I've been offered some good condition twin weber 40's and the guy said he would jet them for me if i knew the jet size, i didn't have a clue, does anyone know? they are going on a 1990 1.8 mk2 golf gti engine. cheers Austin
can anyone help? some one must know!! have i missed out some important info to help someone answer my q? cheers Austin
Cheers for the reply, i'm not really sure at all, i did put a thread on here a while back asking the question, but didn't get any replies, it must be a world first putting carbs on a valver then?...... not!! i've tried ringing a few places and basicly get told anything i want to hear, so they can sell me something!!!
Welcome to the tuning world !!!... if they have it on the shelf (in many case's) thats what they'll want to sell you ! It depends what you want to achieve and the main use of the car, road, track-day, competition.... the "twin carb induction roar" or genuine power improvement with more power in the future ? If its the first, 40's will get the job done as the choke size (the important bit) that you will need at a standard power output (139hp) will be in the 32/33/34mm region. 32mm is the normal choke size a 40 DCOE comes with but can be fitted with a "max" of 34mm which will be the max you'll need on a standard engine (perhaps if you've changed the exhaust manifold and system as well) though 33mm will be a better all round size, a "proper" rolling road session will establish what is needed. If you plan on future mods (modified head, cams, 1900/2 ltr bottom end) then go for the 45's now. They will be a bit too big on a standard engine but will start to come into their own above 150 hp when you will start to need choke's 34mm and bigger. 45's would then be fine up to 190/200hp (38/39mm choke), you'd then need to start looking towards 48's. Now the clincher.... 40's wont give a MASSIVE power increase over the standard injection system, expect more than 4-6hp (depending on final spec/set-up) and you may be dissapointed. The reason being (as stated elsewhere) the standard system can cope with the standard power plus a bit more. To ensure you retain as much torque as possible find the longest inlet manifold available and fit the longest trumpets you can, even if you need to maybe mount the radiator lower to give clearance.... Still wanna fit them ! Depending if you buy them new or used, they should come with close (ish) jetting to get you going (if new) or will possibly have completely incorrect jetting if second-hand (so wont be cheap to jet on the rollers) so bear that in mind in your budget. You will also need a competition type fuel pump. There are various types available, the final choice will depend on you power requirement... go for it !
Awesome advice Mr Hillclimber, thankyou very much, you certainly know you onions!!! I'll keep you posted, thanks again Austin
No problem at all. Thanks for saying but i've never been into cooking ! ... though working at a rolling road in a previous life and breathing cars for nearly 37 years sometimes helps ! Like any good recipe (with or without onions !), use the right ingredients and the results will be pleasing, get it wrong and all you get is a nasty taste, an empty wallet and no satisfaction. Good look and be carefull if you buy used.
