This forum and the users on it have helped me alot with my mk1 gti so in return i think it's only fair that i give something back.
This is about the conversion to twin dellorto dhla 40's or dcoe, it's the same.
In my research on carbs i have found out some basic rules for this car :
-Do not install big carbs on it because it's a small engine an will not build enough speed through the venturi tubes . 40's will be good with 30 or 32 mm venturi tubes. I have also 34 mm venturi tubes but until now i could not get the proper jetting for them . They open up in mid 5000 , way to high for a hillclimb car who need both mid range and hi range rpm.
the compromise is 30 or 32 mm venturis.
-My jetting is as follows :
46 idle jets with 120main jets and 170 air corrector plus .1 emulsion tubes.
225 needle valves and 30 mm venturi tubes
For the conversion you will need a pair of carbs, dellorto or weber, one facet red top fuel pump coupled with a low pressure regulator and a custom intake manifold to suit the dellortos.
After you take the original intake off the car , you need to fix the two hoses for coolant that are attached to the manifold.
Next you attach the carbs+inlet and start to run the new fuel lines and acc cable.
It's easy to tune them if they are in proper working order. Just screw in the idle main screw that opens the butterflys about 2 turns after it hits the lever. The idle mixture screws out 2 turns from complete bottom, and start the car.
Next you have to turn the idle mixture screws in any direction(open or clos them) until maximum rpm is achived (do this to every cilinder), after that, unscrew the main idle screw until the rpm goes down to 1000 and then play with the mixture screws and the main idel screw until the engine starts to die when you rotate the mixture screws half way either side. By now the engine should idle steady with little vibration and no exaust backfires.
If you cannot do the above adjustment look for the following :
-air leaks
-clogged passages in the carbs or jets
-spark plugs
P.S : Set the advance as much as you can on stock engines play with it to see where the engine feels best. They will not ping with 98 octane fuel and carbs.
Please note that after you modify the advance you have to do the above idle adjustment again to properly set the idle AFR mixture. A good engine running on a piar of dellortos in the aboove config should idel at 1000 rpm and ahould have good elasticity and torque.
In my opinion the engine gains 15 or more hp at the wheels from the conversion.
P.P.S: You need to keep your fuel rail and injectors or you can plug the holes with something.You will need to take out the standard inlet brace that bolts to the engine block as it hits the carbs and also find a solution for the center top mount. Plese send me a message when you come up with a simple center mount because i haven't thought about building one yet
Home this post helps some swifters who want to run carbs . The difference in horsepower gain from bike carbs versus dellorto or weber is about 10 to 15% . And the difference in costs is about 40% .
Login
Register
Gallery
FAQ
Search
