MIGHTYMOUSE

iTrader: (59)

i think it backfires because the rpm signal is lost.. no i can't get it to do it any time other than when i'm trying to go fast..

Pro Stock John

iTrader: (34)

If you lose RPM reference, then the car has to shut off. THEN it backfires. That is what is happening right?

MIGHTYMOUSE

iTrader: (59)

all i can say is look at the video, i cant tell if it backfires as it is being cut out or backfiring when power returns.. not sure.

Pro Stock John

iTrader: (34)

Have you tried to load it and then roll into it and see what happens?

Losing crank signal (maybe cam signal too) works like this:
-pcm loses signal
-shuts motor off
-unburnt fuel hits hot pipes
-backfires

Futral

iTrader: (1)

MIGHTY...sounds just like the problem Buster and I had..ours would shoot out the biggest flames out the headers when it acted up. Random and some pulls were clean..just tempermental.

All you have to do is look at the RPM on the datalog..it will drop out past 6500 ,sometimes drop to around 1000 RPM's and them come back up and jump around within a few hundred after that to 7500.

Hope the best for you..we beat our heads about it for 3 months.

MIGHTYMOUSE

iTrader: (59)

yes the rpm on the datalog drops to near zero during the pops..

if you would please... did you find the fix?

i was on the phone with mike at dfi today and he asked if i was able to bring the car... its not possible for me to do so.. he mentioned Futral in the conversation... he said if they could get a car there the fix would be easy.. they just cant reproduce it on the spin machine or the stock ls1 they have there.... somebody's gotta be closer to michigan.

otherwise i'm going to have to start throwing parts at it.. cam and crank sensor and a rewire of them to the pcm are first in order i imagine.

Hawkn01

iTrader: (1)

Guys, this is alittle differant system, but on a MSD Mag 44 ignition the crank trigger air gap was very critical. A buddy runs that system on his Top Fuel dragbike and they had a problem similar to what you guys are having. If I'm not mistaken they ended up opening the gap up more and double grounding system to the motor and frame.
Don't know if that will help or not but thought I would throw it out there.

Pro Stock John

iTrader: (34)

Gen7 uses a eDIST type box? Crank signal goes into that right? Might want to spend some time on that.

MIGHTYMOUSE

iTrader: (59)

yes there is a secondary box that converts the signals for the ignition system separate from the main dfi box.

MIGHTYMOUSE

iTrader: (59)

update* today craig has a new ignition box on its way for me to test this weekend.. fingers crossed.

kp

iTrader: (34)

Let us know, first time trying to make some full power pulls and mine is shutting off around 6800. Checked and double checked everything - tach drops to zero for a second and then BANG. Not everytime but enough to make me give up for today - pretty frustrating. Wont take much more for me to stick an electromotive XDI with a crank trigger and a carb on this thing...

MIGHTYMOUSE

iTrader: (59)

kp call dfi and let em know, maybe they can get you a test box too? i got mine in my hands right now, going to install for the trip to work

kp

iTrader: (34)

I'll see what happens with the one you get before I call, I cant street drive mine so even if I had one in my hands it wouldnt do me any good until I went back to the track or dyno.

nitrorocket

iTrader: (12)

With my gen 7 I had a problem with an intermittant crank signal untill I played with the connection on the crank signal harness to the ecm harness. I have run mine to 7400 a couple times without any noticeable cuttout. I have the 77022 part # and run a hall effect crank and cam signal. Will this same ecm work with a ls1 coil system??? I have it on the motor in my sig, but I have just one coil.

Pro Stock John

iTrader: (34)

JS on the 3rd page of your thread you made a comment about FAST. AFAIK they are not having problems, mine has gone to 7100 a number of times and it's fine.

I just know from older experience that if you lose crank reference with a stock pcm the engine will do what you are describing. I'd make sure the coil box and stuff are getting solid consistent voltage. If so it's other problems.

GrannySShifting

iTrader: (10)

Would it be possible it needs to sync the cam/crank sensors like the factory pcm has to do a crank relearn? I know on the LT1 setups you had to tell it the trigger was like 6 degrees out or something. I would figure that problem would get worse as RPm increases

MIGHTYMOUSE

iTrader: (59)

kp have you contacted accel about this even once yet before giving up on them?

kp

iTrader: (34)

I havent given up on it yet nor do I plan to at this point, I think its a great system and its pretty well integrated into the car right now.

I swapped in a brand new ignition harness yesterday and next time I can get out to the track or to the shop on the dyno I'll try it. My car is way too loud to drive around or even leave running in the driveway so I have to wait to take it to the shop or track and that is keeping me from getting this figured out. I'm not saying anything bad about accel and I dont want to complain until I've tried everything.

When I'm 100% sure its not something in the wiring (I didnt do the original install) then I'll call accel and bitch How did the new box they sent you work?

kp

iTrader: (34)

Spent some time on the phone with Craig at DFI and we are going to try a few things to get the high rpm miss I am having resolved. Accel is serious about getting the issue fixed and pinpointing the cause and I am going to stick with it for a while, car still ran pretty decent yesterday but has some other non-ignition issues. I think its fair to give Accel a chance to fix it (or find the cause) before writing it off.

Joe Overton

Just curious whats the fastest a "ls1" has been with the BIGS iii or the F.a.s.t????