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Sportster Motorcycle Air intake, Carburetor, EFI, Fuel, and Exhaust Problems, advice and/or how tos for Sporster and Buell motorcycle carburators, Electronic Fuel Injection (EFI), Air Intake, Fuel and Exhaust.

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  #1  
Old 23rd December 2008
harleyhornet harleyhornet is offline
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IN changing to a high flow air cleaner from stock on a FI bike is it really necessary to ad some type of fuel controller the maintain correct AFR ? Wouldnt the manifold air pressure sensor sense the increased air flow and change the VE table therefore adjusting the AFR accordingly ?
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Old 23rd December 2008
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Quote:
IN changing to a high flow air cleaner from stock on a FI bike is it really necessary to ad some type of fuel controller the maintain correct AFR ?
IMO if you do absolutely nothing to your EFI scoot it is necessary to add some type of fuel controller to maintain correct AFR. 14.7 AFR is correct only to the EPA, not your scoot or the power it makes. It took me 6 months of research to decide on the PCIII/USB.

To answer your original question, no.
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Old 23rd December 2008
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So am I correct in assuming that the MAP will compensate via the VE table to correct to the target AFR ( even if it is the epa 14.6/1 ) Therfore your running the same AFR regardless of air cleaner modification.
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Old 23rd December 2008
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Quote:
Originally Posted by harleyhornet View Post
So am I correct in assuming that the MAP will compensate via the VE table to correct to the target AFR ( even if it is the epa 14.6/1 ) Therfore your running the same AFR regardless of air cleaner modification.
you are correct

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Old 23rd December 2008
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If you also change the mufflers or exhaust system then you'll have to at least get a reflash (waste of money) or some form of fuel adder.
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Old 24th December 2008
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Its not the MAP sensor thats in play here, that's not checking the A/F ratio but the pressure of the fuel/mix as it enters the manifold and it adjusts for changes in air density like you get at higher altitudes.

The narrow-band O2 sensor in the exhaust is what adjusts the A/F ratio. It and the EFI can cope with a reasonable change such as you might get with just a muffler swap but once you mess with the A/C too then you are working outside its tolerance and you will need a remap.

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Old 25th December 2008
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technically it's the ecm that determines the correct fuel/air ratio.... the O2 sensor(s) only fine tune the fuel to keep it centered ..... it's the MAP that determines the both long and short term fuel trim........

I'm just sayin'

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Old 26th December 2008
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OK I think im getting it, the manifold air pressure sensor is telling the ecm the temp and pressure of the incomming air therefore determining the oxigyn content, the ecm then has to measure that with the ve table which it gets from the x and y axis of the throttle position and engine speed ,the ve table is already pre determined by calculations based on the engine displacement cams intake etc.. soooo if you change your air cleaner without adjusting the ve table accordingly you will need to add a controller to ad more fuel.
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Old 26th December 2008
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oh yea I forgot , the ecm then has to use the data from the ve table , the intake air temp and pressure and measure that against the predetermined afr table to determine the injector pulse width at specific operating conditions. can any one help me with this if I am wrong thanks:
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Old 26th December 2008
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the air cleaner alone won't change the volumetric efficiency enough to matter...... everything will still be within range of normal fuel maps and it will be fine...... if you change to a set of pipes that scavenge better and flow better than the stockers then it would be possible to pull more air thru the engine than the fuel maps can handle........but just an air cleaner won't change anything enough

some good info here.....

http://www.xlforum.net/vbportal/foru...70#post1633470

Ww

Last edited by racerwill; 26th December 2008 at 16:30..
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