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Old 12-05-2006, 09:32 AM   #1
Ziggyrama
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Default Timing vs. fueling, which should b established first

Hey guys,
I think I finally got my boost and WG tables in order and now I'm movnign onto tuning my timing and fueling. They've been conservative up to this point because the focus was to establish the boost first. So now I am faced with a dillema. Since I'm still learning this as I go along, I am not certain which I should establish first, fueling or timing?

My first thought was to raise the timing as much as I could and compensate with fueling if I saw knock indications. I was wokring towards low 10s in high load and RPM ranges. Now I am not sure if this is the right approach. Now, I am starting to head towards leaning out my mixture a bit, low 11s at high load and RPM range and work my way up from there. So, at moderate load and 50% throttle, I would want to be around mid 12s. So, I now I am considering establishing the fueling and adjusting my timing based on that.

What do you guys think? I know too much of anything is not a good thing so leaning out too much is not desirable. Dumping loads of fuel is also not a universal answer. I guess I'm looking for some direction and guidelines when it comes to this. Rough ranges of fueling that people found to work well would be nice. Perhaps any trends that I should be aware of would also be very helpfull. Thank you in advance for the help!
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Old 12-05-2006, 09:50 AM   #2
Zumble
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Boost, Fuel, Timing in that order. This is the way it's ordered in street tuner too. From top to bottom it's Boost, Fuel, Timing.
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Old 12-05-2006, 09:58 AM   #3
Master2192
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As was stated, Boost-Fuel-Timing. If you went with timing first then you might end up with it too advance and even adding fuel can't compensate. If I was tuning, I'd get the boost dialed in to know what kind of engine load I am running, at that point I'd have timing pulled way back until I got the fuel AFRs where I want them. Then increase timing slowly and make any corrections to the fuel map if necessary.
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Old 12-05-2006, 10:12 AM   #4
Ziggyrama
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Excellent info guys. Thanks a bunch. This gives me direction as far as where I need to turn my attention to next. Any pointers on the trends in specific locations of the map? Seems like raising timing and adding fuel as the RPMs and load rises seems to be a standard practise amoung the maps that I have seen.
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Old 12-05-2006, 02:16 PM   #5
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As the rpms increase, there is less time for the fuel to properly burn, so you have to fire the spark plug sooner to to make up for it.

Definitly wanna do fuel first, adjusting your timing afterwards will not change your AFR.
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Old 12-06-2006, 09:02 AM   #6
ride5000
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an important concept is engine load, as defined by denso/fhi.

ign advance will reach a minimum when load is maximum.

some people trend richer at redline to keep egts down.

some people trend leaner at redline to keep torque up.

i keep a flat afr wrt rpm.

with pump gas, more advance = more torque. knock will hold you back from reaching MBT.

i am of the school of thought that adding boost instead of advance is kinder to the bottom end, because the "push" is longer in duration (even if it doesn't max at the ideal 15*atdc). this is why i run 27psi and 9* at torque peak!
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Old 12-06-2006, 10:28 AM   #7
Ziggyrama
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ride5000, since most of us are riding on pump gas, I guess compromise is the name of the game: lean out the mixture a bit and work the timing accordingly. I was shooting for 11 at redline but I might go up a bit higher , 11.5, and pull some timing at redline to see if that feels better and gradually lean out the mixture as the load decreases and adjust the timing accordingly.
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