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Pretty happy how the engine is running now on the twin DHLA40s, especially now the accelerator pedal can open the throttle plates fully Running 30mm chokes with 119 main jet and 200 air corrector. It's all good until about 6100rpm when it becomes a bit sluggish. It's not leaning out, I've played with smaller air correctors and 130 main jet and holey .10 emulsion tube and race tubes both .5 and .7 and I can vary the mixture from 13.2:1 to 12.3:1 at 5500rpm. It's not over rich, a 116 main jet gives 12.8:1 and behaves much the same at high end, but starts a bit late, so midrange is weakened, and I'm not extending idle jet or messing with progression holes to counteract. Once I reach 6000rpm there's some hesitation. I know engine will hit 6800rpm with the Pierburg or a twin choke Weber DMTL on the GK manifold. I'm using trumpets with Ramair foam socks. They are a bit close to the firewall, but I think I can see ram effect pressure (from -8psi cruise vacuum to +0.3psi). Three ideas 30mm chokes are too small foam filters are compressing into the trumpets to not let air through the Aldon Amethyst rev limiter is very subtle (set for 7000rpm, original Dignition limiter is 6800rpm and sudden) So, realising the dello's have been on for 2 years I have given the foam filters a good clean with the raidHP/ramair cleaner and I'll re-impregnate them with the correct polymer snake oil. Might have a short blast without the filters. Or try again with a Sorg inlet plenum but that makes jet changes annoyingly hard.
Hello, I'm French, and I'm here because I don't find enough answer in my country... I have a 1.1L engine GG code (same as HB engine) fitted on a Golf mk1. Nobody in Golf want to tune a "small black", Polo guys know very well ! I want to put twin DHLA or DCOE carbs, but I have few questions... - I don't find many 1.1L fitted with twin carb, but a lot of 1.3L. I want to keep my original engine, so is it possible to have good results ? - The head is a mechnical, and I don't know if a "performance" camshaft exists for this type of head ? - The head has holes for heating the original carb, so I have to close them ? Because the manifold for twin car I find don't close them. - For the fuel pump, the original with a filter king is enough ? Or I need to put an electric pump ? Thanks for your help, and sorry for my bad English...
In the week before Christmas I had to scrape loads of ice off the windows one evening. I didn't bother running the engine while clearing the screen. The twin DHLA 40 have a crude starting device - essentially an extra carb per pair of cylinders. The inlet tract for this is a small hole 3/8" on the back of the carb, no trumpet, no filter and the outlet is downstream of the throttle plate. A cable-operated piston moves to let air (and fuel) pass. It's not as adjustable as a choke flap, so you only get it off, medium, on. Usually I just pump gas pedal 3 times and start with the pumped fuel, bit of nursing while drive away and it's good until the first roundabout, when it might stall if I have to stop completely (rare). It was cold enough to need the starting device and enrichment for about a mile. But that evening there was a traffic and a gap, so I disabled the enrichment and floored it while still cold, when I'll normally try to show restraint until temp gauge has left the white box. And from there the car was down on power, and loud, and according to the AFR gauge, running a bit lean. Could it be the cold, dense air? Surely the fuel in the tank was just as cold. I'm running with trumpets and filter socks. For winter I've got a pipe from exhaust manifold to back of engine bay to carry warmer air to ward off carb freezing in damp. But this was dry frozen air. So, investigation. Infrared thermometer says cylinder 2 is not burning fuel, it's like 40 degrees while 1,3 and 4 are heading to 130 degrees. Compression test(dry) and engine warm gets 220psi for that cylinder 2 and a bit less for the other three - because it's colder? Spark plug looks dry sooty, new plug rested on chassis sparks fine. Clean lead. Clean distributor cap just in case. Swap for another lead. Swap spark plug. It's not electric. Double check timing. Paper held 1" from exhaust pipe occasionally gets sucked onto exhaust. Burnt exhaust valve? Yet compression is fine. Do a leakdown test? Need a really quiet pump to blow air in spark plug hole while both valves closed. No too windy to be able to hear a leak, never mind the pump noise. Aha, using the starter device cylinder 2's exhaust outlet gets hotter. So it's the idle circuit. Unscrew idle jet. It's clear. Unscrew transition hole cover it's clear. Unscrew idle air bleed... a worn 0-ring. Replace O-ring. Refit idle bleed. Fill idle circuit with carb cleaner fluid. Wait 30mins Attach tube to keyboard cleaner compressed air can. Spray through idle circuit pickup to transition holes, and from transition holes to idle barrel orifice, and repeat. Found it - tiny piece of dirt or fuel varnish, resting in the transition hole well it has 6 holes like a colander. Picked out with some tissue, and blown away with the wind. I guess the melting ice water washed it free from a crevice. Reassembled. Got it to idle. All cylinders around 230degrees at exhaust manifold.