"pops and bangs" mapping
09-02-2011, 11:26 AM
#21
I think that the main discrepance in our points of view is that you consider that a lean mixture is easier to ignite (and therefore does not produce unburned fuel), and I think that a leaner mixture is more difficult to ignite.
I guess that we need a engine engineer to clarify this
I guess that we need a engine engineer to clarify this
09-02-2011, 02:09 PM
#22
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Lot of back and forth here but here's a fact: flames from the exhaust originating off a shift or decel come from three factors:
1. rich A/F's
2. not enough timing to ignite all fuel injected
3. very little fresh oxygen due to throttle closure
Exhaust gases get VERY hot when these conditions are met. Once the above happens, the hot & rich mixture sees oxygen at the tail pipe and boom, we see a flame.
Cool looking, but I wouldn't go out of my way to do it. Especially on a N/A car.
1. rich A/F's
2. not enough timing to ignite all fuel injected
3. very little fresh oxygen due to throttle closure
Exhaust gases get VERY hot when these conditions are met. Once the above happens, the hot & rich mixture sees oxygen at the tail pipe and boom, we see a flame.
Cool looking, but I wouldn't go out of my way to do it. Especially on a N/A car.
09-02-2011, 06:31 PM
#23
Gernby is correct. A rich over-run will cause popping and back firing. You see it most often on factory turbo cars that have been de-catted. It happens as soon as they let off the throttle, essentially before the ECU reacts to the throttle snapping closed.
If you have the capability to tune your engine then you should try adding fuel in the over run for yourself. You won't be able to make that area of the map richer with MAF scaling or on a piggyback/AFC.
If you have the capability to tune your engine then you should try adding fuel in the over run for yourself. You won't be able to make that area of the map richer with MAF scaling or on a piggyback/AFC.
09-03-2011, 12:08 AM
#24
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Ok ok.. if I'm wrong, then I apologize 
I did not do much research, I just based it in my own experience (I know that I dont run rich.. actually I don't even run stoichiometric most of the time).
I just did a quick search (wikipedia is the quickest)
http://en.wikipedia.org/wiki/Back-fire
(Before getting to any conclusion, I agree that wikipedia it's wrong in most cases anyway)
I did not do much research, I just based it in my own experience (I know that I dont run rich.. actually I don't even run stoichiometric most of the time).
I just did a quick search (wikipedia is the quickest)
http://en.wikipedia.org/wiki/Back-fire
(Before getting to any conclusion, I agree that wikipedia it's wrong in most cases anyway)
09-03-2011, 12:24 AM
#25
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No, I agree that running rich also pumps unburned fuel outside the combustion chamber (I said that some posts above). But actually I don't have much experience in "rich" setups because running rich is what I want to avoid in most of the cases (note that i said "most" not "all")And to lean out the stock mixture does not necessarily means "lean" (it can be leaner than stock but still rich.. oem setups are very often running on the rich side)
09-04-2011, 12:40 AM
#26
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