coffee break Posted May 25, 2012 Share Posted May 25, 2012 Any ideas on adjusting DCOE's for tailpipe test? My mechanic can get the idle to pass but the 2500 rpm is in the middle stage of the carb. I need suggestions on lowering the HC numbers. Any tips? Preferably tricks that do not require different jets.:bigear: Link to comment Share on other sites More sharing options...
twobone Posted May 25, 2012 Share Posted May 25, 2012 Yikes, good luck! Advancing the ignition and leaning out the carbs is the best I've heard Link to comment Share on other sites More sharing options...
bsimon Posted May 26, 2012 Share Posted May 26, 2012 If you've got type 52 pattern DCOEs, use the air bypass screws to increase the idle thereby keeping the throttle opening smaller. More advance as Two Bone suggests. Change everything back to normal before leaving the test facility and giving the engine any welly. (Methanol is not a Hydrocarbon.) Link to comment Share on other sites More sharing options...
BusaNostra Posted May 26, 2012 Share Posted May 26, 2012 I used to have a Lotus Esprit turbo (dual dellorto 45), I always a hard time passing to the emission. The hydrocarbon always high. So, I always retard the timing and let one vacuum hose unplug. It runs zhyte going to the emission but I always pass it. I also had a set of jets that I put every 2 years I go for emission. I hate it & I sold it! Two of my cars are in Florida and no emission. New England is tough. Link to comment Share on other sites More sharing options...
coffee break Posted May 26, 2012 Author Share Posted May 26, 2012 The carbs are 40 DCOE 151 according to the original spec sheet. I believe this is correct. This is the car when it was for sale in 2007 with less than 3000 miles. http://www.classiccarsltd.com/modules/auto/detail.php?id=388 Link to comment Share on other sites More sharing options...
bsimon Posted May 27, 2012 Share Posted May 27, 2012 The 152 (I mistakenly referred to it as a 52) is a 45mm version of the same Spanish built DCOE as your 151. The 151 should have air bypass screws as well. They were originally intended to balance the individual chokes of a single carburetor, however I've rarely ever seen them used as most DCOEs are balanced adequately without cracking the screws open. Older DCOEs didn't have these air bypass screws. The idea is to get to 2500RPM for the test by only just cracking the throttle blades open. This keeps the mixture control still mostly in the idle circuit and off the intermediates. You'll have more capability of leaning the system out using the idle mixture screw. If all else fails, CH3OH is your friend. Link to comment Share on other sites More sharing options...
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