I'm tuning for fuel using the Moates O meter WB and datalogging to my laptop. Small changes to the injector constant seem to have unpredictable results on AFR. I have been at this for about 6 months now so I'm thinking maybe I have bad injectors, or something else? Fuel Pressure is good.
I can't get the car in closed loop. Typical scenario:
1. run car with inj constant = 26.0
2. Do 55 mph cruise - AFRs running 13-14 - no closed loop
3. reburn chip with 26.5
4. Do 55 mph cruise - AFRs running 15-16 - no closed loop
5. reburn chip with 26.3
6. Do 55 mph cruise - AFRs running 18-19????? - no closed loop
Yet the day before 26.3 seemed nearly perfect - closed loop cruise - 12:1 WOT.
I am running LS1 injectors and I am using "known good PROM" for this setup on an 89 L98 TPI. The car has a ZZ4 cam and Vortech heads, SD Intake, and Edelbrock headers. I was told that I should be at 22 lbs but it was too rich there.
I kept making adjustments and I think I am somewhat close - It'll go into close loop a little the go out. WB AFR is about 13.5-15 cruising. How close do I need to match the commanded AFR to get into closed loop? Is it easy to log the WB in tuner pro?
O2 mv at 444 too much, low cross count numbers, the O2's should swing a little (WB feedback or NB). O2 mv stayed low at WOT only one line at 800 mv 2145. should ramp up as injector pulse increases.
Random lean (23 - 25) commanded AFR's, starts at line 22 and 24, goes randomly as data is logged.
Re: MAF goes lean @ PT
Quote:
Originally Posted by Rebuildman (MAF goes lean @ PT) One problem I run into is at PT with low load on motor watching the WB it will intermittently go very lean, like from 14:1 to 20:1. The inj PW drops by 1/2, the MAF LV8 and MAF grams airflow also drop alot, MAF RAW input does not change nor does the TPS. Suggestions? Thanks!
It sounds like the ECM thinks that the MAF is bad and is creating a default value. If the MAF raw input is OK, but the LV8 and Gms/Sec airflow drop then the ECM isn't using the MAF input.
This may be being caused by a borderline MAF 33 condition. This is where the ECM checks some parameters to see if it can then check the MAF airflow. If the airflow is too high it will go into default mode. With a modified 400 this can happen.
Check the data log for these values (stock ARAP values):
less then 3200 RPM
less then 14.8% TPS
now if the airflow is > 45 gms/sec, there is an issue
This airflow value is stored at $C210 ($6E ARAP), increase it to a value greater then what the data log shows.
RBob.
Also check to see if Highway mode is enabled, this changes the AFR from 14.7 to 15.3 @ 55 MPH.
PE will change AFR to 12, raise "Minimum LV8 to Enable Power Enrichment" 4FD ($6E ARAP) from 50 to 55.
Thanks for the information! I didn't think anything of that radom lean commanded AFR.
Could I need a MAF sensor? The wire is intact. I would've bought one already just as a test if they weren't $300.
Last night I got desperate for closed loop and removed the ls1 injectors for the accel 21lb ones that I had used before - at least I know back then I was running in closed loop most of the time. I'll know tonight once I get the injector constant right for 21lb injectors where I am at.
Thanks. I read the post - I will check the relays and the MAF. I guess I could have a "borderline" issue but I have yet to get a code for MAF. I'd like to know before I buy more for this car that there's a problem. I'll check the diagnostic procedures in the GM shop manual.
If I replace the relays - it sounds like for 89 the relays can be the same..
How close to the target AFR do I need to be to get into closed loop? If I am 16:1 or 13:1 cruising should I be in closed loop?
By the way - tried to do some tuning after replacing the injectors with the 21 lb accel - still couldn't get closed loop for more than a minute.
I started with the injector constant around 22, and I'd lower it about .5 to .1 and then do a short drive. After a few hours, I got it down to 17 lbs - at around 18 lbs I was seeing cross counts but no closed loop. I tried ARAP unmodified and no difference.
ARAP is the same but at a different line location.
;************************************************** ; Closed Loop Enab Param's; ; ABTC, TYPE $32B ECM, MY 87 ;**************************************************
"LC445 ARAP"
LC558 FCB 107 ; 41 Deg c, Min Temp for Closed Loop LC559 FCB 147 ; 70 Deg c, Use Hot C Loop timer If Cool T >= THRESHOLD LC55A FCB 73 ; 15 Deg c, Use Cold C Loop timer if Cool T <= THRESHOLD
Thanks, it's a little cryptic but I will look that over.
I just wanted to share a few things I've noticed (some uber-guru may instantly see a likely culprit):
1. I always need to set the injector const down a good 4 lbs from what it should be to get the car to cruise at around 14.5:1. This is the case with 2 sets of injectors and 2 proms! Car is at like 19:1 with the stock prom and injectors!
2. I never see closed loops or much xcounts unless I am almost flooring it, at which time I will see closed loop for almost a minute.
3. gm/Sec seems low I think - full throttle - 190 idle - 9
4. no check engine light
I did swap relays and it didn't help. I check fuel pressure and it's great - even while driving. I know I have that random 20+:1 commanded AFR - I can see if the diagnostics help with that.
I don't really know where to start other than the MAF relays since they are cheap.
