truckdoug

iTrader: (25)

so i dialed my VE pretty closed in OLSD and i'm trying to turn closed loop back on to fuel at idle/part throttle

but I just can't seem to get it to idle right. It goes super rich. and then when it warms up enough for adaptive idle PID to kick in it gets all surge-y


new territory for me here.

so my current plan is to disable the adaptive idle for now.

then maybe mess with the NB voltage offsets to get them to switch closer to my ideal 15:1 afr?


here's a video that shows what i'm seeing.

Darth_V8r

iTrader: (4)

The issue is idle proportional fueling. The stock proportional fueling swings really far on lots of engines. Open loop doesn't do it. You can disable idle prop fueling, but then what it does is every ten seconds you get a weird surge when it tries to make a large fuel correction

Edit - you might be able to play with the proportional constants and get it to settle down. I've had mixed results screwing with it.

truckdoug

iTrader: (25)

even with a really mild cam? this is like a 216/222 on a 118!

probably i'll just leave the adaptive idle off.

my brain can only learn like 1 or 2 things at a time. just focus on getting the NB's to work.

am I on the right track with using NB voltage offset to move my CL fueling where I want it?

truckdoug

iTrader: (25)

so i used a combo of both altering the proportional constants for CL idle fueling and tweaking the NB voltage offset about 2% at a time. it'll idle around stoich for 8% ethanol now.

I think having them so close to the turbine outlet makes them act funny.

haven't been able to road test it to makes sure it doesn't surge...so much rain!

Darth_V8r

iTrader: (4)

There are times I can get that to work. A cam like yours should do it. Around 300 mV will idle just slightly lean and lower constants will keep the swings to a minimum. Some of the bigger cams, it's better in open loop.

One other thing I tend to see is maf is easier than SD to get a smooth idle in closed loop. So you can plug the maf in to see what its doing and that can help give you a reference point for where the SD tune is off.

truckdoug

iTrader: (25)

I hadn't considered adding the maf back. Are you suggesting it to just dial the idle air or scale it and leave it in? or is there a way to toggle it off when going to PE/BE mode? probably only gonna run 15 or 16 psi with this combo

Darth_V8r

iTrader: (4)

Really I was just thinking to help you get SD dialed in. If your dynamic air is way different than maf, the maf readings can be used to help get VE table dialed in in idle regions where oxygen sensors are less helpful on a cammed engine.

truckdoug

iTrader: (25)

ok gotcha. we'll see. this is my first attempt at closed loop fueling on a boosted application.

prior to this i just used the afr error % to dial my VE. even with rowdy cams and big injectors I was able to dial the VE pretty easily.

Darth_V8r

iTrader: (4)

Yeah. I find on mine I like OLSD. I do also find if I trim by NB or WB, the VE does not end up the same.

TPIZ92

iTrader: (10)

I just did a bunch of work on my proportional, integrator delay and switch points on my car. Stock cam, in SD mode, FIC 42lb injectors with just longtubes and ORY is my current combo as i piece together the final bits of the blower kit. The car was notorious for destorying o2 sensors and throwing switching codes. To make matters worse, while driving in SD mode the car would get stuck adding 25% fuel on one bank so i finally decided to address the issues today.

I was able to fix everything and on its first drive the long terms histogram made sense as opposed to having a cell be adding 25% or whatever and then next cell over reading -2.

I reduced the proportional fuel, increase integrator delays and raised my switch point in the idle area to 450 which seems to be the sweet spot for my particular car. The stock proportional fueling, if the o2's have been moved will, border line drown them. In the hot months its not so bad but in April weather the o2 couldn't recover after a rich swing.

truckdoug

iTrader: (25)

yeah i think that's where my idle rpm +/- surge was coming from.

it's currently very stable and adjusts to idle at stoich for whatever % of alky is in it (currently 25%)

I plan to lean it out from stoich a bit. I find that the more alky you put in it, the more tolerant it is of lean idle and cruise. The alky is very responsive out of PE mode

next up: playing with the flex fuel spark adder

Darth_V8r

iTrader: (4)

This is what I was trying to say earlier in the thread. i've had mixed results with this. if the cam is not too big -- like for example you are running a BTR S2, this approach works pretty decent. I usually multiply the integrator delay by 4 and cut the prop fuel constants to 32 vs 128. As the cam gets larger, this seems to stop working - or rather it seems to get enough overlap to where it presents on the sensor like a persistent lean followed by a really big, long rich wave and then persistent lean again. And idle RPM follows the O2 mV readings perfectly. That's my admittedly limited experience with it. but I do find there comes a point where you just go open loop.

truckdoug

iTrader: (25)

thats a really good observation!

TPIZ92

iTrader: (10)

I am currently tuning in speed density and found that the idle proportional tables do nothing for it. I made all my changes in the normal proportional table and that worked. Being that the idle tables use specifically g/s instead of airflow mode, I assumed it worked only if the maf is being used.

Also I found that reducing idle timing will produce hotter exhaust , further helping the issue.

But yes I agree as the cam gets more aggressive I can see this setup working less and less but I havent used this on a crammed car. I have done alot of older gms but newer stuff has been dodges and fords tuning wise for me

Kawabuggy

iTrader: (1)

Guys I've been following this post and I have to thank all of you for posting the info. It really helps those of us trying to learn to be better tuners. My truck has LT headers, ORY, and O2 locations are moved so the things you guys posted about, apply directly to me and gives me some more areas to look at to really dial my tune in even better than it is now.

Darth_V8r

iTrader: (4)

Good point on idle timing. I find lower does increase EGT but also somewhat detorques idle which helps smooth out some of the lumpiness. Below 16 I have caused red headers so I like to stay around 18

TPIZ92

iTrader: (10)

I left my idle timing alone in PN and in drive there is a significant bump which i left alone as well since I'm on a stock cam. I also raise my idle up just a smidge in attempts to get a cleaner read. Right now the long terms sit at -6 and -8 but that's with zero driving so it's not all that accurate. I also raise my idle in park to 700 and drive at 650. Car seemed to like that. I bet wrapping the headers would make a significant difference in how well these things read but all in all I'm happy with what I'm seeing now.