Getting frustrated with negative trims
Thread Starter
Restricted User
iTrader: (43)
Joined: Nov 2001
Posts: 2,669
Likes: 1
From: Pittsburgh, PA
Getting frustrated with negative trims I have a 408 with a Fast 90/90 setup, 85mm maf, 52# injectors. I constantly am showing negative LTFT in the -9 to -16 range at idleand the STFT will go to 0 and then rise back up to approx -7 then back down again. If I subtract from the VE table, the don't seem to move much and throttle responce goes to crap. If I unplug the MAF I get pretty much the same results. The car starts up and idles fine. The TPS is at 0% the TPS voltage is at .43 and the IAC counts are around 30. I changed the cylinder volume to match the 408. When I take a ride, all the the cells are pretty much in the -16 range. Like I mentioned before, if I lower the VE table then it hesitates of idle. I also changed the O2 sensors and had the same results. I can send anyone a copy of my .bin file. I am using HP Tuners. Any help is much appreciated...
Nice color car!
Are you truly in SD mode when you're making the changes to VE? If not, and I quote TAQuickness here, "it's like nailing one foot down and running as fast as you can".
Check out the stickies on this firum, make sure you are in SD mode and disable PE mode for the purpose of tuning the part throttle.
Finally, when ltrims are negative try 'paste-special-%' instead of adding. When you have -10 and add -10 you can overshoot. With an 01 I assume you only have to change the primary VE ( as in you don't even have a secondary table like me ).
Are you truly in SD mode when you're making the changes to VE? If not, and I quote TAQuickness here, "it's like nailing one foot down and running as fast as you can".
Check out the stickies on this firum, make sure you are in SD mode and disable PE mode for the purpose of tuning the part throttle.
Finally, when ltrims are negative try 'paste-special-%' instead of adding. When you have -10 and add -10 you can overshoot. With an 01 I assume you only have to change the primary VE ( as in you don't even have a secondary table like me ).
I'm not sure how HPT handles the displacement parameter, but in EFILive, changing this parameter initially alters the values in the VE table.
After you change your displacement parameter, save the tune, re-open, then copy the original VE table (the one that you were using before changing the displacement parameter) back into your tune.
After you have done this, follow the stickies in this forum for VE tuning w/ trims. Better yet, pick up a WBO2. WB's make it much easier to tune.
After you change your displacement parameter, save the tune, re-open, then copy the original VE table (the one that you were using before changing the displacement parameter) back into your tune.
After you have done this, follow the stickies in this forum for VE tuning w/ trims. Better yet, pick up a WBO2. WB's make it much easier to tune.
On The Tree
Joined: Sep 2004
Posts: 143
Likes: 0
From: St. Clair
You can always try changing the MAF Sensor Frequency...If I remember correctly, higher frequencies will increase richness, lowering frequencies makes you leaner...
Multiply your entire table by 10% and see what happens for starters...
Peace...Gman
Multiply your entire table by 10% and see what happens for starters...
Peace...Gman
On The Tree
Joined: Sep 2004
Posts: 143
Likes: 0
From: St. Clair
Why not...They work just fine with the factory PE table...Scaling it for a modified PE table should not make a difference
I've done alot of logging over the last 4 years and scaling the MAF table works very well at controlling LTFT's...
Beside...Multiply by MAF Frequencies by 10%...If it will definitely drop his LTRM's...If it doesn't hesitate...Great...If it does, well, then he's no worse off then he was to start with...
Peace...Gman
I've done alot of logging over the last 4 years and scaling the MAF table works very well at controlling LTFT's...
Beside...Multiply by MAF Frequencies by 10%...If it will definitely drop his LTRM's...If it doesn't hesitate...Great...If it does, well, then he's no worse off then he was to start with...
Peace...Gman
Trending Topics
Scaling the MAF table is like putting a big band-aid on the problem. The problem is with the narrowband O2 sensors and the headers...they just don't have enough heat to be accurate anymore, and they are gonna throw off your trims no matter what. That's the nature of the beast. The feedback loop is corrupted. Until that problem gets corrected (as in someone develops a narrowband O2 sensor that specifically works well with long tube headers), it is gonna be an issue.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
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
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 On The Tree
Joined: Sep 2004
Posts: 143
Likes: 0
From: St. Clair
I run long tube headers and my Ltrims are no more inconsistant than they were when I was using the stock manifolds...
If the MAF Frequency's relavence were just a "band aid"...I'm sure that all the manufacturers would develope other ways of scaling the function of the MAF...
Anytime you are below 4000 rpms, the MAF frequency is being used...It is just another part of the equation...
If changing one part of the equation yields results that are unacceptable, i.e. modifying the PE table yields his hesitation problem...Then you need to make a change to another part of the equation, i.e. the MAF scaling or some other parameter until you get the desired results you are looking for...
All the times that I have scaled the MAF, I have never had any negative driveability problems...
Peace...Gman
If the MAF Frequency's relavence were just a "band aid"...I'm sure that all the manufacturers would develope other ways of scaling the function of the MAF...
Anytime you are below 4000 rpms, the MAF frequency is being used...It is just another part of the equation...
If changing one part of the equation yields results that are unacceptable, i.e. modifying the PE table yields his hesitation problem...Then you need to make a change to another part of the equation, i.e. the MAF scaling or some other parameter until you get the desired results you are looking for...
All the times that I have scaled the MAF, I have never had any negative driveability problems...
Peace...Gman
Thread Starter
Restricted User
iTrader: (43)
Joined: Nov 2001
Posts: 2,669
Likes: 1
From: Pittsburgh, PA
Thanks for the replies guys. I tried to get the LTFT with the MAF plugged in and unplugged. I will try fresh again tomorrow. I have the SLP MAF with the resistor removed, so what should I use for the MAF table??? I tired to use one from a Z06 vette. If someone can come up with a good table for me to start with, I would appreciate it. Ok so tomorrow I will put the stock VE table back in, disconnect the MAF, and try again to adjust from there.
Thread Starter
Restricted User
iTrader: (43)
Joined: Nov 2001
Posts: 2,669
Likes: 1
From: Pittsburgh, PA
Originally Posted by Black02SS
Are you giving the car anytime to learn the new tune before you log?
TECH Enthusiast
Joined: Jul 2003
Posts: 608
Likes: 0
From: fortress of solitude
Depending on how you're driving(throttle and load conditions) it takes an hour or 100 miles to get the trims to learn. The cells that you are using most often will learn pretty quickly, while others you will have to make an effort to run through several times to get a decent value. I've read that its best to reset the LTFT when the weather is "moderate" for your area, and to try to get as much driving in as possible within that particular day, since the fuel trims have a tendancy to vary based on weather(then again if you use SD tuning you may not have to worry about that. Maybe someone who knows a bit more about SD can chime in.)
Thread Starter
Restricted User
iTrader: (43)
Joined: Nov 2001
Posts: 2,669
Likes: 1
From: Pittsburgh, PA
Originally Posted by SmokingWS6
This is occouring at idle I assume. Don't always trust the trims, confirm it with a wideband. negative LT trims are not the end of the world, better than being lean 
Thread Starter
Restricted User
iTrader: (43)
Joined: Nov 2001
Posts: 2,669
Likes: 1
From: Pittsburgh, PA
Originally Posted by KALEL
Depending on how you're driving(throttle and load conditions) it takes an hour or 100 miles to get the trims to learn. The cells that you are using most often will learn pretty quickly, while others you will have to make an effort to run through several times to get a decent value. I've read that its best to reset the LTFT when the weather is "moderate" for your area, and to try to get as much driving in as possible within that particular day, since the fuel trims have a tendancy to vary based on weather(then again if you use SD tuning you may not have to worry about that. Maybe someone who knows a bit more about SD can chime in.)
Originally Posted by Gman2002Z06
If changing one part of the equation yields results that are unacceptable, i.e. modifying the PE table yields his hesitation problem...Then you need to make a change to another part of the equation, i.e. the MAF scaling or some other parameter until you get the desired results you are looking for...
Peace...Gman
Peace...Gman
Now, if you start back at the top of this thread we can see he has quite and extensive list of mods. With a lot of potential for his tune to be skewed or incorrect.
From the sounds of it, I'd say it's all boogered up.
One of the first things we need to look at is your Injector Flow Rate table to verify it has been scaled appropriately for your injectors.
You can use this calculator right click save as
Next you need to get your idle set up correctly. More information here. The write up is more geared to C5 with ETC, but i used the procedure on my '00 ws6 and it worked beautifully
Now you need to correct your VE table. Using trims. Using WB.
Then you can re-calibrate your MAF
I'm sure most everyone here will agree, you should spend some time getting familiar with tuning procedures before you start making changes to your tune. As you are doing your searches, and even within this thread, you will also find that just about everyone has a different opinion of the "right way" to tune. Part of what you need to do is decide what is "right" for you.
Most of the above links are posted in the stickies. The rest are easily found with simple WWW searches. Keep in mind also, the above links are not the end all be all ways to do this. For instance, if you do a search here for "injector scaling" you will find more than just the one link I posted for you.
For reference www.hptuners.com, www.efilive.com, and this site are excellent resources for tuning.
Originally Posted by 2001 Pewter WS6
I thought -LTFT was lean??? My O2's are in the 7xx range...
Negative trims indicate a rich condition, hence the PCM is removing fuel to compensate.
Originally Posted by Gman2002Z06
I run long tube headers and my Ltrims are no more inconsistant than they were when I was using the stock manifolds...
If the MAF Frequency's relavence were just a "band aid"...I'm sure that all the manufacturers would develope other ways of scaling the function of the MAF...
Anytime you are below 4000 rpms, the MAF frequency is being used...It is just another part of the equation...
If changing one part of the equation yields results that are unacceptable, i.e. modifying the PE table yields his hesitation problem...Then you need to make a change to another part of the equation, i.e. the MAF scaling or some other parameter until you get the desired results you are looking for...
All the times that I have scaled the MAF, I have never had any negative driveability problems...
Peace...Gman
If the MAF Frequency's relavence were just a "band aid"...I'm sure that all the manufacturers would develope other ways of scaling the function of the MAF...
Anytime you are below 4000 rpms, the MAF frequency is being used...It is just another part of the equation...
If changing one part of the equation yields results that are unacceptable, i.e. modifying the PE table yields his hesitation problem...Then you need to make a change to another part of the equation, i.e. the MAF scaling or some other parameter until you get the desired results you are looking for...
All the times that I have scaled the MAF, I have never had any negative driveability problems...
Peace...Gman
Thread Starter
Restricted User
iTrader: (43)
Joined: Nov 2001
Posts: 2,669
Likes: 1
From: Pittsburgh, PA
I am going top start over from scratch today. I just received my LC-1 wideband. I was waiting to get a new bung installed before using is. Ok now can I pull a stock O2 and temporarily use it for my wideband while tuning in SD mode or do I have to use the stock O2's at the same time???