modok wrote: ↑Tue Mar 13, 2018 7:54 pm
"Close to IAC?" it will idle better without it. -Independent runners- means they are not connected
I'm not kidding man, try it. Let me know when you figure it out
I understand the concept, but in practice this is difficult. For my fueling calculations at this time I need a map sensor. So this will always create a connection between the runners. The issue with map and itb's is that if you choose a small diameter line and common tube for the map, there will inevitably be an effect caused by intake pulsations. A larger chamber for the map smoothes the pulses that it sees but increases the chances for cross talk. For practical reaons map,IAC and brakes are on the same lines and vacuum chamber
This then brings me to Alpha-N fueling. It is a possibility but the issue here is that pure Alpha-N has not enough resolution at lower rpm ( resolution in the sense of airflow vs TP). On higher rpm it's the other way around, map almost doesn't change whereas airflow does. I've tried both methods but none did work well. I settled on ITB load which uses a mix of MAP and TP where at low rpm more map is used to calculate fuel and at high rpm more TP. This requires me to run a map sensor and associated connecting line/chamber/reservoir.
Bear in mind that this engine stays around 8-10% of TP at cruise. So most of the running is in the 1-10%. When accelerating you move well above 15%.
A MAF would have been a good solution and would have let me do away with the map connections, but the problem is that around 15% the airflow fluctuates wildly in the maf making it's signal unusable for fueling. There could be several reasons for this, but so far I've not found the root cause here. Looks like the ITB-effect is to blame.
Doing away with IAC would require me to set the TP at idle high so that it keeps running above 600 rpm (short of using my right foot) when cold which will create a high idle once warm. The cause here lies in the linkage, which expands when warming up and pulls open the throttles. The additional problem you run into is that once the cars sits for an extended time when hot, the linkage tends to heat up further creating an even higher idle. Originally this created a 'hot' idle of 1500+ rpm. A possible solution could be the throttle stop mentioned above. So far I've had no luck finding anything suitable as most electric throttle stops are of the non-stepper type.