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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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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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Ed, Time for another trip to the dyno!
 

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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.
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.
 

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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
 

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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.
 

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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.
 

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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.
 

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Richard Jemison
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Choosing LCs

Read the latest post on my Technical Questions or the Dynoed my 86 Spider thread today.

What others with cam designs totally different from any other doesn`t have any application to your engine.

What is your engine, induction lengths, use, cams installed, VVT or not, these are the factors that determine where to set cams.
As I posted Stock Alfa cams have excessive overlap at 102/102 if that`s what you have.

It`s X-mas -1 and I`m bored so here`s some info

Here`s the Best of Alfa`s production cams the 10548-01 and
Ed`s current cams in red Intake/exh

10548 03200 “ 01" (Cam Data .401 Max Lift 10.2 mm lobe lift
Cam Lift Dur. at “0” lash. Factory LCs 99.5/99.5)
Ed`s cams
.018 286 (off the seat/lash, Paired overlap at 99.5 LCs is 76
.020 278 degrees, & way too much! at 104/104 = 56 degrees
.040 240
.050 230
.100 211
.200 173
.300 118
.350 83
.400 10

Eds intake & Exhaust cams currently RjR575 int 785 exh and next exhaust cam he`s going to install. (The new exh is an extreme power builder.)
Lobe lift Int,.503(12.8mm) Exh,.461"(11.7mm) New exh.495"
Intake RjR 575-----------------Exh RjR785-----------Exh RjRprivate
,010-304-OTS duration/lash-------------------------------276
.012--------------------------------287(lash/OTC---------------
.020-289---------------------------273---------------------264
.040-273---------------------------252---------------------252
.050-267---------------------------247---------------------246
.100-242---------------------------223---------------------228
.200-202---------------------------186---------------------194
.300-156---------------------------145---------------------156
.350-137---------------------------------------------------------
.400-120----------------------------89----------------------110
.450--81---------------------------125-----------------------65
.500---8---------------------------------------------------------
Overlap with cams set at 104LC each (add intake Overlap to Exhaust overlap for total overlap 105/105 LCs will reduce this overlap about 4 degrees total
27 degs.------------------------18.5 degs.-----------------26 degs.
Paired overlap-------------------45.5 degs.---------------- 53 degs.
 

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I did my redneck data logging AFRs on my new motor with the higher compression Alfaholics pistons. My first runs were with 135 mains and 220 ACs. That was to lean.
Then with 135 mains and 210 ACs which gave me [email protected]
and then 130 mains and 200 ACs which was [email protected] I decided on the 135 and 210. The pull in 4th from 2000rpm was smoother with this as well.
The complete jetting is:
135 Mains
210 AC
f11 tubes
34 chokes
55f8 idle
Ed and anyone else, what do you think. Also posting on my new motor thread.
 

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Richard Jemison
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AFRs

I did see 10s & 11s in your video, corresponding to "Tip in". AFRs under full power should be in the high 12s or low-mid 13s, other than the 2-3 seconds where the accelerator jets are spraying. Constant speed on level road about 14-14.5, and on "tip in" (accelerator jets spraying) drop to low 12s then leaner again as above.
Idle no load 14-5 -15 AFRs

Per Jim Steck there is measurabe power loss richer than in the mid 12s
 

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Thanks Ed, Richard. There are two different runs with different jets and thus different numbers in the video. I can get 14-15 at idle but it spits back. Best smoothest idle is at mid 12s. 1st gear WOTs are a few points leaner than 3rd wots which are in the mid 13s with the 135 210 vs the 130 200 which is [email protected] in 1st.
It looks like my biggest deviation from the numbers are the cruise numbers @4000 which are high 12s to mid 13s. The ambient temp was 99 degrees and road was not perfectly level. I think I'm pretty close and will do some runs when it cools off. Also had the aircon on too, just to darn hot! It really is my best motor yet, imho.
 

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Idling is not influenced by anything in the emulsion tube stack. I have always ended up using the smallest MJ/AC combo that makes correct AFR at high power and does not go grossly lean anywhere else, but I have not used F11 tubes.
I did almost all of my testing in 3rd gear uphill. When I had found the best setup I did a final run in 4th. Sometimes it went a bit lean at the top and I had to drop a size or two in AC's.
You should do a test run in January to make sure that you are not tending lean.
 

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Roger that! I have to confess, I would have bet money I had as I stated 55f8 idle jets in there but come to find out they were 45f8s. That was a surprise. Anyway I tried 40f8s and could get a good idle, still not 14 though, but the no load cruising was a lot "choppier". I take it easy on the black top road to my house and driveability is a big deal so I went back to the 45f8s. I'm looking forward to the thicker air and no ac load here in 3 or 4 months.
 

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Dellortos - Not Weber

Hopefully it is appropriate to post some Dellorto tuning results here. If not, I trust the moderators will advise.

I have been setting up a pair of DHLA 40Ls (emissions carbs) in the '78 Spider with a modified 2L. The engine came from Ed Prytherch and is essentially the same as the first engine Ed describes in his "79 Spider on the Dyno" thread. That is, it has Venolia pistons, 10.6:1 compression, a Richard Jemison head, and Richard's 575 intake cam and 785 exhaust cam. I thought it might be useful to post the jetting specs and results and solicit comments.

The original jetting was, as far as I can determine, stock for a 2L Alfa.

148 Main Jets
57 Idle Jets
210 Air Correctors
32mm Vents
7848.3 Aux Vents
41 Pump Jets
7772.1 Emulsion Tubes
8.5g Float

After a fair amount of experimentation, the current jetting is:

140 Mains
60 Idles
195 Air Correctors.

The following graphic shows AFR by RPM in 2nd through 4th gear. These Dellortos seem to go a little rich after about 5700 rpm. Larger air correctors can keep the AFR in an acceptable range but if too large, the AFRs are too lean around 5400. Of course a larger main jet can be used along with larger air correctors but the same "rich" trend occurs at slightly different engine speeds. The current setup seems to be a reasonable compromise. Comments?
 

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I would go a little larger on the air correctors. It should not be a problem if AFR hits 13.5 at 5200 so long as it gradually lowers towards peak HP rpm, probably around 6200. Then do a test run, print out the logged curve and draw a horizontal line at 12.8 AFR. Is there more area above or below the curve. If above then go back down on the AC's.

I am jealous of your nice clean rpm signal and I wonder if there is a problem with my Zeitronix ZT2. Maybe we could put my box in your car and see if the rpm log is still clean?
 

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Thanks Ed. I have a log using 210 ACs giving maximum AFRs of 13.3 between 5200 and 5600 rpm. The thought was to keep things just a smidgen rich but sounds like that is not necessary. I will compare areas above and below 12.8.

We can certainly swap your Zeitronix and see if there is a difference.
 

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Here are a couple of graphics showing logged AFR curves in reference to a horizontal line drawn at 12.8:1. The first curve was captured while using 195 air correctors and the second was captured using 210s. Looking at the acceleration runs for third gear (in the middle of the graphs) and ignoring the initial variability after the shift, the area below the reference line is clearly greater than the area above the line using the 195 ACs. Using 210 ACs, the areas above and below the reference line even out slightly, which confirms Ed's advice above.
 

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