|24/03/2004 20:36:38||Ryan||Could anyone give me a rough guide to setting up a weber 28/36 DCD carburettor for my 96? Iíve fitted a K & N filter along with a jetex exhaust but the car has very little power. I guess itís the mixture or jets (or both) but Iím not sure what to do first. Any help would be appreciated.|
|24/03/2004 23:17:38||Alistair||Ryan - was the carb on before the exhaust & filter and did it work OK then? If so and the filter has made it run a little lean then then just adjusting the mixture screw is all you should need. It shouldn't need rejetting with a change of filter.|
|25/03/2004 07:06:46||Iain||If the carb has been off a manifold for some time the base can distort so it is not flat. You need to make absolutely certain there is no air leak between carb and manifold as this will also make it run lean. With jetex and K&N fitted the engine 'breathes' much better and sucks much harder. Flatten carb base on an emery board and use sealant.|
|25/03/2004 07:44:52||Richard||Have you checked you are getting full opening on the butterflies when the peddel is pressed. If not you will not be getting full throttle.
I probably have some settings for choke/jet combos somewhere.
|25/03/2004 11:02:28||ryan||I bought the complete engine over a year ago which had the carb already fitted (on a S & R manifold). So i've no proir knowledge to how the engine ran. I really just need a starting point for setting it up.|
|25/03/2004 11:40:27||Senor Burt||The combination of the Jetex and the K&N will reduce low-end power in favour of high-end power, so you will need to rev it higher to get the full benefit and to avoid it bogging down when setting off. This is the general effect of most tuning mods. The standard V4 will rev up to around 5500 RPM reasonably happily, so use all those revs!
As has been suggested by my esteemed colleagues here, if the K&N is a new fitment, the mixture will need to be enriched.
Gunson's Colourtune is a nice cheap little device for checking mixture and correct carb operation.
As Richard says, check the butterflies are opening fully. You may need to bend the cranked throttle linkage into a different shape to acheive this.
Investigate these possibilities first before looking at the jetting.
|25/03/2004 13:33:59||Alistair||There's also a service kit you can get for DCD carbs from any specialist like Demon tweeks, might be worth doing that - consists of gaskets, accelarator pump diaphragm (I think) + odds & sods.|
|25/03/2004 21:21:04||Ryan||Many thanks for the advice. Iíve checked the carb this evening and it seems that only the first choke is opening fully, while the second choke only starts to open when the throttle is on the floor. Shortening the connecting (as much as possible) hasnít made much difference. I see that saab offered different throttle bars with weber carbs, is this necessary?|
|26/03/2004 07:51:33||Richard||bolt an extension to the connecting plate on the carb end of the throttle rod, so that you get more leverage. Also I usually chop the rod in two that links the pedel to the throtle bar. I then thread each end and srew them in to a hex bar (tapped to suit), this makes the rod adjustable for length.|
|26/03/2004 10:39:54||Senor Burt||I managed to achieve the same result by re-shaping the existing cranked connecting rod. Can't remember exactly how now.
I think you can buy adjustable rods like Richard made, motorsport specialists?
|26/03/2004 14:02:22||steve h||Yes, i have just helped my farther in law dramatically increase the performance of his new golf in a similar way by sugesting he cuts the corner off the car mats that were getting under the accelerator pedal. A shocking demon tweek that didn't come up on the VW main dealer dignostics system.|
|26/03/2004 14:07:08||steve h||And you can also avoid jerky power uptake on intermediate thottle, especially when coming up to meet the freewheel speed, by making sure the spindles are all lubricated and the rods are adjusted to pull at 90deg to the spindles when first opneing the thottle.|
|02/04/2004 09:27:35||ryan||The throttle opening has now been resolved by fitting a new throttle lever (on the carb) that opens from 2 o'clock. The one that was on the carb opend from 12 o'clock and therefore wouldn't open further than 10 o'clock. Hope this makes sense.|