Carb Tuning with 02 sensor - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 22 (permalink) Old 08-26-2012, 10:41 AM Thread Starter
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Well I was back at it again with some more tuning (one step at a time of course). I am pretty happy with the setup that I have now, I won't bore you with all of the intermediate details, but I ended up moving up to 34mm chokes (which seemed to dramatically reduce the leaning out at the top end full throttle), and then switching to some F16 emulsion tubes. The motor reacts great not only under full load, but is very well behaved on the bottom end also (almost hard to beleive with these large overlap camshafts!), and at cruising speed (3000-4000 rpm with light load), the mixture is nice and lean (or at least not unnecessarily rich as it was before). Enough talk, here's the data:
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69 1750gtv / 73 2000spider / 91 Spider (daily driver)
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post #17 of 22 (permalink) Old 08-26-2012, 03:07 PM Thread Starter
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the curve on the bottom (green triangles) is wide open throttle. I see that it is not on the chart legend.

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post #18 of 22 (permalink) Old 09-10-2012, 05:18 AM Thread Starter
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better power and better fuel mileage!

Just made a trip into germany this weekend, and had a chance ot make a fuel consumption calculation over a combination of secondary roads (50-100kph), and some autobahn (mostly 130kph-150kph), and I used 10.3 l/100km, which I think is very good for a 43 year old 2000cc sports car! This is with "bigger" chokes (34mm) and and "bigger" main jets (145). The last mod was really the emulsion tube (F16), which is think is mainly responsible for keeping things lean at part throttle.
At part load (ie highway cruising), is there a risky limit for lean combustion? it is usually hovering around 0.93 - 0.96, but occasionally jumps goes to 1. Is this a problem? I assume that the risk of melting pistons only occurs on a lean burn at full load. The engine seems to behave fine (excellent in fact). Just notice that at VERY light load, like keeping constant 50-60kph on flat ground, if the lambda gets around 1 there is a very light surge from the engine, but this is really minor.

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post #19 of 22 (permalink) Old 09-28-2012, 06:03 AM
rsj
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Euro - sent you a PM.

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post #20 of 22 (permalink) Old 09-28-2012, 07:49 AM Thread Starter
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strange, there is nothing in my messages. I'll send you a PM to see if that works

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post #21 of 22 (permalink) Old 09-29-2012, 08:32 AM
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Hey 1750, have sent you a new PM and an e-mail as backup.
Thanks.
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post #22 of 22 (permalink) Old 09-30-2012, 07:29 AM
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Hey 1750, I just noticed an old message from you that says you live fairly close by in Armstrong. We should get together before the driving season is over, but I am not sure whether my PM /e-mail messages to you are going through (I post them, but then they disappear - I might need administrator help).
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