Weber tuning with Lambda sensor - Page 10 - Alfa Romeo Bulletin Board & Forums
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post #136 of 225 (permalink) Old 10-31-2016, 10:08 AM
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Idle Jets

I have been educated by Jim Steck. The fuel orifice has most influence at lower rpm and the air bleed orifice(s) have effect at higher rpm. If your idle screws are only out half a turn then you probably need a size smaller in fuel, say move from 55 to 50. If you are good at idle but lean at transition then move to a smaller air bleed, say from F8 to F9. This is helping me a lot as I tune my 45DCOE152's.

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post #137 of 225 (permalink) Old 10-31-2016, 11:14 AM
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Excellent information. I think that fits with efforts with my DCOE44/45s on my 2.0litre on which the PO carried directly over unchanged from the original 1600 motor.

After switching from 30mm to 32mm chokes (and 117 to 135 mains), I have tried 50F8, 55F11 and 55F9. The 50F8 and 55F11 both suffered from what appears to be lean stumble transition and 50F8 appeared to need to be wound out a long way. The 55F9 seem best - possibly too rich?

Would 55F8 be worth trying? or are they very similar to the 55F11.

Also now switched from 180 air correctors to 210 - but have not checked the plugs to see if they are less black.
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post #138 of 225 (permalink) Old 10-31-2016, 01:42 PM
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Where is the 55F9 too rich? F11's are leaner than F8's.

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 #139 of 225 (permalink) Old 10-31-2016, 04:45 PM
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thanks, I'll give some 55f8's a try. I'm short on data - I need to get an AFR sensor rigged up.
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post #140 of 225 (permalink) Old 11-09-2016, 06:43 PM
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F16 or F9 emulsion tubes

My 45DCOE152's have F16 emulsion tubes, 140 main jets and 160 air correctors. They give good AFR at WOT but the part throttle AFR is too low for good fuel consumption so I tried F9's. The part throttle AFR was much better but WOT AFR was too lean and needed 130 AC's to make the high rpm AFR = 13.2. But then other parts of the WOT AFR curve were too rich. My conclusion is that F16's are preferred for a high output motor if fuel consumption is not a big concern.

Ed Prytherch
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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 #141 of 225 (permalink) Old 11-14-2016, 10:33 AM
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Thanks, the 55F8s seem to work well. Not lean stumble like with the 55F11s
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post #142 of 225 (permalink) Old 11-14-2016, 02:16 PM
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Emulsion tubes

Here is the graphical data showing the difference between F16 and F9 emulsion tubes. The main jets were 140 for all tests.
The brown and blue curves are both right at peak power but blue (F16/160 AC) stays closer to 13.2 throughout most of the range than brown ( F9/130 AC). Black (F9/160 AC) is much too lean.
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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 #143 of 225 (permalink) Old 12-13-2018, 09:09 AM
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Awakening the old thread

I have done a lot of test runs during these past few weeks to find the best setup for my new motor and I will post some information on that soon. Here is a 3rd gear WOT AFR/RPM log from today. The Webers are 45DCOE152's with 36mm venturies, 145 mains, 220 AC's, F16 tubes. Cams are RJ575 intake and 785 exhaust.
The AFR is very well controlled with a range of 11.7 to 13.0 all the way from 3300 to 7000 rpm.
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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 #144 of 225 (permalink) Old 12-18-2018, 06:07 AM
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Ed,
Happy to read you back on this thread.
Could you spend a word for me on your cams setup and in particular the lenght of the overlap?
Cheers

Giulia GT 1300 junior stepfront 1970
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post #145 of 225 (permalink) Old 12-18-2018, 06:44 AM
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Ed, Time for another trip to the dyno!

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 #146 of 225 (permalink) Old 12-18-2018, 07:31 AM
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Quote:
Could you spend a word for me on your cams setup and in particular the lenght of the overlap?
My evaluation is from WOT 3rd gear test runs up a hill and I accurately measure the time from 4000 to 6700 from the data logs. I do 5 runs and I use the mean time (which is very similar to the average of the middle three) for comparison. I choose successive days and times so that the air density is the same for each set of runs and I try to get similar humidity. I have found that the same setup will deliver significantly different times if I do them on sunny and cloudy days.

The best LC for the 785 exhaust cam is 105. It is better there than at 102 or 108
I tested the 575 at 99, 102 and 105 and I plan to do one at 108
102 was faster than 99 and 105 was the same as 102 but 105 gives better throttle response at 2400 - 2600 rpm in the higher gears.
The intake LC also changes the rich dip at about 4500 and I plan to post about that after the run at 108.
Quote:
Ed, Time for another trip to the dyno!
I am getting close to that time. I think that I have the Webers and the ignition timing right and I am almost there with the cam timing.

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 #147 of 225 (permalink) Old 12-24-2018, 12:25 AM
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Ed,
This is incredibly thoroughful.
I'm not familiar with the camshafts in you engine.
Simply, what is the lenght in degrees of the overlap of your setup with the best torque at low end?
Best regards

Giulia GT 1300 junior stepfront 1970
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post #148 of 225 (permalink) Old 12-24-2018, 06:09 AM
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I don't have the ability to measure the overlap. Richard Jemison - Alfar7 has posted a link to the profiles of all of his cams including the 785/575 combination. My clearances are .009" intake and .012" exhaust. You should be able to calculate it if you think that it is important.

My methodology is to find the best settings by measuring performance. I don't spend much time thinking about overlap. In my case changes to the intake timing have a bigger effect than changes to the exhaust so overlap may not be the best way of analyzing it.

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 #149 of 225 (permalink) Old 12-24-2018, 07:37 AM
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Ignition timing plays not an insignificant role in low end torque as well. It's another one of the things I like about the 123 Bluetooth distributor. The lake road to my house has small hills and a 35 mph speed limit and I can if I want to stay in fourth gear all the way without "lugging" the motor. It just happily moseys along even with applied throttle up the hills.

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 #150 of 225 (permalink) Old 12-24-2018, 07:45 AM
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The window of ignition advance for max power can be quite narrow when you are using a high compression ratio with pump gas. I am close to the detonation limit with 34 degrees max advance and 93 octane gas. I agree that programmable ignition allows you to optimize advance at lower rpm. During normal driving I rarely hit WOT below 4000 rpm and mine is all in by then.

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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