Quote:
Originally Posted by 8500RPM
Quote:
Originally Posted by jcolley
To run E85, you need to add about 30% mass flow to maintain stoich. Since the O2 sensors are read out as lambda in the DME, the DME always maintains lambda to the target. There is a parameter in the DME for stoich value that isn't changed with any of these kits. What these kits do I suspect is intercept the pulse for the injector and add pulse length to account for the necessary added fuel mass and that percentage increase is based on the value of ethanol per the sensor.
None of the kits I've looked at have any interface to the coils though or any feedback line to the DME that would affect timing. (If they did, the ionic current system would probably throw a fit). The statement was made earlier in this thread that the AFD kit would pull timing up high, but I'm trying to understand by what mechanism that would occur in the DME with the AFD kit vs a stock fuel system. I would suspect if you logged fuel rail pressure on the AFD kit you might see some difficulty with the stock pumps hitting the pressure targets and the DME is pulling timing preventively, but I'd have to go back and look at the mapping to confirm that.
As for the power increase with E85, unless timing is advanced by separate tuning of the DME, all the power gains come from the increased charge cooling as a function of the higher latent heat of vaporization as well as the increased mass flow injected. AFD seems to have based their marketing on that whereas the other company has not.
Even without retuning for increased timing, gains are to be had. The problem with increasing the timing is you better know very well what your ethanol content is because the DME doesn't and can only correct by pulling timing if it does sense knock. Also better make sure your tuner isn't one in favor of disabling knock sensing in the mss60.
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None of these flex fuel kits pull timing. They only interact with the injectors to spray more fuel than normal when running E85. Now if you loaded up a race gas tune and used the Flex Fuel kit with that, you might make some magic with higher timing targets. I'm going to research this... |
Would there be an advantage to running this kit or the AFD kit with a specific e85 tune versus just the e85 tune?