$EE LT1 PCM Questions

[Terminal_Crazy]

Whilst comparing .bins I came across these two inb the XDF.
126d5 Min Inj Pulse
126d7 Use this value when Min Inj Pulse reached

The stock Z28 was set at 1.4ms. A tune I had made years ago had the Min Inj Pulse lowered to 1.01ms but the Use value.
On checking logs I had injPW going lower than 1ms whilst cruising so does this value get used or does the PCM just dump fuel in.


Also I was trawling through some of the LT1/LT4 dissassembly files & it mentions Pump shot a couple of times.
These
2021 Timer to cut fuel for Corvette Special Diagn
12021 Vs Delta tps for?? burst Knock or low baro calc threshold for 2413 v 2414 for % airflow Calc
12413 mult for % airflow calc if delta tps > 2021 Z28 & LT4 set at 2.0
12414 mult for % airflow calc if delta tps < 2021 Z28 0.75 - LT4 1.04
1240a Mas air/Cyl Filter Coefficient Vs map Vs rpm

were around the same area so I was wondering if these were mis labeled.
Something I will have a play with when the new injectors arrive.


Also I have the Rev limiters/ fuel cut off maxed out but also came across this one with a lower value.
167b4 MAX RPM for 0 bpW - max allowed is 6375
Is this an extra fuel kill for over reving?
I wasn't able to test this one out as the roads are a bit cold & wet & the car kept going sideways.


thanks
Mitch

[dzidaV8]

So far I have checked the hardcoded RPM limiter at 167B3. The labels in EEXtra were not correct, there you go with good ones:

0x167B4 Hardcoded Rev Fuel Cut
0x167BA Hardcoded Rev Fuel Resume

Conversion is X*31.25 for both.
Stock files have this limiter set to 7187.5 RPM, both cut and resume. Max possible value is 7968.75 RPM.

Attached corrected XDF.

More as I have it.

[Terminal_Crazy]

Nice one!:happy:

[jthompson122183]

So far I have checked the hardcoded RPM limiter at 167B3. The labels in EEXtra were not correct, there you go with good ones:

0x167B4 Hardcoded Rev Fuel Cut
0x167BA Hardcoded Rev Fuel Resume

Conversion is X*31.25 for both.
Stock files have this limiter set to 7187.5 RPM, both cut and resume. Max possible value is 7968.75 RPM.

Attached corrected XDF.

More as I have it.


Thanks for posting this information, I haven't labeled much on the e-side since ive started a couple of years ago with this eextra project.

[jthompson122183]

"Pump Shot"

12441

[jthompson122183]

1240a
from lyndon wester of westers garage in the facebook group "Tunercat Users"
12442

[Terminal_Crazy]

Can you send a higher res image of that, I can't read it,

Thanks
Mitch

[kur4o]

So i took another look at the supposed pump shot adder. After I examined some logs of data, I finally figured out what is does.
At rapid tps change, the maf readings jumps alot too fast, the pcm use this pump shot as a scale factor to gradually increase or decrease the AFGS.
For example the AFGS jumps from 20 to 100 g/s at one frame interval. PCM blends the increase to 30, 50, 80, 100 over a period of couple of frames. That way you don`t get erratic jumps in fuel bpw and engine runs smoother and more consistent.

So this factors how fast the transitions happen. I guess the lower the value the faster the transition. Still it needs to be confirmed.
It turns out maf reacts faster than the time needed for the air to get to cylinder. That`s why there is no ae build in the code.


That is the final explanation for the so called pump shot adder.
It took me about a year to figure it out and some customs logs to confirm it.

[kur4o]

Whilst comparing .bins I came across these two inb the XDF.
126d5 Min Inj Pulse
126d7 Use this value when Min Inj Pulse reached

The stock Z28 was set at 1.4ms. A tune I had made years ago had the Min Inj Pulse lowered to 1.01ms but the Use value.
On checking logs I had injPW going lower than 1ms whilst cruising so does this value get used or does the PCM just dump fuel in.


Mitch

The logged data don`t correspond to actual data the PCM uses.
The BPW on the datastream is base data that is not corrected with individual fuel trims, Low pulse injector adder and min injector pw.
So in your case when the minimum injector pulse is reached PCM load 126d7 for bpw even that you don`t see it on the datastream.

[Catmaigne]

So i took another look at the supposed pump shot adder. After I examined some logs of data, I finally figured out what is does.
At rapid tps change, the maf readings jumps alot too fast, the pcm use this pump shot as a scale factor to gradually increase or decrease the AFGS.
For example the AFGS jumps from 20 to 100 g/s at one frame interval. PCM blends the increase to 30, 50, 80, 100 over a period of couple of frames. That way you don`t get erratic jumps in fuel bpw and engine runs smoother and more consistent.

So this factors how fast the transitions happen. I guess the lower the value the faster the transition. Still it needs to be confirmed.
It turns out maf reacts faster than the time needed for the air to get to cylinder. That`s why there is no ae build in the code.

That is the final explanation for the so called pump shot adder.
It took me about a year to figure it out and some customs logs to confirm it.

Sorry about the necrobump, but I was wondering how much experimenting has been done with the 1240a pump shot adder table and if lower values actually correlate with faster transitions, ie more fuel. My experience has been the opposite.

I've been having tip-in issues with my car for a while, so much that I would get the occasional stumble/miss for an instant upon snap throttle. My wideband was showing some pretty nasty lean spikes in the logs, so I did some experimenting with the 1240a and found that the lean spikes seemed to decrease as I increased the values in the table. I also noticed that the LT4 values in 1240a are also higher than the LT1, which would make sense if my findings are correct.

A little background on the car:
6 speed f-body
383 @ 9.5:1cr
AFR 210's, a LE blower cam, and 58mm tb

[kur4o]

NOt much experiments were done with the table. I even add a realtime control of the table but never had the chance to test how exactly it works.
You can look at it as a scalar that regulate how fast the maf value is updated. Something like gradual changing rather than abrupt change of value. Smoothing the rapid peaks the maf produce. Or take it like that, the time the metered air fill the cylinder.

It only works with maf enabled. In speed density tune is pointless to tune it.

It will be nice if you post any findings you have. I suggest to try realtime tuning of the table for better control of the output.

[Catmaigne]

Cool, I'll have to get more familiar with EEhack and try to dial it in a little better. I do feel like I've made a good bit of progress just by boosting the 1240a table and reenabling burst knock, no stumbles yet (knock on wood).

Also, do you happen to know if there's a way to keep burst knock active while in PE? I looked around in a bunch of XDFs and didn't see anything. The burst knock seems to get zero'd as soon as PE is enabled, whereas a ramp down would be nice.