bales 1 Posted August 3, 2006 Alright, I know that you can adjust the air fuel ratio on the afm of my car (1989 1.9 gti) by taking the top off the afm and loosening or tightening the spring that holds the notched wheel. My car has got a grp N exhaust and green air filter (behind headlight) and i was wondering whether it is worth richening the mixture slightly. Is this a dodgy way of doing it? and how many notches does actually make a discernable difference. If anyone has any experience of doing this or whether i should just leave well alone, i would appreciate their thoughts on this, cheers. Alex Share this post Link to post Share on other sites
Rob_the_Sparky 9 Posted August 3, 2006 Try a few searches... Bottom line is you can do it but at your own risk and no you will almost certainly no benefit from it. You may gain by cleaning it, breather pipes and a general tune up. Rob P.S. I hope you don't think you already have gained power from the mods done. The filter is good for making space under the bonnet and a nice noise, the exhaust may give you some power but not much. Share this post Link to post Share on other sites
bales 1 Posted August 3, 2006 No I dont think I have gained anymore power, and I wasnt really asking in terms of making more power. Just that my old airfilter was pretty crappy and very restrictive and with a new one and exhaust it might breathe a bit easier hence possibly making it run a bit lean. I am well aware of the minimal gains through exhausts and induction kits, i was more interested in the increments that the notched wheel actually works at. Why is it at my own risk out of interest? i cant see slighly richening or weakening the mixture is going to have any massive detrimental effects unless i dramatically change the settings in which case it wouldnt run well. All you are doing is tricking the afm to require less air for the same fuel settings in which case it just increases the fuelling over the whole rev range. But if there is no gain to be had whatsoever then i may not bother, I just wanted peoples opinion on whether it might rev a bit cleaner. Share this post Link to post Share on other sites
TEKNOPUG 3 Posted August 3, 2006 The AFM's are a bitch to set up properly. If it's working then I would leave well alone. Share this post Link to post Share on other sites
Rob_the_Sparky 9 Posted August 3, 2006 One of the good things about AFMs is that they measure air flow so unlike throttle pots and MAP sensors they are not effected by restrictions in air flow. If it flows better then more air is measured and nmore fuel put in. One of the upsides to having an AFM is that they adjust for better breathing. The spring tension impacts the mixture across the rev and load range (remember it just measures air not revs andload) so adjusting this without a check on the RR is hit and miss. Not too great a risk when richening it but you really don't want to run lean on full load and high revs. Basically there isn't enough info to know how far you can take it either way, hence the "at risk" comment. Idle mixture can be adjusted seperately. They generally they do not need adjustment off idle but feel free to fiddle. A few people have played with adjustable FPRs in the past with limited results (no obvious increases). Rob Share this post Link to post Share on other sites
ALEX 98 1 Cars Posted August 4, 2006 If you do move it mark the original position. A mate knackered his by doing this (because he hadnt marked it). Some mechanic (you know the one who talk like they know everything but don't) said just tighten the AFM spring up to make it go faster! It just makes it run rough and slower. Buy a set of carbs or programmable ECU and throttle bodies. Share this post Link to post Share on other sites
bales 1 Posted August 4, 2006 (edited) If you do move it mark the original position.A mate knackered his by doing this (because he hadnt marked it). Some mechanic (you know the one who talk like they know everything but don't) said just tighten the AFM spring up to make it go faster! It just makes it run rough and slower. Buy a set of carbs or programmable ECU and throttle bodies. Yeah I made sure I marked it beforehand so i always had a reference point, if you tighten it you are weakening the mixture as you are making the flap require more air to move it to the same proportion thus less fuel. I have actually done this now, i just moved it two notches and i have to say i doubt i have gained anything in the way of actual power but it does seem to rev a bit more cleanly and has lost a flat spot at about 4.5k. This may be a placebo effect but it certainly does seem a bit keener. I am also keeping an eye on the plugs to check it is not running too rich but to be honest it is running the best it ever has since i got it. Alex Yeah i'd love to get ecu and bodies but unfortunately i have just finshed uni and dont have any money at the moment, the plan is to get a mi16 and rebuild it over winter with throttle bodies and mappable ecu as i am planning to hillclimb and sprint it next year with my dad. Edited August 4, 2006 by bales Share this post Link to post Share on other sites
Rob_the_Sparky 9 Posted August 7, 2006 A cleaned set of injectors on my 1.9s has certainly given it a bit mre go in the same region that you describe, Interesting that a bit more fuel has a similar effect. Share this post Link to post Share on other sites
