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What needle for 998cc

SEB1972

Freshman Member
Offline
Hello all,
My Mini 998 has a single HS4 carb and was equipped with an ABB needle. Recently I replaced the throttle shaft, it was completely worn out and also replaced the jet. Before the car ran pretty well, not really knowing how well and the potential for running better, it always struggled with some hesitation when accelerating from 4th gear and low rpm's. Based on some advice that most likely the jet was pretty worn too, I went ahead and replaced this along with a new needle ADE.
However I did struggle to make the car run and to do I have to enrichen the mixture - according to colortune it is yellow when idling, but when turning the mixture down to bunson blue it struggles to pick up revs, too weak. I suppose the worn jet must have compensated for this before replacing it, because the mixture screw was not set that rich when running with the ABB needle. Btw the ABB needle makes no difference with the new jet.
I have then discovered that the exhaust manifold is a LCB medium bore 3-2-1 that runs thru a single box RC40 with 2,25" exit. I suppose that would make a difference to the needle selection.
Typing in my details in WinSU this SW tool recommends ACB as the closest match. Guessing I would rather run a little rich than lean the recommendation is AEJ/AEH.
According to WinSU ABB and ADE are both 17% too lean in the top range and 7% respectively 4% too lean in the mid range, which would explain my trouble getting the engine to run right.
AEJ/AEH are 7% too rich in top range and 4% rich in the mid range.
My question is if running 4-7% too rich across the range would be a concern and if not what if I run AAU needle instead which is 7-10% too rich from mid to top range, since this needle is available/in stock at my closest dealer.
Alternatively ABX needle is also possible - 4% too rich in mid range but 5% too lean in top range.
 
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