"D" Carb setup too "meager" - Ferrari Life
 
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post #1 of 11 Old 08-21-2012, 04:45 AM Thread Starter
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"D" Carb setup too "meager"

You may remember that while driving long Autobahn distances to Fled's and so on, the carb setup has been sligthly to a "fater" position with the effect, that when suddenly pushing the accelerator hard down, the exhaust will initially spit some light brown smoke.
I was then told by attendees to get the carbs a less fat setup which I did. The car runs great, but a little smoke is always coming when a initial hard and deep push of the accelerator is applied, but muuuuch less than before.
However when I'm reving up to, lets say 5'000 rpm's and then take my foot totally off the accelerator pedal, I hear lots of little "pam, pam ,pam" explosions in the exhaust. Not that I do not like it (sounds fun) but my mechanic tells me that we may have a little too much "meagerness" with the carb setup.

Anybody any thoughts on it ?

The engine since being restored some 17 years ago has now done about 70'000km's. Maybe that little bit of smoke (only when initially pushing the pedal to the ground...for accelerating very hard) will not get away, even with the best possible carb setup ?!

Any comments welcome!
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post #2 of 11 Old 08-21-2012, 07:28 AM
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212- When you hit the throttle pedal, you activate the accelerator pumps to dump more fuel into the engine for acceleration. The accelerator pumps are adjustable, but are usually ignored in carb tuning. Yours may need to be backed off just a bit.

You may also be pulling a bit of oil past the valve stem seals as they wear. Not an issue with this kind of engine, especially one with 16 liters of oil. In the olden days, that would foul the plugs, but the Daytona has capacitor discharge igntion, which does a good job of burning off any deposits. Especially true with wide heat range NGK plugs.

Popping on throttle release and deceleration is normal, as cold air is drawn into the partial vacuum created by the decrease in exhaust gas flow, and then mixes with unburned fuel vapor and mildly explodes. In extreme cases with rich mixtures like race cars, flames will actually be seen coming out of the exhaust pipes. Sounds great and I would not worry about it.

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post #3 of 11 Old 08-21-2012, 09:41 AM Thread Starter
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Quote:
Originally Posted by tazandjan View Post
212- When you hit the throttle pedal, you activate the accelerator pumps to dump more fuel into the engine for acceleration. The accelerator pumps are adjustable, but are usually ignored in carb tuning. Yours may need to be backed off just a bit.

You may also be pulling a bit of oil past the valve stem seals as they wear. Not an issue with this kind of engine, especially one with 16 liters of oil. In the olden days, that would foul the plugs, but the Daytona has capacitor discharge igntion, which does a good job of burning off any deposits. Especially true with wide heat range NGK plugs.

Popping on throttle release and deceleration is normal, as cold air is drawn into the partial vacuum created by the decrease in exhaust gas flow, and then mixes with unburned fuel vapor and mildly explodes. In extreme cases with rich mixtures like race cars, flames will actually be seen coming out of the exhaust pipes. Sounds great and I would not worry about it.
Terry, as always many thanks!!! For me, you are " Professor Terry" !!!
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post #4 of 11 Old 08-21-2012, 10:40 AM
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212, being "one of the attendees" and having made the comment that I thought the injector pumps were responsible and neaded leaning, I agree with Terry. I would also say that the smoke was, for me, clearly black, a good indication of over-rich fuel air mixture. If you were burning a significant amount of oil I would have expected blue smoke and the smoke was definitely black.
Popping in the exhaust on the overrun was quite common in the exhausts on cars with relatively unn restricted exhaust pipes in the pre catalyst days
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post #5 of 11 Old 08-21-2012, 11:16 AM Thread Starter
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Where have you been Nigel ?? Long time no hear from you! Yes you explained it very well to me in Scotland. And yes, the smoke was black at the time by a "rich" carb setup. That really seems to be handled as by now, the smoke is much less and light brown and really only in moments of strong pushes. Car feels very happy and as i'm comfortable ( thanks to terry's comment) now about the little exhaust explosions not doing any harm to the engine i will go the path of fine adjust the accelerator pumps.
Great to hear from you again, nigel. Please give my best to Genevieve!
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post #6 of 11 Old 09-18-2012, 09:52 PM
 
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post #7 of 11 Old 09-20-2012, 08:28 AM
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I would rather run a little rich and risk the occassional fouled plug, than run lean and risk a burned piston.

i also set my carbs up a little on the rich side to help w/ cold morning starts since I completely removed my choke.
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post #8 of 11 Old 09-20-2012, 08:56 AM Thread Starter
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I would rather run a little rich and risk the occassional fouled plug, than run lean and risk a burned piston.

i also set my carbs up a little on the rich side to help w/ cold morning starts since I completely removed my choke.
Just drove "D" for another 3'500km's in 5 days, still a little on the carb-rich side but much less than before (according to others). And yes you are right...in the morning when I wanted initially leave with "D" for the long journey I foulded 2 plugs. As you said normal from time to time. So quick change and then o.k. for all the distance.

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post #9 of 11 Old 09-21-2012, 09:20 PM
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Originally Posted by 212Export View Post
Just drove "D" for another 3'500km's in 5 days, still a little on the carb-rich side but much less than before (according to others). And yes you are right...in the morning when I wanted initially leave with "D" for the long journey I foulded 2 plugs. As you said normal from time to time. So quick change and then o.k. for all the distance.
Other than a bit of black soot, "D" sounded like it was running very well.
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post #10 of 11 Old 10-05-2012, 06:45 PM
 
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Another minor cause of more than normal popping in the exhaust when letting off could be some very slight exhaust leaks. They suck in added air, and as noted prior, comp cars with straight exhausts do this with every shift!
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post #11 of 11 Old 10-05-2012, 09:28 PM Thread Starter
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Originally Posted by jimmyr View Post
Another minor cause of more than normal popping in the exhaust when letting off could be some very slight exhaust leaks. They suck in added air, and as noted prior, comp cars with straight exhausts do this with every shift!
Thank you for your remarks Jimmy and welcome to F-Life !

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