cheshire190e

Okay so I had a play with the idle jets today. I have managed to improve the stumble by increasing the fuel jet from a .6 to .7 and I have added extra air bleed holes. It's now at 13.5ish on light throttle and cruise and only has a light stumble. I may try .75 fuel jet and see if it continues to improve

Okay I'll stick with the f16's and fiddle with the idle circuit for a while. I'll initially try the same size fuel jet and a smaller air bleed.hopefully it will reduce the tendancy for it to lean out as revs rise through the progression circuit. If that fails I'll go larger on both air and fuel size. I'm going to stick with the 32mm chokes for now until the progression is sorted then I may try 34's. Regarding drilling the progression holes. That's my last option but my carbs don't have a threaded plug into the ports. Mine are the tamper proof pressed blank that goes in there so I'm not sure how I'd go about it.

Ok well I have another update. I have been off work today so decided to try and figure more of the problem out. I changed the chokes to 32mm and took it for a spin. Obviously the afr was rich on the main circuit so I changed the main jets down to 145 and lowered the air corrector to 140. This gave me a steady 12.5-13.0 from 2k to the red line. However the lean stumble is less harsh but it is still there and there is a noticeable loss of top end power. The stumble has been reduced from fitting the smaller chokes though. Currently I'm still idling around 12.5 afr. I'm around 12.5-13.0 on light throttle cruise but when I slowly open the throttle there is still a lean spot before the mains kick in. Would fitting f7 emulsion tubes help with the lean stumble or do the tubes only really have an effect once the mains have kicked in? It's as though I need the idle circuit to be leaner at very slight throttle and progressively richen. Where as currently it gets leaner. The issue here is when I increase the idle jet size the lean stumble reduces but I'm left with a very rich cruise around 11 afr. I've searched everywhere and I can't find any info on 5 hole dcoes to see what others use.

Thanks for such a detailed reply. I will give the 32mm chokes another try and see if it improves things. However My wideband is new so I don't think it could be reading faulty. My F16 emulsion tubes with 140 mains and 180 air correctors hold a steady 12.5-13.0 from 2k right up to 7k My problem is the idle circuit. Regarding the larger jets. I found with a 65 idle jet with a large air bleed it ran better with no hesitation but when on light throttle cruise it would be as low as 10.0 afr. When I tried opening the air bleed up it would not make much difference to the light throttle cruise but it leaned out the entire rev range and raised the main circuit to 14 afr so I changed back to the smaller air bleed. I may be hunting down the wrong road but is the idle air bleed similar to the main in that it works progressively as the revs increase? I.e does increasing the air bleed on the idle jet have more of an effect at higher rpm? Currently it's perfect with the afr at light cruise around 13.0 afr but rises to 15-16 with slight throttle movement. It's like I need it to get richer as I progress through the transition phase. Which to my understanding is a small air bleed to enrichen as rpm rises. Is this theory correct for the idle circuit? And should a large idle air bleed effect the main circuit? Do you have to use a huge main jet and small air bleed with a large idle jet and large air bleed ? Thanks for all the help!

Thanks for your reply. I am using F16 emulsion tubes and I have previously tried 32mm chokes. With the chokes there was a huge loss in power at the top end even with the fuelling correct. Maybe I should try some 34mm ones. I've been playing since and now I have it to cruise around 13.5 and stay around there if I accelerate very slowly. As soon as I reach 2k I can full throttle and everything is fine!

Hi everyone. I've recently installed a pair of 126/127 Weber 40's on my 2.0 8v Mercedes 190E. I'm having a little trouble getting a smooth progression. I have a wideband so know whats happening with the fuelling. So currently the engine is bone stock apart from the carbs and manifold. On WoT I get a steady 12.5-13.0 Afr all the way from 2k rpm. The issue I'm having is at slight slow throttle movement. According to the wideband my idle is averaging 13.0 which gives a nice steady idle speed of around 800rpm. However when driving at a steady speed if I move the throttle a very small amount from closed the mixture goes rich to around 11.5. then as I continue to open the throttle slowly the mixture goes leaner and leaner through the progression phase until it hesitates at around 18.0 afr. Now to try to clear this up a bit as I know it's difficult to describe it is definitely a throttle plate angle which is causing the leanness. It happens at various rpms in all gears. my current set up is: Twin 40's matched pair 126/127 36mm chokes 4.0 aux venturi 140 mains 160 airs 60 idle jet. I started with 45, then 50 etc to remove the hesitation. mixture screws around 2 turns What I feel is the issue is there is not enough flow through the idle jet to provide the 5 progression holes with enough fuel. However by increasing the jet the stumble is decreasing but I'm ending up with a very rich cruise when the throttle is just slightly cracked open. To add the throttle plates are covering the first progression hole when on idle. Any thoughts?