I took some advice and did several highway cruises using decreasing injector constant values (20, 18, 16, 15, 14) I am running a "known good" tune from another member who has my combo except he has LS1 injectors (and ran 22 psi) and I have 21 Accel injectors. I am running the stock pressure.

I can't get cruising BLMs lower than 160! At 15 psi the car runs poorly (hesitation) and at 14 it gives me a check engine light.

Here's a shapshot comparison of the csv datalogs:
http://members.bellatlantic.net/~dantill/datalogs.bmp

Any suggestions appreciated! By the way - I am still very lean even with the stock bin - it's just that this bin runs better with my cam and heads.

 

If this is a port injection setup the stock pressure is 43 psi.
Running at 15 psi will certainly have BLM pegged.

 

I would tend to agree, it sounds like a failing fuel pump.Provided it is a Port fuel engine as the previous poster said.

 

Yes - TPI setup, 5.7, Vortec, zz4.

I did 4 more runs, each run is about 5 miles cruising at about 65 mph. To change things up I raised the fp from 43 to 50.

1. 18 lbs - looking better - BLMs in 140s - thinking AFPR made things better
2. 17 lbs - BLMs pegged at 160, Short term at 180
3. 19 lbs - though maybe I needed to raise the injector but same as #2!
4. 18 lbs - went back to this, but it was still 160/180!

Maybe #1 was better since it was the first run. Maybe I'll investigate the fuel pump.

thanks for the input!

 

torqueaddict, what is your fuel line pressure (say going through the fuel pressure reg)? The pressure should be around 45psi.

 

i think everyone is confused about what hes talking about. when hes saying 17 18 19 lbs, hes refering to the injector constant he is inputing, not the fuel pressure. he stated his fuel pressure as 43 then changed to 50.

 

This is correct. Sorry, it is a bit confusing. From what I've been reading, the reason for the lean condition is not in the tune - it's either due to the fuel pump, regulator, or injectors.

Although my injectors are accel, they are almost brand new, and my regulator seems fine. The pump may be original though but it appears ok. I have always had a fuel odor after after a long drive. Don't know if that points to one of these.

 

Are you adjusting fuel ONLY by injector constant?
That is not the proper way.
Once your air flow tables (MAF)or VE tables (SD) are setup and you "seem" to be close to the top values, then you can fudge the constant.
It should not be the first thing to change.
Doing it prior to proper tuning is just lying to the system and making it that much harder to tune.

I'm thinking you have reached a turning point (as we all have at some point)
Time to grab the starting bin, rehash what you've learned and start again.

 

To answer the question that was asked...
(does lower inj const=richer? can't lower BLMs!)

Lower = Leaner

On a side note....
A question for me "What is a stock inj const number for a 305 or 350
43 PSi, 8 INJ, 21#injectors (or whatever is stock) = --- inj const"
Since I'm TBI and wanted to see if the calculator I'm workin on can do TPI too!

 

That's interesting... My thought was that by making the injector constant lower, you would in essence be telling the ECU to increase the amount of fuel. This is because if the ECU thinks there are smaller injectors, then they need to work harder.

So it doesn't work like this?

I know that I am "fooling" the computer. It's just that at the rate I am working I'll have my car tuned in about 2 years!

 

It depends upon how the XDF was written. If done correctly for #/hr injector size, then a smaller injector flow rate will increase the PW given the same airflow.

RBob.

 

You're not actually fooling the computer, it does have feed back from the O2, if it doesn't like what you've done it'll just undo it.

 

FYI: After many more 65 mph cruising runs, I have my short term at a steady 128 and my long term at about 150.

To do this I have my injector constant at 18lbs, lowered my O2/Air table 600mv, and have my AFPR at 50psi.

I suspect that there is something out of whack where that's causing me to need to do this (I know it's not ideal). The original chip was a known good tune for my setup except for his injectors were LS1 and mine are Accel 21s. I can't imagine our injectors differ this much so I am suspecting a fuel pump, O2 sensor, or pressure reg. problem.

Also, I did raise the constant from 21 to 24 and received a check engine light - O2 Lean Error so for my car higher is leaner.

 

it takes 50 seconds of running lean for code 44 to set.
did the motor stumble from running lean at high rpm?

 

It happened while idling in my garage- never hit the throttle or anything to get it at high rpm. I may have been running rough but I probably ignored it because I was doing it as an experiment. It could have been 50 seconds because it happened while I was setting up the computer to datalog.