weber idf 40 jetting
weber idf 40 jetting
i know this has been discussed many times but i can't seem to find recommendations for UK petrol and for the following set-up:
Engine is 1720, standard cam and i want to keep the 28 venturi.
i will be getting a rolling road session but just don't want to damage the engine getting there.
So, any successful combinations of mains/emulsion/airs/idle/pump numbers would be good.
Engine is 1720, standard cam and i want to keep the 28 venturi.
i will be getting a rolling road session but just don't want to damage the engine getting there.
So, any successful combinations of mains/emulsion/airs/idle/pump numbers would be good.
Adrian Rendle
Re: weber idf 40 jetting
Hi Adrian,
40 IDF's come out of the box with 28 venturi, 115 main, 200 air correctors, F11 emulsion tube, 55 accel. pump jet, 50 idle. They will run ok on a 912 but will be kinda restricted.
Ideally you want to step upto a 32mm Venturi and then change the jets to suit. But might be best to wait until rolling road time to do that, costs can soon mount up if you end up buying everything twice!
From memory I think mine is as follows:
32mm venturis
125 mains
52 idle
180 air correctors
F7 emulsion tubes
55 pumps (I think?)
Best of luck
40 IDF's come out of the box with 28 venturi, 115 main, 200 air correctors, F11 emulsion tube, 55 accel. pump jet, 50 idle. They will run ok on a 912 but will be kinda restricted.
Ideally you want to step upto a 32mm Venturi and then change the jets to suit. But might be best to wait until rolling road time to do that, costs can soon mount up if you end up buying everything twice!
From memory I think mine is as follows:
32mm venturis
125 mains
52 idle
180 air correctors
F7 emulsion tubes
55 pumps (I think?)
Best of luck
Burgundy 69 912
Audi A4 1.8T sport avant
VW T25 magnum multivan
Audi A4 1.8T sport avant
VW T25 magnum multivan
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Re: weber idf 40 jetting
I'm pretty similar to Tim but 190 air correction.
My mains said 115 but the RR found they had been drilled and weren't the same.
However, my 912 engine had 165 main jets. Worthwhile doing a RR
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My mains said 115 but the RR found they had been drilled and weren't the same.
However, my 912 engine had 165 main jets. Worthwhile doing a RR
Sent from my Redmi 7 using Tapatalk
“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
Re: weber idf 40 jetting
thanks guys.....i'll be at sub 3Krpm most of the time so28 venturi's should be ok for me.....thanks Neil, hadn't thought of PO's drilling out jets, i guess there must be some sort of jet gauges available.....do the sizes denote hole size? e.g. 200 is 2mm?
Adrian Rendle
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Re: weber idf 40 jetting
Sorry I was talking about the main jet size.
Have a look at Bruce's article
http://www.sparkingplugs.com/3.html
I strongly suggest you aren't below 3k mostly. Peak torque and happiness in these engines is 3-4.5k. The switch between the idle and main circuit isn't discrete but generally complete by about 3k. The main circuit maybe be dominating long before that.
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Have a look at Bruce's article
http://www.sparkingplugs.com/3.html
I strongly suggest you aren't below 3k mostly. Peak torque and happiness in these engines is 3-4.5k. The switch between the idle and main circuit isn't discrete but generally complete by about 3k. The main circuit maybe be dominating long before that.
Sent from my Redmi 7 using Tapatalk
“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
Re: weber idf 40 jetting
Adrian, if you are staying with the 28mm venturis for now please don't use mine or Neils setup as reference, the correct main jet size is determined by the venturis you are running to a degree. There is a ratio, I think main jet should be 4 - 4.25 x the size of your venturis, so somewhere between 112 and 119 would be your ideal size.
According to this ratio 32mm venturi main jets should be somewhere between 128 and 136, however RR suggested mine was happier on 125 mains.
According to this ratio 32mm venturi main jets should be somewhere between 128 and 136, however RR suggested mine was happier on 125 mains.
Burgundy 69 912
Audi A4 1.8T sport avant
VW T25 magnum multivan
Audi A4 1.8T sport avant
VW T25 magnum multivan
-
- Nurse, I think I need some assistance
- Posts: 7800
- Joined: Mon Apr 16, 2012 4:31 pm
Re: weber idf 40 jetting
Tim I have 28mm chokes. Sorry I should of mentioned that before.
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Sent from my Redmi 7 using Tapatalk
Last edited by neilbardsley on Wed Nov 18, 2020 9:16 pm, edited 1 time in total.
“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
Re: weber idf 40 jetting
I've found that the only way to get the jetting really spot on is lots of expensive time on a rolling road or install an afr gauge and you can do many hours of driving under different loads to get it just right. All part of the tuning fun!
32mm vents
125 mains
F7 emulsion
47 idles
220 air correction
Cheers Rob.
32mm vents
125 mains
F7 emulsion
47 idles
220 air correction
Cheers Rob.
Re: weber idf 40 jetting
Neil, I should have realised, hence the 115 mains.
Burgundy 69 912
Audi A4 1.8T sport avant
VW T25 magnum multivan
Audi A4 1.8T sport avant
VW T25 magnum multivan