$EE / LT1 Injector Swap Running Rich

[spfautsch]

I think you're confusing the offset vs voltage table with low pulsewidth adder. The tune you shared with me had a populated offset table. I've zeroed the low pulsewidth adder table which is what I think you're talking about.

It's idling fairly well, not exactly like it was last month when my "long way to work" road was horribly mutilated by the Missouri Department of Transportation (we rednecks refer to it as chip-n-dip). But it's also 100F ambient and 50% relative humidity here so I haven't run it in this type of weather much to have a "baseline". Driveability is good. The seat of pants dyno says mid-range power isn't great, but again the weather may be a variable. I won't be able to collect much data to verify for quite some time, but my worst trim cell after a 10 minute drive was 5% rich so I'm not thinking a big VE remap will be in order.

I'll experiment some and report back. I'm beginning to think there are some IPW calculations happening during cranking that don't reference the VE table or the injector flow constant.

[spfautsch]

Well color me stupid. No sooner than I clicked "post" it occurred to me there's a "Crank Volumetric Efficiency Vs. %TPS Vs. RPM" table that I hadn't adjusted to match the main VE tables.

I'll have to test more after she cools down but it sprang to life almost as quickly as it used to (feels like within the first 180 degrees of rotation).

[Terminal_Crazy]

I think you're confusing the offset vs voltage table with low pulsewidth adder. The tune you shared with me had a populated offset table. I've zeroed the low pulsewidth adder table which is what I think you're talking about.

It's idling fairly well, not exactly like it was last month when my "long way to work" road was horribly mutilated by the Missouri Department of Transportation (we rednecks refer to it as chip-n-dip). But it's also 100F ambient and 50% relative humidity here so I haven't run it in this type of weather much to have a "baseline". Driveability is good. The seat of pants dyno says mid-range power isn't great, but again the weather may be a variable. I won't be able to collect much data to verify for quite some time, but my worst trim cell after a 10 minute drive was 5% rich so I'm not thinking a big VE remap will be in order.

I'll experiment some and report back. I'm beginning to think there are some IPW calculations happening during cranking that don't reference the VE table or the injector flow constant.

I did say to get your data first!

Nope, no confusion there. I've got the Voltage offsets set, I have since zero'd out the low pulsewidth adder.
As I don't know that they are correct, close or way out, I've removed them from any interference in the data logging.

This motor will start at 7.5:1 or less and 22.4:1 or more without any issue.

If you do adjust your VE table i'd only adjust it fractionally from what you are calculating so it doesn't shift too far from where you are now.

Mitch

[spfautsch]

This motor will start at 7.5:1 or less and 22.4:1 or more without any issue.

You also have another 30 cubic inches of displacement, which is not insignificant.

If you do adjust your VE table i'd only adjust it fractionally from what you are calculating so it doesn't shift too far from where you are now.

I had the opportunity to do some more logging this afternoon and found the trims aren't very far from what they were with the factory injectors. I feel confident I'll be able to tweak the offsets and injector constant to "a happy place" without significant remapping of VE.

The Crank Volumetric Efficiency Vs. TPS Vs. RPM table looks to have the biggest influence on my starting flood problems. Extremely rich pulsewidths on a 24 lb injector are a completely different animal with a ~43.5 lb injector setup. In addition, this cam is right on the edge of ridiculous in my book - the idle cells are around -30% from the factory tune. So far I've tried three different scalings on this table, all with extremely noticeable and some very promising results.

I'll be happy to spend whatever time it takes to get this one just right because it's hard to describe how satisfying the sound is when the engine breathes to life within 500 milliseconds of crank start.

[spfautsch]

Is anyone aware of a "minimum injector pulsewidth" constant in $EE?

I ask because I've removed enough of my Crank VE vs TPS vs RPM table that warm starts are coming in at 0.75ms pulsewidth and don't seem to go lower. I'm just curious because the specs on these injectors show a minimum PW of 0.52ms.

I'm pretty sure I've run the crank VE table too lean, but it's hard to tell. It seems to be starting rough (long crank, sputtering start) when cool, warm and hot now. There seems to be a "black hole" startup spot where the ECT reads around 140f where once the valves have cooled down the difference between flooding and firing is awfully narrow.

[dzidaV8]

There you go, I updated Steve's EEX.xdf with some parameters, including minimal injector PW.
Stock minimal PW is 1.4ms.

EEX injector parameters.png

[spfautsch]

There you go, I updated Steve's EEX.xdf with some parameters, including minimal injector PW.
Stock minimal PW is 1.4ms.

Well thanks, but this just raises about a dozen more questions.

1) if the minimum is 1.4ms why am I seeing 0.75?

2) I must have been using an extremely outdated version of steveos xdf, or have you added / changed a lot more?

1st Prime Pulse Width Vs. Coolant Temp. table controls the injector pulse width of the first prime fuel pulse during cranking as a function of engine coolant temperature.
Similarly the 2nd Prime Pulse Width Vs. Coolant Temp. table controls the injector pulse width of the second prime fuel pulse during cranking as a function of engine coolant temperature. These tables were in the '96/97 LT1 calibrations. In the '94/95 LT1 calibrations these two tables are combined into a single table (Prime Pulse Width Vs. Coolant Temp.).

If the engine is still cranking after the time specified by the 'Added Prime Pulse Enable Crank Time Vs. Cool. Temp.' table then another (Added) prime pulse is output and the pulse width of this added pulse is specified by the 'Added' column.

<mind blown>

The version I was using had these three tables separate, and none had any info about what the parameters effect.

Questions 3-12) can anyone explain the $EE startup routine in detail? The description of the prime pulse width table makes it sound like there are no AFR calculations happening during this "prime" sequence. What are the conditions for the prime sequence to be entered? What is the function of the "Ext. Crank AFR vs. Low Res Pulse vs. Coolant Temp" table? This one also makes it sound like AFR calculations are not referencing VE or the injector flow constant.

When cranking, the AFR must be determined using the low resolution pulse only, as not enough stable data is available from the MAF or SD systems. This table configures the ratio of fuel to low res pulse.

This has me wondering if there's an annotated disassembly floating around somewhere. I'm too old to try deciphering motorola byte code again - my brain will turn to dust.

[dzidaV8]

Yes, I modded the XDF here and there to suit me better.

Commented disassembly is here.

Basically, at startup there will be two prime pulses delivered (1st and 2nd, as per tables) at each low res pulse (IIRC). After the first 2 prime pulses, fuel is delivered using Crank VE table and Cranking AFR table. If the engine doesn't go above running RPM in certain time (Added Prime Pulse Crank Time table), there will be another (added) prime pulse, as per 3rd table.

As for PW lower than minimal, I think that prime pulse might not be limited by that? Need to check the disassembly.