Kenno 3 2 Cars Posted July 31, 2007 Hiya, I got a friend that works in a pug garage & I was worried about my car & emissions. I have set up a piper 285 cam with vernier a boost valve & rebuilt head with polished ports. Took it down as he rang me that I could pop it on the co2 machine, got down there & I had it ticking over around 8k well it was bad!! I upped the revs & seemed to lower it, one of the techs come along a fiddle with the afm & the throttle body!! & got it just a bit lower & at that point I had to get the car out. The tech guy said it would be best to take off the boost valve for the MOT!! Well got the mot this thurs so took off the boost valve & the engine seems all over the place. As ant will tell you when we was over at the ring the colour of the plugs when we took one out looked fine & like it was running really well & I think that it was was doing well on petrol on the way there & on the way back. Now this guy has touched it & i have taken off the boost valve Im not sure what the settings are like. I just wonder if any of you would know what the setting of the Throttle body screw would be ie: 3 complete turns out from screwed in & the same with the AFM please, any help please as hve mot on thurs?? I have colour tune so was gonna use that later but I need a starting point!!! Cheers I dont have carbs for the 285 yet but will later on I think Share this post Link to post Share on other sites
Anthony 1,003 Posted July 31, 2007 There isn't a "magic setting" that'll definately work unfortunately. The screw on the throttle body is there to set the idle speed, and if you're struggling with emissions it might be an idea to knock the idle up a few hundred rpm as this will drop the emissions right down. The screw on the AFM is the one that you need to adjust, as that's what sets the idle mixture. Unscrewing this (ie anti-clockwise) will lean the mixture out and bring down the CO, which is what I'm assuming you're struggling with. I'd be tempted to refit the PBV as the engine ran well with that and idled amazingly smoothly for that cam, but chances are that if it's "all over the place" with the standard regulator then it's probably running rich and leaning it off (as above) will probably help - a rich mixture will typically "hunt" and the revs will be going up and down and probably stall alot too. As a ballpark guide, clean the throttle body and breathers, unscrew the screw on the AFM until the engine note starts to sound lumpy and hollow (difficult on your car as it sounds lumpy as you like anyway), and then bump the idle speed upto about 1200rpm or so. That should get through the emissions even with a lumpy cam like yours - the non-CAT emission test is only 3.5% CO and 1200ppm HC, which is very easy to get through Share this post Link to post Share on other sites
Rob_the_Sparky 9 Posted July 31, 2007 You could try a few AFMs or a re-tracked one. I've struggled with my car on tick-over emissions and have a few AFMs in stock. I return good mpg but (as Anthony will agree) my tick-over is a tad lumpy and struggles with the MOT time idle mixture (unknown re-profiled cam and 10.4:1 compresion). Some AFMs will allow me to pass the MOT quite easily but doesn't do the power output any good. When really having a problem can just swap the AFM to get it through! Rob Share this post Link to post Share on other sites
Miles 331 1 Cars Posted July 31, 2007 As Ant's said, I;d stick the FSE valve back on as these set up correctly cause no problems at all, The tech people just don;t under stand them really, The ECU isn;t meant to work with that cam so the emmsions will be bad, but you can turn the tick over up (Again as Ant's sugestion) You could cheat and stick a tube in the exhaust with a blanked end just allowing the gases to escape round the edge so when the probe goes in it measure's nothing bar some gasses which will get in. Share this post Link to post Share on other sites
snillet 1 Posted August 1, 2007 Engine will hunt at idle with somewhat to lean mixture to, especially on a wild cam. You usually get the best idle with a wild cam at a tad bitch rich mixture and then if you lean it back to a setting suitable for a standard cam it will start to stutter/jidder a bit, but the CO reading mostly goes down anyway. Nothing is "bone safe" with wild cams/emissions/afr:s though. Share this post Link to post Share on other sites
Kenno 3 2 Cars Posted August 1, 2007 (edited) Cheers guys, I got it running a bit smoother yesterday, & used a colour tune to get the colour as best as I could thats with the boost valve still off. Gonna leave it at that & its ticking over at @ 1200rpm just have to have my fingers crossed & fiddle with it when im there if the tester will let me. Tanks for all your help . Edited August 1, 2007 by SR i Kenno Share this post Link to post Share on other sites
tom_m 0 Posted August 1, 2007 Cheers guys, I got it running a bit smoother yesterday, & used a colour tune to get the colour as best as I could thats with the boost valve still off. Gonna leave it at that & its ticking over at @ 1200rpm just have to have my fingers crossed & fiddle with it when im there if the tester will let me. Tanks for all your help . 1200 will be fine for the MOT, tho you might get an advisory for it. i always up the idle and lean the mix for the MOT. its not failed me yet, tho the last guy to comment said if the hot idle had been any higher he'd have failed me Share this post Link to post Share on other sites
