Lean on "tip-in"

[Cheatin_Chad]

I seem to be getting knock on throttle "tip-in". This is my first foray into EFI tuning. So I don't know what to do here.

If this were a Carb I would up the accelerator pump shot.

Any ideas? I have a '98 F-Body w/A4

[TT_Vert]

im in the same boat. Going from the higher timing areas to the lower timing cells causing some KR sometimes during the transition .

Dave

[jimmyblue]

I was looking at somebody's log and saw a bad "lean
hole" right at tip-in (O2s crashed, then went rich w/
true WOT TPS% but too late, the KR was already on it.

So far I haven't seen anything like an ePumpShot in
the available fueling fields. You might want to play with
the Burst Knock as a "cover-up", that does some kind
of timing pull when it sees large CylAir delta flow. It
might suppress knock at least.

But I would be interested to hear of a proper, "leading
edge enrichment adder" and see it brought into the
menus (or, if it's hiding there already, identified).

[luv2spd]

I'm also having the same problem. It usually happens after I shift at wot. I don't know how to correct it. I've heard that the ve table could be used b/c at the throttle transition, the maf is inaccurate and fueling is based off the ve for that instant. Anybody know if this is true?

[Cheatin_Chad]

I'd be very happy if it turned out there was something along the lines a "pump_shot" buried in the VCM that we could access.
I appreciate you guys suggestions but I really can't say I know enough to act on them.

Should I do some VE table "smoothing" where I am having the problem?

Should I lower the numbers in "burst knock"?

I know I have seen other people mention this on LS1tech.com.

[Chris@HPTuners]

i don't see any pump shot equivalent.

The answer is inside the VE/MAF relationship and the way the PCM uses the VE table to correct the MAF airflow during throttle transients. In a carb engine the pumpshot is there to cover the main circuits delay in delivering fuel, in an EFI engine its all about getting the airflow transient correctly predicted/measured.

Try this:
- locate the MAP/RPM area that is causing problems and increase VE and see if it makes a difference.

The only other means i know of is burst knock as a reactionary precaution against KR during transients as jimmyblue said.

[luv2spd]

Why don't 98's have the burst knock retard? Is my only option the ve table since i can't change the values for burst knock? thanks

[jimmyblue]

In airflow-testing my MAFs I have seen that the MAF
response time is pretty poor (thermal-based as it is).
So that probably accounts for -why- the hole (MAF
still reports the old airflow for a tick or two, though it
has jumped up).

Would the open-loop A/F table have any applicability
here? Is the open loop table referred to on transients
or is it just the SD calculation, still closed-loop?

[TT_Vert]

can someone explain burst knock a bit more thorougly for me and what it does and how changes will affect things?

Thanks

dave

[Magic_Chicken]

Here's a newbie questions for you.

What exactly do you all mean by "tip-in?"

[luv2spd]

Tip in can be defined as a large change in throttle position. The maf cannot accurately meter this big change in volume quick enough to accurately deliver fuel. I think a diff. fueling table is used at this instance like the ve table.

Burst knock is when the computer predicts that timing will need to be pulled. It isn't technically knock retard because the computer pulls it in anticipation of knock.

[Magic_Chicken]

Thanks, that was a good explanation.

[Cheatin_Chad]

I'm going to work on the VE changes this weekend.

[luv2spd]

I'm going to work on the VE changes this weekend.

Let us know how it goes!