slow acceleration on transition ,
what way would you suggest to go ?

Main fuel from 120 down to 115
or Air from 180 up to 190 ?
What gives me a smoother quicker transition ?
_________________
1958 Dragster 1835cc Topchop
1962 Split Panelvan Camper
1967 Herbie the love Bug
1970 Karmann Ghia 14

[Danwvw]

This engine has the CB-2280 cam right?
_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[[email protected]]

Try bumping the air up 10
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[samotorsport]

Yes i ve got the CB2280
F11 tubes
Ok i will give it a try by bumping up the air to 190
_________________
1958 Dragster 1835cc Topchop
1962 Split Panelvan Camper
1967 Herbie the love Bug
1970 Karmann Ghia 14

[modok]

Are the flats set at 10mm?
Set float level to 12mm

[Alstrup]

Its Italian 36és. Then 12 mm is a lot. Try 11 mm. I would be carefull with going further.
It is not uncommon to have to go down to about 0,50 idle with Italian 36és. Your cruise AFR (80-90 km/h) should be targeted at about 14,4 with a 009 distributor in a bus.
T

[modok]

The OE float level was 9-10mm with the f-55 57 or 67 emulsion tubes.
Float level needs to match the emulsion tube.

If the float level is too high it floods the 8 holes of the f-11/15/2 series emulsion tube, so when the mains SHOULD start it momentarily delays, then then goes rich for a moment as that extra fuel clears out. I am not sure if that is the same as what is happening here, but maybe?

I use these carburetors by choosing an idle jet size that works right, then changing the venturi size and main jetting to match what the idle circuit does.
This is actually the normal way, IMO

Others try to modify the idle air bleeds and transfer ports to make it function like the inferior 40-idf-70 model, but I don't know why.

[Alstrup]

Correct. But I never had to go to 12 mm to make even f11'work in italian idfs. Spanish is another matter.

[[email protected]]

Don't you mean float level too low (fuel level too high)?

[modok]

Interesting. I wonder what the difference is?
I don't think I ever had a set where all the parts actually came from the same country.

[modok]

John, It's a wild guess based on knowing not much, besides it goes over-rich momentarily when the mains kick-in.

Debating a half mm of fuel level is a small thing.
I'd rather be too low than too high on the fuel level, and come to think of it I tend to use 2.0 SOLID needle and seat, electric pump, measured with gasket, OE float. All that matters just as much, as you know. Most of the original stuff may be worn out by now anyway, so one guess is as good as another.

[samotorsport]

Thanks guys , the floats are at 10 mm with the gasket installed .
I tried 190 air instead of 180 .
Feels better , sounds „more free“ more willing to go up.
Over the complete band the AFR went leaner .
Warm idle 14,3 , cruising 13,5 , where the hassle was it leans out to 15,5 15,6 but keeps going , then when the main circuit is in it doesn go under 12,5 . So over all way better . I gonna drive it for a couple days and pull the plugs to see how they look . Today was a pretty hot day , around 30 degree celsius . So will see what happens an keep you posted . Maybe i will try 200 airs after that but i guess in that case i have to go from 120 fuel to 125 , otherwise i guess it is getting to lean and hot .
_________________
1958 Dragster 1835cc Topchop
1962 Split Panelvan Camper
1967 Herbie the love Bug
1970 Karmann Ghia 14