Proportional-Integral Fueling Capability Question
Thread Starter
Joined: Jul 2014
Posts: 10,450
Likes: 1,873
From: My own internal universe
Originally Posted by truckdoug
ay is that a cam in some cleavage in your avatar?
Last edited by Darth_V8r; Feb 2, 2017 at 08:52 AM.
12 Second Club
iTrader: (10)
Joined: Sep 2005
Posts: 948
Likes: 0
From: From Ohio now in that state up north
I don't think the current system was set up to ever run as described because the cat is using the products of rich combustion to help clean up lean combustion and vice versa.
However I would think the PCM is hardware capable of that type of control but you would need some type of "custom operations system" to use it.
I know there are shops that use proprietary software to edit not just the tables but the control loops themselves that might have the ability to use this kind of control however I don't know if they sell the software for you to do it yourself.
However I would think the PCM is hardware capable of that type of control but you would need some type of "custom operations system" to use it.
I know there are shops that use proprietary software to edit not just the tables but the control loops themselves that might have the ability to use this kind of control however I don't know if they sell the software for you to do it yourself.
Thread Starter
Joined: Jul 2014
Posts: 10,450
Likes: 1,873
From: My own internal universe
Originally Posted by 98redorangeta
I don't think the current system was set up to ever run as described because the cat is using the products of rich combustion to help clean up lean combustion and vice versa.
However I would think the PCM is hardware capable of that type of control but you would need some type of "custom operations system" to use it.
I know there are shops that use proprietary software to edit not just the tables but the control loops themselves that might have the ability to use this kind of control however I don't know if they sell the software for you to do it yourself.
However I would think the PCM is hardware capable of that type of control but you would need some type of "custom operations system" to use it.
I know there are shops that use proprietary software to edit not just the tables but the control loops themselves that might have the ability to use this kind of control however I don't know if they sell the software for you to do it yourself.
It can be done but not with the stock OS.
I appreciate the answers
12 Second Club
iTrader: (10)
Joined: Sep 2005
Posts: 948
Likes: 0
From: From Ohio now in that state up north
I would think you are right about the control. I am not great with all the emissions stuff but I think the reason for the big swings is cat efficiency it can actually get lower emissions from the big swings then it can from the smaller ones.
Here's my thought on that Jake. Lock in your IAC. Position and your spark timing in the scanner. If it starts surging really badly it's fuel, and these adjustments could help - especially if you're seeing the wideband look like a roller coaster. If you lock in your spark and air, and its steady, probably not the issue.
Force open loop, park or block the IAC and start playing with the fuel and air. Add/subtract till the engine is happy regardless of what AFR your WB reads.
It's like a woman, give it what it wants, not what YOU think it should have regardless if you agree with it.
Too much spark will make it oscillate but I'm sure that you probably already know that.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo Thread Starter
Joined: Jul 2014
Posts: 10,450
Likes: 1,873
From: My own internal universe
Originally Posted by LilJayV10
You are on the right track. If you have a good idea of how much air the IAC is passing that will help.
Force open loop, park or block the IAC and start playing with the fuel and air. Add/subtract till the engine is happy regardless of what AFR your WB reads.
It's like a woman, give it what it wants, not what YOU think it should have regardless if you agree with it.
Too much spark will make it oscillate but I'm sure that you probably already know that.
Force open loop, park or block the IAC and start playing with the fuel and air. Add/subtract till the engine is happy regardless of what AFR your WB reads.
It's like a woman, give it what it wants, not what YOU think it should have regardless if you agree with it.
Too much spark will make it oscillate but I'm sure that you probably already know that.
I found dropping idle spark to 18 and increasing spark in the main tables to 28 was the best combo even though everyone says make them the same. Then when I let out clutch I gain torque, but at idle it stays stable. The only real issue I have is when it warms up and goes closed loop. I can tune it to run steady at almost any commanded AFR but when the fuel trims start, is when it gives me a fit returning to idle.
I know I can just put it open loop, but I was trying to see if there was a way to not resort to open loop.
You know what I did? I went back to open loop at idle. On my big cam, I had to. It would not idle stable in CL with 16.5 degrees of overlap.
I figured with the new cam and 6 degrees it would idle in CL. And it does. I can even enrich it and it does fine. But on return to idle, I get that annoying little dippity-doo blip. Even after fixing the follower airflow. The way I test to make sure my fueling is spot on is to throw it in neutral while coasting. It's a good way to tune the cracker table too. But if you get any sort of waviness in your MAP or wideband then your fueling is off (and you're out of the idle routines at that point - so this is like the best way to tune off-idle). And if it's in CL and it's more pronounced than what's normal when the O2s are oscillating, then you can work on tightening up the CL routines. But if you have OL programmed from 0-1200RPM, I bet you don't have that and the coast down is completely uneventful.
I figured with the new cam and 6 degrees it would idle in CL. And it does. I can even enrich it and it does fine. But on return to idle, I get that annoying little dippity-doo blip. Even after fixing the follower airflow. The way I test to make sure my fueling is spot on is to throw it in neutral while coasting. It's a good way to tune the cracker table too. But if you get any sort of waviness in your MAP or wideband then your fueling is off (and you're out of the idle routines at that point - so this is like the best way to tune off-idle). And if it's in CL and it's more pronounced than what's normal when the O2s are oscillating, then you can work on tightening up the CL routines. But if you have OL programmed from 0-1200RPM, I bet you don't have that and the coast down is completely uneventful.
Funny you make that comment about give it what you want not what you want it to want.
I found dropping idle spark to 18 and increasing spark in the main tables to 28 was the best combo even though everyone says make them the same. Then when I let out clutch I gain torque, but at idle it stays stable. The only real issue I have is when it warms up and goes closed loop. I can tune it to run steady at almost any commanded AFR but when the fuel trims start, is when it gives me a fit returning to idle.
I know I can just put it open loop, but I was trying to see if there was a way to not resort to open loop.
I found dropping idle spark to 18 and increasing spark in the main tables to 28 was the best combo even though everyone says make them the same. Then when I let out clutch I gain torque, but at idle it stays stable. The only real issue I have is when it warms up and goes closed loop. I can tune it to run steady at almost any commanded AFR but when the fuel trims start, is when it gives me a fit returning to idle.
I know I can just put it open loop, but I was trying to see if there was a way to not resort to open loop.
Last edited by LilJayV10; Feb 12, 2017 at 06:32 PM.
Thread Starter
Joined: Jul 2014
Posts: 10,450
Likes: 1,873
From: My own internal universe
Originally Posted by LilJayV10
Most people get hung up on numbers, especially AFR at or near idle. Give it what it wants to make it happy. Most people will try to get it to idle around 14.7 and its chugging black smoke out of the exhaust making your eyes water and can't understand why it doesn't work and will chase their tales.
I'll have to attach a video or something. But like I said, I can do open loop and it's fixed. I was just trying to see if it could be resolved closed loop.
Yeah. And I should probably be clear that what I'm doing is chasing perfection. I bet many people would be happy with what it's doing. I'm just watching the wideband swing massively under idle or idle like conditions. And coasting to a stop, itsca very gentle sine wave from 900-1100 rpm. By gentle i mean like six seconds between peaks. And it follows the WB perfectly. I don't have it where it's even close to stalling - even hard braking after spirited driving. And idle isn't hanging or anything. It's just like the idle fuel trims are inducing a variable.
I'll have to attach a video or something. But like I said, I can do open loop and it's fixed. I was just trying to see if it could be resolved closed loop.
I'll have to attach a video or something. But like I said, I can do open loop and it's fixed. I was just trying to see if it could be resolved closed loop.
I understand man. Like I tell my customers. If you want it to drive like stock, you should have left it stock.
I'm just giving you a hard time.
Thread Starter
Joined: Jul 2014
Posts: 10,450
Likes: 1,873
From: My own internal universe
That's pretty funny! And true. PID I get pretty well. Fueling just doesn't do it. It's always in a proportional loop. Unless you run open loop.
Edit - what mean is that the goal of most PID loops is to achieve steady state. The goal of the ECU re: fueling appears to be to achieve an oscillating state that is centered instead of a steady state. In fact, i'm starting to realize the ECU would see steady state O2 readings as an error - insufficient switching.
PS - for Integral - airbags?
Edit - what mean is that the goal of most PID loops is to achieve steady state. The goal of the ECU re: fueling appears to be to achieve an oscillating state that is centered instead of a steady state. In fact, i'm starting to realize the ECU would see steady state O2 readings as an error - insufficient switching.
PS - for Integral - airbags?
Last edited by Darth_V8r; Feb 13, 2017 at 08:43 AM.
