Tuning "Tip-In" lean issue

[KwikSilvr]

I use the sct pro racer software, and I have my truck tuned pretty good, I just have 1 or maybe 2 problems, which I think might be related, and need to know how to correct it...

I have a crazy lean tip-in, but from a stop its not so bad... its when im cruising down the highway at 60-70+ mph and I give it a little gas to speed up or pass somebody, it will go lean like 17:1 a/f and the truck shakes, for a second, then it richens up...

I have already adjusted the Manifold Volume up and down, and it does not seem to help it at all...

Im not too familiar with transient fuel yet, so I was hoping it might be there and that somebody could help me out?

I have tried the SCT forums, but nobody repsonds...

again, its just tip in, once its past that, its all good...

thanks...

 

[ecoastkid]

How low did you go with the manifold volume?...mine is around 10. Thats how far I had to put it to eliminate the issue.

I have heard, although im not sure how true it is, trasient fuel stuff is handled by the failed maf table. I've read on the SCT pro racer forum that lots of guys actually tune that table...dunno how tho. I didn't mess with mine.

 

[KwikSilvr]

I put my manifold volume at 5 and it has trouble starting up... it did seem to help the tip in issue a little...

i will try 10 and see...

but I always thought you wanted to add to the volume not take away?

 

[ecoastkid]

Just another thought. What load vs RPM is this occuring at? Go look at your borderline knock table and you might need to add or subtract some timing. My timing was way low in the mid range and, althoug it wouldn't shake, it would hesitate and feel like its loading up...i'd have to lift off the throttle to make it accel better. After adding more timing...all was better.

 

[ecoastkid]

I put my manifold volume at 5 and it has trouble starting up... it did seem to help the tip in issue a little...

i will try 10 and see...

but I always thought you wanted to add to the volume not take away?

From what I have read, the lightnings and cobra's work opposite of other vehicles. Maybe because its a roots style blower...:shrug:

One last thing...if you have your wide band sampling up very high, you will notice things like a lean spike that is 1/100 of a second...turn the sampling down a bit so you dont see that stuff because you cannot tune out 100% of that stuff. If the lean spike is 1/10 or more of a second...thats real data you want to see.

Mine still has the typical lightning hot start condition. Crank and roll your foot down until it starts. I havent tackled it yet, but there is a table that allows you to lean it out on start up...Thats my next thing to try and tune up.

 

[KwikSilvr]

Just another thought. What load vs RPM is this occuring at? Go look at your borderline knock table and you might need to add or subtract some timing. My timing was way low in the mid range and, althoug it wouldn't shake, it would hesitate and feel like its loading up...i'd have to lift off the throttle to make it accel better. After adding more timing...all was better.

yeah, i was gonna go back and put some timing in the mid range...

this is a good idea..

it seems to stumble at about .400 load, and 2200-2400 rpm... thats when it goes lean...

 

[KwikSilvr]

here is my spark table, let me know if you think i can up something

 

[ecoastkid]

here is my spark table, let me know if you think i can up something

Cant see this until I get home..lol

Photobucket is blocked at work.

 

[Fade 2 Black]

You shouldn't scale down or lower the manifold volume. Mine is set to stock. Have you adjusted the fuel trims all the way up to the OL cell in the maf table? Force OL and log the a/f vs. maf counts and load to see where things are.

 

[KwikSilvr]

You shouldn't scale down or lower the manifold volume. Mine is set to stock. Have you adjusted the fuel trims all the way up to the OL cell in the maf table? Force OL and log the a/f vs. maf counts and load to see where things are.

no i have not... but the thing is, its only with slight throttle..
so it being an open loop issue is not it...

and yes, I have adjusted my maf transfer functions from 0 to 1023 to match almost perfectly with my base fuel tables...

the only problem area i have is when cruising and hitting the gas just a little to speed up a tad...

it goes so lean that the engine stumbles, but if I step on it a little more, then it goes to where its supposed to go...

 

[IneritaSVT]

How much did you scale you load tables? Some time when you scale you load to much you start to loss resolution and experance those same problems.

 

[KwikSilvr]

How much did you scale you load tables? Some time when you scale you load to much you start to loss resolution and experance those same problems.

are you referring to the Engine displacement adjustment?

maybe I should just use the stock engine displacement and not mess with it?

JJ from woodbine, that I want my load to be between .18 and .23 at idle in drive...

thats where its at, but I could alsways go back up... I think I will put my manifold volume back to stock and the engine displacement back to stock and see what that does...