slapping some carbs on a 20v.

[dabill]

right then people, just want some help on an idea...

thinking of putting carbs on my normally aspirated audi 20v.

what are the basics i need to know about carbin an engine...

i, quite clearly, dont have a clue.

rob

[Diamond Hell]

You'll need mapped ignition, or an archaic vacuum advance dizzi.  If you can run a dizzi then Digifant could possibly be hooked up to just run the ignition.  These guys are probably the industry standard: http://www.msdignition.com/

You should leave the in-tank pump wired in, as it lifts the fuel out of the tank.  You will then need a low pressure pump like a Facet pump to deliver the fuel to the carb and an appropriate pressure regulator on the end of the fuel control system, controlling the return to the tank.

Then you'll need a set of bike carbs, with a custom manifold.  If they know what motor the carbs are going on a business like Bogg Bros. will take your carbs and jet them appropriately, when they make your manifold.  You'll probably still need to jet them on a rolling road to get them really working properly.

If you read any of Dave Walker's articles (Emerald EFI) he does talk a lot about how inaccurate fuel delivery from carbs is - they can only deliver the correct amount of fuel over a relatively narrow rev-range - hence most people use throttle bodies, with injection systems that can be controlled a lot more accurately, just like mapped ignition.

[dabill]

humm, lots of ideas to be going on with there then, thanks for takin the time to reply, i'll have words with my dub guru and see whats what and then i'll start sorting my self out.

what size carbs you reckon?

[Diamond Hell]

Re-jetted carbs off a 1000cc bike should do you - after all, you're not revving your motor to 10-15,000RPM!

There's normally a few on Fleabay, budget £100 for carbs, plus £170-200 for the manifold and re-jetting (http://www.boggbros.co.uk/), a few quid for a Facet pump, then sort your ignition to suit.

Good luck.

[dabill]

iiiinnnteeeeresting!

[Mew]

I don't get why bike carbs are "needed"? 

[Diamond Hell]

The reason for proposing bike carbs for a high performance car engine is that they're basically four individual carbs with individual flaps for each cylinders (like throttle bodies).

They're designed to be light-weight and accurate in their fuel delivery, over a large rev-range.  The technology in them ismuch more modern than in car carbs.

[Conker]

Aren't even well setup carbs supposed to more often than not ruin your fuel consumption???

[Diamond Hell]

Well they won't do it any favours, for the reasons already mentioned - they can only work efficiently over part of the engine's rev-range.

This again goes back to why you'd use bike carbs - they're available from much later machinery, so are better designed, more efficient, less worn and should work better.

[dabill]

will the carbs show a better performance than just a specially made map.

i'll explain the situ:

got the 20v in my mk2, its hooked up to ford running gear, which im presuming is re-mapped specifically for the 20v, so im guessing no one would do this unless they have a very good map created to run the engine. all i want to know is, will this more likely be better than running the engine on carbs?

rob