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frisco · New user Joined: 16 Jun 2007 Posts: 11

Opinions please.

I have got a set of 40DCOEs on an opel 2.0 engine.
They are set up as follows
150 mains
200 air correctors
F16 emulsion tubes
55F9 idle jets
and 36mm chokes
Timing is set at 15 degrees advance at idle getting to 35 deg at 3500rpm with no sign of pinging

What is happening now is that it runs rich on idle and on full throttle but on part throttle it goes massively lean and splutters.

So its fine at idle and when i nail it but it wont cruise at any speed or in any gear, as soon as im holding it at about 1/4 throttle it goes lean.

Any thoughts?

bigjim5551212 · Posted: Sat Nov 17, 2007 12:55 am Post subject:

the idles are too big for sure. You need about a 45 F 9. then for your lean issue, I think you need to experiment with emulsion tubes. You need to try something like F11 . Make sure your fuel pressure is below 3.5 psi as well. I think as well, your main jets are too large. Maybe 140s. The emulsion tubes will help in the mid range.
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Steve Williams · New user Joined: 09 Dec 2007 Posts: 8

Is it a 16 valve engine?

I acquired a 2.0 litre Ford Zetec engine with 2 DCOE 40s with the following:

130 Mains
180 Airs
F2 Emulsions
55F8 Idles
36mm Chokes

Also these have the standard 3 progression holes.

Not dissimilar to yours, and I also had horrible flat spot/lean cut problems around 2,500 to 3,000 rpm on throttle opening. Rapid throttle opening was better with the pump jet offsetting the lean-ness, but part throttle was terrible.

I have been experimenting with the jets and have got to the following:

130 Mains
160 Airs
F2 Emulsions
65F2 Idles

So far this combination is much more driveable, but I haven't put it on a rolling road to check the emissions yet. There is also a mod for DCOEs running on a Zetec which involves drilling 2 more progression holes, but if this is done incorrectly it reduces your DCOEs to junk by all accounts.

My understanding is that smaller air correctors bring the main jet in earlier, and the larger idle and larger idle air bleed improve fuel flow and mixture through the 3 standard progression holes, thus all but eliminating the flat spot.

I suggest you try reducing the size of the air correctors to 160 as a start, then acquire a spare set of idle jets, say 45F9, which you can experiment with by drilling out to sizes that improve things. Once you have established the optimum sizes, purchase a new set of idles that match the drilled set. The mixture at idle can be adjusted using the idle adjuster screws.

The mains are definitely too large, I doubt you'd need more than 130s or 140s at most.

Once this is done, you can adjust part throttle economy by adjusting the emulsion tubes, and emissions. This is best done on a rolling road with a gas analyser.

Hope this helps.