What can cause them to go negative 25 when i accelerate, there fine sitting idling, 01 camaro ss 408, tfs245s,244/248 cam ,fast 102/102

 

Going rich. The trims don't update when you go into PE Mode, so your MAF or VE table must be off as you part-throttle accelerate.

 

try disabling the ltft. and just use the stft. do u have a wideband? what is your afr at wot if u do?

 

Thanks Jake

 

Brandon i dont have a wideband

 

Don't go WOT until you get the wideband. However, you can tune part throttle with the O2s no problem. You want to get it to within 10% or less and ideally 5% off. Of course, the O2s correct for it, but you can still get it closer.

You need to setup that in the scanner and build the VE table (MAP sensor down the side in 5 10 15 20 etc to 105) and (Engine Speed 400 800 1200 to 7000 across the top) and then log STFTs as a percentage error. I'd just do the STFT under Closed Loop fueling and get the avg. Multiply the numbers that populate into the log into your VE table and multiply by %. Hand smooth any weird stuff by just taking out peaks and valleys by pulling them down in line with the things around them in the 3D graph.

Then do it again - try to log for 20-30 mins each time. And the next time do the paste multiply by half. It should be pretty close.

Also make sure you log at operating temp ~176 degrees.

And yes, disable LTFTs. Then when you get your wideband, double-check your VE table and tune PE mode and WOT in Open Loop and take the O2s out of the equation. You'll want to be within 5% or better with the Wideband.

 

With that nice setup u are running a wideband will be money well spent. U will be happy once u get to tuning with one. Things go a lot better faster.

Shoot for around 12-12.5 AFR WOT. Take baby steps to make sure things don't get out of control. Research and google are your best friends!!!

 

Well going -25 is better than going +25 on the fuel trims. Were you referring to short term, long term or both on the trims? I use LTFT for tuning the VE table. Using the scanner, I make a histogram, now called a graph in HPtuners 3.0 and newer? Dunno why they changed it, it isn't a graph? When I think graph I think of a curve or a bar graph, not a spreadsheet of rows and columns, but no matter what it is called you need to set it up so the row, and column labels match your VE table in the editor. As Jake said you need to copy this from the scanner and paste it into the editor, on your VE table using paste special, using multiply by % or multiply by 1/2%.

My understanding is the LTFTs are just a composite of the average of STFTs determined by the PCM. If you use the scanner, you normally put the graph or histogram in average, so they both should come out to be about the same. I just see a little less noise in the LTFT graph.

If you get your VE table dialed in really close using these long term fuel trims, when you go into power enrichment you will get very close to what you are commanding under power enrichment, usually about 1.18 will give you 12.5 AFR. If my VE table has been correct, meaning I did a good job with it using the fuel trims, my wide band only verified that it was spot on. Basically the wide band is only insurance you've got everything correct, using the fuel trims, but necessary insurance.

Another thing to note is you need to do this all without the MAF functional, in speed density mode. When I started out tuning years ago, I made the mistake of just trying to tune with the MAF active. If you do, you have a moving target, you have the computer making calculations based upon both the VE, and the MAF as the engine moves through dynamic to steady state modes. You need to set the MAF to fail at 0 (zero) and get the VE table right in SD mode before you mess with the MAF. Calibrate the MAF, after your good with your VE table and your AFR without the MAF active.

Your MAF could be fine, at a steady state in idle the computer is going to revert to MAF data as its primary for fueling calculations, as you transition to cracking the throttle the engine will start using the VE table in the calculation. The computer uses both the VE table and the MAF data to calculate fueling, under very dynamic conditions the VE gets a heavier weighting, and under steady state like cruise, and idle the MAF gets priority in the calculation. It could be your VE table is poor everywhere, even at idle? You won't know this without failing the MAF.

Also what fuel are you using, and what is your Stoich set at?

 

Thanks guys

 

Could i have a vaccuum leak

 

Slight correction on the LTFT. The LTFT basically sees the average STFT, say -11, and sets itself there so the STFT can oscillate -5 to +5. If the LTFT and STFT are both -11, you're actually trimming -22

 

Scotty Bg my stoich is set at 14.6 and my fuel is 93

 

That should be fine. I usually set it to 14.1 because now we are all running 10% ethanol wither we like it or not. That will only make your problem worse though. What you need to do is fail your MAF and use the fuel trims to correct your VE table. Set up a histogram that matches your VE table. And data log the car cruising around at part throttle. Once you have this populated, copy it to your VE table in your tune file useing paste %, then write the calibration to the PCM. Remember to clear the fuel trims before you start logging. Repeat this if necessary until all your fuel trims at 3% or less.

After this turn your MAF meter back on by replacing the 0Hz with the original value. Hopefully this fixes your problem and your car responds better. If you still have the problem your MAF calibration is off.

 

Any more advice available

 

Trims are now -35

 

That means that you are running 35% more fuel in your tune, than the car needs. You need to determine why this fuel is being added. It is likely in the VE table or the calibration of the MAF?

 

Nope. Not everyone. Plenty of 100% gas around here. Very easy to find. Lots around the rest of the country too. Costs .30-.40/gal more than E10 around here. To find it in your state check here. http://pure-gas.org/

 

I wonder if you know for sure the injector data is right?

 

Yes,the injectors came with data

 

Infinity injectors