$EE Tuning Low Map VE Cells

Hi guys,
Is it common to get a crease in the VE table?
I'm finding when i cruise & lift and go into decel, the AFR gauge just maxes out.
I'm getting a crease in the table about 30 map where I'm having to ramp up the VE cells again.

The car does seem to be improving.
Anytime there is some load it's fine it's just at the point you hold/lift the throttle & vacuum rises (map in 15-35 range).

I've just raised the IAC vs Vehicle speed & IAC park position to see if letting more air in will reduce the high vacuum reading on decel.
Not had a chance to test this out though.

Any other ideas ?


Thanks
Mitch

you want lots of vacuum on decel, and not much fuel, engine braking is good. having it go a bit lean where you're between light cruise and decel is okay too. i wouldn't tune so much by your wideband in decelleration range as combustion there is too poor to measure properly, but if your AFR gauge maxes out, you're probably enterting DFCO. even if you aren't, decel enleanment is a good thing. you don't want to make power down there, and there isn't really enough cylinder pressure and heat to cause any harm from enleanment.

Thanks for the reply Steveo

At higher speeds it's not a problem. It's the last 5-10 mph and the car seems to fall on its face.
I've got the car running off idle and it'll take the load with no throttle and roll ok.
If i then apply the smallest amount of throttle and lift off it buck.
My VE table slopes down to the idle cells but by 30 map it's starting to rise up where it goes lean.
I'm not sure what the car needs or wants.
More fuel seems to help but the VE table looks odd.
Would increasing the timing help in this lean region? most tables seem to drop off at this point.

Last data log with averaged data.

I'll post some pics later.

Display WB AFR values
=======================

5 10 15 20 25 30 35 40 45
400 . . . . . . . . .
600 . . . . . . . . .
800 . . . . . . . 15.16 14.48
1000 . . . . . . 15.10 14.23 14.33
1200 . . . . . 15.65 14.12 14.36 14.41
1400 . . . . . 15.41 14.01 14.50 14.80
1600 . . . . 16.62 15.17 14.21 14.71 15.05
1800 . . . 16.99 16.29 14.67 14.28 15.04 15.13
2000 . . . 16.81 15.80 13.91 14.72 15.12 14.96

(Web Gurus: Any way we can force a non proportional font change ?)

Thanks
Mitch

It looks like timing issue. Log advance and see if there is huge difference with light throttle and lift off.
You can try blending the closed tps spark table with the main spark tables at the 25-30 map region.

Cheers, I'll play with timing more now the fueling has settled down some.

Would I be looking for more or less advance in such a lean area?

Not at the PC now but I had gone back earlier to the Stock LT1 timing table.
IIRC i'm in high 30's/low 40's for timing in the low map areas.

Closed TPS advance is currently about 30 at idle rising to about 37 as the rpm's increase.

Thanks
Mitch

I've spent the weekend playing around, adding fuel and pulliing timing.

After reading up on some articles i've been playing with the Fuel Injector Adder table and ramped it up.
I noticed the InjectorPW was was in the 1.30's but fueling was all over the place when ever I got it back to low 14's AFR.
Whenever it ras idling rich, the fueling was always smoother.

So now the Injectors have
about 840 uS on the Injector Voltage (supplied with the injectors)
530 uS on the Injector Offset Adder table whilst idling.

Injector PW is around 1.00mS at idle but i'm now rich idling at about 12.5 as expected.

Driving the car seemed much improved (not certain yet as the car is pig rich low down).
It did quite happily pull away in 3rd gear.
After logging, the previous severley lean areas of the VE table all needed to be lowered making it look more normal.

I'll report back when i see where this goes.


On a side note, this motor starts off very lean vs the commanded AFR and goes progressively richer as it warms up.
I've increased the Initial Startup AFR Enrichment Vs coolant temp without much change.
Restarting today at 60-70C it starts in the 15's and drops down to 13's by the time it's hit the 90's.

I've read about heat soak with the IAT (MAT) affecting fueling but what i've read suggests the older TPI cars with MAT sensors suffered heat soak & leaned out the mixture.

Has anyone played with these tables ?


Thanks
Mitch

Evening guys.
OK tried the car again tonight.
It always starts very lean and richens up as it warms up.
I've no idea why.
I jacked up the initial startup AFR enrichment to 25% but it still starts lean vs commanded... not really an issue

As it heats up the target & AFR cross over and it was idling very rich but really smooth and stable idle, so I scaled the Injector adder down about 60%.
Now it's idling between 14 & 16 AFR
The Inj PW is sat at 0.98 and WILL NOT go any lower.
======================

My Inj Voltage offset is about 854 & Inj Offsets are about 320ms
Min Inj pulse is set at 0.4ms & use 0.4ms when below

I suspect my injectors can't operate this low. (Tell me otherwise).

I don't know which way to go now or if I can try anything else.

Suggestions please.
Another set of injectors is too expensive just at the moment.
I do have a set of 30# i could put back in but I don't see the point.

Would lowering the fuel pressure down a little with an adjustable reg be worthwhile ?

Thanks
Mitch