Weber tuning with Lambda sensor - Page 8 - Alfa Romeo Bulletin Board & Forums
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post #106 of 225 (permalink) Old 01-20-2015, 09:29 AM
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That's pretty good. Usually it takes me 21.5 seconds to shift from 1st to 2nd gear. Alfa pause, you know.
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post #107 of 225 (permalink) Old 01-26-2015, 12:41 PM
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I was happy with 150MJ/170AC until I measured the high EGT’s at high cruising speeds. 155MJ/200 AC fixed that but now my WOT mixtures are fat below 5000. They were fat below 4000 before. That costs torque – I know that from the dyno. The torque drops off when the AFR drops below 11. So I want to lean out that area and I decided to block the lowest row of holes in the F34 emulsion tubes. When I went to block these holes I “discovered” that I had already blocked two of them before I got the EGT sensor. Now with all 4 blocked there is no noticeable improvement on the WOT mixture but my cruising temperatures have gone up – the exact opposite of what I was looking for. So I unblocked all 4 holes and now my cruising temperatures are much lower and my high power AFR is a little bit fatter. So the next step is to return to 150MJ/170AC and see if my cruising EGT’s are acceptable. If they are not then I will drill some more low holes in the emulsion tubes. This confirms what John Passini wrote - that emulsion tubes have a small effect at full throttle and a large effect at part throttle.

I had done a 7 to 100 mph rolling start pull up the hill in 21.3 last week. I do not do standing start pulls because I don't want to abuse the clutch. Today I did 17.1 going down the hill. The two way average is 19.2. I figure a good driver could go from zero to 7 mph in 1 second so my 0 to 100 is about 20.2 seconds – 1 second faster than a stock Montreal in the 1973 R&T European test.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke

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post #108 of 225 (permalink) Old 01-26-2015, 04:59 PM
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I'm with you on the rolling start. now I'm curious what I'll get from 3500 in 1st to 100 with a 410 rear end. Weather is perfect here to hit my favorite strip of road.

The passenger seat is 15 miles an hour faster than the drivers seat.

currently
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71 Berlina in 2L restored driver
the ones that got away:
1959 750 series Giulietta Spider Veloce
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post #109 of 225 (permalink) Old 01-26-2015, 05:20 PM
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I'm with you on the rolling start. now I'm curious what I'll get from 3500 in 1st to 100 with a 410 rear end. Weather is perfect here to hit my favorite strip of road.
Go for it!

You will not be in 1st gear very long if you start at 3500. I went from 2000 to 6000 in 1.4 seconds today.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke

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post #110 of 225 (permalink) Old 08-05-2015, 05:37 PM
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Emissions 40's vs Classic 45's

I posted several AFR curves while I was tuning my 40DCOE116/117's and they had an S shape. I have swapped them out for a pair of 45DCOE152's and here are comparison curves of WOT runs in 3rd gear. The black one is the best torque/HP with the emissions carbs. The brown one is with the 45's with 150 MJ/200 AC/F16 ET and stock accelerator jets. The red one is the same setup as the brown but with "0" accelerator pump bleed back valves. The difference in the shape of the curves is striking. I made no other changes to the engine.
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2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #111 of 225 (permalink) Old 08-06-2015, 05:00 AM
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Thats interesting that the emission carbs are richer in the low speed circuit.

Jason
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post #112 of 225 (permalink) Old 08-06-2015, 05:18 AM
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Jetting

Before changing ACs swap the main jets to something significantly smaller (140s, then 145s) see what happens in the blend area from 3000 to 6000 where the rich dip is currently.
If you have "adequate" size jets then there should be enough fuel supply for the higher RPMs.

I`m afraid that changing IJs will lean out "tip-in" AFRs which are good.

Like we talked about yesterday, see what "cruseing" AFRs are at 2500 to 5000 which is typical hwy driving. On a race car this isn`t as important and WOT is AFRs are critical.

Richard Jemison
RJR Racing

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post #113 of 225 (permalink) Old 08-06-2015, 05:52 AM
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Thats interesting that the emission carbs are richer in the low speed circuit.
Not what you would expect. Emissions carbs give better fuel consumption but the gains are clearly not at WOT.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #114 of 225 (permalink) Old 08-06-2015, 08:18 AM
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Both the above are what I've suspected reworking the emission Webers for years. I've had a feeling these were funstioning as you have shown.The ease working with non-emission is now explained, as well as RJ comments on my set-up for non emission.
These last two posts are IMPORTANT for those following this thread.
At least three of us share the same opinion here.


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post #115 of 225 (permalink) Old 08-06-2015, 01:14 PM
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Make that 4
Just how common are "emission" webers and how can one tell the difference? I've heard of Weber carburetors since I cleaned my first butterfly but have never heard of, except here, and Ed's are the only ones I know of. Scratching head

The passenger seat is 15 miles an hour faster than the drivers seat.

currently
2017 Giulia Q4
74 GTV restored daily driver
71 Berlina in 2L restored driver
the ones that got away:
1959 750 series Giulietta Spider Veloce
1962 Giulietta Spider normale
1965 Giulia Sprint normale
1972 GTV
1974 GTV
1974 GTV
1977 Spider
1974 Spider
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post #116 of 225 (permalink) Old 08-06-2015, 04:25 PM
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Quote:
Just how common are "emission" webers
They were in Shankle's conversion kits and maybe some others. I bought mine from a guy in Italy. They were OE on a number of European Afa's in the 70's and 80's. They would still be my choice for a 160 -170 HP motor for road use.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke

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post #117 of 225 (permalink) Old 08-06-2015, 10:59 PM
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Originally Posted by gigem75 View Post
Make that 4
Just how common are "emission" webers
In Europe, very common, all starting from alfetta´s, 75´s onwards where fitted with Emision webers and/or (emision) Dellortos instead of webers
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post #118 of 225 (permalink) Old 08-07-2015, 03:11 AM
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Before changing ACs swap the main jets to something significantly smaller (140s, then 145s) see what happens in the blend area from 3000 to 6000 where the rich dip is currently.
Just out of curiosity; wont that shift the whole AFR curve leaner? Why not adjust the AC's to target that RPM range?

Jason
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post #119 of 225 (permalink) Old 08-21-2015, 05:36 PM
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I had a few problems with the 45DCOE152's, mainly due to inferior manufacturing. Two of the threads in the carb body for the emulsion tube holder were not completely tapped and were causing the threads to bind before the main jet was seated. Both float needle valves were damaged and I encountered fuel starvation at high speed that was only corrected by setting the pressure regulator to 5 psi. 140 main jets were too small and they caused the AFR curve to take a big shift upwards and I have settled for 145's. The unexpected result is that I have to run big air correctors. Here are curves for 200, 220 and 280 which is pretty good. I will probably stick with this combination and then play around with pump jets. I bought a couple of sets off Ebay and they don't quite fit so I will have to reduce the diameter of the spindles until they will slide in.

I tried 50F8 idle jets are they were much too lean. I now have 60F8 and they are pretty good. The car drives very well except for some lean hesitations when I get on the gas.
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Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #120 of 225 (permalink) Old 08-21-2015, 07:07 PM
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Whoever had the carbs before you must have had a fit with them with the main jet not seating. Glad you got that sorted! I guess it's time for a drive to the dyno you used last time? I for one can't wait.

The passenger seat is 15 miles an hour faster than the drivers seat.

currently
2017 Giulia Q4
74 GTV restored daily driver
71 Berlina in 2L restored driver
the ones that got away:
1959 750 series Giulietta Spider Veloce
1962 Giulietta Spider normale
1965 Giulia Sprint normale
1972 GTV
1974 GTV
1974 GTV
1977 Spider
1974 Spider
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