Hi guys, let me start by the fact i cannot pull data from my car. I have a feedback problem that does not allow me to data log. Im using tuner pro. I was looking for injector pulse width in tuner pro but i dont see that option to adjust for more fuel overall. I am running lean and i just want to know what setting to just richen my tuning overall. I have a .30 over, 58mm throttle body, mid length headers, cold air intake with a mass airflow sensor and 24lbs injectors.

 

How did you determine it's running lean - plug appearance, loss of power at high RPM/WOT, long term fuel trims, etc.?

What kind of HP are you making? Problem could be the 24 #/HR injectors are too small, and maxing out. Have you checked the fuel pressure with the engine under full load (at WOT, above 5,000 RPM)? Also, what does the “mass airflow sensor” consist of, if it’s anything other than stock? Could be a calibration problem if not stock.

Also should add the year of your car.

 

Thanks for your response. I determined im running lean by the plugs, they are white and starting to pit. I also have a digital o2 sensor read out showing me running around16.7 to 14.9 afr. As for fuel trims, i cannot get that data because of the feedback my system is giving me when trying to data log. So i can only go off plugs and o2 sensor as a live feed.
im making just slightly higher than stock Hp. Maybe 315. No dyno data to back any numbers up.
i know my fuel pressure is around the right numbers, i checked it at idle, but not at WOT.
the mass air flow (pipework) is not stock. Its in a 85 elco and its been custom piped.
Ive considered the the injectors the problem but i have no data (knowledge) on how to determine if thats the problem.
I was hoping for that magic setting in tuning i may have missed.

 

For fuel pressure, you need to test at wide open throttle to ensure pressure does not drop. Testing at idle is only a baseline.

What makes you say your HP is at 315? Could you list out the cars specs/mods?

 

Injectors are adequate at that HP level. Fuel pressure still needs to be checked with engine under full load.

What is the “feedback” problem? I've been reviewing data logs for LT1 owners for 20 years, and have never had anyone with that issue. We have an electrical engineer here who knows the LT1 PCM internals very well. Perhaps he could help.

What wideband system are you using? Is the sensor monitoring only one bank of the engine, or the combined flow of both banks? Where is it located? When do you see those A/F ratio numbers - in closed loop during moderate driving, or at WOT when the PCM is in power enrichment (PE) mode? If it's running lean in PE mode, there are two program tables you can use to adjust the target A/F ratio.

So.... you have the stock MAF sensor, but in a different ducting arrangement? GM changed the MAF sensor for the LS1 engines, and eventually discontinued the LT1 MAF sensor and came out with a universal replacement MAF sensor. I've seen some vague references to possible problems w/ the replacement sensor when used in the LT1. Do you have a part #? Does the MAF sensor still have the “screen” on the inlet side? Is the MAF sensor facing in the correct direction (inlet -> outlet)?

Would still be helpful if you advise the year of the PCM, and of the engine.

 

The 315 HP is just a guess, i have no idea to be honest. I have a 1993 lt1 with stock crank, rods, cam & aluminum heads, the ecm and wiring were converted to work with a 94/95 ecm. 0.30 over pistons, 58mm throttle body, mid length headers, cold air intake with a stock mass airflow sensor and 24lbs injectors.

 

The feedback i am having Makes the ecm to connect and disconnect continuously from my pc, but only when the engine is running. When key is on it connects, car running it sends errors forcing a disconnect.

I am not using wideband. I am only using narrow band sensors. I have two digital readouts, one for each sensor. I have no idea if i am in closed loop or open loop. I normally refer to the numbers while my engine is warmed up.

The maf is a stock lt1 maf with the screen attached with it faced in the correct direction (I believe)

93 engine with a 94/95 ecm.

Im not sure if its leaning out in WOT, my numbers peg out to 12.1, but i know that narrowband doesn’t work in PE/WOT mode. I have thought about tuning out PE to see what numbers i get in WOT.

But since i dont drive around in PE mode all the time, i figure its lean based on my spark plugs.

 

What software are you using to connect, and what operating system is the computer running the software?

 

My main pc for tuning uses windows xp. I use TunerPro RT to look and change my tune. I use CATS win flash for my ecm flashing. Ive also used EEHack in the past and Scan9495 to pull data (when data logging was possible on windows xp and windows 10).

I can connect just fine while my car is on so i can flash my ecm and see some inputs like voltage but once its running i loss the capability to data log.

 

Are you still trying to datalog with Scan9495? The software developer, Gary Doug, still frequents the site an may be able to provide some guidance. I know he will also want to know what kind of cable you are using.

 

If you don't have heads or cam, you aren't making enough HP to max out the 24 # injectors. They can routinely handle 370 HP at the flywheel before the duty cycle goes into the problem zone, depending on how efficiently your engine is using the fuel.(brake specific fuel consumption).

I'll ask our data logging/PCM guru to take a look at the "feedback" problem. He actually wrote Scan9495, and has an LT1 PCM in a simulator where he can replicate unusual problems.

The typical target A/F ratio in PE mode is 11.7:1. That's on the rich side for peak power, based on conventional wisdom that suggests the optimum lies between 12.8:1 and 13.2:1. Seems GM wanted a cushion to prevent detonation. You do not want to try and run the engine to peak power without the PCM going into PE mode. You are likely to encounter serious detonation. The narrow band sensors "work" at PE/WOT, they just lose accuracy because at the rich and lean extremes, the operating temperature of the sensor has a larger impact than the A/F ratio. The PCM ignores the O2 sensor readings because of this inaccuracy, but the sensors are still working, and will show up in a data log.

How are you reading your A/F ratio when the engine is warmed up? It should go into closed loop (after 206 seconds, coolant above ~140-degF, O2 sensors hot enough to start working ~600-degF), where the PCM toggles the A/F ratio back and forth between slightly rich and slightly lean to make the cat work. The O2 sensor voltage should be changing wildly (~9 times per second) back and forth between .0xx - .9xx volts, which should turn the digital readout into a psychedelic light show. That's why no one uses them.for closed loop analysis... just for PE mode where they are not toggled back and forth.

 

Yes, i have, i have the same problem with the "feedback". I say it like that because i reached out to the developer of EEHack and thats what he called it once he was able to review the data log EEhack uses to monitor the traffic between the ecm and pc. I am using a red devil river aldl cable. The maker of that aldl cable sent me a new one because i thought mine had gone out, but still have the same feedback problem.

 

Thanks for the super detailed information and for asking the developer to look into the feedback problem. I normally review my cruising afr after 5 min or so of normal driving and my temp is usually running 180°F.

 

Do you think by changing Stoich AFR Target in tuner pro rt from 14.7 to 14.0 ill have a richer fueling overall? Is that the setting im looking for an overall richer condition?

 

I have no idea. I don’t tune the stock PCM. I ditched mine 20 years ago and went with an aftermarket engine management system.

It will be a mistake to start making random changes to the tune without looking at a data log.

To add a bit, people have sent me eeHack data logs, and they seem to be extremely unwieldy, with hundreds of data columns that have data which in my opinion isn’t very useful, at the level I'm reviewing the logs. Moving columns of data and reformatting took a huge amount of time, and I'm not willing to put all that effort into it. Scan9495 has 52 columns, and I have a template I use to modify the .csv file appearance. Even that takes some effort, but it’s doable. Try to go thoroughly through 10,000+ lines of data (500,000+ individual pieces of data), and it’s time consuming.