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Some answers Posted by Kevin K [Email]  (#374) [Profile/Gallery]
(more from Kevin K) on Sun, 9 Sep 2001 23:52:00
In Reply to: C900/9000 16V-T, Big Inj'r Fuel Control Upgrade, HKS, Kevin K [Profile/Gallery]
, Sat, 8 Sep 2001 18:49:07
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1)rpm is important compensation input, more than boost.
Going to 20 psi from idle is a 2.9x increase in absolte pressure. going from idle to 6K rpms is a 10X increase in basic displaced air volume.
remember this is based on a big injector install, and the need to compensate ecu map thru the power range. want 50% more hp, go with 50% larger inj's, but correct the basic maps accordingly thru the whole range. Ex, 50% bigger inj's, so amm output scaled down to 2/3 of normal output. so say at 4500rpm and zero boost, duty cycle at inj is reduced from 30% to 20% with HKS. but when u nail it and boost jumps to say instant 15 psi, amm flow doubles, and duty cycle jumps to 40% with big inj's, instead of 60% with oem setup. Boost is still taken care of, and u have much more headroom before duty cycle gets too high.
The reason the HKS looks good to me is that the oem amm output is not linear with flow, and is calibrated with ecu and stock inj's. Adding much bigger inj's can't be compensated with a fixed amm correction thru the whole flow range. the 11 band allows the comensation to be more correct regarding actual flow levels, with big inj's.
2) The 2nd inj controller is not a good path here because:
a) u never get even fuel delivery to all cyl's, like with just 4 inj's.
b) u still exceed max duty cycle too soon with no amm correction, so the xtra injector must be set for sudden heavy flow at this point. Somewhat crude tunning based on maxed out reg injectors. ( This is like corky's old way, except he used monster fuel pumps and 10:1 gain crossover type rrfpr that kicked in at high boost).
c) for the cost of the controller alone, the HKS unit can be had ($330 USD)
3) RRFPR and 24# inj's would not be as good.
Say at 20 psi boost, spg9 reg set to 2.5 like stock. The 24# give 14% more flow, and at 20 psi the reg gives 18% more fuel, if pump and wirring are healthy. At 3.8K and 20 psi, inj'r duty cycle is not too high per oem maps, but u don't need 32% more fuel than stock set up would supply. Even if u were at a too high 14:1 stock ratio, 10.6:1 would result ...way too rich. this shows on the dyno plots. And 32# inj's have 52% more fuel flow, to make things even richer midway.
Remember, stock talon's and eclipse 2L turbos have 45 lb/hr injectors. Classic saabs used 21 lb/hr with light 2.5 fpr's, and high stock duty cycles.
posted by 63.10.14...
, Sat, 8 Sep 2001 18:49:07, Sun, 9 Sep 2001 23:52:00 <-- Viewing This Message
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