Weber 45 DCOE Jetting/Tuning - Page 3 - Alfa Romeo Bulletin Board & Forums
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post #31 of 85 (permalink) Old 05-28-2015, 08:49 PM
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Quote:
Originally Posted by Gary Williams View Post
The jetting.exe file is clunky to run on a modern computer, but this little program works great for doing initial carb setup. I paid for a Weber expert and for dyno time. After that, I checked Gron's settings with jetting.exe and found them almost identical. There a link to jetting.exe here, under "Setting Up Your Carbs." Alfa 105 Series Tech Info ? 1 | The Williams Family ... Now and Then
You can also download jetting.exe here, last post. I stuck it on the BB as it's pretty small.

http://www.alfabb.com/bb/forums/carb...-happened.html

Playing with the numbers it looks like your mains are too small, but the exact answer depends on where you expect peak power. Can't say the program is perfect but it's a decent starting point.

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post #32 of 85 (permalink) Old 05-29-2015, 02:56 PM Thread Starter
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I haven't made any other changes at this point. I'll checkout the spreadsheet when I'm on my laptop.

I must say that WOT at just about any rpm performs great having changed to the 140 main jets, so I'm very happy. The only "lumpy" part is when in traffic trying to hover around 1500 to 2000 rpms... I hear an occasional "cough" and it will stumble. The idle is really pretty good too, no complaints there.

I'm going to do some further diagnosis following the procedures in Pat Braden's book and report back.

Thanks for your support and advice.

Michael.
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post #33 of 85 (permalink) Old 05-29-2015, 03:07 PM
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Ah, okay - I missed the bit where you went to 140s. Jetting.exe seems to be suggesting 145-150s, so maybe you're still a little lean? Setting Webers towards the rich side can hide a lot of sins...

Anyway, sounds like you're reasonably close. At this point, I'd find someone who has a wideband sensor you can stick in the tailpipe and look at your AFRs while driving: that'll tell you exactly where to go. Without that you're going to be guessing quite a bit.

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post #34 of 85 (permalink) Old 05-29-2015, 07:22 PM
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I haven't made any other changes at this point. I'll checkout the spreadsheet when I'm on my laptop.

I must say that WOT at just about any rpm performs great having changed to the 140 main jets, so I'm very happy. The only "lumpy" part is when in traffic trying to hover around 1500 to 2000 rpms... I hear an occasional "cough" and it will stumble. The idle is really pretty good too, no complaints there.

I'm going to do some further diagnosis following the procedures in Pat Braden's book and report back.

Thanks for your support and advice.

Michael.
Hmm, I have a very similar setup and I a get the cough at running steady around 2,500 rpm. Pulls smooth and hard when I step on it. I'll be interested to hear your progress.

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post #35 of 85 (permalink) Old 09-04-2015, 09:12 AM Thread Starter
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Hi,

I've left the jetting as is and adjusted the idle/timing to where I was pretty happy with it. I tracked the car in late June and was extremely happy with the performance. I just did a second track day on Wednesday of this week and during the second session the engine started loosing power in sharp right hand turns. It also made what sounded like a "banging" noise that at first I thought was the exhaust hitting the heat shield. It felt like it was running on three cylinders when this happened.

I'm wondering if I was experiencing a fuel-delivery issue and the sound was an intermittent empty intake causing a change in sound from the carbs. I had about 1/4 tank of gas at this point and if I pressed the throttle slowly through the turn it behaved better.

Anyone else have a similar experience? Thoughts?

Thanks.
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post #36 of 85 (permalink) Old 09-04-2015, 05:22 PM Thread Starter
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Hmmm...

Looked through the venturis with a mirror while car was running and saw fuel dripping from the accelerator pump tube on front carb at idle. I attempted (and think succeeded at) adjusting the float level on that carb, but still have a slow (slower than before) "drip".

The car now behaves badly at full acceleration or with any load (going up hills). The float needle and seat look good and I wonder if my distributor came loose and moved? The "bad" behavior was very sudden on-track, so I can't imagine this being a float adjustment issue.

Thanks.
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post #37 of 85 (permalink) Old 09-04-2015, 06:13 PM
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The check valve on the dripping pump jet may have crud in it. Maybe more than one, do both drip? The passages that feed the pump is buried under the Weber in what I call the "catacomb" passages. The higher cross passage feeds the pump, the lower 2 passages, the starter circuit.
Are BOTH floats set the same? How have you set them?
Below is a diagram of the pump circuit, not a DCOE, but the operating principal is the same. Running, the weight above the ball, diagram parts #21, keeps the ball seated to prevent vacuum ( while running) from sucking fuel from the pump jets. It is possible, the bleed-back or pump exhaust jet (#23) is allowing fuel pick up to the circuit from running vacuum. These are a one way check valve to allow pump fill (#26) without allowing the pump to pump back into the bowl except by the small vent in the side. If the check ball in this jet is stuck up, fuel can be sucked by vacuum through the circuit and dribble while running, but then the pump will not pump properly, giving you variable squirt from the pump jets #24.
Does this help?
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post #38 of 85 (permalink) Old 09-04-2015, 07:17 PM
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The loud banging sound MAY have been a lean condition which caused the motor to backfire through the intake. It can sound like a grenade going off under the hood. Webs can suffer fuel starvation, lean, in hard cornering.

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post #39 of 85 (permalink) Old 09-05-2015, 06:27 AM Thread Starter
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Does this help? Yes! Thank you.

I adjusted the float per the manual, measuring the distance between the float and cover while holding the cover vertically. I only set the one that was dripping, and yes, both drip in the one carb.

Quote:
Originally Posted by Gordon Raymond View Post
The check valve on the dripping pump jet may have crud in it. Maybe more than one, do both drip? The passages that feed the pump is buried under the Weber in what I call the "catacomb" passages. The higher cross passage feeds the pump, the lower 2 passages, the starter circuit.
Are BOTH floats set the same? How have you set them?
Below is a diagram of the pump circuit, not a DCOE, but the operating principal is the same. Running, the weight above the ball, diagram parts #21, keeps the ball seated to prevent vacuum ( while running) from sucking fuel from the pump jets. It is possible, the bleed-back or pump exhaust jet (#23) is allowing fuel pick up to the circuit from running vacuum. These are a one way check valve to allow pump fill (#26) without allowing the pump to pump back into the bowl except by the small vent in the side. If the check ball in this jet is stuck up, fuel can be sucked by vacuum through the circuit and dribble while running, but then the pump will not pump properly, giving you variable squirt from the pump jets #24.
Does this help?
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post #40 of 85 (permalink) Old 09-05-2015, 06:28 AM Thread Starter
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The loud banging sound MAY have been a lean condition which caused the motor to backfire through the intake. It can sound like a grenade going off under the hood. Webs can suffer fuel starvation, lean, in hard cornering.
Definitely sounds like that. Weird that it started suddenly while on track and now does it whenever I try to accelerate.
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post #41 of 85 (permalink) Old 09-05-2015, 07:19 AM Thread Starter
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I think I may be seeing two separate symptoms of the same problem. While looking down the venturi and working the throttle I don't see the "squirt" of fuel from the accelerator pump that I'm used to seeing... more like a dribble. This is on both carbs.

Maybe all that rocking and rolling on the track stirred up some crude and clogged my accelerator jets and/or the check valves? This might explain both the lean condition on acceleration and the leaking at idle.
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post #42 of 85 (permalink) Old 09-05-2015, 07:28 AM
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clean the carbs , and pay carefull attention that all the jets are really clean too! and maybe clean the tank too? do you have sufficient fuel filtering?

Check the timing on the cams, if there are as specified for your use and state of tune of te engine.

is the ignition up to its job , also in the high rpm?

And please put the car on the rolling road/dyno if not yet done.

Part of your problems may well be lean running in the high rpm`s, so it is fully understandable that the problem which you did not notice but may allready been there came to light under these condition, namely much more high rpms..

I really do not understand why people spend a lot of money on tuning engines, and forget the most logical thing to end the job..

and a question:

you were told there were F60 in. ok redrilled 50 and 55`s to 60. You changed them out for new F55 . Why ? I do not read the set up from Richard did not work?

Last edited by Veep; 09-05-2015 at 09:02 AM.
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post #43 of 85 (permalink) Old 09-05-2015, 10:03 AM Thread Starter
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Are you channeling RJ? There's a lot of assumptions and critisism in your post...

The initial carb setup was not adequate. Changing out the jets made a huge difference. In fact, I was first in class in both the autocross and time trials at this year's convention.

Cam and ignition timing are spot-on. I do plan on getting it on a dyno, but having too much fun with it now.

Quote:
Originally Posted by Veep View Post
clean the carbs , and pay carefull attention that all the jets are really clean too! and maybe clean the tank too? do you have sufficient fuel filtering?

Check the timing on the cams, if there are as specified for your use and state of tune of te engine.

is the ignition up to its job , also in the high rpm?

And please put the car on the rolling road/dyno if not yet done.

Part of your problems may well be lean running in the high rpm`s, so it is fully understandable that the problem which you did not notice but may allready been there came to light under these condition, namely much more high rpms..

I really do not understand why people spend a lot of money on tuning engines, and forget the most logical thing to end the job..

and a question:

you were told there were F60 in. ok redrilled 50 and 55`s to 60. You changed them out for new F55 . Why ? I do not read the set up from Richard did not work?
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post #44 of 85 (permalink) Old 09-05-2015, 10:20 AM
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Are you channeling RJ? There's a lot of assumptions and critisism in your post...
please grow up.. just trying to help a fellow alfist

That the 60 were not adequate is in fact nowhere mentioned, or I did misread, excuse for that then. So thats why I am making assumptions. Because some very important things are not being mentioned. just that, nothing else.

But I will stop bothering you...
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post #45 of 85 (permalink) Old 09-05-2015, 10:23 AM
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Almost ANY Weber conversion, from one running engine to another will require some jetting adjustments somewhere. After over 50 years of DCOE work, I can say for SURE that some base-line set-ups work Ok across the board, particularly with 40DCOE2's and 45DCOE9's, BUT for best top end power and stagger free transition, an A/F meter and experimentation will give you the best set-up for your particular engine.
So, any set-up RJ sent was base-line, and would require some work to get it dead on for MLC's specific application.
MLC, My guess is the pump jets are now giving inadequate squirts causing the banging as mixture goes lean on acceleration. My Ausca 1600 test engine did this on the dyno with huge flames from the header collector and B O O M! Replacing #35 pump jets with #40 solved that. Check the bleed back jets in the bottom of the bowls first. These can prevent pumps from filling or long enough squirts. Then move up to the ball check valves, being higher, they are probably Ok. Blow Brakeclean through first the #35 hole in the pump jets, then plug the feed hole in the side with a finger while squirting Brakeclean through the top of the jet to note if the .35 hole squirts correctly.
Further questions, give me a call, or e-mail <[email protected]>. As my BB customers and readers will tell you, I like Webers!


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