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 Post Posted: Mon Sep 17, 2012 8:36 pm 
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What effect does the fuel level in the bowl have on the AFR at wot? My previous understanding is that it will effect the fuel mixture. But my troubleshooting my fuel pump problems seems to suggest different. APD recommended that I convert my pump to an internal regulator and they did this for me for free. Well. fuel pressure would nose dive on launch for about a second to about 1 psi at which point it would pop and fuel pressure would recover. But looking at the log, there is no significant change in AFR till the engine starts to pop. So have I always missunderstood this or does/should it effect it? Thinking about it, it just seems to me, once the engine start to eat, the engine is pulling the fuel through the jets and as long as the jets are getting a supply of fuel all is happy.

What is your take?

Thanks

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 Post Posted: Mon Sep 17, 2012 8:54 pm 
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Joined: Sat Feb 07, 2009 4:12 pm
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Location: Adelaide Australia
Lowering the fuel level by one flat of the nut will show a change leaner on an engine that has correct combustion balance. Many racers can firm this. Not all engines will show minute changes of mixture.


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 Post Posted: Mon Sep 17, 2012 10:06 pm 
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Just curious. Rear fuel cell and belt drive pump? :-k

If yes, what's the short time and is this off a transbrake? :-k


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 Post Posted: Mon Sep 17, 2012 10:18 pm 
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I will further explain why some engines dont show.
There is only one result of perfect complete combustion. The gas species produced are well understood and its easy to recognize. If an engine has issues like for example, inadequate vaporization, or inadequate exhaust removal or inconsistent intake mixture preparation there is no way that correct balance of gas species can be obtained.

A well designed and functioning engine can have a correct balance of gases even though there may be a fault with the completeness of combustion in some chamber areas, this is easy to determine when using gas benches as tuning tools. Even if the engine has a fault such as this it will still respond to a slight mixture change with observable results, however if the engine has a fault like mentioned in the first paragraph the gas species will change in a swapping style. What i mean is it ill swap some CO for some CO2 or some HC even. The end result may be no detectable change in cylinder pressure production as an average for the stroke.
I have done tests that deliberately crippled one cylinder but the other ones gained due to the constituency of the exhaust gas emitted from the crippled cylinder. There is far more to understanding engine combustion than most tuners realize.

Engines are cylinder connected via the exhaust and things such as flow differences per cylinder manifest as different contamination levels in cylinders, When the mixture is changed at the carby the exhaust species and heat are changed and the effect of flow variations alters the power balance of each cylinder. Some cylinders may gain some may loose, the overall result of power can be the same as before.


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