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you think this guys theory on the sfc is......................?

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you think this guys theory on the sfc is......................?

Old 12-30-2006, 05:22 PM
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Default you think this guys theory on the sfc is......................?

The SFC portion of the SFC-VTEC operates by "spoofing" MAP signals to the ECU, which in turn, causes the computer to either add or subtract fuel. One thing that remains uncertain in my mind is whether the ECU continues to rely upon the MAP signals at WOT (wide open throttle) or not. If so, the SFC would continue to affect the fuel delivery, even at WOT. Typical speed density systems (Honda uses a speed density system) ignore MAP at WOT and read the fuel straight from the fuel maps in the ROM (open loop). BUT, I have been informed by a few people that the Honda system deviates from the "norm" and continues to use MAP even at WOT, so the SFC-VTEC would presumably continue to alter the curves. Evidence supporting this is reflected in the dyno tests available below. If you happen to be a subject matter expert, please feel free to contact me ([email protected]) and give me the dirt. The other thing is that will the computer try to correct itself based on the changes it sees in the O2 sensors? In other words, if you set the SFC to increase the fuel by 10%, it will alter the MAP signals to the ECU, which will in turn increase the duty cycle of the injectors, which will richen the mixture, which will cause the voltage on the O2 sensor to increase, which will theoretically cause the computer to recalibrate itself and decrease the injector duty cycle again. There's no proof of this, but it's something that needs to be answered. So many questions, so few answers...
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Old 12-30-2006, 05:36 PM
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Default Re: you think this guys theory on the sfc is......................?

I don't know nothing bout the sfc but it has to work. I'm running a vafc on my 99 civic si boosting 10psi and it works good, the tunner was able to increase and decrease fuel adequatly and I haven't had a problem with it for two years now. That guy in your post seems to know what he's talking about but that ----'s confusing. If it aint broke don't fix it.
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Old 12-31-2006, 12:20 AM
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Default Re: you think this guys theory on the sfc is......................?

Originally Posted by bitchasscracker
Typical speed density systems (Honda uses a speed density system) ignore MAP at WOT and read the fuel straight from the fuel maps in the ROM (open loop). BUT, I have been informed by a few people that the Honda system deviates from the "norm" and continues to use MAP even at WOT
Since the fuel maps are tables of RPM vs MAP, ignoring MAP at WOT is the intellectual result of someone being completely hopped up on JDM V-tech.

They sell basic fuel injection theory books at any of the chain bookstores. This ---- is not that difficult if you stop turning to riceboys with 16 second cars, or HT, for information.
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Old 12-31-2006, 12:42 AM
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Default Re: you think this guys theory on the sfc is......................?

i didnt, it was temple of v-tec



i just searched google for sfc wiring and this came up
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Old 12-31-2006, 09:14 PM
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Default Re: you think this guys theory on the sfc is......................?

From what I've seen, the stock ecu corrects the mixture w/the o2 signals except at WOT (or at least when its under heavy load or near 0psi). It then reads the cell for the given pressure/rpm, and uses it w/o looking at the o2 signal. If it did correct, then wouldn't the FPR jockeys with AFR's that go way lean or way rich. I also know it can only reduce/increase fuel to a certain extent.

With that said, if you slap 450's in there and tell it to decrease fuel all over besides in boost, it will do so by dropping the MAP voltage [that the ecu sees] very low, and if still rich and not WOT, the ecu may add/subtract some itself.

In the end its a moot point. You can buy a used laptop & obd1 ecu for less than a v-afc & do the same 'guessing' tune with free crome, except you get timing tables to mess up too. For a bit more you can buy wideband and even know where your AFR's are. CromePro makes v-afc tuning just look stupid.
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Old 12-31-2006, 11:19 PM
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Default Re: you think this guys theory on the sfc is......................?

Originally Posted by HiProfile
You can buy a used laptop & obd1 ecu for less than a v-afc


that is a dumb statement
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Old 01-01-2007, 12:36 AM
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Default Re: you think this guys theory on the sfc is......................?

contact skunk2 and they should give you the answers, i've got the sfc boxer2. and they gave me the instructions and a ---- load of stickers!! this is the guys email that helped me out [email protected]
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Old 01-01-2007, 08:12 AM
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Default Re: you think this guys theory on the sfc is......................?

Originally Posted by bitchasscracker


that is a dumb statement
nope..it doesnt..
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Old 01-01-2007, 12:13 PM
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Default Re: you think this guys theory on the sfc is......................?

Originally Posted by Walter
nope..it doesnt..


yea i'd love to see where i can buy a labtop and a chipped ecu for $100
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Old 01-01-2007, 01:12 PM
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Default Re: you think this guys theory on the sfc is......................?

Originally Posted by bitchasscracker


yea i'd love to see where i can buy a labtop and a chipped ecu for $100

Ebay and DIY....Around here most of the kids want like 120-160 for safc/vafc's.I allready have a laptop for school so If I didn't allready have my setup I would only have to buy the chipping stuff burner and cable.Theres tons of early/mid 90's laptops floating around on ebay,hell I gave one away for free since I had no use for it and it had dead pixels on the screen.
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