Lean spikes commanded vs actual AFR
Thread Starter
On The Tree
Joined: Dec 2005
Posts: 126
Likes: 0
Lean spikes commanded vs actual AFR First let me start by saying I'm using EFI Live with COS3. I've been working on setting up my VE table but I noticed some cells that are way out of wack with the rest.
I then started looking VERY closely at my logs and noticed that everytime I step on the gas and go into a KPA above 95 I get these lean spikes when my commanded AFR goes to 11.7. Is this lean tip in that people talk about? How can I make it go away or is it just normal and I shouldn't be worried about it?
Thanks,
Bill
I then started looking VERY closely at my logs and noticed that everytime I step on the gas and go into a KPA above 95 I get these lean spikes when my commanded AFR goes to 11.7. Is this lean tip in that people talk about? How can I make it go away or is it just normal and I shouldn't be worried about it?
Thanks,
Bill
Do you have a screen shot where you accelerate from idle in 1st gear and go through at least 1st and 2nd gear at wide open throttle without letting off the throttle? Basically a quarter mile type log.
post your tune and logs made on that tune, it's much easier to see what's going on that way, since this is ~100kPa, this is the transition period into boost, things happen quickly, fueling changes, different tables take over... it might be a lot of different things, logs can only suggest where to look for the problems, not explain what causes them
Thread Starter
On The Tree
Joined: Dec 2005
Posts: 126
Likes: 0
Red Hard Supra hit it on the head, it's the transitional period that I'm worried about. Something else that I've noticed is that I only have the "mountianous" spike when kPa is greater than 105, anything less and it follows the commanded nicely.
I've enclosed a copy of the log and the tun.
Thanks,
Bill
I've enclosed a copy of the log and the tun.
Thanks,
Bill
the tune is actually quite well done, all tables are consistant and well blended, no harsh transitions anywhere, which was what i was suspecting.
there's some parameters that might be worth playing with: B3643..5 talk about how quickly the transition will occur. you have short gears too, so you simply might be needing these changes occur quicker.
another thing to try is to change the PE triggers (B3610,B3613) and see if the spikes follows or stays where it was. this would at least localize if the problem is PE transition related, or something else.
try it, report back, i'm kinda curious what it will be
there's some parameters that might be worth playing with: B3643..5 talk about how quickly the transition will occur. you have short gears too, so you simply might be needing these changes occur quicker.
another thing to try is to change the PE triggers (B3610,B3613) and see if the spikes follows or stays where it was. this would at least localize if the problem is PE transition related, or something else.
try it, report back, i'm kinda curious what it will be
Trending Topics
oh ok, i think i know what it is: user error 
click on 'n' so it shows you the count of samples per cell gathered. the crazy cells show 1--no wonder the averages are off! then do some filtering for steady airflow, and even less cells show up. dont make changes to the VE table based on such minimal amount of data, i like to get at least 15-25 samples per cell. it's not going to be easy. the fact that things change so quickly once you hit any positive boost usually means small turbo, capable of creating large changes in a short period of time. you're gonna have to find a really nice set of filters to fix it for you.
the best way to fix this situation is you need to log a lot more data, with a lot more GENTLE & STEADY throttle inputs. without that, you just fly through the cells quickly gathering barely any data, and the data you gather is in transition, so the errors are large.
also, watch out for your fuel/injectors. your IFR is flat, which suggests return fuel system, but is this really the flow you get? try to measure fuel pressure, see what comes out.
click on 'n' so it shows you the count of samples per cell gathered. the crazy cells show 1--no wonder the averages are off! then do some filtering for steady airflow, and even less cells show up. dont make changes to the VE table based on such minimal amount of data, i like to get at least 15-25 samples per cell. it's not going to be easy. the fact that things change so quickly once you hit any positive boost usually means small turbo, capable of creating large changes in a short period of time. you're gonna have to find a really nice set of filters to fix it for you.
the best way to fix this situation is you need to log a lot more data, with a lot more GENTLE & STEADY throttle inputs. without that, you just fly through the cells quickly gathering barely any data, and the data you gather is in transition, so the errors are large.
also, watch out for your fuel/injectors. your IFR is flat, which suggests return fuel system, but is this really the flow you get? try to measure fuel pressure, see what comes out.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
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
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote Thread Starter
On The Tree
Joined: Dec 2005
Posts: 126
Likes: 0
RHS,
I really can't take much credit for the tune because I've gotten a lot of help from others, without it I wouldn't be nearly as close as I am.
I modified all of the factors that you mentioned (and other had mentioned as well) in the PE tables and it makes a small difference in the "easy transition", but a quick stab still gives me a "mountainous spike". If I follow these spikes back to their origin in the VE table this is where they are for the most part. Something else I wondered about that may be a contributing factor is the fact that I have a manual transmission. If I had an auto it would problably shift down before it got to these areas and may not be a problem (just a theory).
You also mention a set of really nice filters, where do I get those at? Or better yet what is it I should be filtering?
It is VERY hard to get that many cell counts in some of the cells as you mention. To bad there isn't a way to continue logs on different trips, although it would problably take weeks to gather that much data.
Lastly on the fuel pressure, if you look at map C you'll see that I am logging my fuel pressure. I started doing this after I read all of the info that you posted on it. I'm also changing my fuel system around so what I think is a better set up to try and get more consistant numbers.
Thanks,
Bill
I really can't take much credit for the tune because I've gotten a lot of help from others, without it I wouldn't be nearly as close as I am.
I modified all of the factors that you mentioned (and other had mentioned as well) in the PE tables and it makes a small difference in the "easy transition", but a quick stab still gives me a "mountainous spike". If I follow these spikes back to their origin in the VE table this is where they are for the most part. Something else I wondered about that may be a contributing factor is the fact that I have a manual transmission. If I had an auto it would problably shift down before it got to these areas and may not be a problem (just a theory).
You also mention a set of really nice filters, where do I get those at? Or better yet what is it I should be filtering?
It is VERY hard to get that many cell counts in some of the cells as you mention. To bad there isn't a way to continue logs on different trips, although it would problably take weeks to gather that much data.
Lastly on the fuel pressure, if you look at map C you'll see that I am logging my fuel pressure. I started doing this after I read all of the info that you posted on it. I'm also changing my fuel system around so what I think is a better set up to try and get more consistant numbers.
Thanks,
Bill
