2.0 Zetec with Weber DCOE 45 Balancing Query

[quantum_man]

Hello again Ginetta forum!

The good news is that my G27 is back on the road

The bad news is that my twin Weber DCOE 45's seem a bit out of balance! I got 20 mpg from my last tank and I am getting a lot of popping and crackling under 2,500 - 3,000 RPM, think this may be due to the throttle idle?

Also, the spark plugs are very sooty/black which to my knowledge suggests it's running rich (unburnt fuel causing trouble?)

Can anyone suggest some balancing tips? Is there an ideal jet size for the 2.0 Ford Zetec with DCOE 45's?

Any help would be very much appreciated!

[whiteonyx]

twin webbers can be a bugger to set up just right, best to book a session on a rolling road who will balance everything in a fraction of time that will be spent adjusting all the screws, plus you will get a real readout of bhp and peak power graphs for optimum gear change, etc.

[ginettag27]

whiteonyx said:

twin webbers can be a bugger to set up just right, best to book a session on a rolling road who will balance everything in a fraction of time that will be spent adjusting all the screws, plus you will get a real readout of bhp and peak power graphs for optimum gear change, etc.

+1

My car is "only" a 1.8 Zetec with twin 45s, but once it was balanced, properly by a known rolling road it was a totally different car No more flames tho.. It's well worth the cost. I think it started to return 28MPG and wasn't being driven too tardily..
I then also mated them with a Dunnell 3D ECU.

[quantum_man]

Well, I'd better start saving!

Out of interest, which Rolling Road did you use? Can you give a rough figure as to the cost?

I spent some time yesterday on the car and now have it running fairly smoothly, although it was mainly guess work! Will do until I can get it properly sorted.

Thanks for all the advice

[eps]

It was years ago... It was in the Bicester / North Oxfordshire area.. Junction 9/10 of the M40. Actually the garage I used (no longer around) took it to the rolling road for me, I'll see if I've still got the paperwork, to work out where they took it.

[Comadis]

i´m wondering why you ask about the jet size?

it sounds that your car has never run properly,nor the 45´s have been jetted correctly to suit your engine?

so first to ask:

did you buy the engine and the carbs separately?

yes? where did you buy the carbs? have you bought them new? and how comes that they are jetted like they are?



bring your car to a weber specialist with the risk that you need to change, jets, chokes, venturis...but finally have a well performing engine, incl. a big invoice.

or try yourselves with the risk that you have a complete set of venturis, jets without any use at the end, investigations over certain months and finally you are still not sure if you did your job correctly.

[blitzracing]

Haynes manuals used to do an excellent manual on setting the DCOE range of carbs up, but as already said its pretty complex, as its not just the jet sizes, but the types of emulsion tubes used that control how the mixture is controled over a specfic jet range. You have 3 jet stages (idle, progression and full power) plus various drillings in the castings that control how the stages interreact.There are sub model types of the DCOE range that specify how these internal passages work on specific engines. There is also an accelerator pump that puts in more fuel when you boot it. If you want to set up from scratch you will need some sort of mixture measurment system, like a wide range lambda probe in the exhaust and a gauge to read it, but you are looking at around £300 just to set this up to read the mixture. Then you can acurately read the various jetting stages and choose jets and emulsion tubes accordingly to weaken or richen the mixture (with the manual in your hand!!). In the past Ive cheated and bought only the smallest jets plus some model makers drills, and simply kept drilling them bigger and bigger until the mixture was correct, but its a crude way of doing it, although more cost effective than buying lots of jets. Id think you best bet to start with is to ask on say a Caterham forum (as there are thousands of these) to see if someone has a working set like yours so you can get the jet and venturi sizes.

[330p4]

Tim assuming you have the correct jets & it is just set up i set the idle screws with a colortune plug & then buy a synchrometer from weber about £40 stick it in the bellmouth & it measures the airflow into the carb set each pair to the same flow at the correct idle speed makes it easy. If no colortune lean each idle jet a bit at a time until it cuts out then richen a quarter turn & small adjustments for max idle speed
Ian

[quantum_man]

Thanks for all the advice, I have been pretty busy over the last couple of weeks but will try and take a look at it next weekend! I've got a Gunson's Carbalancer, so hopefully this will help matters. To be honest, last time I had the car out I tweaked the mixture screws and leaned them all off resulting in smoother running overall. It still pops a bit on deceleration but perhaps this is only to be expected.

Certainly learning a lot about carbs, which is great

[blitzracing]

If all you worry about is the carb balance, I think you can simply remove the two brass blanking plugs that cover the progression holes (Im assuming here the DCOE45 is the same as the DCOE40, but it was a long time ago I was tweeking- If you cant find the plugs, Im probibly thinking of Delorto's) and if you look carefully through the holes you can see the edge of the butterfly as you open or close the throttle. All you then have to do is tweek the adjustments between the two carbs so the butterflys are at the same point. Then set the idle screws up to the same number of turns to get an even tick over and you should be some where near correct. I used to use a colour tune for each cylinder at the same time, and then you could see the difference in the burn colour and intensity to get a smooth tick over, as they are a b**ger to set up otherwise. Its a steep learning curve!

[h4887]

Here's what I've got on a standard 2 litre:

Chokes 36
Tube F4
Main 138
Air 155
Slow run 55F8

As supplied by Webcon except for a larger slow run. it's surprising how much difference that makes, it certainly affects pick up at as much as 3000rpm.

Geoff