3.1 MPFI tune

[torq455]

I have a stock 3.1 with a couple of bolt-ons as you can see in my sig. i've just had some weird variance with my VE tables and wondered if anyone out there could send me a finished bin, or close to it, so I can do some comparing.

My issue: adjusted idle VE and got a nice 126 BLM in park and 128 BLM in drive. I drove in town not quite a quarter mile and stopped at a light. The BLM in drive went down to 116. I have also noticed my BLM while driving can vary from day to day as well. Can anyone tell me why?

[robertisaar]

because o2 sensors aren't perfect? you can only get the VE tables so close before any changes don't make a difference. i don't have any A1 tunes to send you, still running the wife's GP on 88...

[torq455]

damn...you again??? i guess, but i've noticed that since i started tuning over a year ago. i'd expect some variation, but, for the BLM to vary that much i don't understand.

[robertisaar]

how much does it vary?

[Superdave]

One of the biggest problems in the world of OBD1 tuning is the idea that BLM's have to be 128 all the time.

the basis for the closed loop system is that the ECM corrects fueling based on environmental variables. On a hot humid day your BLM's at 2K RPM might be 120, the next day it's dry and colder.. BLM's might change to 130. The idea is to get the main VE table tuned to where the BLM's don't max out in either direction during all seasons of the year. Also to get the WOT fueling correct.. but that's another issue.

[robertisaar]

One of the biggest problems in the world of OBD1 tuning is the idea that BLM's have to be 128 all the time.

the basis for the closed loop system is that the ECM corrects fueling based on environmental variables. On a hot humid day your BLM's at 2K RPM might be 120, the next day it's dry and colder.. BLM's might change to 130. The idea is to get the main VE table tuned to where the BLM's don't max out in either direction during all seasons of the year. Also to get the WOT fueling correct.. but that's another issue.

X2 and WOT tuning is pretty cut and dry compared to the VE tables...

[torq455]

BLM went from 126 to 116 within 60 seconds. was fine sitting, drove maybe an eighth mile and stopped at a light. engine temp, baro, or IAT didn't vary that much to cause idle to run 9% richer that quickly.

[robertisaar]

here's a tip: to rule out everything else, don't log ANYTHING until the motor is at full temp. once you have the base VE done, then deal with the warm-up stuff. that 180* stat will hold back a perfect tune unless you modify enough settings to make the ECU think 180* IS full temp, but since its close enough to 195, don't bother swapping it unless you were planning on it

[Superdave]

watch your injector pulsewidth as well, the BLM dropping just means that it's pulling fuel from the base VE table. That could be related to any number of things.


you're beating a dead horse.. lol

[torq455]

it's all back to normal now! it was a bad CTS. it reads about 190 heat soaked instead of 167! lol thanks for the help all!

[robertisaar]

that doesn't seem like it would explain all of it, but i guess...

[torq455]

a colder engine needs more gas. the ECM was thinking the engine was cold. had the same issue two years ago, before i started tuning. the only symptom was rich chugging and black smoke from the tail pipe in open loop. i found that at 45 degrees, the ECM thought it was -4 degs. had a good day tuning today. i took my usual 4% out of the base VE and got pretty close like i did last time. so, needless to say, i'm pretty happy about that. i did an idle relearn, though, i began the process with a temp of 127 degs. that may explain it. the hunting is better. for the most part, it's not as extreme and recovers after several seconds. i may try again when it's not sitting in a 105 deg garage. at the moment, she's running pretty good!

[robertisaar]

didn't you say it was leaning out so badly, it ran like shit? thats why the coolant temp sensor didn't make sense to me...

[torq455]

opposite. BLM was about 115 and INT was 76. cold loop was leaning out after some time. that's ok now.

[robertisaar]

"no, it's stupid lean. 02 is right around .450 mV. some datalogs it stays there for 7-8 seconds, others it says there for 15 seconds. you can tell the engine needs more fuel. it runs a little rough until it gets it. why is it with Ben's chip it doesn't wait even a second. granted, the ECM won't use it to adjust fueling. the 02 will read simply due to the amount of oxygen atoms passing bye"

thats from the other thread you had.

thats what i meant by you saying it was ridiculously lean, thats why the coolant temp sensor was confusing me...