Alex Wong1697456877 Posted May 31, 2007 Share Posted May 31, 2007 My Weber TB's have an IACV - something I've not had on my previous setups. At idle, should the butterflies be completely shut, thus letting the IACV control the idle or are they slightly open? If they're shut, do you have to balance them with the throttle held slightly open? Ta! Alex Edited by - Alex Wong on 1 Jun 2007 08:51:12 Link to comment Share on other sites More sharing options...
Peter T Posted May 31, 2007 Share Posted May 31, 2007 Surely adjusting them on the IACV will change your throttle site 1? R500 260 BHP Mango Madness Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted May 31, 2007 Author Share Posted May 31, 2007 The IACV has no adjustment that I can access - Weber wont release the software to the public. I just wanted to balance the throttle bodies but dont know how to if there is an IACV controlling the idle. Link to comment Share on other sites More sharing options...
Mr Locust Posted May 31, 2007 Share Posted May 31, 2007 With standard EU3 Rover setup (only one tb I know), I have found the best results are from setting up the idle as desired with the IACV capped off and only then letting the IACV do its stuff to control fast idle, fast throttle close transients etc. I worked on the assumption that the least intervention the IACV needed to make to keep the engine running, the less obtrusive it would be in use. Setting up a TB system in this way would (presumably) allow you to balance the throttles at low openings to allow better slow running. Ian Green and Silver Roadsport 😬 Edited by - Mr Locust on 31 May 2007 11:10:15 Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted May 31, 2007 Author Share Posted May 31, 2007 OK - I understand that and as the slightest touch of the throttle stops the lumpy idle, I probably try just upping the idle speed a bit - as you say, I can then balance them as well. Link to comment Share on other sites More sharing options...
DohNut Posted May 31, 2007 Share Posted May 31, 2007 Alex The intention of the Weber setup is to have the throttles completely shut and control the idle entirely by the iacv. The throttles should be balanced by default as If they are completely closed every time you shut the throttle, if you required confirmation then you could balance them so that they are all zero. You can smooth the idle by forcing the throttles slightly open on the throttle stop which will take it off the idle load site and possilbly disable the iacv. I have an early Weber iacv which is analogue, in that is is not a stepper motor, I improved my idle by disassembling the iacv cleaning and lubricating the piston. Unfortunatley I think the crux of it is that the idle speed is set too low, it sounds great to have a lumpy irregular beat but it shakes my car around, resting my foot on the throttle to got 800rpm to 1100rpm smoothes it out completely - but sounds boring Nick Link to comment Share on other sites More sharing options...
DohNut Posted May 31, 2007 Share Posted May 31, 2007 Just thought - there may be idle screws that bypass the butterflys N Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted May 31, 2007 Author Share Posted May 31, 2007 Nick - thanks for that. Will try cleaning out the IACV and look to see if there are bypass valves. I think somethings changed because it used to idle very smoothly. Will also check throttle pot connections as I've meddeled with these. IME, if you set up the idle with bybass screws alone, you get great popping on overrun! Alex Edited by - Alex Wong on 31 May 2007 12:20:32 Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted May 31, 2007 Author Share Posted May 31, 2007 Nick, what spec is your engine? Just wondering if you have a JPE (and therefore probably the same map as me). Alex Link to comment Share on other sites More sharing options...
DohNut Posted May 31, 2007 Share Posted May 31, 2007 Alex I have an old Skool X-flow with forged pistons and 244 cam etc. I was having a chat with the Alpha guys at Weber and they mentioned that they would be happy with a standardish 16v engine to run without an IACV but that an 8v engine in my state of tune would struggle to idle. I guess if you have approaching a JPE state of tune your engine would be equally cantankerous at idle. The bleed screws I am thining of are 4mm diameter brass thread (without a proper head) and lock nut. N Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted May 31, 2007 Author Share Posted May 31, 2007 It's a pukka Swindon JPE engine but OTOH, I've seen much higher spec engines idle fine without an IACV. Thanks for your help. Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted June 1, 2007 Author Share Posted June 1, 2007 Well the idle valve works because it wont start at all without it connected. The readings on the intake air speed were 5--5--5.5--3 I've tweeked the central adjustment for balance and it instantly idled smoothly - great! But it still isn't perfect - 5--5--6--4.5 I'm not too bothered about this but is it possible to adjust between butterflies on the same TB? I did try using the idle bleed but the screw head just broke off! Link to comment Share on other sites More sharing options...
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