How to tune a GRW 1.8 header?

[betancourtl]

I recently installed a GWR 1.8 header and started going down the tuning rabbit hole. I've made a lot of mistakes along the way and even though I'm closer I'm still very lost.

After logging a few WOT pulls I noticed that the car runs very lean on higher RPMS. Initially I thought I could adjust the MAF sensor and increase the g/s on higher voltages to get actual lambda to match desired (or what is on my fuel map because desired is always 1 in the logs).

This worked and I was able to get my lambdas down to .85, but after reading multiple docs on tuning headers I believed I followed the wrong approach and should have been changing the Volumetric Efficiency Load Multiplier Table.

For my second attempt. I set all the OL Partial WOT table , OL APP WOT, OL Global AFR fuel tables to target .85 lambda so that I always target .85 lambda on OL. I then did multiple WOT pulls, calculated how off in % actual is from desired. Made the corrections on the Load Scaling table (Increased values) and then verified with another WOT pull.

I did the procedure mentioned above 4 times and I was not able to get actual lambda to match target. I'm at a loss right now. I'm not sure what I could be doing wrong.

[CrazyCanadian]

Can you post your tune and some logs.

I remembered some more details about the desired being stuck at one. I don't use Versatuner to log so I don't know if it'll allow you to change the logged decimal point.. In ForScan and the OEM software, you've gotta change this in the parameter settings. Other wise it's just rounding up to 1.. You need 2 - 3 decimal points.

[xbrandino]

Leave the Volumetric Efficiency table stock and just modify your MAF calibration to keep your AFRs in check.

Also on a side note, targeting 0.85 lambda on NA with headers (assuming deleted cats) is probably a bit richer than I would go, try around 0.88-0.90 lambda.

Any logs would be sweet too.

[CrazyCanadian]

Leave the Volumetric Efficiency table stock and just modify your MAF calibration to keep your AFRs in check.

Also on a side note, targeting 0.85 lambda on NA with headers (assuming deleted cats) is probably a bit richer than I would go, try around 0.88-0.90 lambda.

Any logs would be sweet too.

I disagree... Its a mix between the two since you have changed the VE of the motor with the headers. Modifying the VE tables is like fine tuning the MAF curve.

[xbrandino]

You're not wrong but for someone that's new to tuning, trying to get both MAF and VE correct maybe be hard to understand and not necessarily required as with a correct MAF calibration it will be pretty close to target.

Each to their own though.

[mituc]

Having the VE table spot on may help in calculating better the fuel trims, but on ECUs with MAF all you have to do is to get the MAF calibration right.
Let's take an extreme example of a head or cam combination that will lower your VE from 0.9 to 0.8 in a certain rpm/load area. That's a 12% variation in that area. Now, the way this works, the VE will be affected in various ways but the tendency will be consistent based on the cams profile. But the MAF will measure exactly how much air flows through, the VE will only dictate how much the cylinders fill at that RPM/load/throttle opening.
And then the fuel trims have this only job, to correct the fueling punctually as well as learn these deviations. So you can leave the VE table untouched, no problem at all, just get your MAF calibration right.

On ECUs which operate in speed density where you have no MAF, the cylinder filling is highly dependent on the new head/cam profile in addition to the other known/normal parameters (temperature and manifold pressure). In these cases it's a lot more important to get your VE table right because it's a lot more important, it's basically going to be your MAF calibration just that will be 2D instead of 1D.
But even in speed density you still have fuel trims, so you can rely on them there as well (you have to, there's no other way). Just that the VE table will be of higher importance than on ECUs paired with MAF sensors.
This is basic stuff, there is no debate in agreeing or not agreeing with it, it's just how things work.

So get your MAF calibration right after you make sure there is no post-MAF leaks or any other weird stuff (brake booster/EVAP/whatever).