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Hacking up Honda's ECU
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PostPosted: Sat Jul 21, 2012 11:00 pm 
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Joined: Tue Dec 21, 2010 10:08 pm
Posts: 9
The O2 sensor "controls" the AF ratio to 14.7 which is stochiometric and best for emissions and catalytic converter efficiency. Max power is AF ratio between 12-13. Program the the 80% or greater throttle position in the computer fuel tables (foot in it) for 12.5 (right in the middle) of the best power band. I tune with o2 sensor unplugged for 14.7 AF ratio driving around town and 12.5 Af ratio foot in it (greater than 80%) which sets the base map for the engine (base map = o2 sensor failure fallback) When throttle position in greater than 80% the computer ignores the O2 sensor and reverts to the base map....LIKE WHEN YOU FLOOR IT.

The 80% or greater throttle position condition fuel map is typically all a dyno tune will affect because the O2 sensor will override the tuning (fuel map adjustments) when active and throttle position is less that 80 % wide open.

Even if you don't need or run a catalytic converter on your motor the computer thinks its still there and tries to adjust the AF ratio for maximum Cat efficiency based on O2 sensor feedback.

The b16 engine mods described do not change the air flow all that much to require 30% larger (320 cc) injectors. The stock 240 cc injectors should work fine and only require minor tweaks in the fuel base map for optimum power. The B16 stock computer fuel base map is setup for 12.5 AF ratio at wide open throttle so modding the engine to flow more air short of turbo charging typically does not need a re-tune or bigger injectors.


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PostPosted: Tue Jul 24, 2012 8:59 pm 
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Joined: Sun Nov 22, 2009 5:42 pm
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Location: Cincinnati, Ohio
Why unplug the o2 sensor? Just tune the car in open loop. When done tuning and you want the ecu to operate on the fuel table provided in the tune leave it in open loop.

Im saying imo I only tune cars @ 12.5 or richer if its boosted. Thats about where I run a stock motor runing about 8psi. I would tune it @ about 13.2-13.0. Thats were I would be in order to get the max amount of power and still being safe.


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PostPosted: Tue Jul 24, 2012 9:38 pm 
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Joined: Tue Dec 21, 2010 10:08 pm
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unplugging the o2 sensor forces the ecu into open loop. If you have another way to accomplish the same thing, go for it. Or better yet, share it. Forums are for idea exchange

Max economy is 17-1 AFR min emissions is 14.7-1 AFR max power is 12.5-13.5 AFR Turbo or NA. Its been that way since model t fords and carburetors. There is nothing magic about boost other than you are exceeding 100% volumetric efficiency relative to a NA motor. Max power AFR is the same boosted or not


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