VE Table in V-6 questions

[MMGT1]

"Leave the VE alone in a V-6"... OK got it, but...

I would really like to wrap my head around it if anyone cares to embellish me. I get the fact that it is a % table, but a % of what?

I know that with my WB I can tune this one but that is not what I'm after here. NA I am so far from stock it's not funny. If I am reading this thing right, the VCM does reference this table to look for MAF failure. Could this table cause a "False MAF Failure" if it is too far out of range for what it is seeing compared to MAF Hz?

Is it the injector duty % that the Primary VE table is displaying?

If someone has a couple of mins and would be willing to get into this one, please do! I'm thinking with 36lb injectors and a .559 lft cam in a 3400, this table should not be ignored. Anyway, you tell me!

[oakleafresin]

"Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio (or percentage) of what quantity of fuel and air actually enters the cylinder during induction to the actual capacity of the cylinder under static conditions. Therefore, those engines that can create higher induction manifold pressures - above ambient - will have efficiencies greater than 100%. Volumetric efficiencies can be improved in a number of ways, but most notably the size of the valve openings compared to the volume of the cylinder and streamlining the ports. Engines with higher volumetric efficiency will generally be able to run at higher speeds (commonly measured in RPM) and produce more overall power due to less parasitic power loss moving air in and out of the engine."

As far as tuning it, if you have the time go for it, but I wouldn't waste any on it. Instead, set the bit to "3" inside the .bin and tell the ECM to reference the "default air" table instead, on a MAF failure.

I'm not sure if the PCM actually uses the values in the table so much as it just checks to see if something's there. I zeroed out the table in my friends car and he called me 5 minutes later to tell me his car stalled and wouldn't start back up. When I put the VE table back it fired right up.

The early OS's only have half of the default air table, which is kind of a bummer.

[MMGT1]

"Something else I've thought about that could easily be called out as right or wrong, is that the ECM might look at the VE if you surpass the MAF allowed delta airflow values."

Now your headed somewhere with this. I have dealt with a "shudder" in mid accel for months now. I have changed axles, TRANS.. yea even a transmission, 3 MAF's, all suspension parts inc new control arms with poly bushings and nothing is fixing this thing. I was looking at a scan earlier and saw that change in g/cyl in my car can be as much as 12 in a 1 second time period! But I tried a couple of years ago to raise that table and the car went nuts, and stalled. Put it back close to stock and it fired right up. I think I do understand the table a little better now and I think I can do a better job of adding to the MAF allowed flow table where it is needed. Im going to leave the lower region where it is and work the mid range a little and see if I cant get this thing to accel smooth.

[oakleafresin]

Lol I edited that out of my post because I didn't think it made sense :P I guess it could be a possibilty.

I really think the VE table is used for nothing more as a periodic check to see if the MAF is functioning correctly/within reason. Like many others, I tried zeroing out the table as I said above, in my friends 98 Regal GS (98 OS also). Transient air is set to 0 (use nothing) and set to use the VE table on maf failure. The fact that it stalled is troublesome to me because of those bits being set that way. Unless his maf failed, but we were scanning it all day and it never showed any issues.

I have the stock VE table on my car and just tune the MAF. While I get horrible mileage (it's 20* F here and I'm XP cammed with a stall and gears) I haven't noticed any drivability issues that I could say weren't caused by inaccurate fueling. The wideband is always showing good numbers. I just adjust the maf when I have a fueling issue.

I run 24/7 open loop, if that has any effect on things.

WOT fueling is highly (if not completely) based off the MAF output because when mine was missing the screen, and I was seeing a rough MAF output at high airflows, the IPW's were very rough and jagged too. This was obviously reflected in the wideband output too

[MMGT1]

Russ had told me some time ago that when we go into PE my VCM uses the MAF only, but it will carry any trims it sees as it goes into it. This is why I have always used the NB to tune cruise and then the WB to tune from my "switch point" to the top of my scale. *Since when the NB is back in it will only change the trims anyway*. It has worked great as I get 0 trims when entering PE almost every time. The most I see is a .8 difference sometimes, but even that is rare. I have tuned for 12.8 at WOT with this cam and it pulls like an animal in PE, no shudder and will break the tires loose at even 100kms if I hammer it in that range. This is why I am pretty dam sure my shudder is in the tune, just have to find the cause....
New thought, I wonder if I need to install a longer honeycomb in front of the MAF sensor? It is a stock sensor and has the screen in place. The problem seems to be multiplied in severity by temp as well. Since turning cold here it has just gotten worse and worse. I did test the range of the IAT sensor with a heater and it seems to react just fine. Two nights ago I replaced the MAP, coils, ignition module, plugs and wires. Under the hood this thing is now pretty much new again. I've completely rebuilt it from the ground up. So I am pretty confident it has to be in the tune.

[bilemke]

The VE, during normal operation of the MAF, is partially used. It is used to compare what airflow should be occurring vs what the MAF is sensing/reading. Otherwise, how would the PCM check the MAF for accuracy?

Zeroing it out would make the check fail unless you severely changed the MAF Max Delta values that the PCM checks for between MAF/VE. If the MAF fails and you have the failure mode not set to VE or Default Air Table, what will the PCM use to determine airflow????? Nothing, so your engine wll stall.

[bilemke]

BTW, I have posted in another forum that with the help of a another piece of editing software that you can change your tune so that it will always have 0 fuel trim in cell 3, and thus if you make sur that you are in cell 3 when in PE, you could always have 0 fuel trims in PE. oakleafresin knows the forum as I see him there every so often

To me, this type of setup makes the perfect balance of closed loop and PE (without the need for completely crippling closed loop by forcing Open Loop).

[MMGT1]

So, if I am reading you right bilmke, the VE table could cause a MAF error reading in a modded V6? This one is a 3400 with a 559 lift cam, stage 2 heads shaved .020", and 36lb injectors. I am dead nuts sure that the VE table is nowhere near where it should be... lol

[bilemke]

So, if I am reading you right bilmke, the VE table could cause a MAF error reading in a modded V6? This one is a 3400 with a 559 lift cam, stage 2 heads shaved .020", and 36lb injectors. I am dead nuts sure that the VE table is nowhere near where it should be... lol

Yes, VE (as a basis for a calculation) vs MAF is what P0101 is... P0102 and P0103 are just maf frequency range checks.

The MAF Max Delta (not Max Negative/Positive Ariflow we see in HPT now) is the table that defines how much delta/difference between the VE calculated airflow can be different from the MAF senses airflow before th PCM assumes the MAF is incorrect (throws the P0101) and has to decide what to do (fail to VE, Default Air Table or nothing).

Bad VE table or severely changed MAF table could cause P0101 to come up even if the MAF sensor is really working. Skewing the IFR and MAF enough cold cause this if the VE table wasnt skewed as well.

Is your MAF related error code P0101? If so, time to update the VE or (via TinyTuner or somethign with it mapped) update the MAX Airflow Delta that is used to compare VE vs MAF.

[murphinator]

BTW, I have posted in another forum that with the help of a another piece of editing software that you can change your tune so that it will always have 0 fuel trim in cell 3, and thus if you make sur that you are in cell 3 when in PE, you could always have 0 fuel trims in PE. oakleafresin knows the forum as I see him there every so often

To me, this type of setup makes the perfect balance of closed loop and PE (without the need for completely crippling closed loop by forcing Open Loop).

someone familiar with doing this and where it is in the hidden ( to hpt users) portion of the tune should post it in the request to add section of this forum - not carrying trims into PE would simplify a lot of things ...