Area of a circle formula says a 44 idle jet is 5% bigger than a 43 idle jet.

But the Ethanol needs 3% more fuel flow.

So back to 44 in .1 holders

or

careful jet needle file and micrometer to get about 43.5 idles.

Don't have to stick to round number of 0.01mm

and mixture screw fiddling when there's lots of progression holes

Pierburg 2e2 carb in mk2 Golf with tad smaller choke and 1.8 engine used

027129415 - idling jet

that was 42.5.

Reamed 4 new 43 idle jets to 43.5ish.

Fitted.

Feels much nicer with hot engine, but that might be the lovely cold dense air.

Idle speed a little high (cause bigger than the 43s) so that's easy adjust. Currently will pull the car along on 3rd at about 15mph. No more surging leanness. Quite nice for 20mph zones though.

AFR gauge showing cruise at 14.5 to 16.5.

No more 12s at 2500rpm low load like i had with 44s.

Will need to download the AFR log.

And start measuring fuel consumption again.

On 17/11/2025 at 22:53, dvderlm said:

Pierburg 2e2 carb in mk2 Golf with tad smaller choke and 1.8 engine used

027129415 - idling jet

that was 42.5.

But only for the primary choke... of the 22/26.

22mm diameter+ 26mm diameter circles

are 380mm^2 + 530mm^2 = 910mm^2

which is same area as a 34mm diameter circle.

And engine is 1781cc so about 1.4x larger.

But makes max torque and power at lower revs.

Also used on the 1.6liter 55kW engine.

"Leerlaufdüse g 42,5 1,6 / 55KW / 75PS + 1,8 /62KW / 85PS"

https://www.ruddies-berlin.de/index2.htm

vergaser->2e2

Looks like there is no changeable secondary idle/slow running jet in a 2e2. Part 6 in this diagram is primary. What are parts 7 8 9?

http://www.gowerlee.dircon.co.uk/2E2type.html

Not secondary idle.

Vac operated secondary throttle plate whose closed position is factory set to not bind in the bore, but will also let a small amount of air and fuel to pass.

Edited 22 November, 2025Nov 22 by dvderlm

The dash rev counter under-reads Used a timing light with its own digital rev counter off number 1 spark plug lead.

Dash showed about 1000rpm.

Timing light measured 1180rpm.

Brought it down to 960rpm and opened the idle screws about 3/8th of a turn each.

Dash showing about 850.

AFR says 14.9 at idle, which came out as ~14.2 at my MOT tester. Drives sweet.

Will just about manage 12mph in 3rd gear on the flat not touching gas pedal without stalling.

The 43.5 in .3 holder runs out of oomph around 2700rpm (I know this because it was paired with 98 mains rather like the Vauxhall Nova Sport homologation, which meant laggy take-up until 3500 then wheel spin in the wet).

Almost tempted to remove the mains and use the gears to stay below 2500rpm.

Tried a small tweak to the pump jet stroke but there's still a bog. Reverted that.

Okay, bigger mains.

So they start earlier, but leaner emulsion and bigger air corrector so not too rich at top end.

Trying 110 in .10 tubes with 200 air.

I think the AFR says 12.8 to 1 at 5000+.

Need a quiet hill in daylight.

Reached 12.65:1 AFR up hill.

But it might be too lean elsewhere, low load so not burning the exhaust valves or melting the plugs ( at approximately sea level).

Also slight lean bog at 1700rpm half throttle, so been driving in lower gears.

Some cold starts with the choke/starting device too.

Managed about 38mpg which is less than I have managed, but I queued for an hour or so due to an accident one evening commute home, so hard to know.

Richer main jet or smaller air corrector to start earlier?

3% larger area than 110 main is 114 I think.

Ordered some 112 jets from the awesome Green Spark Plug co, who are sadly going into liquidation. Do platinum and iridium plugs last so long that people don't replace them? Does ECU fuel management mean plugs are less stressed?

I think 60,000 mile interval in a TSI engine.

The 112 jets arrived.

I should retitle this thread

dergo air filter

One fell off, shaken loose by fenland roads I think and did not survive the fall or HGV wheels.

Of course it was the one that was easiest to access.

Not the one which requires raising the engine to go through a bulkhead grommet.