I have 55F9 idle jets installed and the low end, part throttle performance has never been better since I switched to 45DCOE152's. Anything richer than those would be unusual. I have some 60 series idle jets that I used before I opened up the progression holes and I was never happy with them. I am not too concerned about the lean band between 3000 and 3500 because it is only there at WOT and the car cruises very well in that region. But as my last tank of 93 octane was only $1.63/gallon perhaps I should try to richen it up a bit without making the rich dip at 4500 rpm any bigger.
Current main jets are 150 and I am sure that they are the best choice. Anything smaller sends it very lean. Air correctors are 178 (#50 number drill) and I should probably try some a little smaller. I was running 190's before. The temperature and humidity favors bigger AC's in the summer. I have done most of my recent testing on cool, dry mornings. I am shooting at a moving target.
EDIT: I have a set of 60F8 idle jets that I will try.
What about 60 F-13 or F-2 (Both leaner), or even a 50-F6 or F12 Richer, smaller fuel inlet but smaller air hole for richness but the 50 would limit the flow at higher a higher RPM range which should cut into the rich curve after 3000 ??
I may have some 50F12's but I will try the 60F8's first.
I turned a set of 230 AC's into 170's this afternoon. There is a number drill, maybe 51 that is exactly 1.7.mm. While I was soldering up the 230 holes I had extra solder run through into the main bore of the jets which was a pain to remove. Then I got the idea of sitting each jet on the shank of a drill which was a close fit in the bore while I soldered up the hole and no extra solder ran through the orifice. I hope that I remember this trick the next time I make jets smaller.
I did four 3rd gear WOT runs today with 60F8 idle jets. Two runs were with F11 tubes and 170 then 178 air correctors and the other two runs were with modified F16 tubes and 170 then 180 air correctors. All the runs were completed within 30 minutes over exactly the same strip of road. I plotted the data onto Excel and here is the graph. It is clear that F11's run leaner than F16's above 4500 rpm and the air correctors suited them well. The F16s want larger air correctors and I plan to do 4 more runs with 190 and 200 AC's.
The very good news is that the motor loves the 60F8's. The low end response was pretty good to begin with and now it is even better. On the last run I floored the gas pedal at 2200 rpm and it pulled away with little hesitation and that was on a 3% uphill grade.
It is. (The 1 in the Duetto. The Coupe has a Autometer and has little wires for "Something" I`ll have to find the instructions for both.
I`d like to have a built-in component that I can easily understand it`s operation.
Electrical devices you know.........
I did additional 3rd gear WOT runs today. Same format as yesterday about 10 minutes between each run over an identical strip of road. Here are the results.
The F11/178AC and the modifiedF16/200 AC are pretty much the same from 4500 to 7000 rpm.
The F16/200 has a small advantage from 3600 to 4500
The F11/178 AC has a big advantage below 3500 rpm.
So I have to decide whether I want to have more torque from 3600 to 4500 or to be able to slam the throttle wide open and pick up well from 2500 rpm (or less) in 35rd gear. I will drive around and see if I can discern any difference in low rpm, part throttle operation.
AFR and Torque
After comparing my dyno torque curve and the AFR curve for the stock F16 emulsion tubes that I was using at the time, there is a visible drop in torque when the AFR is lower than 11.8 and higher than 13.5. I believe that range of 11.8 to 13.5 should be the target when making carburetor adjustments. Getting close to 12.8 is the bulls eye but I don't see much gain in getting closer once you are within 11.8 to 13.5 zone.
I tried to edit the above posts and I was blocked by the max number of edits control. What a stupid feature.
Anyway, I discovered today that when I did the comparisons between the F16 and F11 tubes I had 150 main jets in the F11's and 155 main jets in the F16's. I wrongly concluded the F11's run leaner above 4500 rpm when in fact they are the same. So the main difference between the two emulsion tubes is that the F16's are richer between 3500 and 4500 rpm.
I drove around at relatively low rpm two days in a row, first day with F11 emulsion tubes and second with the modifies F16's. The ambient conditions were similar and all other jetting stayed the same. Driveability was very good with both but the F11's certainly are superior.
The motor has now done 4700 miles and I decided to do a warm compression test so that I have a benchmark.
1 – 183
2 – 175
3 - 186
4 – 184
Retested #2, still 175. Added a little oil to #2 – 190
Jim's comments were:
All but #2 are amazingly close. Maybe it wasn't quite as round as the others. Overall very good. The absolute value is very dependent on intake valve closing angle.
45DCOE152 progression holes.
My 45DCOE152's are the early type with 3 progression holes and a previous owner of them added an extra hole to make them like 45DCOE152G's. The link below is a post from Hunttheshunt that shows the position and size of the holes. They did not run very well and I opened up the first three holes a little at a time. I measured the again today for Richard and they are:
1 (nearest the engine and covered by the throttle plate) = 1.5 mm
2 = 1.3 mm
3 = 1.3 mm
4 = 0.8 mm (unchanged)
With these holes the motor runs well with 60F8 idles jets
I am looking for information about the progression holes on 45DCOE152G's. My understanding is that there are 5. Anyone know the hole sizes and locations, particularly the first one, closest to the throttle plate? Thanks.
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