Below are the symptoms, the mods to the car, and I can provide any amount of datalogging you need, my ls1edit file, etc.... whatever it takes. been working on this over the course of the last few months with no luck.

Symptoms: Under decel the car goes rich as in 11-12:1 and ltrims hit -15% then when I get back on the throttle the car goes very lean as in as high as 17-18:1 for a split second then the car recovers and it goes back to a nice 14.7:1 Between shifts it does the same but goes even richer. So basically any on/off throttle transition is really screwed up. Not only is it incredibly annoying when the car does this as alot of times it will cause it to buck or stutter for that split second but it also causes instant KR if I want to stab the throttle. This is incredibly bad as the car is supercharged so needless to say I can't stomp the throttle right now. PLEASE NOTE THESE SYMPTOMS WERE PRESENT PRE-BLOWER so don't get overly foucused on that.

Cruising around town/freeway ltrims are perfect +/- 1%. If I roll into the throttle again everything is fine. Zero KR, Ltrims zero out, car pulls nicely. For the life of me though I cant figure out why it's going so rich under decel/gear changes and so darn lean on initial tip in. If I could get this problem solved I would be golden. Thus the request for help. Also note that when the car is first fired up and running open loop for that first 30 seconds or so it behaves correctly. So if I literaly fire it up when it's cold and immediately start to drive it's ok for those first 30 seconds or so until it goes into closed loop. Between shifts it leans out, under decel it holds 14.7 or goes a touch lean, upon light tip in it stays in the 14's where it should.


Mods - 98 Formula, Lucas 42# injectors, Racetronix PNP fuel pump, CAS referenced FP regulator, Mildly ported heads, 212/218 .522/.529 114LSA cam, LS6 intake w/EGR, ported throttle body, MAC headers w/CATS, custom ATI blower setup (again these symptoms were pre-blower and are exactly the same with the blower installed)

I have checked top to bottom for vacum leaks, put in new 02's, swapped back to a stock TB, no luck.

Since I can find no mechanical reason for the behavior I am assuming at this point I need to tune around it.

Has anybody experienced anything similiar or have any ideas how to fix???

Again I have efli-live and ls1-edit, in car wideband, etc.... so I can try and test suggestions easily.

Lets hear em!

Thanks in advance!

 

Does the car do this with the stock program in it???? Try flashing the stocker in and see if it does it.

 

well unfortunately I do not have my stock injectors so I cannot do that. I have contacted another member though and he too has lucas 42's and his car does the same thing. now I am wondering if the lucas injectors require tweaking of the offset table to function correctly in low pulsewidth situations.

 

i notice my pulsewidths never drop below 2.
shouldn't they pretty much go to zero under decel?

 

If it is the tune then most likely it is your injector offset curve or your injector flow rate curve (if its not flat).

The proper way to fix a poor offset curve to is to obtain an offset curve for your injectors. The chances of you getting one though are about as good as me nailing Nicole Kidman

That leaves us with the 'not so right' guess work....

Try shifting your offset curve down in the lower voltages. The larger injectors form more of an 'L' shape than the smaller stock injectors and don't climb as high on the left side of the graph.

Try shifting your Injector Flow Rate Curve way up for the low vacuum situations that you are having this problem (right side of the line)


And perhaps the best way to fix your problem is to try switching injectors.

Good Luck

 

I will give those suggestions a try, and yah your final suggestion is where I have been leaning for a while now. Luckily I can borrow a set of SVO's and see if the problem disappears.

 

Heath any progress? Did you swap Inj.'s

 

The TeamZR1 dude has talked about there being a problem
when the MAF output falls off the bottom of the table.
This seemed to me to be a 'Vette-only problem since my
car never goes below 1500RPM even at warm park idle.

But with a custom intake tract maybe you have some
deal where this can happen, pressurizing air in the manifold
and then ceasing to draw it you might zero the MAF
airflow briefly?

I would look over your logs for any sign that the MAF
frequency is dropping out like this; it might need you to
pay more attention to the speed-density (VE?) for
whatever cell it throws you to, if so.

 

01- gonna swap them this weekend.

Jimmy - thanks for the tip. I will go thru the logs and take a look.