I've datalogged a few drives back and forth to work, and LTFT's are all + or - 2% or less, pretty much just like they were after spending several hours on the original street tuning.

I did add some fuel and timing at WOT since it did lean out a bit from about 4400rpm's up, after the headers and ORY. The added timing was something I just tried for the heck of it since I only run 87 octane...it seemed to like it.

Would you guys not even worry about doing any VE or MAF tuning since it appears to be fine as-is?

 

Personally, I redo the Ve amd MAF after every little mod out of spite and to see just what each mod does.

 

+1. You should ALWAYS retune after any modification. PERIOD

 

Normally, I do too. Just didn't think I'd be able to improve on + or - 2% LTFT's

I'm just very curious as to why datalogs show it still being well within an acceptable range, even after the header swap/cat delete? I thought it'd be way off, but it isn't logging that way.

 

It may be within an "acceptable" range but it needs to be perfect otherwise why even mod? I like my stuff to run razor sharp.

 

With the MAF you will only see a slight change in your fuel trims with a change like headers but now a change like that has a much more pronounced effect on the VE table. If I were a betting man I would say if you disabled the MAF and went back to tune the VE table you will now find that things aren't quite in line as they were before the headers.

This is where it can get tricky say if somebody is running pure speed density tune that was tuned through a full exhaust and then goes to the track and opens up a cutout for a nice opened up exhaust then you are going to end up being lean. That MAF sensor is very versatile and accurate and for certain changes in your setup post MAF will only show up as slight changes alot of times but now if you are talking about a change to a cold air intake or a supercharger then you will see the much bigger change to the MAF.


Like others have said I would definately go back and retune your VE and MAF.

 

Why would headers affect the ve more than the maf? I am not doubting you at all just curious.

 

I think you are doubting me Corey!


Just kidding.


Well because the Mass Airflow systems have such a simple and straightforward calculation for engine load and fueling needs. A change in throttle position simply put restrict the airflow. Partial load (vacuum) is seen by the computer as a smaller mass airflow value. Any kind of change in airflow that are within the MAF sensor's range and resolution can be instantly accommodated for by the computer. So even any kind of major change like a larger cam, headers, manifold, etc.... show up to the computer as slightly higher flow rates resulting in slighly higher fuel delivery.

As far as Speed Density goes and I wont get into a big discussion about it because I could be here all night but as you well know that they are much more complicated and quite a bit more goes into fueling calculations as compared to the fueling calcs. using the MAF.


Make sense?

The VE table is important for transient fueling however if done right I dont see a problem running pure MAF either.

 

Ya, it helps and makes sense... I am aware of the fueling calcs for the VE table... So once the MAF table is tuned for the particular hardware attached to it, basically it is good until you make more intake path changes? Correct?

Now the VE table, since it does not directly read airflow, it uses calculations to generate airmass, it should be retuned?

 

Just to update...

I took the advice and decided to do some VE tuning (first), and after only 2 logs and reflashes, STFT's are right back at 2-3% or less.

Heading back out to tweak the MAF, but I think 1 or 2 more logs and flashes will get the MAF right back in line as well...or at least I am hoping....