Country Boy

iTrader: (24)

Yeah, I know.... another damn VE question again.. LOL If it wasnt for this VE stuff, Id tune my own PCM in a heartbeat.

Now, if you have a VE table that is way off, what would the side affects be?

jimmyblue

iTrader: (11)

VE is the "fudge factor" in the speed density mode
mass airflow calculation.

Speed density is used any time the MAF is expected
to be unreliable at airflow measuring. This includes

- low RPM
- changing MAP

Idle seems to be almost entirely speed-density.

The changing-MAP aspect can manifest as "lean
holes" when you punch the throttle; this in turn can
give you KR. See this as a brief, sudden drop in
O2 volts on rising TPS accompanied one or two
ticks later by a KR blip.

Country Boy

iTrader: (24)

So.. would this show up on a a/f graph as a lean spike before it figures out the right a/f mixture? Like.... when you hit the throttle on the dyno, and you see the A/F go lean for a couple hundred RPM and then come down to where it needs to be?

jimmyblue

iTrader: (11)

Right. The MAF is thermal based, slow; on a fast
air surge it's still reporting "yesterday's news". So
you shoot less fuel than needed unless the SD tune
takes over. But, most people don't screw with the
VE table even though they hand on all kind of bolt-
ons and bolt-ins meant entirely to improve (increase)
the VE of the motor. So you flow more air than the
SD tune represents too, and stuck with transient
leanout.

Country Boy

iTrader: (24)

Cool, so I can attribute this dyno to the messed up VE then? Also, is there any drving characteristics of a bad VE table?

So a perfect VE table really isnt entirely nessary if the PCM only uses it for quick MAP changes and low RPMs (how low?).

P Mack

iTrader: (6)

Everyone needs to read this thread if they haven't before http://www.hptuners.com/forum/YaBB.p...1555;start=0#0

Basically it figures in ve below 2400 rpm, and if manifold pressure is changing under 4000 rpm. Above 4000 rpm it's all maf.

P Mack

iTrader: (6)

For boltons like a lid, ram air, ported throttle body, etc, i don't think you need to change the ve tables. Although you really are making the engine more efficient, the map senses the increased pressure in the manifold. For boltons like intake manifold, headers, exhaust, etc yeah, then the ve tables would be off.

Country Boy

iTrader: (24)

Im asking because I have a H/C motor with the X3 cam and I have no idea how my VE is.

WS6snake-eater

Hey country boy...I have a VE table that you can try...I've got the same cam, with stage II ls6 heads...on my 01 ws6. I'm sure it will make your drivability a lot better. Let me know if you want to take a look...I'm assuming that your using HPtuners.

Matt

CHRISPY

you are too lean across the board...

You need to richen your PEvsRPM significantly from 3000-4000rpm and a richen it a little less from 4000-7000rpm.

You should try to hit around 12.4ish:1 at torque peak and ramp up to around 12.8-13.1:1 at RWHP peak depending on octane/timing/compression and cam characteristics...

cne411

WS6snake-eater
Can I see a copy of that VE file, I have a G5x2. Im hoping it might ge me in the right direction.

Another_User

I am having excellent luck with the 2002 Z06 VE table. And I added 10% to my MAF airflow to compensate for a lean condition. I am seeing pretty much 0 trims (ltft) across the board, except in the middle it is between -1 and -5. Works for me.

WS6snake-eater

I'll try and post if up when I get home tonight

moehorsepower

iTrader: (3)

Exactly, you will see the spike go all the way to 18.1 or depending on how much you adjusted the VE table.