S2002S

Using HP tuners I tweaked the VE table (SD style tuning) to obtain zero LTFTs with the stock MAF disconnected.

As an experiment I installed a set of MAF ends (MAF still disconnected) and collected a log to understand the affect on the LTFTs. I was expecting the trims to be affected, but they weren't...still around zero as before. So what does this mean?

The MAF ends don't affect downstream airflow?

The main restriction in the intake is the oval opening from the Blackwing lid so can I assume that removing the MAF screen and stock MAF restrictions has no affect? If this is the case, I'll reinstall the stock MAF components.

It would seem that MAF ends should increase the amount of air available.

Opinions and comments are appreciated.

Thanks,

Brad

S2002S

Anyone???

LS1derfull

They do affect the air flow but with a stock cam(assuming yours is) the upper limits of flow thru maf ends is not reached. A head/ cam car running from torque peak to hp peak will move additional air that modified maf allows.

Another_User

What he said. On my car I noticed a difference when I swapped the MAF out for my MAF replacement tube (82.5mm). But yes, it does affect VE, because I had to retune my table.

S2002S

Some data, for what it is worth:

Yesterday morning I did a 35-80MPH pass (2nd gear in the A4) using my baseline tune with MAF ends installed. The basic tune had VE table and MAF freq. changes to acheive 0 LTFTs. The data logged was used to estimate horsepower using a standard Excel spreadsheet (HPTracking.xls). That same afternoon, I installed the orginal stock MAF with it's baseline tune and made the same identical run for comparision. For these two cases, the stock MAF actually outperformed the MAF ends by about 5 HP. Interesting eh? It could be that the HP change seen was within the normal variation. I'm not sure what the torque curve would look like.

Assuming the spreadsheet is reasonable, it appears for a basically stock setup with a few bolt-ons, MAF ends don't add anything.

Comments appreciated!

tici

iTrader: (1)

Brad,
How did you tune the VE? Using the NoGo or the HP Tuners system?
With my 98 I can adjust some cells just a little. Sometimes it's ok, sometimes no.
I had more success with the NoGo system using the MAF: when I disconnect the MAF my A4 shifts with the TCC locked, and it's not nice at all. Also the STFT jump up and down and to find out how to correct the VE is a real pain.
Do you have a suggestion?

This of MAF ends and your VE: I don't see why it should change. With less air you are still on the same RPM vs MAP table but with a little less MAP. As it was before with a smaller TPS angel. VE will change if you change the way the cylinders suck in air. If with the same MAP and RPM your big cam will "spit back" some air, VE will be lower. If air will flow better because a smoother runner surface VE will be higher.

S2002S

I tuned the VE table with the MAF disconnected and spark tables adjusted as described in the HPTuners forum (I'm using HPTuners). This was straight forward and only took a couple of passes to get it right. I wasn't concerned about the TCC since I wasn't doing any full-throttle runs. Once the LTFT were stable around zero, I plugged the MAF back in and then scaled the MAF frequency to bring them back down. I used this approach for the stock MAF and with the MAF ends. I tried tuning part-throttle by just tweaking the VE and failed.

Brad

tici

iTrader: (1)

Did you also work with the STFT (added to the LTFT)?
My LTFT are constant, but the STFT always jump up and down (+5 / -5) and make any calculation almost impossible.
Are the STFT following the O2 cycling? Is it really a good thing to use the STFT or it's maybe better to go with the LTFT only?

Right now I put back the stock 98 VE table and just tuned the MAF scanning frequency, cell and LTFT's. I've changed the G/sec using cells 0-15 only: this brings all the LTFT between 0 and -2.
I just wonder if messing aroud with the VE will improve something...

S2002S

I'd recommend that you use the LTFTs, provided they are stable. The STFTs vary depending on the current operating condition. I typically drive around watching the STFTs until they center around 0 in the cell of interest and the LTFTs stop changing and use that data. My STFTs varied about +/- 2 after the LTFTs stabilized.

I don't believe that the STFTs follow the O2 sensor cycling you see on a trace.

Brad

Are you using HPTuners?

screamn03

The motor is only going to use as much air as it needs, even when more is available it doesn't mean the motor will use it. When you are running SD it doesn't matter what the inlet looks like, the same amount of air is going into the engine at part throttle (where LTFTs work). When you go WOT you may see some affect-only if the inlet is restrictive.

Now when you are running the car with the MAF it will change things because the ends change the way air flows across the meter which will cause it to read a different amount of air.

S2002S

Good point. I guess with the stock head and cam, the MAF ends don't contribute much. Looks like I need to do some internal mods to take advantage of the MAF ends.