Blackbird

what parameters do I tweak for this.
example of symptoms. 6th gear 65 mile per hour. release throttle completely now lightly touch throttle and car sputters and a/f goes to 19:1. a touch more throttle it clears up.

it does it in all gears at extremely light throttle. you can really tell from going from giving it no gas to a little. if your already giving it some gas and give it more it's less noticeable.

seems like a problem with tip in enrichment, but there is no such field in ls1-edit like I am used to seeing with Fords.

Thanks in advance.

AzzHauler

iTrader: (3)

Have you changed the ve tables any?

Slowhawk

iTrader: (12)

Is this a supercharger setup like whats in your sig??Please give all your car mods that will help find the problem.

Blackbird

mods are currently....

42# injectors
racetronix pnp fuel pump
CAS 1:1 vacum/boost referenced fp regulator
mildly ported heads
small cam 212/218 .522/.529 114
mac headers with cats
ls6 intake

I am in between blower setups so the car is running NA right now.

Yes I have mucked with VE. from 800 rpm down I reduced it 10% to help with the stinky starts in the morning. I figured since I drive at 1000 rpm or more it would be ok but maybe not?

to be more accurate in my description I noticed this morning I don't even have to give it more throttle to get A/F back in line. so basically go from no gas and give it like 3% throttle then a/f leans way out then comes back in line. but the car will have a very slight constant studder to it. if the load is higher lets say cruise in 5th gear at 2,000 rpms with more throttle vs 6th gear at 1700 rpms with less throttle then the problem is less noticeable but still there. so it almost seems load dependent?

White_Hawk

iTrader: (3)

Heath, I am looking at this same problem right now with a car at a local shop. It is a heads/cam 382 stroker and it exhibits the identical symptom as far as the sputtering (haven't logged the O2's yet). The thing is, it was doing it before the tuning (with the stock tuning) and is still doing it now with Ed Wright tuning. The mail order tune they got is dead nuts, as far as driveability and everything, it is just when you are cruising and barely touching the throttle that it starts acting up.

Because it did it before and after the tune, they think it is sensor related, so they are going to start swapping MAF, TPS, IAC, and O2's first. Let me know what you find, and I'll keep you posted too.

-Geoff

jimmyblue

iTrader: (11)

The vacuum referenced FPR is really going to bend
the fuel shot at light throttle / high vacuum; it
will decrease line pressure (it maintains constant
line - manifold pressure, not line-ambient, the
negative manifold pressure will drop your rail
pressure from 58PSI (say) to 44PSI and your fuel
shot for the same PW will be much reduced over
stock. The stock injector flow tables would
represent a constant rail and you have changed this?

The injector flow w/ MAP is probably the right place
to represent this difference, I think.

Blackbird

Geoff - Thanks! Definetly keep me posted. My car, just like the one you mention, drives great everywhere except barely touching the throttle.

Jimmy - You kinda lost me. The way I understood things is my rail pressure using a referenced FP regulator would always remain constant. So no matter what during vacum or boost my rail pressure should remain 50psi (thats what I set my base pressure to) and as such I would use the same IFR value accross the board because there is no need to skew it one way or the other for varying fuel pressure like you have with the stock FP regulator. So are you saying that maybe I should be looking at richening up with the IFR table at the very low end of the table? Thanks!

jimmyblue

iTrader: (11)

The manifold referenced FPR -will- keep the
pressure across the injector constant. The
problem is that this isn't how the car was
originally built, so the stock PCM program
has the effects of manifold pressure variation
built into its tables that you don't need.

At (say) 0 MAP, you have -14.7PSI manifold and
58PSI rail for almost 73PSI across the injector.
Or, so the PCM "thinks". But your manifold
referenced FPR keeps it at 58PSI. So the shot the
PCM thinks is good to make 14.7:1 is really 11%
short. Or something like that. By my calcs that
should only lean you to 16.5:1, but you can add
in any other problems (like VE and MAF low-end
infidelity) and maybe get even worse.

I'd guess with the manifold referenced regulator
your MAP injector effects table (I presume there
is one just for that) would all want to be the
WOT (MAP=14.7) value. This is where the stock
regulator's reference pressure (ambient) and
manifold pressure are the same - zero vacuum,
14.7PSI MAP (corrected for your favorite altitude
as need be).

White_Hawk

iTrader: (3)

Jimmy, I see what you are saying, but we seem to have an identical problem on two completely different cars. The 382 stroker has a stock fuel system with an upgraded pump and stock injectors. I sent an email to Ed Wright and asked his opinion, too, in case it could be tune related.

-Geoff

ZTwentyAteU

iTrader: (12)

seems like you need to log it and see what kpa vs throttle is where this is happening. stab 1.15 x into it there and see what it does.

On your log you should see the narrowbands plummet to small numbers when it does it to find the spot

BLK02WS6

iTrader: (2)

Just because you have similar symptoms does not mean you have an identical problem...

BLK02WS6

iTrader: (2)

Did you do an open loop tune on the VE table and then the MAF table using a wideband? To do it properly, you have to tune the entire table using the wideband feedback...