Electronic Fuel Injection - Developement & Tuning
https://pcmhacking.net/forums/
Making progress with this. The hunting has calmed down but the wideband says its 14.7 still. Need to reread the whole forum a few times again.vlad01 wrote:try bringing the timing back up around 25-30º and then then the AFR to about 13:1, the kpa should drop. Max vac means the timing and fuel is optimal. You need to get both optimal to get the vac to be at max.
I reckon this hits the nail right on the head. I experienced exactly what you are describing and I was changing timing and the VE tables every which way but it still wasn’t idling properly. At cruise it was spot on. The tuner guy found that it wasn’t going to closed loop at idle. I’m sorry but I can’t tell you exactly how he changed it because I had to go back to work and missed how he fixed it but I think there is a table where you input the AFR you want at a particular RPM and when it is on closed loop it will automatically adjust to that AFR. I remember this used to show on the tune in tunerpro at 13.5 but unless closed loop is on it doesnt have ant effect. A more experienced member might be able to help out with this in more detail.vlad01 wrote:yeah I agree, I would aim for around 13:1, but it may well be that its not in closed loop idle and using the main table which is about what you have for those areas on the table, ok to cruise on but useless to be idling on that.
I can't recall exactly but I thing there is a scalar somewhere to tell it when it is to use closed loop idle, like the kpa it suppose to expect for idle I think?. You can see in the main dash there is a block called "close loop idle" it goes green when its active. that will tell you what its doing.
Otherwise the cells in the VE table look right for the engine, nothing too out of the ordinary.
changing timing will change how much air it uses to maintain idle, I would say generally though, if its sucking more that means its using more IAC to maintain the same idle, I would suggest that it has too much timing, you want to find the point where the engine is idling with the least amount of IAC as that's probably the most efficient. (aim for 15-20 iac steps at warm idle)h4x0r wrote:With 20deg timing it was in the 13:1 range I increased timing to 28deg and it went 14.2:1 and the hissing/sucking sounds got worse. With this tune I have to open the throttle for it to start. I might take the timing back out and have another try.
thanks for clearing that upHolden202T wrote:I think people are confusing closed loop idle and idle afr's .....
firstly closed loop idle means that when active the ecu will adjust spark timing to maintain the desired idle rpm .... that is all it does.
idle air fuel ratio table is what you use to richen the tune up once the car comes to a stop, you will see this in the target AFR display changing from 14.7 to something usually in the low 14's or high 13's .... and the time it takes to switch from the main air fuel ratio table to the idle air fuel ratio table is defined in a scalar for this, how long after idle to use idle afr table ..... its normally something like 20 seconds .... you might want to make this 5 seconds or something.
if you want to get VE right at idle change the idle afr table to be the same as the open loop afr table values, get the VE dialled in then copy back the richer idle afr table values.
changing timing will change how much air it uses to maintain idle, I would say generally though, if its sucking more that means its using more IAC to maintain the same idle, I would suggest that it has too much timing, you want to find the point where the engine is idling with the least amount of IAC as that's probably the most efficient. (aim for 15-20 iac steps at warm idle)h4x0r wrote:With 20deg timing it was in the 13:1 range I increased timing to 28deg and it went 14.2:1 and the hissing/sucking sounds got worse. With this tune I have to open the throttle for it to start. I might take the timing back out and have another try.
Also if you need to give it throttle to start, you might need to open the butterfly more so its using the IAC less which will help it start better and less chance of stalling coming to a stop or after a quick rev, but also it can depend, if the injector data for cranking is wrong this can make it flood which will make it not want to start without throttle.
