Greg Fell

iTrader: (9)

hello, need a sanity check.

my car bucks pretty good at 1700ish at ~70 kpa. when i command 13.5 or so, it smooths out a lot.

if i richen the VE table in those cells, wont it just fuel trim its way back to '14.7'? would love to get out of bucking, and not really wanting to do OL.

edcmat-l1

iTrader: (10)

The simple answer is yes, it will go back to stoich.
The bucking is usually a symptom of other things. I've never fixed bucking by richening the mixture.
What are the cam specs?

Greg Fell

iTrader: (9)

253/259 112+2

you can notice map improves when u richen up, as well.

in my experience, cammed motors like to run a bit richer.

edcmat-l1

iTrader: (10)

How big is the engine? That's a bit of a cam. FWIW, most of the cammed engines I've done, EFI or not, like to be just a bit richer than stoich. I've never had to run anything part throttle at 13:1 A/F. And I'm talkin solid roller 260/270 cams in 500+cid BBCs.
Most of the time, you can tame some of the buck by knocking the timing out of it. But with that cam, you'll never get all of it out.
BTW, I'd probably be running that thing OLSD anyways.
Can you post, email a datalog and your tune? From start up, including about 30-60 seconds of idle, and then some cruising.

Greg Fell

iTrader: (9)

its in a 440, so not all that radical.

i have some logs and a tune, what email?

edcmat-l1

iTrader: (10)

edcmat-l1@msn.com

BLK02WS6

iTrader: (2)

If you put in a custom operating system from EFILive, you could run semi-open loop and richen it up in that area only...

The Alchemist

iTrader: (19)

Well, can't you go in and change what you are requiring stoich to be? Can't you change it from 14.68:1 down to 14.4:1 which would then richen up everything?

jimmyblue

iTrader: (11)

At 70kPa you might well want to be in PE mode but
maybe the 1700RPM is holding you off (see PE enable
RPM).

I guess this must be a M6 car because no decent A4
converter would let you lug it like that. And that maybe
is your real answer, "powerband management" by the
stick.

tazinhawaii

iTrader: (1)

I had been trying to fix this same problem with my setup. just recently figured out what the car likes to minimize the 1600 RPM bucking. A LOT of timing and a LOT of fuel. I set up 43 degrees of timing and 13.0:1 AFR in those cells and the bucking has gotten much better. As soon as I lean it out in those cells, the bucking comes back and if I take out timing the bucking comes back violently. So, I say no, this isn't unusual. In fact it's the only thing that worked with my car. And yes, for me it's between 60-75 kpa (car idles at 70-75 kpa).

Derrick

Slowhawk

iTrader: (12)

Your probly getting a misfire from the cam in those area's which causes the bucking.It's a common problem.You can richen up the commanded A/F in that area.

jimmypop13

iTrader: (17)

I'm running a maf tune, well I tuned in SD and then enabled the maf again, on my car and get some bad bucking around 1600rpm. I've got the timing up to 44 in that area, no knock, but still bucking. I've been wanting to richen it up in that area but I'm not sure how since I'm running a maf. Can someone help?