Steve R Posted August 28, 2003 Share Posted August 28, 2003 I've been doing some reasearch on sizing jets, emulsion tubes etc for the twin 40DCOE's on my x-flow. I'm totally confused by the logic in the jet numbering system - for example, according to Dave Andrew's utility the range for idle jets is as follows (lean to rich): F3, F1, F7, F5, F4, F2, F13, F11, F8, F9, F12, F6 Am I being daft or is this a totally illogical numbering system?! Could anybody explain why they aren't sequentially numbered from weak to rich? Regarding emulsion tubes I currently have F14's but the program suggests F9/F16 - is this similar enough to stick with initially until I get to a rolling road? Many thanks in advance, Steve. PS Yes I have done a search, and yes I do plan on getting a RR session as soon as it's on the road - I just want to get it approximately right until it's registered to save trailer hire expense to get it to a RR at present. Quote Link to comment Share on other sites More sharing options...
Blatman Posted August 28, 2003 Share Posted August 28, 2003 Dave Andrews programme is excellent, IMO. It correctly calculated the jet sizes for my 48's on my ported Cossie engine. The rolling road operator almost couldn't believe it. So I would trust it's judgement. You can do no more until you get it to the rollers anyway, but I doubt it's going to be far out. Sadly I have no idea how the sizing/numbering system works, so I don't know how close F14's (which don't seem to be in your list ) are to F9/F16's. See if your local supplier (or better yet the RR operator) is willing to do a sale/swap deal if you were to buy F9/F16's but they turned out to be incorrect once the machinery had had a chance to analyse what's required...... Quote Link to comment Share on other sites More sharing options...
Steve R Posted August 28, 2003 Author Share Posted August 28, 2003 Thanks Blatman, I've heard of several other people who have had success using this program so will give it a go as a starting point. Anybody got a set of four F9/F16 emulsion tubes kicking around in their garage that they would like to part with??! (yes I am a cheapskate and don't want to fork out £40 on new ones if possible in case they aren't quite right for my engine) Steve. Quote Link to comment Share on other sites More sharing options...
stu999 Posted August 28, 2003 Share Posted August 28, 2003 For the record, there is no 'logic' for jet sizing on Webers (unlike Dellortos). In his 'Engine Management' book, Dave Walker suggests something along the lines that jets were given an identity as and when they were developed/required, probably so the storeman knew where they were located and not in any order of size. Quote Link to comment Share on other sites More sharing options...
PeteBishop Posted August 28, 2003 Share Posted August 28, 2003 Here is a list of the idle jet sizes to help make sense of the F numbers. The popular sizes are f8,9,2,11 The number is the fuel jet size and are metric sizes e.g 45 is .45 mm. The F number is the air jet size in the side of the idle jet. F6 .70 mm F12 .90 mm F9 1.00 mm F8,F11,F14 1.20 mm F13 1.30 mm F2,F4 1.40 mm F5 1.60 mm F7 1.70 mm F1 2.00 mm F3 2.30 mm Hope that helps Peter. Quote Link to comment Share on other sites More sharing options...
Enterpryse Posted August 29, 2003 Share Posted August 29, 2003 Where can I get the software, sounds good ! Stuart FOUND IT!! no worries, S Quote Link to comment Share on other sites More sharing options...
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