Lemansz06fan

A few months ago I had a cam installed in my c5z and everything was working well. I had a road tune done by the installing shop which did an excellent job tuning part throttle and getting the car to run properly. I noticed that I was running out of fuel at WOT (installed a WB after getting the car back) so I installed a set of GTP injectors (Bosch 0 280 155 811 injectors). Using the info I found here on CF as well as on the HP Tuners site, I managed to get it within +-3% on AFR error, however the car will now not go into DFCO. This is causing the car to go pig rich (11:1 or less) on decel and I really don't feel too good about that regarding my cats.

Since I've installed the injectors, very slow speeds (like in a parking lot, or creeping in traffic) letting off the throttle causes the car to buck a bit, like I don't know how to drive stick, except its with gear engaged and off throttle completely.

Some notes:
2003 C5 Z06 (LS6)
226/230 .598/.600 116LSA cam
Vararam intake w/ power duct
LS7/9 exhaust manifolds and cats to stock TI exhaust
Bosch 0 280 155 811 injectors

Car did the whole daily driving thing perfectly before installing the injectors, so I'm pretty sure it has to be an issue with the injector data.

I'm attaching my tune and data log/configs for reference.

Any critique would be appreciated too.

Thanks!

RedRiderZR1

It does sound like the data on the injectors. Between bucking and rich decel your inj data, Injector pulse width table, and/or short pulse adder tables are more than likely out of spec. Need to find the right data for them, or you will be tracing one issue after another fudging the tables. I have not looked at any of your data, but from what you said, sounds likely that is the issue. Will look at your data in a bit.

edit: The issue with the rich decel, go into transient fuel (engine, fuel, transient) then go to Min fuel Milligrams ((and set it to 0.002 ( currently at 0.028)). See if that leans it out on decel. It should. You can play with that setting and get it to where you want the AFR on decel. Mine is set to 0.002, but changed my VE table to help out AFR. Also set an aggressive DFCO routine so it spends a lot of time in DFCO on decel.

Lemansz06fan

Thanks,

I will try that fuel milligrams setting out (original injector data said to put it at .0032, so maybe I didn't go far enough)
Which injectors are you tuned for?

EDIT: Figured out what the reason was it would not get into DFCO... I have a Tick master cylinder and it seems because of where the pedal was adjusted, it was not tripping the clutch up sensor and therefore the car did not think the clutch was all the way out.

still have the slow speed bucking issue though. In a more informed note, it is worse when the car is hot.

tblu92

On most all cammed engines I disasble the DFCO The triggers to activate DFCO include several parameter----With a larger cam the parameter that affects DFCO is the MAP table activation parameter-----A stock cam will idle with a low KPA manifold pressure-- However when you install a larger cam the car will idle at a much higher manifold pressure
Stock DFCO activation is at 19 KPA an d deactivation is at 25 KPA
Most cammed cars will idle at around 50-70 KPA---depending on duration the more duration the higher the idle KPA--------So DFCO will never be activated because it does not hit the KPA or MAP triggers-----
You can tune these tables to accommodate the higher KPA idle numbers to insure DFCO will trigger
However my opinion is that you are too concerned about something that is at worst a very un common problem----CAT failures from an over rich decel-----
DFCO shuts the fuel OFF upon deceleration-----BUT the ECM will also go very lean upon decel like in the 16's to protect the cats---This protection is a part of the "COT" system in your tune (cat overtemp protection) Which will protect the cats from a very rich or very lean decel condition------
I would simply leave the DFCO OFF and the COT will protect your cats----

Lemansz06fan

I have figured out why the DFCO was not coming on. It seems the clutch up switch was not engaged due to a tick adjustable clutch master cylinder.

The cam I have has very low overlap and is still able to idle in the 14kpa-20kpa range that the stock dfco settings were used in. It seems it was just the clutch transition settings not allowing it into dfco

the reason I was concerned is that after a WOT run the AFR would dip into the 10s or less. In the period DFCO is supposed to he active

RedRiderZR1

The 0.0032 setting is what the stock injectors were set for also. I too have the LS7 manifolds and cats and H pipe going into Aftermarket catback. After putting that in (stock exhaust before except catback.. California Seriously Sucks) I was running 8.6x AFR on decel (OUCH, Could really smell it) My setting was also 0.0032 I tried everything down to 0.0010 and still was running rich. Finally set it to 0.0002 as others have done, after that it went to 16.xx AFR on decel. So I really had to cut that parameter to get results. Just running to fat so it would not lean out enough on decel. Reset the fuel trims afterwards, Leaned out the VE table some in the decel areas and drove it and let it learn. Now my decel is at 14.6-14.7 throughout on decel w/o DFCO.

The Injectors I'm running are siemens 60#.

You say it is bucking in first just idling through a parking lot. IIRC you mentioned an AFR gauge install. Is it still in the car? What are the readings on the gauge when you do that? At idle you might be running a bit rich if your injector data is not correct and that could make it buck while going through a parking lot. You mentioned it ran well before the injectors being swapped, so i'm guessing the injectors is what is causing the issue and not something to do with the cam or timing issues. Just compared your Inj data to data I have here for Injectors. The data installed in your car is for the Bosch 868 Injectors. Some have mentioned that data does not work perfectly with the Bosch 811 injectors you have. Only thing the tuner did differently is they reduced the Minimum Inj Pulse. The 868 injector calls for 1.277 and they put in 0.152. You need to do a scan on your car just idling around while it bucks to see what is going on and know what cells the car is using when this happens and go from there.