cj68

I need some help from a DFI guru or just a good tuner.

I have been trying to fix a few unresolved problems with my tune after paying a tuner over $500 to tune my Jeep on a chassis dyno and walking away unhappy.

My drivetrain is right up your guys' alley so I keep finding threads here on thirdgen.org.

I have been all over google and searched and read a bunch threads on here, yellowbullet, and others. I am going crosseyed. I have been tinkering with this here and there for a couple years now. The engine runs OK and pulls plenty strong but I know it can be better. Now that I am spending less time on fabrication tasks and actually driving this thing more, it is time to get serious about sorting this ECM out for once and for all.

Engine:
Small Block Chevy stroker 383
10.4:1 compression
Hypereutectic pistons
190cc AFR heads
Comp Cams 8-500-8 small base circle cam:
Hyd roller
258/264 Advertised Duration
0.48/.488 Lift (with 1.5:1 rockers)
108* intake CL
Scorpion Roller Rockers 1.5:1
Tuned Port Intake with Accel High flow base plate, runners, and 1000cfm TB
Accel Dual Sync Distributor
32lb/hr injectors
Accel DFI GEN 7 ECU with the most recent firmware (as of 2011)
Accel wide band O2 sensor and signal conditioner.
MSD 6AL CD ignition box

Trans:
700R4, reverse full manual VB
~2000rpm stall 10" TCI converter



I have a few nagging issues.

#1 hard to start when hot. It always starts but it takes a lot of cranking and opening the throttle blades. The motor will seem to catch a couple times while cranking as well. I think this catching but not starting attributed to a recent starter nose explosion... If you shut it down hot and immediately restart it, the amount of cranking is reasonable. When dead cold, it fires up when you just look at the key. I have tinkered with the startup enrichment vs. ECT table and did nothing but take too much fuel out at lower ECT's and made it almost impossible to start when cold. Recently, I set the IAC to wide open when cranking at high ECT's. That helps but pretty much only made it so I do not have to open the throttle with my foot. The tuner I paid good money for gave up and blamed heat soak of the TPI manifold. I don't buy that. Does everyone else with a TPI have this problem?

#2 Lean tip in fueling when blipping the throttle at low speeds (might be at other operating points as well). I recently figured out how to data log and noticed this in the log. When using light throttle to move around the shop or driveway, I see AFR's spike up. I am not sure what transient fuel table to adjust first. I think the Tau vs. MAP/ECT is the first place to start but I am not sure. Aside from this off-idle tip in, actual AFR's stick pretty close to my target AFR with not as much need for improvement.

#3 Pulling timing excessively. The tuner complained that the ECM kept pulling timing and he didn't know why. He blamed the 37" tires and their massive rotating mass and basically gave up because he has no experience tuning heavy, big tired vehicles... Again, I am not buying it. As far as the engine is concerned, a load is a load. Torque is torque so tuning for the load profile should be a no brainer. I can get the ECM to retard the timing with light load changes with the trans in neutral and see a more consistent retard while cruising with very light load changes. I believe I am experiencing a false knock situation but have no idea how to diagnose and test this. After some conversations with Lee at HESCO performance he suggested adjusting my timing map for 30deg total timing @ WOT and 35-48 @ cruise. This is only slightly more conservative that the timing map that the tuner had setup. When cruising, the ECM will pull timing down to 20deg and would pull it lower if the limits would allow so something is going on here.

#4 When cruising under light load or holding the engine in the ~2000-3000rpm range under no load, I can here a random miss-fire. If this was a carb'd engine, I would think nothing of it but I am supposed to have the bad *** sequential EFI system so what gives? Is this a symptom of the timing retard?

efiguy

iTrader: (2)

Send me your current cal. Email it to fastone01@hotmail.com, I'll take a look at it and see what's what.
This is me.

cj68

Hey Mark,

I forgot I had your contact info. You helped with a base cal file for this engine when I just getting it running. I just sent you an email with three cal files. Your original base cal, the cal file as the tuner left it and the cal file I have been tweaking after the tuner.