Weyro Posted July 23, 2012 Share Posted July 23, 2012 (edited) Im trying to understand how an fcd affects fueling so hoping someone can help.The fuel cut defender intercepts the signal from the MAP sensor.On the 4efte the map sensor shows roughly 4v at 0.85bar. The ECU will cut if it sees over 4v.A clamp type FCD such as an HKS will not allow a signal higher than 4v to get to the ECU.Does that then mean that, if i am running 1bar of boost, and reach 0.85bar at 2200rpm, the ecu will only see 4v from then until redline?So the ecu can only calculate fuel for the engine running up to 0.85bar.So running at 1bar boost will only have 0.85 bar worth of fuel for each combustion? Edited July 23, 2012 by Weyro Quote Link to post Share on other sites
AdamB Posted July 23, 2012 Share Posted July 23, 2012 You got it mate, a FPR is a mechanical device which can alter the fuel pressure which is why it is needed. The flow rate of the injectors is then increased due to the pressure being increased.The stock ecu is able to fuel upto 0.8/0.85 bar where it reaches fuel cut. Although doing this method does not allow for any ignition advance changes, so it is best to ensure the AFR is setup using a wideband and det cans, if there is any det the fuel pressure can be backed off, but backing off the fuel pressure will increase the AFR @WOT which is not what we want, causing the engine to run lean.This is why this type of setup is not really recommended although it does the job, its still not the best way, its like running your car with 3 wheel bolts, it will do the job, but far from the safest method. Quote Link to post Share on other sites
Weyro Posted July 23, 2012 Author Share Posted July 23, 2012 I will eventually buy emb, but in the meantime im looking at getting an SAFC2. I already have a rrFPR, fcd, and wideband.Would it be the case of upping the fuel pressure until it runs rich throughout the rev range. Then using the SAFC to reduce the richness so its perfect at individual rev points? Quote Link to post Share on other sites
AdamB Posted July 24, 2012 Share Posted July 24, 2012 I'm not really clued up on the SAFC tbh so don't really know. But you want to be aiming for a target AFR between 11.2-11.8 @ WOT. Like I said, to ensure it is safe it needs to be checked using det cans. Quote Link to post Share on other sites
*Zoe* Posted July 27, 2012 Share Posted July 27, 2012 Check out the FCD thread in ELectronics section very clear Quote Link to post Share on other sites
Weyro Posted July 27, 2012 Author Share Posted July 27, 2012 Yea it was good, now im just trying to understand how, and to what ratio an HKS fcd lowers the voltage over the range Quote Link to post Share on other sites
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