A tuning tale: BLMs say lean, plugs say rich

[XfireZ51]

I got the Accel injectors back from testing yesterday. Only the #7secondary had an aerator that was disintegrated. However, the process of disintegrating progresses from behind the aerator which is exposed to the injector’s high pressure fuel stream. So basically, it wears away over time until there’s nothing left in the middle of the aerator. Altho #7S showed that, it eventually would demonstrate itself in the other injectors.

[XfireZ51]

Here's a graphic representation of the difference between stock, Accel and Delphi injectors re: voltage bias. Clearly the Delphis are " faster" reacting than either the Accels or the Stock injectors.
BTW, the volts on the X axis, is not the actual Voltage value. The graph is simply meant to demonstrate the difference in the injector latency between stock, my current Accels, and the Delphis I recently installed. The Delphis are nearly 2x of the Accels. The implication here is that especially at low PW conditions, the voltage bias plays a significant role in the overall PW calc. Getting it right makes a difference in developing a proper tune.

[XfireZ51]

Today was a good day to take the car out for the first time after having put things together. Had the opportunity to do some datalogging.
The FIC injectors are rated at 21.5# while the Accels rate at 21#. So my expectation was to see richer BLMs, but in fact, the BLMs demonstrated an overall lean condition. Next step is to check the spark plugs for confirming evidence of this.
However, one issue that appears to have been resolved is knock counts at cruise. Driving for 20 minutes or so at 1800-2000rpm did not result in additional knock counts, unlike previous. I will start to “bump” timing in this area to determine how much more timing can be used here.

[Ccmano]

Good to hear. Looks like the reseal of the IH’s did the trick and stopped the oil injection. Any difference in idle smoothness with the new injectors?
H

[XfireZ51]

Originally Posted by Ccmano

Good to hear. Looks like the reseal of the IH’s did the trick and stopped the oil injection. Any difference in idle smoothness with the new injectors?
H

On the basis of SOTP, yes idle feels smoother, but looking at the log, it needs tuning. Large areas of the VE tables need modifying because it is running lean. However, the motor, again, feels more responsive and quieter at cruise.
It’ll be warmer here tomorrow, so I’ll have a chance to do some datalogging on a new tune. I’ll pull a couple of plugs tomorrow just to corroborate the lean indication from the datalog.
I can “induce” knock counts by stabbing the throttle and backing off. But that could be the trans in combination w a SM flywheel. Mashing the throttle, I don’t get counts just tires spinning.

[XfireZ51]

Ok, the next datalog shows an overall rich condition. Pretty typical pattern u get when tuning. U get swings back and forth but the narrowing the BLM window until its close enough, ie +/- 3 counts. So anywhere from 125-131 BLM as an average.
The basic relationship between left and right banks has not changed. Right is the on the rich side, while left is lean. The first tune appeared to make the motor run smoother. The next tune will have smaller increments of change both lean and rich.

Below are pics of the #2 cylinder plug w right side being previous to upgrade of injectors, left after first datalog.

[Ccmano]

I suspect that difference in the plugs is more fixing the IH oil leak than the injector change.
H

[XfireZ51]

Originally Posted by Ccmano

I suspect that difference in the plugs is more fixing the IH oil leak than the injector change.
H

Hans,

On this particular cylinder, #2, I would agree w you. #7 on the other hand, had indications of more normal combustion rather than lean as it was. That would point towards the injector swap affecting fuel mixture.

Also regarding knock, I decided to roll back timing to utilize the stock table in the area of the SA table where I encountered knock occurring. I believe this area of the SA table is a critical one for eliminating knock because the motor spends quite a bit of its operating time in this area. After rolling back to stock timing, it essentially eliminated knock from occurring. I may decide to bump it a couple of degrees to test the boundaries, but I'm not certain that it would make much difference relative to the overall performance at those points.

[XfireZ51]

Happy Holidays to everyone. I believe we are getting close to wrapping this up.
I pulled plenum to check out coils, primary and secondary windings. All tested fine. Checked plug wires as well. Fine.
Since the plenum was off, I decided to check it for "flatness". Plenum was warped. Straightedge rocked by about .020". Spoke w Dr. Greekenstein (aka Pete). He told me that most plenums have some warpage to them. Suggested silicone gasket around the ports. I used Blue RTV since it is safe for O2 sensors.
Silicone gasket maker can kill an O2 sensor by contaminating it.
Finished installing plenum and took it out for a spin and logging session.
The difference was pretty clear from idle all the way thru. The BLM split was much tighter now w both right and left sides converging closer. Right was still richer than left but now the diff in BLMs was 124-132 or an average of 130 which is close enough. Idle was much more stable @ 925-950rpm and pulling about 48kPa which is pretty good considering Pete's cams.
Also, no knock counts. So I can start inching SA up a bit to see how close I can "tickle" the knock sensor.
So this wasn't The Silver Bullet. BUT, it was one of the pieces of the puzzle.

To summarize so far:

1. Broken injector, poor spray pattern and deteriorated aerator(s)

2. Oil seepage from crankcase vents into combustion chamber.

3. Warped plenum allowing additional air into fuel flow.

All of this points to areas that we probably take for granted when we have our motors apart. Should add these to the list of things to check when doing a plenum pull. It also goes to prove, before any tuning, its important to verify that all components are operating at nominal levels, otherwise tuning is like a dog chasing its tail.
This also suggest that you verify the datalogging measurements with some good old fashioned "eyes on" the motor. The car was running well. I believe had you driven the car. you would not suspect the issues that have been uncovered. Marc thought the car ran well when he drove it several weeks ago before I started this rehab. But had I brought it to a dyno, I likely would have been disappointed.

The datalog I just recorded shows some additional tweaking needed as expected. But not to the extent previous. I know I'll be re-checking torque on plenum after a few heat cycles.

[Top Toy]

Congratulations Dom! Thanks for sharing everything you've learned along the way with the rest of us! Wishing you many happy miles in 2019!